0001564590-21-007578 | 10-K | XBRL Viewer

Net periodic benefit of defined benefit pension plans

462

489

534

Non-cash lease expense

146

148

(196)

(135)

(163)

Provision for doubtful receivables from clients

Provision for/(benefit from) deferred income taxes

(72)

(115)

Share-based compensation

Net (gain)/loss on disposal of operations

(81)

Non-cash foreign exchange (gain)/loss

(6)

Other, net

(41)

Changes in operating assets and liabilities, net of effects from purchase of subsidiaries:

Accounts receivable

(261)

Fiduciary assets

(1,774)

(365)

(839)

Fiduciary liabilities

1,774

365

839

Other assets

(205)

(269)

(22)

Other liabilities

215

(264)

(20)

Provisions

(138)

(23)

Net cash from operating activities

1,774

1,081

1,288

CASH FLOWS USED IN INVESTING ACTIVITIES

Additions to fixed assets and software for internal use

(223)

(246)

(268)

Capitalized software costs

(63)

(59)

(54)

Acquisitions of operations, net of cash acquired

(69)

(1,329)

(36)

Net proceeds from sale of operations

212

Other, net

(17)

Net cash used in investing activities

(160)

(1,614)

(341)

CASH FLOWS (USED IN)/FROM FINANCING ACTIVITIES

Net payments on revolving credit facility

(131)

(754)

Senior notes issued

282

997

998

Proceeds from issuance of other debt

1,100

Debt issuance costs

(2)

(13)

(8)

Repayments of debt

(327)

(995)

(170)

Repurchase of shares

(150)

(602)

Proceeds from issuance of shares

Payments of deferred and contingent consideration related to acquisitions

(12)

(57)

(50)

Cash paid for employee taxes on withholding shares

(14)

(15)

(30)

Dividends paid

(346)

(329)

(306)

Acquisitions of and dividends paid to non-controlling interests

(28)

(55)

(26)

Other, net

(3)

Net cash (used in)/from financing activities

(434)

397

(903)

INCREASE/(DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH

1,180

(136)

Effect of exchange rate changes on cash, cash equivalents and restricted cash

(2)

(41)

CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF YEAR

^[1]

895

1,033

1,030

CASH, CASH EQUIVALENTS AND RESTRICTED CASH, END OF YEAR

^[1]

$ 2,096

$ 895

$ 1,033

[1]

As a result of the acquired TRANZACT collateralized facility (see Note 10 — Debt), cash, cash equivalents and restricted cash included $7 million and $8 million of restricted cash at December 31, 2020 and 2019, respectively, which is included within prepaid and other current assets on our consolidated balance sheets. There were no restricted cash amounts held at December 31, 2018 and 2017.

Consolidated Statements of Cash Flows (Parenthetical) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted cash	$ 7,000,000	$ 8,000,000	$ 0	$ 0
Prepaid Expenses and Other Current Assets [Member] \| Tranzact Collateralized Facility [Member]
Restricted cash	$ 7,000,000	$ 8,000,000

Consolidated Statements of Changes in Equity - USD ($)
shares in Thousands, $ in Millions

Total

Cumulative Effect Period of Adoption Adjustment [Member]

Shares outstanding [Member]

Ordinary shares and APIC [Member]

Retained earnings [Member]

Cumulative Effect Period of Adoption Adjustment [Member]

Treasury shares [Member]

AOCL [Member]

^[1]

Total WTW shareholders' equity [Member]

Cumulative Effect Period of Adoption Adjustment [Member]

Non-controlling interests [Member]

Redeemable Non-controlling interest [Member]

Equity, beginning balance at Dec. 31, 2017

$ 10,249

$ 10,538

$ 1,104

$ (3)

$ (1,513)

$ 10,126

$ 123

Equity, beginning balance (Adoption of ASC 606 [Member]) at Dec. 31, 2017

$ 317

Equity, beginning balance (in shares) at Dec. 31, 2017

132,140

Temporary equity, beginning balance at Dec. 31, 2017

^[2]

$ 28

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Shares repurchased

(602)

Shares repurchased (in shares)

(3,919)

Net income

713

695

Net income, redeemable

^[2]

Net income, total

715

Dividends declared

(313)

Dividends attributable to non-controlling interests

(24)

Dividends attributable to non-controlling interests, redeemable

^[2]

(2)

Other comprehensive (loss)/income

(446)

(448)

Other comprehensive income/(loss), redeemable

^[2]

(2)

Other comprehensive income/(loss), total

(448)

Issuance of shares under employee stock compensation plans

Issuance of shares under employee stock compensation plans (in shares)

701

Share-based compensation and net settlements

Foreign currency translation

Equity, ending balance at Dec. 31, 2018

9,971

10,615

1,201

(3)

(1,961)

9,852

119

Equity, ending balance (Accounting Standards Update 2018-02 [Member]) at Dec. 31, 2018

(36)

Equity, ending balance (in shares) at Dec. 31, 2018

128,922

Temporary equity, ending balance at Dec. 31, 2018

^[2]

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Shares repurchased

(150)

Shares repurchased (in shares)

(788)

Net income

1,067

1,044

Net income, redeemable

^[2]

Net income, total

1,073

Dividends declared

(339)

Dividends attributable to non-controlling interests

(21)

Dividends attributable to non-controlling interests, redeemable

^[2]

(2)

Other comprehensive (loss)/income

(230)

Other comprehensive income/(loss), total

(230)

Issuance of shares under employee stock compensation plans

Issuance of shares under employee stock compensation plans (in shares)

556

Share-based compensation and net settlements

Acquisition of non-controlling interests

(7)

(6)

(1)

Acquisition of non-controlling interests, redeemable

^[2]

$ (30)

Foreign currency translation

Equity, ending balance at Dec. 31, 2019

10,369

10,687

1,792

(3)

(2,227)

10,249

120

Equity, ending balance (in shares) at Dec. 31, 2019

128,690

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Net income

1,020

996

Net income, total

1,020

Dividends declared

(354)

Dividends attributable to non-controlling interests

(22)

Other comprehensive (loss)/income

(131)

(132)

Other comprehensive income/(loss), total

(131)

Issuance of shares under employee stock compensation plans

Issuance of shares under employee stock compensation plans (in shares)

275

Share-based compensation and net settlements

Reduction of non-controlling interests

^[3]

(2)

(11)

Other

(3)

Foreign currency translation

(7)

Equity, ending balance at Dec. 31, 2020

$ 10,932

$ 10,748

$ 2,434

$ (3)

$ (2,359)

$ 10,820

$ 112

Equity, ending balance (in shares) at Dec. 31, 2020

128,965

[1]	Accumulated other comprehensive loss, net of tax (‘AOCL’)
[2]	The redeemable non-controlling interest was related to Max Matthiessen Holding AB. The Company purchased the remaining non-controlling interest of Max Matthiessen Holding AB during the year ended December 31, 2019.
[3]	Attributable to the divestiture of businesses that are less than wholly-owned or the acquisition of shares previously owned by minority interest holders.

Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Stockholders Equity [Abstract]
Dividends declared per share	$ 2.75	$ 2.60	$ 2.40

Nature of Operations

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Operations

Note 1 — Nature of Operations

Willis Towers Watson plc is a leading global advisory, broking and solutions company that helps clients around the world turn risk into a path for growth. The Company has more than 46,000 employees and services clients in more than 140 countries.

We design and deliver solutions that manage risk, optimize benefits, cultivate talent, and expand the power of capital to protect and strengthen institutions and individuals.

Our risk management services include strategic risk consulting (including providing actuarial analysis), a variety of due diligence services, the provision of practical on-site risk control services (such as health and safety and property loss control consulting), and analytical and advisory services (such as hazard modeling and reinsurance optimization studies). We also assist our clients with planning for addressing incidents or crises when they occur. These services include contingency planning, security audits and product tampering plans.

We help our clients enhance business performance by delivering consulting services, technology and solutions that optimize benefits and cultivate talent. Our services and solutions encompass such areas as employee benefits, total rewards, talent and benefits outsourcing. In addition, we provide investment advice to help our clients develop disciplined and efficient strategies to meet their investment goals and expand the power of capital.

As an insurance broker, we act as an intermediary between our clients and insurance carriers by advising on their risk management requirements, helping them to determine the best means of managing risk and negotiating and placing insurance with insurance carriers through our global distribution network.

We operate a private Medicare marketplace in the U.S. through which, along with our active employee marketplace, we help our clients move to a more sustainable economic model by capping and controlling the costs associated with healthcare benefits. Additionally, with the acquisition of TRANZACT in July 2019 (see Note 3 – Acquisitions and Divestitures), we also provide direct-to-consumer sales of Medicare coverage.

We are not an insurance company, and therefore we do not underwrite insurable risks for our own account. We believe our broad perspective allows us to see the critical intersections between talent, assets and ideas - the dynamic formula that drives business performance.

Proposed Combination with Aon plc

On March 9, 2020, WTW and Aon plc (‘Aon’) issued an announcement disclosing that the respective boards of directors of WTW and Aon had reached agreement on the terms of a recommended acquisition of WTW by Aon. Under the terms of the agreement each WTW shareholder will receive 1.08 Aon ordinary shares for each WTW ordinary share. At the time of the announcement, it was estimated that upon completion of the combination, existing Aon shareholders will own approximately 63% and existing WTW shareholders will own approximately 37% of the combined company on a fully diluted basis.

The transaction was approved by the shareholders of both WTW and Aon during meetings of the respective shareholders held on August 26, 2020 and remains subject to other customary closing conditions, including required regulatory approvals. The antitrust regulatory review of the transaction remains ongoing. In addition, there are numerous other regulatory approvals and other closing conditions that need to be met. The parties expect the transaction to close in the first half of 2021, subject to satisfaction of these conditions.

Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements

Note 2 — Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements

Basis of Presentation

The accompanying audited consolidated financial statements of Willis Towers Watson and our subsidiaries are presented in accordance with the rules and regulations of the SEC for annual reports on Form 10-K and are prepared in accordance with U.S. GAAP. All intercompany accounts and transactions have been eliminated in consolidation.

Risks and Uncertainties Related to the COVID-19 Pandemic

The COVID-19 pandemic has had an adverse impact on global commercial activity, including the global supply chain, and has contributed to significant volatility in the global financial markets including, among other effects, occasional declines in the equity markets, changes in interest rates and reduced liquidity on a global basis. In light of the effects on our own business operations and those of our clients, suppliers and other third parties with whom we interact, the Company has regularly considered the impact of COVID-19 on our business, taking into account our business resilience and continuity plans, financial modeling and stress testing of liquidity and financial resources.

Generally, the COVID-19 pandemic did not have a material adverse impact on our overall financial results during 2020; however, during 2020, the COVID-19 pandemic negatively impacted our revenue growth, primarily in our businesses that are discretionary in nature. We believe such level of impact will continue through much of 2021, at least until a sufficient portion of the populations in jurisdictions where we do business have been vaccinated and social-distancing orders are lessened or lifted.

As part of the significant estimates and assumptions that are inherent in our financial statements, we have considered the impact COVID-19 will have on our client behavior and the economic environment looking forward to 2021 and throughout the geographies in which we operate. These estimates and assumptions include the collectability of billed and unbilled receivables, the estimation of revenue, and the fair value of our reporting units, tangible and intangible assets and contingent consideration. With regard to collectability of receivables, we believe we may continue to face atypical delays in client payments going forward. The demand for certain discretionary lines of business has decreased, and we believe that decrease may continue to impact our financial results in succeeding periods. Non-discretionary lines of business have also been, to some extent, adversely affected and may be adversely affected in the future. Further, reduced economic activity or disruption in insurance markets could reduce the demand for or the extent of insurance coverage. For example, we have seen instances where the reduced demand for air travel has reduced the extent of insurance coverage needed. Also, the increased frequency and severity of coverage disputes between our clients and (re)insurers arising out of the pandemic could increase our professional liability risk. We will continue to monitor the situation and assess any implications to our business and our stakeholders.

The extent to which COVID-19 impacts our business and financial position will depend on future developments, which are difficult to predict. These future developments may include the severity and scope of the COVID-19 outbreak, which may unexpectedly change or worsen, and the types and duration of measures imposed by governmental authorities to contain the virus or address its impact. We continue to expect that the COVID-19 pandemic will negatively impact our revenue and operating results in fiscal 2021. We believe that these trends and uncertainties are similar to those faced by other comparable registrants as a result of the pandemic.

CARES Act

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security (‘CARES’) Act was enacted in the U.S. to provide relief to companies in the midst of the COVID-19 pandemic and to stimulate the economy. The assistance includes temporary tax relief and government loans, grants and investments for entities in affected industries.

With regard to the income tax provisions of the CARES Act, the Company has reviewed its eligibility requirements, including if and how they apply and how they will affect the Company, particularly provisions that (i) eliminate the taxable income limit for certain net operating losses (‘NOLs’) and allow businesses to carry back NOLs arising in 2018, 2019 and 2020 to the five prior tax years; (ii) generally relaxed the business interest limitation under section 163(j) from 30 percent to 50 percent; and (iii) fix the ‘retail glitch’ for qualified improvement property.

During the three months ended June 30, 2020, the Company elected to use the section 163(j) 50 percent business interest limitation for tax years 2019 and 2020. Utilizing this temporary provision, the Company realized a cash tax benefit in 2020 of approximately $38 million for tax years 2019 and 2020. The Company recognized tax expense of approximately $29 million and $32 million for the 2019 and 2020 tax years, respectively, primarily related to an incremental Base Erosion and Anti-Abuse Tax (‘BEAT’).

Additionally, the CARES Act offers an employee retention credit to encourage employers to maintain headcounts even if employees cannot report to work because of issues related to COVID-19 as well as a temporary provision allowing companies to defer remitting the employer share of some payroll taxes to the government. The payroll tax provisions of the CARES Act were not material for 2020.

Significant Accounting Policies

Principles of Consolidation — The accompanying consolidated financial statements include the accounts of Willis Towers Watson and those of our majority-owned and controlled subsidiaries. Intercompany accounts and transactions have been eliminated.

We determine whether we have a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity (‘VIE’). Variable interest entities are entities that lack one or more of the characteristics of a voting interest entity and therefore require a different approach in determining which party involved with the VIE should consolidate the entity. With a VIE, either the entity does not have sufficient equity at risk to finance its activities without additional subordinated financial support from other parties, or the equity holders, as a group, do not have the power to direct the activities that most significantly impact its financial performance, the obligation to absorb expected losses of the entity, or the right to receive the expected residual returns of the entity. The entity that has a controlling financial interest in a VIE is referred to as the primary beneficiary and is required to consolidate the VIE.

Voting interest entities are entities that have sufficient equity and provide equity investors voting rights that give them the power to make significant decisions related to the entity’s operations. The usual condition for a controlling financial interest in a voting interest entity is ownership of a majority voting interest. Accordingly, we consolidate our voting interest entity investments in which we hold, directly or indirectly, more than 50% of the voting rights.

Use of Estimates — These consolidated financial statements conform to U.S. GAAP, which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as well as disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Our estimates, judgments and assumptions are continually evaluated based on available information and experience. Because of the use of estimates inherent in the financial reporting process, actual results could differ from those estimates. Estimates are used when accounting for revenue recognition and related costs, the selection of useful lives of fixed and intangible assets, impairment testing, valuation of billed and unbilled receivables from clients, discretionary compensation, income taxes, pension assumptions, incurred but not reported claims, legal reserves and goodwill and intangible assets.

Going Concern — Management evaluates at each annual and interim period whether there are conditions or events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date that the consolidated financial statements are issued. Management’s evaluation is based on relevant conditions and events that are known and reasonably knowable at the date that the consolidated financial statements are issued. Management has concluded that there are no conditions or events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date of these financial statements.

Fair Value of Financial Instruments — The carrying values of our cash, cash equivalents and restricted cash, accounts receivable, accrued expenses, revolving lines of credit and term loans approximate their fair values because of the short maturity and liquidity of those instruments. We consider the difference between carrying value and fair value to be immaterial for our senior notes. The fair value of our senior notes and note receivable are considered Level 2 financial instruments as they are corroborated by observable market data. See Note 11 — Fair Value Measurements for additional information about our measurements of fair value.

Investments in Associates — Investments are accounted for using the equity method of accounting, included within other non-current assets in the consolidated balance sheets, if the Company has the ability to exercise significant influence, but not control, over the investee. Significant influence is generally deemed to exist if the Company has an equity ownership in the voting stock of the investee between 20 and 50 percent, although other factors, such as representation on the board of directors, the existence of substantive participation rights, and the impact of commercial arrangements, are considered in determining whether the equity method of accounting is appropriate. Under the equity method of accounting, the investment is carried at the cost of acquisition, plus the Company’s equity in undistributed net income since acquisition, less any dividends received since acquisition.

The Company periodically reviews its investments in associates for which fair value is less than cost to determine if the decline in value is other than temporary. If the decline in value is judged to be other than temporary, the cost basis of the investment is written down to fair value. The amount of any write-down is included in the consolidated statements of comprehensive income.

Cash and Cash Equivalents — Cash and cash equivalents primarily consist of time deposits with original maturities of 90 days or less. In certain of the countries in which we conduct business, we are subject to capital adequacy requirements. Most significantly, Willis Limited, our U.K. brokerage subsidiary regulated by the Financial Conduct Authority, is currently required to maintain $140 million in unencumbered and available financial resources, of which at least $51 million must be in cash, for regulatory purposes. Term deposits and certificates of deposits with original maturities greater than 90 days are considered to be short-term investments. As a result of the acquired TRANZACT collateralized facility (see Note 10 — Debt), we had $7 million and $8 million of restricted cash at December 31, 2020 and 2019, respectively, which is included within prepaid and other current assets on our consolidated balance sheet.

Fiduciary Assets and Liabilities — The Company collects premiums from insureds and, after deducting commissions, remits the premiums to the respective insurers. The Company also collects claims or refunds from insurers on behalf of insureds. Certain of our health and welfare benefits administration outsourcing agreements require us to hold funds on behalf of clients to pay obligations on

their behalf. Each of these transactions is reported on our consolidated balance sheet as assets and corresponding liabilities unless such balances are due to or from the same party and a right of offset exists, in which case the balances are recorded net.

Fiduciary assets on the consolidated balance sheets are comprised of both fiduciary funds and fiduciary receivables:

Fiduciary Funds – Unremitted insurance premiums and claims are recorded within fiduciary assets on the consolidated balance sheets. Fiduciary funds are generally required to be kept in certain regulated bank accounts subject to guidelines which emphasize capital preservation and liquidity. Such funds are not available to service the Company’s debt or for other corporate purposes. Notwithstanding the legal relationships with insureds and insurers, the Company is entitled to retain investment income earned on fiduciary funds in accordance with industry custom and practice and, in some cases, as supported by agreements with insureds. The period for which the Company holds such funds is dependent upon the date the insured remits the payment of the premium to the Company, or the date the Company receives refunds from the insurers, and the date the Company is required to forward such payments to the insurer or insured, respectively.

Fiduciary receivables – Uncollected premiums from insureds and uncollected claims or refunds from insurers are recorded as fiduciary assets on the consolidated balance sheets. In certain instances, the Company advances premiums, refunds or claims to insurance underwriters or insureds prior to collection. Such advances are made from fiduciary funds and are reflected in the consolidated balance sheets as fiduciary assets.

Fiduciary liabilities on the consolidated balance sheets represent the obligations to remit all fiduciary funds and fiduciary receivables to insurers or insureds.

Accounts Receivable — Accounts receivable includes both billed and unbilled receivables and is stated at estimated net realizable values. Provision for billed receivables is recorded, when necessary, in an amount considered by management to be sufficient to meet probable future losses related to uncollectible accounts. Accrued and unbilled receivables are stated at net realizable value which includes an allowance for accrued and unbillable amounts. See Note 4 — Revenue for additional information about our accounts receivable.

Acquired Accounts Receivable — As part of the acquisition accounting for the TRANZACT business (see Note 3 – Acquisitions and Divestitures), the acquired accounts receivable arising from direct-to-consumer Medicare broking sales were present-valued at the acquisition date in accordance with ASC 805, Business Combinations (‘ASC 805’). Cash collections for these receivables are expected to occur over a period of several years. Due to the provisions of ASC 606, Revenue From Contracts With Customers (‘ASC 606’), these receivables are not discounted for a significant financing component when initially recognized. The acquired renewal commissions receivables will be accounted for prospectively using the cost-recovery method in which future cash receipts will initially be applied against the acquisition date fair value until the value reaches zero. Any cash received in excess of the fair value determined at acquisition will be recorded to earnings when it is received at a future date. The adjusted values of these acquired renewal commissions receivables will be included in prepaid and other current assets or other non-current assets, as appropriate, on the consolidated balance sheets.

Income Taxes — The Company recognizes deferred tax assets and liabilities for the estimated future tax consequences of events attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating and capital loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which the differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of changes in tax rates is recognized in the consolidated statement of comprehensive income in the period in which the change is enacted. Deferred tax assets are reduced through the establishment of a valuation allowance at such time as, based on available evidence, it is more likely than not that the deferred tax assets will not be realized. The Company adjusts valuation allowances to measure deferred tax assets at the amounts considered realizable in future periods when the Company’s facts and assumptions change. In making such determinations, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies and recent financial operating results. We place more reliance on evidence that is objectively verifiable.

Positions taken in the Company’s tax returns may be subject to challenge by the taxing authorities upon examination. The Company recognizes the benefits of uncertain tax positions in the financial statements when it is more likely than not that a position will be sustained on the basis of the technical merits of the position assuming the tax authorities have full knowledge of the position and all relevant facts. Recognition also occurs upon either the lapse of the relevant statute of limitations or when positions are effectively settled. The benefit recognized is the largest amount of tax benefit that is greater than 50 percent likely to be realized on settlement with the tax authority. The Company adjusts its recognition of uncertain tax benefits in the period in which new information is available impacting either the recognition or measurement of its uncertain tax positions. Such adjustments are reflected as increases or decreases to income taxes in the period in which they are determined.

The Company recognizes interest and penalties relating to unrecognized tax benefits within income taxes. See Note 6 — Income Taxes for additional information regarding the Company’s income taxes.

Foreign Currency — Transactions in currencies other than the functional currency of the entity are recorded at the rates of exchange prevailing at the date of the transaction. Monetary assets and liabilities in currencies other than the functional currency are translated at the rates of exchange prevailing at the balance sheet date and the related transaction gains and losses are reported as income or expense in the consolidated statements of comprehensive income. Certain intercompany loans are determined to be of a long-term investment nature. The Company records transaction gains and losses from re-measuring such loans as other comprehensive income in the consolidated statements of comprehensive income.

Upon consolidation, the results of operations of subsidiaries and associates whose functional currency is other than the U.S. dollar are translated into U.S. dollars at the average exchange rates, and assets and liabilities are translated at year-end exchange rates. Translation adjustments are presented as a separate component of other comprehensive income in the financial statements and are included in net income only upon sale or liquidation of the underlying foreign subsidiary or associated company.

Derivatives — The Company uses derivative financial instruments to alter the risk profile of an existing underlying exposure. Forward foreign currency exchange contracts are used to manage currency exposures arising from future income and expenses and to offset balance sheet exposures in currencies other than the functional currency of an entity. We do not hold any derivatives for trading purposes. The fair values of derivative contracts are recorded in other assets and other liabilities in the consolidated balance sheets. The effective portions of changes in the fair value of derivatives that qualify for hedge accounting as cash flow hedges are recorded in other comprehensive income. Amounts are reclassified from other comprehensive income into earnings when the hedged exposure affects earnings. If the derivative is designated and qualifies as an effective fair value hedge, the changes in the fair value of the derivative and of the hedged item associated with the hedged risk are both recognized in earnings. The amount of hedge ineffectiveness recognized in earnings is based on the extent to which an offset between the fair value of the derivative and hedged item is not achieved. Changes in the fair value of derivatives that do not qualify for hedge accounting, together with any hedge ineffectiveness on those that do qualify, are recorded in other income, net or interest expense as appropriate.

The Company evaluates whether its contracts include clauses or conditions which would be required to be separately accounted for at fair value as embedded derivatives. See Note 9 — Derivative Financial Instruments for additional information about the Company’s derivatives.

Commitments, Contingencies and Provisions for Liabilities — The Company establishes provisions against various actual and potential claims, lawsuits and other proceedings relating principally to alleged errors and omissions in the ordinary course of business. Such provisions cover claims that have been reported but not paid and also unasserted claims and related legal fees. These provisions are established based on actuarial estimates together with individual case reviews and are believed to be adequate in light of current information and legal advice. In certain cases, where a range of loss exists, we accrue the minimum amount in the range if no amount within the range is a better estimate than any other amount. To the extent such losses can be recovered under the Company’s insurance programs, estimated recoveries are recorded when losses for insured events are recognized and the recoveries are likely to be realized. Significant management judgment is required to estimate the amounts of such unasserted claims and the related insurance recoveries. The Company analyzes its litigation exposure based on available information, including consultation with outside counsel handling the defense of these matters, to assess its potential liability. These contingent liabilities are not discounted. See Note 14 — Commitments and Contingencies and Note 15 — Supplementary Information for Certain Balance Sheet Accounts for additional information about our commitments, contingencies and provisions for liabilities.

Share-Based Compensation — The Company has equity-based compensation plans that provide for grants of restricted stock units and stock options to employees and non-employee directors of the Company. Additionally, the Company has cash-settled share-based compensation plans that provide for grants to employees.

The Company expenses equity-based compensation, which is included in Salaries and benefits in the consolidated statements of comprehensive income, primarily on a straight-line basis over the requisite service period. The significant assumptions underlying our expense calculations include the fair value of the award on the date of grant, the estimated achievement of any performance targets and estimated forfeiture rates. The awards under equity-based compensation are classified as equity and are included as a component of equity on the Company’s consolidated balance sheets, as the ultimate payment of such awards will not be achieved through use of the Company’s cash or other assets.

For the cash-settled share-based compensation, the Company recognizes a liability for the fair-value of the awards as of each reporting date. The liability for these awards is included within other current liabilities or other non-current liabilities in the consolidated balance sheets depending when the amounts are payable. Expense is recognized over the service period, and as the liability is remeasured at the end of each reporting period, changes in fair value are recognized as compensation cost within Salaries and benefits

in the consolidated statements of comprehensive income. The significant assumptions underlying our expense calculations include the estimated achievement of any performance targets and estimated forfeiture rates.

See Note 18 — Share-based Compensation for additional information about the Company’s share-based compensation.

Fixed Assets — Fixed assets are stated at cost less accumulated depreciation. Expenditures for improvements are capitalized; repairs and maintenance are charged to expense as incurred. Depreciation is computed primarily using the straight-line method based on the estimated useful lives of assets.

Depreciation on internally-developed software is amortized over the estimated useful life of the asset ranging from 3 to 10 years. Buildings include assets held under finance leases and are depreciated over the lesser of 50 years, the asset lives or the lease terms. Depreciation on leasehold improvements is calculated over the lesser of the useful lives of the assets or the remaining lease terms. Depreciation on furniture and equipment is calculated based on a range of 3 to 10 years. Land is not depreciated.

Long-lived assets are tested for recoverability whenever events or changes in circumstance indicate that their carrying amounts may not be recoverable. An impairment loss is recognized if the carrying amount of a long-lived asset is not recoverable and exceeds its fair value. Recoverability is determined based on the undiscounted cash flows expected to result from the use and eventual disposition of the asset or asset group. Long-lived assets and certain identifiable intangible assets to be disposed of are reported at the lower of carrying amount or fair value less cost to sell. See Note 7 — Fixed Assets for additional information about our fixed assets.

Leases (effective from January 1, 2019) — The following policies were effective beginning with the 2019 fiscal year as a result of the adoption, on January 1, 2019, of ASC 842, Leases (‘ASC 842’). The lease policies in effect prior to 2019 are reflected in the next section.

As an advisory, broking and solutions company providing services to clients in more than 140 countries, we enter into lease agreements from time to time, primarily for the use of real estate for our office space. We determine if an arrangement is a lease at the inception of the contract, and the nature of our operations is such that it is generally clear whether an arrangement contains a lease and what underlying asset is being leased. The majority of the leases into which we enter are operating leases. Upon entering into leases, we obtain the right to control the use of an identified space for a lease term and recognize these right-of-use (‘ROU’) assets on our consolidated balance sheets with corresponding lease liabilities reflecting our obligation to make the related lease payments. ROU assets are amortized over the term of the lease.

Our real estate leases are generally long-term in nature, with terms that typically range from 5 to 15 years. Our most significant lease supports our London market operations with a lease term through 2032. Our real estate leases often contain options to renew the lease, either through exercise of the option or through automatic renewal. Additionally, certain leases have options to cancel the lease with appropriate notice to the landlord prior to the end of the stated lease term. As we enter into new leases after the adoption of ASC 842, we consider these options as we assess lease terms in our recognized ROU assets and lease liabilities. If we are reasonably certain to exercise an option to renew a lease, we include this period in our lease term. To the extent that we have the option to cancel a lease, we recognize our ROU assets and lease liabilities using the term that would result from using this earlier date. If a significant penalty is required to cancel the lease at an earlier date, we assess our lease term as ending at the point when no significant penalty would be due.

In addition to payments for previously-agreed base rent, many of our lease agreements are subject to variable and unknown future payments, typically in the form of common area maintenance charges (a non-lease component as defined by ASC 842) or real estate taxes. These variable payments are excluded from our lease liabilities and ROU assets, and instead are recognized as lease expense within other operating expenses on the consolidated statement of comprehensive income as the amounts are incurred. To the extent that we have agreed to fixed charges for common area maintenance or other non-lease components, or our base rent increases by an index or rate (most commonly an inflation rate), these amounts are included in the measurement of our lease liabilities and ROU assets. We have elected the practical expedient under ASC 842 which allows the lease and non-lease components to be combined in our measurement of lease liabilities and ROU assets.

From time to time we may enter into subleases if we are unable to cancel or fully occupy a space and are able to find an appropriate subtenant. However, entering subleases is not a primary objective of our business operations and these arrangements represent an immaterial amount of cash flows.

We are required to use judgment in the determination of the incremental borrowing rates to calculate the present values of our future lease payments. Since the majority of our debt is publicly traded, our real estate function is centralized, and our treasury function is centralized and generally prohibits our subsidiaries from borrowing externally, we have determined it appropriate to use the Company’s consolidated unsecured borrowing rate, and we adjust for collateralization in accordance with ASC 842. Using the resulting interest rate curves from publicly traded debt at this collateralized borrowing rate, we select the interest rate at lease

inception by reference to the lease term and lease currency. Over 90% of our leases are denominated in U.S. dollars, Pounds sterling or Euros.

Our leases generally do not subject us to restrictive covenants and contain no residual value guarantees.

See Note 13 — Leases for additional information about our operating leases.

Operating Leases (effective before January 1, 2019) — Rentals payable on operating leases were charged on a straight-line basis to other operating expenses in the consolidated statements of comprehensive income over the lease terms prior to the implementation of ASC 842.

Goodwill and Other Intangible Assets — In applying the acquisition method of accounting for business combinations, amounts assigned to identifiable assets and liabilities acquired were based on estimated fair values as of the date of acquisition, with the remainder recorded as goodwill. Intangible assets are initially valued at fair value using generally accepted valuation methods appropriate for the type of intangible asset. Intangible assets with definite lives are amortized over their estimated useful lives and are reviewed for impairment if indicators of impairment arise. Intangible assets with indefinite lives are tested for impairment annually as of October 1, and whenever indicators of impairment exist. The fair values of intangible assets are compared with their carrying values, and an impairment loss would be recognized for the amount by which a carrying amount exceeds its fair value.

Acquired intangible assets are amortized over the following periods:



	Amortization basis	Expected life (years)
Client relationships	In line with underlying cash flows	5 to 20
Software	In line with underlying cash flows or straight-line basis	4 to 7
Trademark and trade name	Straight-line basis	14 to 25
Other	In line with underlying cash flows or straight-line basis	3 to 20

Prior to the adoption of ASC 842, favorable and unfavorable acquired lease agreement intangible assets and liabilities were amortized straight-line over the remaining terms of the leases. These amounts have been subsumed into the ROU assets upon adoption of ASC 842.

Goodwill is tested for impairment annually as of October 1, and whenever indicators of impairment exist. Goodwill is tested at the reporting unit level, and the Company had eight reporting units as of October 1, 2020. In the impairment test, the fair value of each reporting unit is compared with its carrying value, including goodwill. If the carrying value of a reporting unit exceeds its fair value, the difference is recognized as an impairment loss. The Company’s goodwill impairment tests for the years ended December 31, 2020 and 2019 have not resulted in any impairment charges. See Note 8 — Goodwill and Other Intangible Assets for additional information about our goodwill and other intangible assets.

Pensions — The Company has multiple defined benefit pension and defined contribution plans. The net periodic cost of the Company’s defined benefit plans is measured on an actuarial basis using various methods and actuarial assumptions. The most significant assumptions are the discount rates (calculated using the granular approach to calculating service and interest cost) and the expected long-term rates of return on plan assets. Other material assumptions include rates of participant mortality, the expected long-term rates of compensation and pension increases and rates of employee termination. Gains and losses occur when actual experience differs from actuarial assumptions. If such gains or losses exceed ten percent of the greater of the market-related value of plan assets or the projected benefit obligation, the Company amortizes those gains or losses over the average remaining service period or average remaining life expectancy, as appropriate, of the plan participants. In accordance with U.S. GAAP, the Company records the funded status of its pension plans based on the projected benefit obligation on its consolidated balance sheets.

Contributions to the Company’s defined contribution plans are recognized as incurred. Differences between contributions payable in the year and contributions actually paid are shown as either other assets or other liabilities in the consolidated balance sheets. See Note 12 — Retirement Benefits for additional information about our pensions.

Revenue Recognition — We recognize revenue from a variety of services, with broking, consulting and outsourced administration representing our most significant offerings. All other revenue streams, which can be recognized at either a point in time or over time, are individually less significant and are grouped in Other in our revenue disaggregation disclosures in Note 4 — Revenue. These Other revenue streams represent approximately 5% of customer contract revenue for the years ended December 31, 2020, 2019 and 2018.

Broking — Representing approximately 52%, 50% and 48% of customer contract revenue for the years ended December 31, 2020, 2019 and 2018, respectively, in our broking arrangements, we earn revenue by acting as an intermediary in the placement of effective

insurance policies. Generally, we act as an agent and view our client to be the party looking to obtain insurance coverage for various risks, or an employer or sponsoring organization looking to obtain insurance coverage for its employees or members. Also, we act as an agent in reinsurance broking arrangements where our client is the party looking to cede risks to the reinsurance markets. Our primary performance obligation under the majority of these arrangements is to place an effective insurance or reinsurance policy, but there can also be significant post-placement obligations in certain contracts to which we need to allocate revenue. The most common of these is for claims handling or call center support. The revenue recognition method for these, after the relative fair value allocation, is described further as part of the ‘Outsourced Administration’ description below.

Due to the nature of the majority of our broking arrangements, no single document constitutes the contract for ASC 606 purposes. Our services may be governed by a mixture of different types of contractual arrangements depending on the jurisdiction or type of coverage, including terms of business agreements, broker-of-record letters, statements of work or local custom and practice. This is then confirmed by the client’s acceptance of the underlying insurance contract. Prior to the policy inception date, the client has not accepted nor formally committed to perform under the arrangement (i.e. pay for the insurance coverage in place). Therefore in the majority of broking arrangements, the contract date is the date the insurance policy incepts. However, in certain instances such as employer-sponsored Medicare broking or Affinity arrangements, where the employer or sponsoring organization is our customer, client acceptance of underlying individual policy placements is not required, and therefore the date at which we have a contract with a customer is not dependent upon placement.

As noted, our primary performance obligations typically consist of only the placement of an effective insurance policy which precedes the inception date of the policy. Therefore, most of our fulfillment costs are incurred before we can recognize revenue, and are thus deferred during the pre-placement process. Where we have material post-placement services obligations, we estimate the relative fair value of the post-placement services using either the expected cost-plus-margin or the market assessment approach.

Revenue from our broking services consists of commissions or fees negotiated in lieu of commissions. At times, we may receive additional income for performing these services from the insurance and reinsurance carriers’ markets, which is collectively referred to as ‘market derived income’. In situations in which our fees are not fixed but are variable, we must estimate the likely commission per policy, taking into account the likelihood of cancellation before the end of the policy term. For employer-sponsored Medicare broking, Affinity arrangements and proportional treaty reinsurance broking, the commissions to which we will be entitled can vary based on the underlying individual insurance policies that are placed. For employer-sponsored Medicare broking and proportional treaty reinsurance broking in particular, we base the estimates of transaction prices on supportable evidence from an analysis of past transactions, and only include amounts that are probable of being received or not refunded (referred to as applying ‘constraint’ under ASC 606). This is an area requiring significant judgment and results in us estimating a transaction price that may be significantly lower than the ultimate amount of commissions we may collect. The transaction price is then adjusted over time as we receive confirmation of our remuneration through receipt of treaty statements, or as other information becomes available.

We recognize revenue for most broking arrangements as of a point in time at the later of the policy inception date or when the policy placement is complete, because this is viewed as the date when control is transferred to the client. For employer-sponsored Medicare broking, we recognize revenue over time, as we stand ready under our agreements to place retiree Medicare coverage. For this type of broking arrangement, we recognize the majority of our placement revenue in the fourth quarter of the calendar year when most of the placement or renewal activity occurs.

Beginning on July 30, 2019 with the acquisition of TRANZACT (see Note 3 — Acquisitions and Divestitures), we have a direct-to-consumer Medicare broking offering. The contractual arrangements in this offering differ from our previously existing employer-sponsored Medicare broking offering described above. The governing contracts in our direct-to-consumer Medicare broking offering are the contractual arrangements with insurance carriers, for whom we act as an agent, that provide compensation in return for issued policies. Once an application is submitted to a carrier, our obligation is complete, and we have no ongoing fulfilment obligations. We receive compensation from carriers in the form of commissions, administrative fees and marketing fees in the first year, and depending on the type of policy issued, we may receive renewal commissions for up to 25 years, provided the policies are renewed for such periods of time.

Because our obligation is complete upon application submission to the carrier, we recognize revenue at that date, which includes both compensation due to us in the first year as well as an estimate of the total renewal commissions that will be received over the lifetime of the policy. This variable consideration estimate requires significant judgment, and will vary based on product type, estimated commission rates, the expected lives of the respective policies and other factors. The Company has applied an actuarial model to account for these uncertainties, which is updated periodically based on actual experience, and includes an element of ‘constraint’ as defined by ASC 606 such that no significant reversal is expected to occur in the future. Actual results will differ from these estimates.

The timing of renewal payments in our direct-to-consumer Medicare broking offering is reflective of regulatory restrictions and insurance carriers’ protection for cancellations and varies based on policy holder decisions that are outside of the control of both the

Company and the insurance carriers. As such, the estimate of these renewal commissions receivables has not been discounted to reflect a significant financing component.

Consulting — We earn revenue for advisory and consulting work that may be structured as different types of service offerings, including annual recurring projects, projects of a short duration or stand-ready obligations. Collectively, our consulting arrangements represent approximately 30%, 32% and 34% of customer contract revenue for the years ended December 31, 2020, 2019 and 2018, respectively.

We have engagement letters with our clients that specify the terms and conditions upon which the engagements are based. These terms and conditions can only be changed upon agreement by both parties.

In assessing our performance obligations, our consulting work is typically highly integrated, with the various promised services representing inputs of the combined overall output. We view these arrangements as representing a single performance obligation. To the extent we do not integrate our services, as is the case with unrelated services that may be sourced from different areas of our business, we consider these separate performance obligations.

Fee terms can be in the form of fixed-fees (including fixed-fees offset by commissions), time-and-expense fees, commissions, per-participant fees, or fees based on assets under management. Payment is typically due on a monthly basis as we perform under the contract, and we are entitled to be reimbursed for work performed to date in the event of termination.

The majority of our revenue from these consulting engagements is recognized over time, either because our clients are simultaneously receiving and consuming the benefits of our services, or because we have an enforceable right to payment for performance rendered to date. Additionally, from time to time, we may be entitled to an additional fee based on achieving certain performance criteria. To the extent that we cannot estimate with reasonable assurance the likelihood that we will achieve the performance target, we will ‘constrain’ this portion of the transaction price and recognize it when or as the uncertainty is resolved.

We use different progress measures to determine our revenue depending on the nature of the engagement:

•

Annual recurring projects and projects of short duration. These projects are typically straightforward and highly predictable in nature with either time-and-expense or fixed fee terms. Time-and-expense fees are recognized as hours or expenses are incurred using the ‘right to invoice’ practical expedient allowed under ASC 606. For fixed-fee arrangements, to the extent estimates can be made of the remaining work required under the arrangement, revenue is based upon the proportional performance method, using the value of labor hours spent to date compared to the estimated total value of labor hours for the entire engagement. We believe that cost represents a faithful depiction of the transfer of value because the completion of these performance obligations is based upon the professional services of employees of differing experience levels and thereby costs. It is appropriate that satisfaction of these performance obligations considers both the number of hours incurred by each employee and the value of each labor hour worked (as opposed to simply the hours worked).

•

Stand-ready obligations. These projects consist of repetitive monthly or quarterly services performed consistently each period. As none of the activities provided under these services are performed at specified times and quantities, but at the discretion of each customer, our obligation is to stand ready to perform these services on an as-needed basis. These arrangements represent a ‘series’ performance obligation in accordance with ASC 606. Each time increment (i.e., each month or quarter) of standing ready to provide the overall services is distinct and the customer obtains value from each period of service independent of the other periods of service.

Where we recognize revenue on a proportional performance basis, the amount we recognize is affected by a number of factors that can change the estimated amount of work required to complete the project such as the staffing on the engagement and/or the level of client participation. Our periodic engagement evaluations require us to make judgments and estimates regarding the overall profitability and stage of project completion that, in turn, affect how we recognize revenue. We recognize a loss on an engagement when estimated revenue to be received for that engagement is less than the total estimated costs associated with the engagement. Losses are recognized in the period in which the loss becomes probable and the amount of the loss is reasonably estimable.

Outsourced Administration — We provide customized benefits outsourcing and co-sourcing solutions services in relation to the administration of defined benefit, defined contribution, and health and welfare plans. These plans are sponsored by our clients to provide benefits to their active or retired employees. Additionally, these services include operating call centers and may include providing access to, and managing, a variety of consumer-directed savings accounts. The operation of call centers and consumer-directed accounts can be provisioned as part of an ongoing administration or solutions service, or separately as part of a broking arrangement. The products and services available to all clients are the same, but the selections by a client can vary and portray customized products and services based on the customer’s specific needs. Our services often include the use of proprietary systems

that are configured for each of our clients’ needs. In total, our outsourced administration services represent approximately 12% of customer contract revenue for the years ended December 31, 2020, 2019 and 2018.

These contracts typically consist of an implementation phase and an ongoing administration phase:

•

Implementation phase. Work performed during the implementation phase is considered a set-up activity because it does not transfer a service to the customer, and therefore costs are deferred during this phase of the arrangement. Since these arrangements are longer term in nature and subject to more changes in scope as the project progresses, our contracts generally provide that if the client terminates a contract, we are entitled to an additional payment for services performed through the termination date designed to recover our up-front costs of implementation.

•

Ongoing administration phase. The ongoing administration phase includes a variety of plan administration services, system hosting and support services. More specifically, these services include data management, calculations, reporting, fulfillment/communications, compliance services, call center support, and in our health and welfare arrangements, annual onboarding and enrollment support. While there are a variety of activities performed, the overall nature of the obligation is to provide an integrated outsourcing solution to the customer. The arrangement represents a stand-ready obligation to perform these activities on an as-needed basis. The customer obtains value from each period of service, and each time increment (i.e., each month, or each benefits cycle in our health and welfare arrangements) is distinct and substantially the same. Accordingly, the ongoing administration services represent a ‘series’ in accordance with ASC 606 and are deemed one performance obligation.

We have engagement letters with our clients that specify the terms and conditions upon which the engagements are based. These terms and conditions can only be changed upon agreement by both parties. Fees for these arrangements can be fixed, per-participant-per-month, or in the case of call center services, provided in conjunction with our broking services, with an allocation based on commissions. Our fees are not typically payable until the commencement of the ongoing administration phase. However, in our health and welfare arrangements, we begin transferring services to our customers approximately four months prior to payments being due as part of our annual onboarding and enrollment work. Although our per-participant-per-month and commission-based fees are considered variable, they are typically predictable in nature, and therefore we generally do not ‘constrain’ any portion of our transaction price estimates. Once fees become payable, payment is typically due on a monthly basis as we perform under the contract, and we are entitled to be reimbursed for work performed to date in the event of termination.

Revenue is recognized over time as the services are performed because our clients are simultaneously receiving and consuming the benefits of our services. For our health and welfare arrangements where each benefits cycle represents a time increment under the series guidance, revenue is recognized based on proportional performance. We use an input measure (value of labor hours worked) as the measure of progress. Given that the service is stand-ready in nature, it can be difficult to predict the remaining obligation under the benefits cycle. Therefore, the input measure is based on the historical effort expended each month, which is measured as labor cost. This results in slightly more revenue being recognized during periods of annual onboarding since we are performing both our normal monthly services and our annual services during this portion of the benefits cycle.

For all other outsourced administration arrangements where a month represents our time increment under the series guidance, we allocate transaction price to the month we are performing our services. Therefore, the amount recognized each month is the variable consideration related to that month plus the fixed monthly or annual fee. The fixed monthly or annual fee is recognized on a straight-line basis. Revenue recognition for these types of arrangements is therefore more consistent throughout the year.

Reimbursed expenses — Client reimbursable expenses, including those relating to travel, other out-of-pocket expenses and any third-party costs, are included in revenue, and an equivalent amount of reimbursable expenses is included in other operating expenses as a cost of revenue as incurred. Reimbursed expenses represented approximately 1% of customer contract revenue for the years ended December 31, 2020, 2019 and 2018. Taxes collected from customers and remitted to government authorities are recorded net and are excluded from revenue.

Interest income — Interest income is recognized as earned.

Other income — Other income includes gains on disposal of intangible assets, which primarily arise from settlements through enforcing non-compete agreements in the event of losing accounts through producer defection or the disposal of books of business.

Cost to obtain or fulfill contracts — Costs to obtain customers include commissions for brokers under specific agreements that would not be incurred without a contract being signed and executed. The Company has elected to apply the ASC 606 ‘practical expedient’ which allows us to expense these costs as incurred if the amortization period related to the resulting asset would be one year or less. The Company has no significant instances of contracts that would be amortized for a period greater than a year, and therefore has no contract costs capitalized for these arrangements.

Costs to fulfill include costs incurred by the Company that are expected to be recovered within the expected contract period. The costs associated with our system implementation activities and consulting contracts are recorded through time entry.

For our broking business, the Company must estimate the fulfillment costs incurred during the pre-placement of the broking contracts. These judgments include:

•

which activities in the pre-placement process should be eligible for capitalization;

•

the amount of time and effort expended on those pre-placement activities;

•

the amount of payroll and related costs eligible for capitalization; and,

•

the monthly or quarterly timing of underlying insurance and reinsurance policy inception dates.

We amortize costs to fulfill over the period we receive the related benefits. For broking pre-placement costs, this is typically less than a year. In our system implementation and consulting arrangements, we include the likelihood of contract renewals in our estimate of the amortization period, resulting in most costs being amortized for a greater length of time than the initial contract term.

Recent Accounting Pronouncements

Not adopted for 2020

In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, which clarifies and amends existing guidance, including removing certain exceptions to the general principles of accounting for income taxes. This ASU becomes effective for the Company on January 1, 2021. Some of the changes must be applied on a retrospective or modified retrospective basis while others must be applied on a prospective basis. Early adoption is permitted. The Company does not plan to adopt this ASU early and does not expect it to have a material impact on our consolidated financial statements.

Adopted for 2020

In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments, which amended the guidance on the impairment of financial instruments. The ASU added an impairment model (known as the current expected credit loss (‘CECL’) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance its estimate of lifetime expected credit losses on assets measured at amortized cost, which is intended to result in more timely recognition of such losses. The ASU was also intended to reduce the complexity of U.S. GAAP by decreasing the number of credit impairment models that entities use to account for debt instruments. Further, the ASU made targeted changes to the impairment model for available-for-sale debt securities. Additional ASUs were subsequently issued which provided amended and additional guidance for the implementation of ASU No. 2016-13. All related guidance has been codified into, and is now known as, ASC 326, Financial Instruments—Credit Losses (‘ASC 326’). ASC 326 became effective for the Company on January 1, 2020, at which time we adopted it. This ASU did not have a material impact on our consolidated financial statements.

In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. In computing the implied fair value of goodwill under Step 2, previous U.S. GAAP required the performance of procedures to determine the fair value at the impairment testing date of assets and liabilities (including unrecognized assets and liabilities) following the procedure that is required in determining the fair value of assets acquired and liabilities assumed in a business combination. Instead, the amendments under this ASU require the goodwill impairment test to be performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge would be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The ASU became effective for the Company on January 1, 2020, at which time we adopted it. The amendments in this ASU are applied on a prospective basis. There was no immediate impact to our consolidated financial statements upon adopting this ASU, and the most recent goodwill impairment test resulted in fair values in excess of carrying values for all reporting units at October 1, 2020.

In August 2018, the FASB issued ASU 2018-13, Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement as part of its disclosure framework project. The focus of this project is to improve the effectiveness of disclosures in the notes to the financial statements by facilitating clear communication of the information required by U.S. GAAP that is most important to users of an entity’s financial statements. This ASU removes certain disclosure requirements and adds or modifies other requirements. This ASU was effective for the Company on January 1, 2020, at which time we adopted it. Certain provisions of the ASU were required to be adopted retrospectively, while others were required to be adopted prospectively. This ASU did not have a material impact on the notes to our consolidated financial statements.

In March 2020, the SEC issued a final rule that amends the disclosure requirements related to certain registered securities under SEC Regulation S-X, Rules 3-10 and 3-16 which currently require separate financial statements for subsidiary issuers and guarantors of registered debt securities unless certain exceptions are met, and affiliates that collateralize registered securities offerings if the affiliates’ securities are a substantial portion of the collateral. The final rule is generally effective for filings on or after January 4, 2021, however early application is permitted. The most pertinent portions of the final rule that are currently applicable to the Company include: (i) replacing the previous requirement under Rule 3-10 to provide condensed consolidating financial information in the registrant’s financial statements with a requirement to provide alternative financial disclosures (which include summarized financial information of the parent and any issuers and guarantors, as well as other qualitative disclosures) in either the registrant’s Management’s Discussion & Analysis section or its financial statements; and, (ii) reducing the periods for which summarized financial information is required to the most recent annual period and year-to-date interim period. The Company elected to early-adopt the provisions of the final rule during the three months ended March 31, 2020. Further, the new reduced quantitative disclosures and accompanying qualitative disclosures as required by this final rule are included within Item 7 Management’s Discussion and Analysis of Financial Condition and Results of Operations on this Form 10-K.

In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides optional expedients and exceptions for accounting for contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. This ASU became effective for the Company on March 12, 2020. The Company may apply the changes relating to contracts from January 1, 2020 or from a later date. The Company has made no contract modifications thus far to transition to a different reference rate, however, it will consider this guidance as future modifications are made.

In August 2020, the SEC issued amendments to its disclosure rules to modernize the requirements in Regulation S-K, Item 101 ‘Business’, Item 103 ‘Legal Proceedings’, and Item 105 ‘Risk Factors’. These amendments are intended to improve the readability of disclosures, reduce repetition, and eliminate immaterial information, thereby simplifying compliance for registrants and making disclosures more meaningful for investors. The amendments to the disclosure requirements related to a registrant’s description of its business and risk factors are intended to expand the use of a principles-based approach that gives registrants more flexibility to tailor disclosures. The amendments to the disclosure requirements related to legal proceedings continue to reflect the current, more prescriptive approach because those requirements depend less on a registrant’s specific characteristics. Further, additional human capital disclosures are required as part of the amendments to the description of the business. The final rule became effective on November 9, 2020, and the Company has incorporated these changes as part of this Form 10-K.

In November 2020, the SEC issued amendments to its disclosure rules to modernize the requirements in Regulation S-K, Item 301 ‘Selected Financial Data’, Item 302 ‘Supplementary Financial Information’ and Item 303 ‘Management’s Discussion and Analysis of Financial Condition and Results of Operations’. Like the previous modernization amendments to Regulation S-K, the amendments are intended to eliminate duplicative disclosures and enhance management’s discussion and analysis for the benefit of investors, while simplifying compliance efforts for registrants. Certain amendments codified interpretive guidance released by the SEC historically, and as such, these amendments were already reflected in the Company’s Form 10-K. The most impactful of these amendments to the disclosure requirements include the following: registrants are no longer required to provide selected financial data for each of the last five fiscal years; registrants are generally not required to disclose selected quarterly financial data for each of the most recent two fiscal years, unless there is a material retrospective change to any of these quarters; and the removal of the requirement for separate sections and certain tabular disclosures of future obligations, off-balance sheet obligations and material commitments for capital expenditures, and instead emphasizes that these obligations should be discussed as part of the results of operations and liquidity discussions of cash requirements in the next fiscal year and beyond. The final rule became effective on February 10, 2021 and must be applied in a registrant’s Annual Report on Form 10-K for its first fiscal year ending on or after August 9, 2021, however early adoption is allowed on an item-by-item basis. The Company has incorporated these changes as part of this Form 10-K.

Acquisitions and Divestitures

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Acquisitions and Divestitures

Note 3 — Acquisitions and Divestitures

The following disclosures discuss significant transactions during the three-year period ended December 31, 2020.

Acquisitions

TRANZACT Acquisition

On July 30, 2019, the Company acquired TRANZACT, a U.S.-based provider of comprehensive, direct-to-consumer sales and marketing solutions for leading insurance carriers in the U.S. TRANZACT leverages digital, data and direct marketing solutions to deliver qualified leads, fully-provisioned sales and robust customer management systems to brands seeking to acquire and manage large numbers of consumers. Pursuant to the terms of the acquisition agreement, subject to certain adjustments, the consideration

consisted of $1.3 billion paid in cash at closing. Additional contingent consideration in the form of a potential earn-out of up to $17 million is to be paid in cash in 2021 based on the achievement of certain financial targets. The acquisition was initially funded in part with a $1.1 billion one-year term loan (see Note 10 — Debt for a description of the term loan and its repayment), with the remainder being funded from the Company’s existing revolving credit facility. TRANZACT operates as part of our Benefits Delivery and Administration segment and enhances the Company’s existing Medicare broking offering, while also adding significant direct-to-consumer marketing experience.

A summary of the fair values of the identifiable assets acquired, and liabilities assumed, of TRANZACT at July 30, 2019 are summarized in the following table.

Cash and cash equivalents	$	7
Restricted cash		2
Accounts receivable, net		3
Renewal commissions receivable, current ⁽ⁱ⁾		36
Prepaid and other current assets		22
Renewal commissions receivable, non-current ⁽ⁱ⁾		130
Fixed assets		9
Intangible assets		646
Goodwill		718
Right-of-use assets		19
Other non-current assets		2
Collateralized facility ⁽ⁱⁱ⁾		(91	)
Other current liabilities		(55	)
Deferred tax liabilities, net		(100	)
Lease liabilities		(19	)
Net assets acquired	$	1,329

______________

(i)

Renewal commissions receivables arise from direct-to-consumer Medicare broking sales. Cash collections for these receivables are expected to occur over a period of several years. Due to the provisions of ASC 606, these receivables are not discounted for a significant financing component when initially recognized (see Note 2 – Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements). However, as a result of recognizing the fair value of these receivables in accordance with ASC 805, these receivables have now been present-valued at the acquisition date. Prior to this fair value adjustment, the carrying value of these receivables was $231 million. The adjusted values of these acquired renewal commissions receivables will be included in prepaid and other current assets or other non-current assets, as appropriate, on the consolidated balance sheets. The acquired renewal commissions receivables will be accounted for prospectively using the cost-recovery method in which future cash receipts will initially be applied against the acquisition date fair value until the value reaches zero. Any cash received in excess of the fair value determined at acquisition will be recorded to earnings when it is received at a future date.

(ii)	See Note 10 — Debt for a description of the acquired collateralized facility debt.

Intangible assets consist primarily of $612 million of customer relationships, with an expected life of 15.4 years. Additional intangibles acquired consist of domain names.

Goodwill is calculated as the difference between the aggregate consideration and the acquisition date fair value of the net assets acquired, including the intangible assets acquired, and represents the value of TRANZACT’s assembled workforce and the future economic benefits that we expect to achieve as a result of the acquisition. None of the goodwill recognized on the transaction is tax deductible, however there is tax deductible goodwill that will be carried forward from previous acquisitions by TRANZACT.

During the year ended December 31, 2020, purchase price allocation adjustments were made primarily to adjust the deferred tax liabilities. The purchase price allocation as of the acquisition date is now complete.

Alston Gayler Acquisition

On December 21, 2018, the Company, through its majority-owned subsidiary, Miller, completed the transaction to acquire Alston Gayler, a U.K.-based insurance and reinsurance broker, for total consideration of $67 million. Cash consideration of $35 million was paid upon completion of the acquisition, with the remaining $32 million deferred consideration to be paid in equal installments on the first, second and third anniversaries of the date of acquisition. As part of our forthcoming Miller divestiture (see discussion below), the Alston Gayler business is expected to be divested during the first quarter of 2021.

The Company has recognized $36 million of intangible assets, primarily arising from client relationships, and $24 million of goodwill. The purchase price allocation for this transaction is complete.

Other Acquisitions

Other acquisitions were completed during the year ended December 31, 2020 for combined cash payments of $79 million and contingent consideration fair valued at $9 million.

Max Matthiessen Divestiture

In September 2020, the Company completed the transaction to sell its Swedish majority-owned subsidiary MM Holding AB (‘Max Matthiessen’) for total consideration of SEK 2.3 billion ($262 million) plus certain other adjustments, resulting in a tax-exempt gain on the sale of $86 million, which is included in Other income, net in the consolidated statement of operations. Of the total consideration, the Company financed a SEK 600 million ($68 million) note repayable by the purchaser. The note has no fixed term but is repayable subject to certain terms and conditions and bears an interest rate that could range from 5% to 10%, increasing the longer the note remains outstanding. This note receivable is included in Other non-current assets in the consolidated balance sheet. The Company entered into certain foreign currency transactions to hedge the consideration to be received against fluctuations in foreign exchange rates (see Note 9 — Derivative Financial Instruments). Prior to disposal, Max Matthiessen was included within the Investment, Risk and Reinsurance segment.

Miller Divestiture

In November 2020, the Company entered into an agreement to sell its majority-owned subsidiary Miller for total consideration of GBP 591 million ($808 million at December 31, 2020) plus certain other adjustments. The divestiture is expected to close during the first quarter of 2021. Miller provides wholesale insurance services to its clients and is included in the Investment, Risk and Reinsurance segment.

As of December 31, 2020, the net assets of Miller are approximately $350 million notwithstanding intercompany debt. The actual amounts disposed of will be determined at the date of closing and will depend upon foreign exchange rates and intercompany transactions in effect at the time, among other factors.

Revenue

12 Months Ended

Dec. 31, 2020

Revenue From Contract With Customer [Abstract]

Note 4 — Revenue

Disaggregation of Revenue

The Company reports revenue by segment in Note 5 — Segment Information. The following table presents revenue by service offering and segment, as well as a reconciliation to total revenue for the years ended December 31, 2020, 2019 and 2018. Along with reimbursable expenses and other, total revenue by service offering represents our revenue from customer contracts.

Year Ended December 31,	Broking		Consulting		Outsourced Administration		Other		Total revenue by service offering		Reimbursable expenses and other ⁽ⁱ⁾		Total revenue from customer contracts		Interest and other income ⁽ⁱⁱ⁾		Total revenue
HCB
2020	$	302	$	2,215	$	503	$	241	$	3,261	$	50	$	3,311	$	17	$	3,328
2019		278		2,269		466		262		3,275		61		3,336		23		3,359
2018		266		2,224		484		235		3,209		62		3,271		24		3,295
CRB
2020		2,707		154		66		11		2,938		2		2,940		39		2,979
2019		2,692		132		71		5		2,900		1		2,901		46		2,947
2018		2,578		163		65		9		2,815		—		2,815		37		2,852
IRR
2020		1,006		393		15		231		1,645		8		1,653		6		1,659
2019		975		421		10		205		1,611		9		1,620		26		1,646
2018		905		430		—		185		1,520		8		1,528		36		1,564
BDA
2020		834		—		525		—		1,359		12		1,371		—		1,371
2019		514		—		521		—		1,035		12		1,047		—		1,047
2018		272		—		486		—		758		7		765		—		765
Corporate ⁽ⁱ⁾
2020		1		5		—		3		9		2		11		4		15
2019		—		11		—		4		15		22		37		3		40
2018		—		13		—		4		17		17		34		3		37
Total
2020	$	4,850	$	2,767	$	1,109	$	486	$	9,212	$	74	$	9,286	$	66	$	9,352
2019	$	4,459	$	2,833	$	1,068	$	476	$	8,836	$	105	$	8,941	$	98	$	9,039
2018	$	4,021	$	2,830	$	1,035	$	433	$	8,319	$	94	$	8,413	$	100	$	8,513

_______

(i)	Reimbursable expenses and other, as well as Corporate revenue, are excluded from segment revenue, but included in total revenue on the consolidated statements of comprehensive income.

(ii)	Interest and other income is included in segment revenue and total revenue, however it has been presented separately in the above tables because it does not arise directly from contracts with customers.

Individual revenue streams aggregating to 5% of total revenue for the years ended December 31, 2020, 2019 and 2018 have been included within the Other column in the table above.

The following table presents revenue by the geography where our work was performed for the years ended December 31, 2020, 2019 and 2018. The reconciliation to total revenue on our consolidated statements of comprehensive income and to segment revenue is shown in the table above.

Year Ended December 31,	North America		Great Britain		Western Europe		International		Total revenue by geography
HCB
2020	$	1,859	$	491	$	584	$	327	$	3,261
2019		1,901		475		566		333		3,275
2018		1,849		481		562		317		3,209
CRB
2020		1,176		630		679		453		2,938
2019		1,112		656		661		471		2,900
2018		1,044		648		631		492		2,815
IRR
2020		474		824		193		154		1,645
2019		449		788		216		158		1,611
2018		416		732		218		154		1,520
BDA
2020		1,351		—		—		8		1,359
2019		1,033		—		—		2		1,035
2018		758		—		—		—		758
Corporate
2020		7		—		2		—		9
2019		13		—		1		1		15
2018		16		—		1		—		17
Total
2020	$	4,867	$	1,945	$	1,458	$	942	$	9,212
2019	$	4,508	$	1,919	$	1,444	$	965	$	8,836
2018	$	4,083	$	1,861	$	1,412	$	963	$	8,319

Contract Balances

The Company reports accounts receivable, net on the consolidated balance sheet, which includes billed and unbilled receivables and current contract assets. In addition to accounts receivable, net, the Company had the following non-current contract assets and deferred revenue balances at December 31, 2020 and 2019:

	December 31, 2020		December 31, 2019
Billed receivables, net of allowance for doubtful accounts of $41 million and $37 million	$	1,697	$	1,831
Unbilled receivables		445		434
Current contract assets		413		356
Accounts receivable, net	$	2,555	$	2,621
Non-current accounts receivable, net	$	34	$	30
Non-current contract assets	$	329	$	105
Deferred revenue	$	549	$	538

The Company receives payments from customers based on billing schedules or terms as written in our contracts. Those balances denoted as contract assets relate to situations where we have completed some or all performance under the contract, however our right to consideration is conditional. Contract assets result most materially in our Medicare broking and proportional treaty broking businesses. The significant increases in both current and non-current contract assets for the year ended December 31, 2020 relate to our direct-to-consumer Medicare broking business. Billed and unbilled receivables are recorded when the right to consideration becomes unconditional. Deferred revenue relates to payments received in advance of performance under the contract and is recognized as revenue as (or when) we perform under the contract.

Accounts receivable are stated at estimated net realizable values. The following table presents the changes in our allowance for doubtful accounts for the years ended December 31, 2020, 2019 and 2018.

	December 31, 2020			December 31, 2019			December 31, 2018
Balance at beginning of year	$	37		$	40		$	45
Additions charged to costs and expenses		29			9			9
Deductions/other movements		(29	)		(10	)		(15	)
Foreign exchange		4			(2	)		1
Balance at end of year	$	41		$	37		$	40

During the year ended December 31, 2020, revenue of approximately $497 million was recognized that was reflected as deferred revenue at December 31, 2019.

During the year ended December 31, 2020, the Company recognized revenue of approximately $37 million related to performance obligations satisfied in a prior period.

Performance Obligations

The Company has contracts for which performance obligations have not been satisfied as of December 31, 2020 or have been partially satisfied as of this date. The following table shows the expected timing for the satisfaction of the remaining performance obligations. This table does not include contract renewals or variable consideration, which was excluded from the transaction prices in accordance with the guidance on constraining estimates of variable consideration.

In addition, in accordance with ASC 606, the Company has elected not to disclose the remaining performance obligations when one or both of the following circumstances apply:

•

Performance obligations which are part of a contract that has an original expected duration of less than one year, and

•

Performance obligations satisfied in accordance with ASC 606-10-55-18 (‘right to invoice’).

		2021				2022				2023 onward				Total
Revenue expected to be recognized on contracts as of December 31, 2020		$	540			$	392			$	497			$	1,429

Since most of the Company’s contracts are cancellable with less than one year’s notice and have no substantive penalty for cancellation, the majority of the Company’s remaining performance obligations as of December 31, 2020 have been excluded from the table above.

Costs to obtain or fulfill a contract

The Company incurs costs to obtain or fulfill contracts which it would not incur if a contract with a customer was not executed.

The following table shows the categories of costs that are capitalized and deferred over the expected life of a contract.

	Costs to fulfill
	December 31, 2020			December 31, 2019			December 31, 2018
Balance at beginning of the year	$	177		$	148		$	126
New capitalized costs		493			488			465
Amortization		(465	)		(460	)		(442	)
Impairments		(1	)		—			—
Foreign currency translation		2			1			(1	)
Balance at end of the year	$	206		$	177		$	148

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Segment Information

12 Months Ended

Dec. 31, 2020

Segment Reporting [Abstract]

Segment Information

Note 5 — Segment Information

Willis Towers Watson has four reportable operating segments or business areas:

•

Human Capital and Benefits (‘HCB’)

•

Corporate Risk and Broking (‘CRB’)

•

Investment, Risk and Reinsurance (‘IRR’)

•

Benefits Delivery and Administration (‘BDA’)

Willis Towers Watson’s chief operating decision maker is its Chief Executive Officer. We determined that the operational data used by the chief operating decision maker is at the segment level. Management bases strategic goals and decisions on these segments and the data presented below is used to assess the adequacy of strategic decisions and the method of achieving these strategies and related financial results. Management evaluates the performance of its segments and allocates resources to them based on net operating income on a pre-tax basis.

The Company experiences seasonal fluctuations of its revenue. Revenue is typically higher during the Company’s first and fourth quarters due primarily to the timing of broking-related activities.

Under the segment structure and for internal and segment reporting, Willis Towers Watson segment revenue includes commissions and fees, interest and other income. U.S. GAAP revenue also includes amounts that were directly incurred on behalf of our clients and reimbursed by them (reimbursable expenses), which are removed from segment revenue. Segment operating income excludes certain costs, including (i) amortization of intangibles; (ii) restructuring costs; (iii) certain transaction and integration expenses; (iv) certain litigation provisions; and (v) to the extent that the actual expense based upon which allocations are made differs from the forecast/budget amount, a reconciling item will be created between internally-allocated expenses and the actual expenses that we report for U.S. GAAP purposes.

The following table presents segment revenue and segment operating income for our reportable segments for the years ended December 31, 2020, 2019 and 2018.

	Segment revenue						Segment operating income
	Years ended December 31						Years ended December 31
	2020		2019		2018		2020		2019		2018
HCB	$	3,278	$	3,298	$	3,233	$	853	$	848	$	789
CRB		2,977		2,946		2,852		630		578		528
IRR		1,651		1,637		1,556		457		420		384
BDA		1,359		1,035		758		320		244		144
Total	$	9,265	$	8,916	$	8,399	$	2,260	$	2,090	$	1,845

The following table presents reconciliations of the information reported by segment to the Company’s consolidated amounts reported for the years ended December 31, 2020, 2019 and 2018.

	Years ended December 31,
	2020			2019			2018
Revenue:
Total segment revenue	$	9,265		$	8,916		$	8,399
Reimbursable expenses and other		87			123			114
Revenue	$	9,352		$	9,039		$	8,513

Total segment operating income	$	2,260		$	2,090		$	1,845
Amortization		(462	)		(489	)		(534	)
Restructuring costs ⁽ⁱ⁾		(24	)		—			—
Transaction and integration expenses ⁽ⁱⁱ⁾		(110	)		(13	)		(202	)
Provision for significant litigation ⁽ⁱⁱⁱ⁾		(65	)		—			—
Unallocated, net ^(iv)		(416	)		(259	)		(300	)
Income from operations		1,183			1,329			809
Interest expense		(244	)		(234	)		(208	)
Other income, net		399			227			250
Income from operations before income taxes	$	1,338		$	1,322		$	851

(i)	Restructuring costs relate to minor restructuring activities carried out by various business lines throughout the Company.

(ii)	Includes transaction costs related to the proposed Aon combination in 2020, the TRANZACT acquisition in 2019, and transaction and integration expenses related to the Merger and the acquisition of Gras Savoye in 2018.

(iii)

For additional information, see the disclosure under Willis Towers Watson Merger-Related Securities Litigation in Note 14 — Commitments and Contingencies.

(iv)	Includes certain costs, primarily related to corporate functions which are not directly related to the segments, and certain differences between budgeted expenses determined at the beginning of the year and actual expenses that we report for U.S. GAAP purposes.

The Company does not currently provide asset information by reportable segment as it does not routinely evaluate the total asset position by segment.

None of the Company’s customers represented a significant amount of its consolidated revenue for the years ended December 31, 2020, 2019 and 2018.

Below are our revenue and long-lived assets for Ireland, our country of domicile, countries with significant concentrations, and all other foreign countries for each of the years ended December 31, 2020, 2019 and 2018:

	Revenue						Long-Lived Assets ⁽ⁱ⁾
	2020		2019		2018		2020		2019		2018
Ireland	$	157	$	144	$	138	$	110	$	103	$	78

United States		4,650		4,370		3,970		12,652		12,786		11,068
United Kingdom		1,920		1,934		1,926		2,840		2,901		2,349
Rest of World		2,625		2,591		2,479		2,533		2,527		2,411
Total Foreign Countries		9,195		8,895		8,375		18,025		18,214		15,828
	$	9,352	$	9,039	$	8,513	$	18,135	$	18,317	$	15,906

(i)	Long-lived assets do not include deferred tax assets.

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 6 — Income Taxes

Provision for income taxes

An analysis of income from operations before income taxes by taxing jurisdiction is shown below:

	Years ended December 31,
	2020			2019			2018
Ireland	$	(5	)	$	(11	)	$	(16	)
U.S.		25			178			(101	)
U.K.		332			337			182
Rest of World		986			818			786
Total	$	1,338		$	1,322		$	851

The components of the provision for income taxes include:

	Years ended December 31,
	2020			2019			2018
Current tax expense:
U.S. federal taxes	$	(27	)	$	(108	)	$	(98	)
U.S. state and local taxes		(5	)		(43	)		(25	)
U.K. corporation tax		(45	)		(43	)		(16	)
Other jurisdictions		(142	)		(127	)		(112	)
Total current tax expense		(219	)		(321	)		(251	)
Deferred tax (expense)/benefit:
U.S. federal taxes		(78	)		56			79
U.S. state and local taxes		1			14			12
U.K. corporation tax		(48	)		(15	)		(6	)
Other jurisdictions		26			17			30
Total deferred tax (expense)/benefit		(99	)		72			115
Total provision for income taxes	$	(318	)	$	(249	)	$	(136	)

Effective tax rate reconciliation

The reported provision for income taxes differs from the amounts that would have resulted had the reported income before income taxes been taxed at the U.S. federal statutory rate. The principal reasons for the differences between the amounts provided and those that would have resulted from the application of the U.S. federal statutory tax rate are as follows:

	Years ended December 31,
	2020			2019			2018
INCOME FROM OPERATIONS BEFORE INCOME TAXES	$	1,338		$	1,322		$	851
U.S. federal statutory income tax rate		21	%		21	%		21	%
Income tax expense at U.S. federal tax rate		(281	)		(278	)		(179	)
Adjustments to derive effective tax rate:
Non-deductible expenses and dividends		(20	)		(34	)		(44	)
Non-deductible acquisition costs		(15	)		(2	)		(2	)
Disposal of non-deductible goodwill		—			—			1
Impact of change in rate on deferred tax balances		(7	)		—			7
Effect of foreign exchange and other differences		(3	)		1			1
Changes in valuation allowances		(8	)		6			80
Net tax effect of intra-group items		90			93			99
Tax on disposal of operations		16			—			—
Tax differentials of non-U.S. jurisdictions		3			(2	)		(2	)
Tax differentials of U.S. state taxes and local taxes		(3	)		(21	)		(77	)
Global Intangible Low-Taxed Income (GILTI)		(3	)		(7	)		(15	)
Base Erosion Anti-Abuse Tax (BEAT)		(81	)		—			—
Other items, net		(6	)		(5	)		(5	)
Provision for income taxes	$	(318	)	$	(249	)	$	(136	)

Included in the BEAT expense for 2020 is an approximate $29 million true-up related to the 2019 tax year as a result of certain elections of the CARES Act. The BEAT effectively applies a 10 percent minimum tax if modified taxable income, as adjusted for base erosion payments, is greater than the regular tax liability for a year. Included in the changes in valuation allowance for 2018, the Company recorded a deferred income tax benefit for approximately $71 million related to the valuation allowance release of certain state deferred tax assets.

Willis Towers Watson plc is a non-trading holding company tax resident in Ireland where it is taxed at the statutory rate of 25%. The provisions for income tax on operations have been reconciled above to the U.S. federal statutory tax rate of 21% due to significant operations in the U.S.

Deferred income taxes

Deferred income tax assets and liabilities reflect the effect of temporary differences between the assets and liabilities recognized for financial reporting purposes and the amounts recognized for income tax purposes. We recognize deferred tax assets if it is more likely than not that a benefit will be realized.

Deferred income tax assets and liabilities included in the consolidated balance sheets at December 31, 2020 and 2019 are comprised of the following:

	December 31,
	2020			2019
Deferred tax assets:
Accrued expenses not currently deductible	$	212		$	201
Net operating losses		92			116
Capital loss carryforwards		40			33
Accrued retirement benefits		334			326
Operating lease liabilities		165			181
Deferred compensation		90			86
Stock options		25			18
Financial derivative transactions		1			—
Gross deferred tax assets		959			961
Less: valuation allowance		(84	)		(76	)
Net deferred tax assets	$	875		$	885
Deferred tax liabilities:
Cost of intangible assets, net of related amortization	$	788		$	865
Operating lease right-of-use assets		159			177
Cost of tangible assets, net of related depreciation		78			53
Prepaid retirement benefits		152			121
Financial derivative transactions		1			3
Accrued revenue not currently taxable		163			120
Deferred tax liabilities	$	1,341		$	1,339
Net deferred tax liabilities	$	466		$	454

The net deferred income tax assets are included in other non-current assets and the net deferred tax liabilities are included in deferred tax liabilities in our consolidated balance sheets.

	December 31,
	2020		2019
Balance sheet classifications:
Other non-current assets	$	95	$	72
Deferred tax liabilities		561		526
Net deferred tax liability	$	466	$	454

At December 31, 2020, we had U.S. federal and non-U.S. net operating loss carryforwards amounting to $258 million of which $209 million can be indefinitely carried forward under local statutes. The remaining $49 million of net operating loss carryforwards will expire, if unused, in varying amounts from 2021 through 2040. In addition, we had U.S. state net operating loss carryforwards of $621 million, of which $97 million can be indefinitely carried forward, while the remaining $524 million will expire in varying amounts from 2021 to 2040.

Management believes, based on the evaluation of positive and negative evidence, including the future reversal of existing taxable temporary differences, it is more likely than not that the Company will realize the benefits of net deferred tax assets of $875 million, net of the valuation allowance. During 2020, the Company increased its valuation allowance by $8 million, primarily related to non-U.S. deferred tax assets. During 2019, the Company decreased its valuation allowance by $5 million, primarily related to non-U.S. deferred tax assets now considered realizable. During 2018, the Company decreased its valuation allowance by $81 million primarily related to the completion of an internal U.S. restructuring. The U.S. restructuring provided a source of positive evidence and enabled the Company to release its valuation allowance on certain state deferred tax assets now considered realizable. In addition, the Company reassessed certain state net operating losses and determined certain losses and the related valuation allowance would never be realized.

At December 31, 2020 and 2019, the Company had valuation allowances of $84 million and $76 million, respectively, to reduce its deferred tax assets to their estimated realizable values. The valuation allowance at December 31, 2020 primarily relates to deferred tax

assets for U.K. capital loss carryforwards of $39 million, which have an unlimited carryforward period but can only be utilized against U.K. capital gains and U.S. state and non-U.S. net operating losses of $26 million and $19 million, respectively.

An analysis of our valuation allowance is shown below.

	Years ended December 31,
	2020			2019			2018
Balance at beginning of year	$	76		$	81		$	162
Additions charged to costs and expenses		17			7			18
Deductions		(9	)		(12	)		(99	)
Balance at end of year	$	84		$	76		$	81

In 2020, the net change in valuation allowance was an $8 million increase, primarily related to non-U.S. deferred tax assets. In 2019, the net change in valuation allowance was a $5 million decrease, primarily related to non-U.S. deferred tax assets now considered realizable. This amount differs from the 2019 rate reconciliation due to changes in foreign currency translation. In 2018, the net change in valuation allowance was an $81 million decrease, of which $80 million was a reduction to tax expense primarily related to an internal U.S. restructuring.

The Company recognizes deferred tax balances related to the undistributed earnings of subsidiaries when the Company expects that it will recover those undistributed earnings in a taxable manner, such as through receipt of dividends or sale of the investments.

At December 31, 2018, as a result of an international restructuring, we determined that we may repatriate $2.1 billion, which was previously deemed indefinitely reinvested. Of the original $2.1 billion under consideration, $1.4 billion remains permanently reinvested at December 31, 2020. The cumulative earnings related to amounts reinvested indefinitely as of December 31, 2020 were approximately $8.9 billion, the majority of which are non-U.S. earnings not subject to U.S. tax. It is not practicable to calculate the tax cost of repatriating these unremitted earnings. If future events, including material changes in estimates of cash, working capital, long-term investment requirements or additional guidance relating to U.S. Tax Reform necessitate that these earnings be distributed, an additional provision for income and foreign withholding taxes, net of credits, may be necessary.

Uncertain tax positions

At December 31, 2020, the amount of unrecognized tax benefits associated with uncertain tax positions, determined in accordance with ASC 740-10, excluding interest and penalties, was $50 million. A reconciliation of the beginning and ending balances of the liability for unrecognized tax benefits is as follows:

	2020			2019			2018
Balance at beginning of year	$	49		$	49		$	59
Increases related to acquisitions		4			—			—
Increases related to tax positions in prior years		1			2			2
Decreases related to tax positions in prior years		—			(1	)		(4	)
Decreases related to settlements		(3	)		—			(4	)
Decreases related to lapse in statute of limitations		(2	)		(1	)		(5	)
Increases related to current year tax positions		—			—			3
Cumulative translation adjustment and other adjustments		1			—			(2	)
Balance at end of year	$	50		$	49		$	49

The liability for unrecognized tax benefits for the years ended December 31, 2020, 2019 and 2018 can be reduced by $3 million, $3 million and $2 million, respectively, of offsetting deferred tax benefits associated with timing differences, foreign tax credits and the federal tax benefit of state income taxes. If these offsetting deferred tax benefits were recognized, there would be a favorable impact on our effective tax rate. There are no material balances that would result in adjustments to other tax accounts.

Interest and penalties related to unrecognized tax benefits are included as a component of income tax expense. At December 31, 2020, we had cumulative accrued interest of $5 million. At December 31, 2019, the cumulative accrued interest was $4 million. Accrued penalties were immaterial in both 2020 and 2019.

Tax expense for both the years ended December 31, 2020 and 2019 includes $1 million of interest expense.

The Company believes that the outcomes which are reasonably possible within the next 12 months may result in a reduction in the liability for unrecognized tax benefits in the range of $4 million to $8 million, excluding interest and penalties.

The Company and its subsidiaries file income tax returns in various tax jurisdictions in which it operates.

Willis North America Inc. and subsidiaries’ federal income tax filings for the tax years ended December 31, 2017 and December 31, 2018 are currently under examination by the Internal Revenue Service (‘IRS’). As of December 31, 2020, the IRS has not advised the Company of any proposed changes.

We have ongoing state income tax examinations in certain states for tax years ranging from calendar years ended December 31, 2014 through December 31, 2018. The statute of limitations in certain states remains open back to calendar year 2014.

All U.K. tax returns have been filed timely and are in the normal process of being reviewed by Her Majesty’s Revenue & Customs. The Company is not currently subject to any material examinations in other jurisdictions. A summary of the tax years that remain open to tax examination in our major tax jurisdictions are as follows:



	Open Tax Years (fiscal year ending in)
U.S. — federal	2017 and forward
U.S. — various states	2014 and forward
U.K.	2010 and forward
Ireland	2016 and forward
France	2010 and forward
Germany	2010 and forward
Canada - federal	2013 and forward

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

Property Plant And Equipment [Abstract]

Fixed Assets

12 Months Ended

Dec. 31, 2020

Fixed Assets

Note 7 — Fixed Assets

The following table reflects changes in the net carrying amount of the components of fixed assets for the years ended December 31, 2020 and 2019:

	Furniture, equipment and software			Leasehold improvements			Land and buildings			Total
Cost: at January 1, 2019	$	1,130		$	488		$	92		$	1,710
Additions		268			68			—			336
Acquisitions		7			3			—			10
Disposals		(117	)		(15	)		—			(132	)
Reclassification due to ASC 842 ⁽ⁱ⁾		—			—			(3	)		(3	)
Foreign exchange		14			6			1			21
Cost: at December 31, 2019		1,302			550			90			1,942
Additions		238			31			—			269
Acquisitions		1			—			—			1
Disposals		(64	)		(12	)		(1	)		(77	)
Abandonment of long-lived asset ⁽ⁱⁱ⁾		(35	)		—			—			(35	)
Foreign exchange		31			9			1			41
Cost: at December 31, 2020	$	1,473		$	578		$	90		$	2,141

Depreciation: at January 1, 2019	$	(519	)	$	(197	)	$	(52	)	$	(768	)
Depreciation expense		(179	)		(57	)		(4	)		(240	)
Disposals		109			11			—			120
Foreign exchange		(5	)		(2	)		(1	)		(8	)
Depreciation: at December 31, 2019		(594	)		(245	)		(57	)		(896	)
Depreciation expense ⁽ⁱⁱ⁾		(214	)		(55	)		(4	)		(273	)
Disposals		56			10			—			66
Foreign exchange		(17	)		(6	)		(1	)		(24	)
Depreciation: at December 31, 2020	$	(769	)	$	(296	)	$	(62	)	$	(1,127	)

Net book value:
At December 31, 2019	$	708		$	305		$	33		$	1,046

At December 31, 2020	$	704		$	282		$	28		$	1,014

(i)	Pertains to certain lease incentives which have been included within right-of-use assets upon the adoption of ASC 842. See Note 2 — Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements for further information.

(ii)	Depreciation expense on the statement of comprehensive income for the year ended December 31, 2020 includes both the depreciation expense presented here as well as the abandonment of an internally-developed software asset of $35 million prior to being placed in service.

Included within land and buildings are the following assets held under finance leases:

	December 31,
	2020			2019
Finance leases	$	28		$	29
Accumulated depreciation		(20	)		(19	)
	$	8		$	10

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

Note 8 — Goodwill and Other Intangible Assets

Goodwill

The components of goodwill are outlined below for the years ended December 31, 2020 and 2019:

	HCB			CRB			IRR			BDA			Total
Balance at December 31, 2018
Goodwill, gross	$	4,300		$	2,308		$	1,792		$	2,557		$	10,957
Accumulated impairment losses		(130	)		(362	)		—			—			(492	)
Goodwill, net - December 31, 2018		4,170			1,946			1,792			2,557			10,465
Goodwill acquired		—			10			—			727			737
Goodwill disposals		—			(6	)		—			—			(6	)
Foreign exchange		(2	)		(3	)		3			—			(2	)
Balance at December 31, 2019
Goodwill, gross		4,298			2,309			1,795			3,284			11,686
Accumulated impairment losses		(130	)		(362	)		—			—			(492	)
Goodwill, net - December 31, 2019		4,168			1,947			1,795			3,284			11,194
Goodwill acquired		15			30			2			3			50
Goodwill disposals		(12	)		(1	)		(117	)		—			(130	)
Acquisition accounting adjustment		—			—			—			(9	)		(9	)
Foreign exchange		45			40			14			—			99
Balance at December 31, 2020
Goodwill, gross		4,346			2,378			1,694			3,278			11,696
Accumulated impairment losses		(130	)		(362	)		—			—			(492	)
Goodwill, net - December 31, 2020	$	4,216		$	2,016		$	1,694		$	3,278		$	11,204

Other Intangible Assets

The following table reflects changes in the net carrying amounts of the components of finite-lived intangible assets for the year ended December 31, 2020 and 2019:

	Client relationships			Software			Trademark and trade name			Favorable agreements ⁽ⁱ⁾			Other			Total
Balance at December 31, 2018:
Intangible assets, gross	$	3,401		$	749		$	1,052		$	14		$	102		$	5,318
Accumulated amortization		(1,415	)		(421	)		(132	)		(5	)		(27	)		(2,000	)
Intangible assets, net - December 31, 2018		1,986			328			920			9			75			3,318
ASC 842 reclassification ⁽ⁱ⁾		—			—			—			(9	)		—			(9	)
Intangible assets acquired ⁽ⁱⁱ⁾		626			—			—			—			34			660
Intangible asset disposals		(9	)		(1	)		—			—			—			(10	)
Amortization		(313	)		(125	)		(45	)		—			(6	)		(489	)
Foreign exchange		8			—			—			—			—			8
Balance at December 31, 2019:
Intangible assets, gross		4,029			753			1,051			—			134			5,967
Accumulated amortization		(1,731	)		(551	)		(176	)		—			(31	)		(2,489	)
Intangible assets, net - December 31, 2019		2,298			202			875			—			103			3,478
Intangible assets acquired		30			—			—			—			32			62
Intangible asset disposals		(19	)		—			—			—			(48	)		(67	)
Amortization		(301	)		(103	)		(43	)		—			(15	)		(462	)
Foreign exchange		26			3			2			—			1			32
Balance at December 31, 2020:
Intangible assets, gross		4,065			761			1,054			—			108			5,988
Accumulated amortization		(2,031	)		(659	)		(220	)		—			(35	)		(2,945	)
Intangible assets, net - December 31, 2020	$	2,034		$	102		$	834		$	—		$	73		$	3,043

(i)	On January 1, 2019, in accordance with ASC 842, we reclassified our favorable lease agreement assets to right-of-use assets within our consolidated balance sheet.

(ii)	Includes $612 million and $34 million of client relationship and domain name intangible assets, respectively, associated with our acquisition of TRANZACT.

For the year ended December 31, 2018, we recorded amortization related to our finite-lived intangible assets, exclusive of the amortization of our favorable lease agreements, of $534 million.

Our acquired unfavorable lease agreement liabilities were $21 million at December 31, 2018 and were recorded in other non-current liabilities in the consolidated balance sheet. On January 1, 2019, in accordance with ASC 842, we reclassified our unfavorable lease liabilities as a reduction to our right-of-use assets within our consolidated balance sheet.

The weighted-average remaining life of amortizable intangible assets and liabilities at December 31, 2020 was 13.3 years.

The table below reflects the future estimated amortization expense for amortizable intangible assets for the next five years and thereafter:

Years ended December 31,	Amortization
2021	$	389
2022		328
2023		274
2024		239
2025		217
Thereafter		1,596
Total	$	3,043

Derivative Financial Instruments

12 Months Ended

Dec. 31, 2020

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

Note 9 — Derivative Financial Instruments

We are exposed to certain foreign currency risks. Where possible, we identify exposures in our business that can be offset internally. Where no natural offset is identified, we may choose to enter into various derivative transactions. These instruments have the effect of reducing our exposure to unfavorable changes in foreign currency rates. The Company’s board of directors reviews and approves policies for managing this risk as summarized below. Additional information regarding our derivative financial instruments can be found in Note 2 — Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements, Note 11 — Fair Value Measurements and Note 17 — Accumulated Other Comprehensive Loss.

Foreign Currency Risk

Certain non-U.S. subsidiaries receive revenue and incur expenses in currencies other than their functional currency, and as a result, the foreign subsidiary’s functional currency revenue and/or expenses will fluctuate as the currency rates change. Additionally, the forecasted Pounds sterling expenses of our London brokerage market operations may exceed their Pounds sterling revenue, and the entity with such operations may also hold significant foreign currency asset or liability positions in the consolidated balance sheet. To reduce such variability, we use foreign exchange contracts to hedge against this currency risk.

These derivatives were designated as hedging instruments and at December 31, 2020 and December 31, 2019 had total notional amounts of $340 million and $499 million, respectively, and represented net fair value assets of $5 million and $8 million, respectively.

At December 31, 2020, the Company estimates, based on current exchange rates, there will be $3 million of net derivative gains on forward exchange rates reclassified from accumulated other comprehensive loss into earnings within the next twelve months as the forecasted transactions affect earnings. These amounts include gains for contracts held by Miller, which is expected to be sold in the first quarter of 2021 (see Note 3 — Acquisitions and Divestitures). At December 31, 2020, our longest outstanding maturity was 1.7 years.

The effects of the material derivative instruments that are designated as hedging instruments on the consolidated statements of comprehensive income for the years ended December 31, 2020, 2019 and 2018 are below. Amounts pertaining to the ineffective portion of hedging instruments and those excluded from effectiveness testing were immaterial for the years ended December 31, 2020, 2019 and 2018.

	Loss/(gain) recognized in OCI (effective element)
	2020			2019		2018
Foreign exchange contracts	$	(13	)	$	15	$	(22	)

Location of loss reclassified from Accumulated OCL into income (effective element)	Loss reclassified from Accumulated OCL into income (effective element)
	2020			2019			2018
Revenue	$	(5	)	$	(5	)	$	—
Salaries and benefits		(4	)		(4	)		—
Other income, net		—			—			(28	)
	$	(9	)	$	(9	)	$	(28	)

We also enter into foreign currency transactions, primarily to hedge certain intercompany loans and other balance sheet exposures in currencies other than the functional currency of a given entity. These derivatives are not generally designated as hedging instruments, and at December 31, 2020 and December 31, 2019, had notional amounts of $1.5 billion and $931 million, respectively, and represented net fair value assets of $15 million and $21 million, respectively.

The effects of derivatives that have not been designated as hedging instruments on the consolidated statements of comprehensive income for the years ended December 31, 2020, 2019 and 2018 are as follows:

	Location of (loss)/gain	(Loss)/gain recognized in income
Derivatives not designated as hedging instruments:	recognized in income	2020			2019		2018
Foreign exchange contracts	Other income, net	$	(3	)	$	18	$	—

On June 10, 2020, we entered into certain foreign currency transactions to hedge the consideration to be received from the then-pending divestiture of our Max Matthiessen business (see Note 3 — Acquisitions and Divestitures) against fluctuations in foreign exchange rates. The notional value of these contracts was approximately $273 million, of which approximately $181 million had been

designated as a hedge of net investment, on an after-tax basis, against the carrying value of the net assets of Max Matthiessen. The settlement of the hedging instruments resulted in a $1 million loss during the year ended December 31, 2020, which was included in the net gain on disposal.

Debt

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Debt

Note 10 — Debt

Current debt consists of the following:

	December 31,
	2020		2019
5.750% senior notes due 2021	$	500	$	—
3.500% senior notes due 2021		449		—
Current portion of collateralized facility		22		24
Term loan due 2020		—		292
	$	971	$	316

Long-term debt consists of the following:

	December 31,
	2020		2019
Revolving $1.25 billion credit facility	$	—	$	—
Collateralized facility ⁽ⁱ⁾		33		60
5.750% senior notes due 2021		—		499
3.500% senior notes due 2021		—		448
2.125% senior notes due 2022 ⁽ⁱⁱ⁾		659		604
4.625% senior notes due 2023		249		249
3.600% senior notes due 2024		647		646
4.400% senior notes due 2026		546		546
4.500% senior notes due 2028		596		595
2.950% senior notes due 2029		726		446
6.125% senior notes due 2043		271		271
5.050% senior notes due 2048		395		395
3.875% senior notes due 2049		542		542
	$	4,664	$	5,301

(i)	At December 31, 2020 and 2019, the Company had $98 million and $127 million, respectively, of renewal commissions receivables pledged as collateral for this facility (see below for additional information).

(ii)	Notes issued in Euro (€540 million).

Guarantees

All direct obligations under the 5.750% senior notes are issued by Willis Towers Watson and guaranteed by Willis Netherlands Holdings B.V., Willis Investment UK Holdings Limited, TA I Limited, Trinity Acquisition plc, Willis Group Limited, Willis North America Inc., Willis Towers Watson Sub Holdings Unlimited Company and Willis Towers Watson U.K. Holdings Limited.

All direct obligations under the 3.600%, 4.500%, 2.950%, 5.050% and 3.875% senior notes are issued by Willis North America Inc. and guaranteed by Willis Towers Watson and each of the subsidiaries that guarantees the Company notes, except for Willis North America Inc. itself.

All direct obligations under the 4.625%, 6.125%, 3.500%, 4.400% and 2.125% senior notes are issued by Trinity Acquisition plc and guaranteed by Willis Towers Watson and each of the subsidiaries that guarantees the Company notes, except for Trinity Acquisition plc itself.

Revolving Credit Facility

$1.25 billion revolving credit facility

On March 7, 2017, Trinity Acquisition plc entered into a $1.25 billion amended and restated revolving credit facility (the ‘RCF’), that will mature on March 7, 2022. The RCF replaced the previous revolving credit facility. Amounts outstanding under the RCF shall bear

interest at LIBOR plus a margin of 1.00% to 1.75%, or alternatively, the base rate plus a margin of 0.00% to 0.75%, based upon the Company’s guaranteed senior unsecured long-term debt rating.

Senior Notes

2.950% senior notes due 2029 and 3.875% senior notes due 2049

On September 10, 2019, the Company, together with its wholly-owned subsidiary, Willis North America Inc., as issuer, completed an offering of $450 million aggregate principal amount of 2.950% senior notes due 2029 (the ‘initial 2029 senior notes’) and $550 million aggregate principal amount of 3.875% senior notes due 2049 (‘2049 senior notes’; collectively, the ‘2019 senior notes offering’). On May 29, 2020, the Company, together with its wholly-owned subsidiary, Willis North America Inc., as issuer, completed an offering of an additional $275 million aggregate principal amount of 2.950% senior notes due 2029 (the ‘additional 2029 senior notes’). The additional 2029 senior notes will be treated as a single class with, and otherwise identical to, the initial 2029 senior notes other than with respect to the date of issuance, the issue price and the amounts paid to holders for each class of note on the first interest payment date. The effective interest rates of the initial 2029 senior notes and 2049 senior notes are 2.971% and 3.898%, respectively, which include the impact of the discount upon issuance. The effective interest rate of the additional 2029 senior notes is 2.697%, which includes the impact of the premium upon issuance. Both 2029 senior notes offerings will mature on September 15, 2029, and the 2049 senior notes will mature on September 15, 2049. Interest on the 2019 senior notes offering has accrued from September 10, 2019 and is paid in cash on March 15 and September 15 of each year. Interest on the additional 2029 senior notes has accrued from March 15, 2020 and is paid in cash on March 15 and September 15 of each year. The net proceeds from the 2019 senior notes offering, after deducting underwriter discounts and commissions and estimated offering expenses, were approximately $988 million and were used to prepay a portion of the amount outstanding under the Company’s one-year term loan commitment (described below) and to repay borrowings under the Company’s $1.25 billion revolving credit facility. The net proceeds from the additional 2029 senior notes offering were used to repay $175 million of the full principal amount and related accrued interest under the term loan facility, which was set to expire in July 2020, as well as repay $105 million of borrowings outstanding under the Company’s $1.25 billion revolving credit facility and related accrued interest.

4.500% senior notes due 2028 and 5.050% senior notes due 2048

On September 10, 2018, the Company, together with its wholly-owned subsidiary, Willis North America Inc. as issuer, completed an offering of $600 million of 4.500% senior notes due 2028 (‘2028 senior notes’) and $400 million of 5.050% senior notes due 2048 (‘2048 senior notes’). The effective interest rates of the 2028 senior notes and 2048 senior notes are 4.504% and 5.073%, respectively, which include the impact of the discount upon issuance. The 2028 senior notes will mature on September 15, 2028 and the 2048 senior notes will mature on September 15, 2048. Interest has accrued on both the 2028 senior notes and 2048 senior notes from September 10, 2018 and is paid in cash on March 15 and September 15 of each year. The net proceeds from this offering, after deducting underwriter discounts and commissions and estimated offering expenses, were $989 million and were used to prepay in full $127 million outstanding under the Company’s term loan due December 2019 and to repay a portion of the amount outstanding under the Company’s RCF.

3.600% senior notes due 2024

On May 16, 2017, Willis North America Inc. issued $650 million of 3.600% senior notes due 2024 (‘2024 senior notes’). The effective interest rate of the 2024 senior notes is 3.614%, which includes the impact of the discount upon issuance. The 2024 senior notes will mature on May 15, 2024, and interest has accrued on the 2024 senior notes from May 16, 2017 and is paid in cash on May 15 and November 15 of each year. The net proceeds from this offering, after deducting underwriter discounts and commissions and estimated offering expenses, were $644 million and were used to pay down amounts outstanding under the RCF and for general corporate purposes.

2.125% senior notes due 2022

On May 26, 2016, Trinity Acquisition plc issued €540 million ($609 million) of 2.125% senior notes due 2022 (‘2022 senior notes’). The effective interest rate of these senior notes is 2.154%, which includes the impact of the discount upon issuance. The 2022 senior notes will mature on May 26, 2022. Interest has accrued on the notes from May 26, 2016 and will be paid in cash on May 26 of each year. The net proceeds from this offering, after deducting underwriter discounts and commissions and estimated offering expenses, were €535 million ($600 million). We used the net proceeds of this offering to repay a portion of the previous 1-year term loan facility, which matured in 2016, and related accrued interest.

3.500% senior notes due 2021 and 4.400% senior notes due 2026

On March 22, 2016, Trinity Acquisition plc issued $450 million of 3.500% senior notes due 2021 (‘2021 senior notes’) and $550 million of 4.400% senior notes due 2026 (‘2026 senior notes’). The effective interest rates of these senior notes are 3.707% and 4.572%, respectively, which include the impact of the discount upon issuance. The 2021 senior notes and the 2026 senior notes will mature on September 15, 2021 and March 15, 2026, respectively. Interest has accrued on the notes from March 22, 2016 and will be paid in cash on March 15 and September 15 of each year. The net proceeds from these offerings, after deducting underwriter discounts and commissions and estimated offering expenses, were $988 million. We used the net proceeds of these offerings to: (i) repay $300 million principal under the prior $800 million revolving credit facility and related accrued interest, which was drawn to repay our previously-issued 4.125% senior notes on March 15, 2016; (ii) repay $400 million principal on another portion of the previous 1-year term loan facility and related accrued interest; and (iii) pay down a portion of the remaining principal amount outstanding under the previous revolving credit facility and related accrued interest.

4.625% senior notes due 2023 and 6.125% senior notes due 2043

On August 15, 2013, Trinity Acquisition plc issued $250 million of 4.625% senior notes due 2023 (‘2023 senior notes’) and $275 million of 6.125% senior notes due 2043 (‘2043 senior notes’). The effective interest rates of these senior notes are 4.696% and 6.154%, respectively, which include the impact of the discount upon issuance. The proceeds were used to repurchase other previously issued senior notes. The 2023 senior notes will mature on August 15, 2023 and the 2043 senior notes will mature on August 15, 2043.

5.750% senior notes due 2021

In March 2011, the Company issued $500 million of 5.750% senior notes due 2021. The effective interest rate of these senior notes is 5.871%, which includes the impact of the discount upon issuance. The proceeds were used to repurchase and redeem other previously- issued senior notes. The notes will mature on March 15, 2021.

Collateralized Facility

As part of the acquisition of TRANZACT, the Company assumed debt of $91 million related to borrowings by TRANZACT whereby certain renewal commissions receivables were pledged as collateral. The Company is required to remit cash received from these pledged renewal commissions receivables on a quarterly basis to the lenders until the borrowings and related interest are repaid, after the payment of certain fees and other permitted distributions. No borrowings have been made against this collateralized facility since the acquisition.

The maturity date of the borrowing is in January 2033, at which time all remaining outstanding principal and unpaid accrued interest will be payable. The collateralization facility may be prepaid in November 2021 or earlier if approval is obtained from at least half of the lenders. Loans under the agreement bear interest at LIBOR plus an applicable margin of 3.95%. The collateralization facility contains financial covenants, including requirements to separately and securely maintain the collateral. As cash is received for these pledged assets, it is classified as restricted cash within prepaid and other current assets on our accompanying consolidated balance sheet. Accumulated cash receipts are applied against the principal and interest on a quarterly basis.

Additional Information Regarding Fully Repaid Senior Notes and Term Loan Facilities

7.000% senior notes due 2019

In September 2009, Willis North America Inc. issued $300 million of 7.000% senior notes due 2019. The effective interest rate of these senior notes was 7.081%, which included the impact of the discount upon issuance. A portion of the proceeds was used to repurchase and redeem other previously issued senior notes. In August 2013, $113 million of the 7.000% senior notes due 2019 were repurchased. In September 2019, the Company repaid in full the remaining $187 million outstanding on the 7.000% senior notes due 2019 with borrowings against its revolving credit facility.

Term loan due December 2019

On January 4, 2016, we acquired a $340 million term loan in connection with the Merger. On November 20, 2015, Towers Watson Delaware Inc. entered into a 4-year amortizing term loan agreement for up to $340 million with a consortium of banks to help fund the pre-Merger special dividend. On December 28, 2015, Towers Watson Delaware Inc. borrowed the full $340 million. During 2018, we prepaid the remaining $127 million outstanding under the term loan with proceeds from the issuance of the 2028 senior notes and 2048 senior notes discussed above.

One-year Term Loan Commitment

As part of the acquisition of TRANZACT, the Company secured financing of up to $1.1 billion in the form of a one-year unsecured term loan. Borrowing occurred in conjunction with the closing of the acquisition on July 30, 2019.

Amounts outstanding under the term loan bore interest, at the option of the borrowers, at a rate equal to (a) LIBOR plus 0.75% to 1.375% for Eurocurrency Rate Loans or (b) the highest of (i) the Federal Funds Rate plus 0.5%, (ii) the ‘prime rate’ quoted by Bank of America, N.A., and (iii) LIBOR plus 1.00%, plus 0.00% to 0.375%, in each case, based upon the Company’s guaranteed senior-unsecured long-term debt rating. In addition, the Company paid a commitment fee in an amount equal to 0.15% per annum on the undrawn portion of the commitments in respect of the term loan, which we had accrued from May 29, 2019 until the closing date of the acquisition.

The term loan was pre-payable in part or in full prior to the maturity date at the Company’s discretion. Covenants and events of default were substantively the same as in our existing revolving credit facility. The remaining outstanding balance on the term loan was repaid in full upon issuance of the additional 2029 senior notes discussed above.

Covenants

The terms of our current financings also include certain limitations. For example, the agreements relating to the debt arrangements and credit facilities generally contain numerous operating and financial covenants, including requirements to maintain minimum ratios of consolidated EBITDA to consolidated cash interest expense and maximum levels of consolidated funded indebtedness in relation to consolidated EBITDA, in each case subject to certain adjustments. The operating restrictions and financial covenants in our current credit facilities do, and any future financing agreements may, limit our ability to finance future operations or capital needs or to engage in other business activities. At December 31, 2020 and 2019, we were in compliance with all financial covenants.

Debt Maturity

The following table summarizes the maturity of our debt and interest on senior notes and excludes any reduction for debt issuance costs:

	2021		2022		2023		2024		2025		Thereafter		Total
Senior notes	$	950	$	660	$	250	$	650	$	—	$	3,100	$	5,610
Interest on senior notes		197		171		162		140		131		1,418		2,219
RCF		—		—		—		—		—		—		—
Collateralized facility		22		17		13		3		—		—		55
Total	$	1,169	$	848	$	425	$	793	$	131	$	4,518	$	7,884

Interest Expense

The following table shows an analysis of the interest expense for the years ended December 31, 2020, 2019 and 2018:

	Years ended December 31,
	2020		2019		2018
Senior notes	$	227	$	206	$	166
Term loans		6		9		4
RCF		4		8		26
Collateralized facility		3		1		—
Other⁽ⁱ⁾		4		10		12
Total interest expense	$	244	$	234	$	208

(i)	Other primarily includes debt issuance costs, interest expense on financing leases and accretion on deferred and contingent consideration.

Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 11 — Fair Value Measurements

The Company has categorized its assets and liabilities that are measured at fair value on a recurring and non-recurring basis into a three-level fair value hierarchy, based on the reliability of the inputs used to determine fair value as follows:

•

Level 1: refers to fair values determined based on quoted market prices in active markets for identical assets;

•

Level 2: refers to fair values estimated using observable market-based inputs or unobservable inputs that are corroborated by market data; and

•

Level 3: includes fair values estimated using unobservable inputs that are not corroborated by market data.

The following methods and assumptions were used by the Company in estimating its fair value disclosure for financial instruments:

•

Available-for-sale securities are classified as Level 1 because we use quoted market prices in determining the fair value of these securities.

•

Market values for our derivative instruments have been used to determine the fair values of forward foreign exchange contracts based on estimated amounts the Company would receive or have to pay to terminate the agreements, taking into account observable information about the current foreign currency forward rates. Such financial instruments are classified as Level 2 in the fair value hierarchy.

•

Contingent consideration payable is classified as Level 3, and we estimate fair value based on the likelihood and timing of achieving the relevant milestones of each arrangement, applying a probability assessment to each of the potential outcomes, which at times includes the use of a Monte Carlo simulation and discounting the probability-weighted payout. Typically, milestones are based on revenue or earnings growth for the acquired business.

The following tables present our assets and liabilities measured at fair value on a recurring basis at December 31, 2020 and December 31, 2019:

		Fair Value Measurements on a Recurring Basis at December 31, 2020
	Balance Sheet Location	Level 1		Level 2		Level 3		Total
Assets:
Available-for-sale securities:
Mutual funds / exchange traded funds	Prepaid and other current assets and other non-current assets	$	8	$	—	$	—	$	8
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Prepaid and other current assets and other non-current assets	$	—	$	27	$	—	$	27
Liabilities:
Contingent consideration:
Contingent consideration ⁽ⁱⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	—	$	45	$	45
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	7	$	—	$	7

		Fair Value Measurements on a Recurring Basis at December 31, 2019
	Balance Sheet Location	Level 1		Level 2		Level 3		Total
Assets:
Available-for-sale securities:
Mutual funds / exchange traded funds	Prepaid and other current assets and other non-current assets	$	20	$	—	$	—	$	20
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Prepaid and other current assets and other non-current assets	$	—	$	32	$	—	$	32
Liabilities:
Contingent consideration:
Contingent consideration ⁽ⁱⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	—	$	17	$	17
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	3	$	—	$	3

(i)	See Note 9 — Derivative Financial Instruments for further information on our derivative instruments.

(ii)

Probability weightings are based on our knowledge of the past and planned performance of the acquired entity to which the contingent consideration applies. The weighted-average discount rates used on our material contingent consideration calculations were 9.46% and 10.16% at December 31, 2020 and December 31, 2019, respectively. The range of these discount rates was 3.53% - 13.00% at December 31, 2020. Using different probability weightings and discount rates could result in an increase or decrease of the contingent consideration payable.

The following table summarizes the change in fair value of the Level 3 liabilities:

Fair Value Measurements Using Significant Unobservable Inputs (Level 3)	December 31, 2020
Balance at December 31, 2019	$	17
Obligations assumed		9
Payments		—
Realized and unrealized gains		18
Foreign exchange		1
Balance at December 31, 2020	$	45

There were no significant transfers between Levels 1, 2 or 3 during the years ended December 31, 2020 and 2019.

Fair value information about financial instruments not measured at fair value

The following tables present our assets and liabilities not measured at fair value on a recurring basis at December 31, 2020 and 2019:

	December 31, 2020				December 31, 2019
	Carrying Value		Fair Value		Carrying Value		Fair Value
Assets:
Long-term note receivable	$	71	$	73	$	—	$	—
Liabilities:
Current debt	$	971	$	985	$	316	$	319
Long-term debt	$	4,664	$	5,488	$	5,301	$	5,694

The carrying values of our revolving credit facility and collateralized facility approximate their fair values. The fair values above are not necessarily indicative of the amounts that the Company would realize upon disposition, nor do they indicate the Company’s intent or ability to dispose of the financial instruments. The fair values of our respective senior notes and long-term note receivable are considered Level 2 financial instruments as they are corroborated by observable market data.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

Compensation And Retirement Disclosure [Abstract]

Retirement Benefits

12 Months Ended

Dec. 31, 2020

Retirement Benefits

Note 12 — Retirement Benefits

Defined Benefit Plans and Post-retirement Welfare Plans

Willis Towers Watson sponsors both qualified and non-qualified defined benefit pension plans and other post-retirement welfare (‘PRW’) plans throughout the world. The majority of our plan assets and obligations are in the U.S. and the U.K. We have also included disclosures related to defined benefit plans in certain other countries, including Canada, France, Germany and Ireland. Together, these disclosed funded and unfunded plans represent 99% of Willis Towers Watson’s pension and PRW obligations and are presented herein.

As part of these obligations, in the U.S., the U.K. and Canada, we have non-qualified plans that provide for the additional pension benefits that would be covered under the qualified plan in the respective country were it not for statutory maximums. The non-qualified plans are unfunded.

The significant plans within each grouping are described below:

United States

Legacy Willis – This plan was frozen in 2009. Approximately one-quarter of the Legacy Willis employees in the United States have a frozen accrued benefit under this plan.

Willis Towers Watson Plan – Substantially all U.S. employees are eligible to participate in this plan. Benefits are provided under a stable value pension plan design. The original stable value design came into effect on January 1, 2012. Plan participants prior to July 1, 2017 earn benefits without having to make employee contributions, and all newly eligible employees after that date are required to contribute 2% of pay on an after-tax basis to participate in the plan.

United Kingdom

Legacy Willis – This plan covers approximately one-quarter of the Legacy Willis employees in the United Kingdom. The plan is now closed to new entrants.

Legacy Towers Watson – Benefit accruals earned under the Legacy Watson Wyatt defined benefit plan (predominantly pension benefits) ceased on February 28, 2015, although benefits earned prior to January 1, 2008 retain a link to salary until the employee leaves the Company. Benefit accruals earned under the legacy Towers Perrin defined benefit plan (predominantly lump sum benefits) were frozen on March 31, 2008.

Legacy Miller – The plan provides retirement benefits based on members’ salaries at the point at which they ceased to accrue benefits under the scheme.

Other

Canada (Legacy Willis and Legacy Towers Watson) – Participants accrue qualified and non-qualified benefits based on a career-average benefit formula. Additionally, participants can choose to make voluntary contributions to purchase enhancements to their pension.

France (Legacy Gras Savoye) – The mandatory retirement indemnity plan is a termination benefit which provides lump sum benefits at retirement. There is no vesting before the retirement date, and the benefit formula is determined through the collective bargaining agreement and the labor code. All employees with permanent employment contracts are eligible.

Germany (Legacy Willis and Legacy Towers Watson) – The defined benefit plans are closed to new entrants and include certain legacy employee populations hired before 2011. These benefits are primarily account-based, with some long-service participants continuing to accrue benefits according to grandfathered final-average-pay formulas.

Ireland (Legacy Willis) – The defined benefit plans provided pension benefits for approximately one-third of legacy Willis employees in Ireland and were closed to new entrants. Benefit accruals ceased effective from December 31, 2019; however accrued benefits for active employees are indexed to salary increases (to a maximum annual salary of €150,000) until the member leaves the Company. A future service retirement provision is being provided on a defined contribution basis.

Ireland (Legacy Towers Watson) – Benefit accruals earned under the scheme’s defined benefit plan ceased on May 1, 2015. Benefits earned prior to this date retain a link to salary until the employee leaves the Company.

Post-retirement Welfare Plan

We provide certain healthcare and life insurance benefits for retired participants. The principal plan disclosed herein covers participants in the U.S. who have met certain eligibility requirements. This post-retirement benefit plan was primarily unfunded, with the remaining assets being paid out during the year ended December 31, 2019. Retiree medical benefits provided under our U.S. post-retirement benefit plan were closed to new hires effective January 1, 2011. Life insurance benefits under the plan were frozen with respect to service, eligibility and amounts as of January 1, 2012 for active participants.

Amounts Recognized in our Consolidated Financial Statements

The following schedules provide information concerning the defined benefit pension plans and PRW plan as of and for the years ended December 31, 2020 and 2019:

	2020												2019
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Change in Benefit Obligation
Benefit obligation, beginning of year	$	4,768		$	4,259		$	842		$	90		$	4,187		$	3,666		$	728		$	87
Service cost		72			15			21			1			65			14			20			1
Interest cost		131			73			15			2			157			93			18			3
Employee contributions		15			—			—			3			15			—			—			6
Actuarial losses		509			494			65			5			535			472			88			5
Settlements		(10	)		(27	)		(4	)		—			(6	)		(8	)		(3	)		—
Benefits paid		(194	)		(146	)		(32	)		(10	)		(185	)		(140	)		(26	)		(12	)
Plan amendments		—			9			—			—			—			—			—			—
Business disposal		—			—			(1	)		—			—			—			—			—
Transfers in		—			—			—			—			—			—			2			—
Other		—			—			1			—			—			—			—			—
Foreign currency changes		—			166			48			—			—			162			15			—
Benefit obligation, end of year	$	5,291		$	4,843		$	955		$	91		$	4,768		$	4,259		$	842		$	90
Change in Plan Assets
Fair value of plan assets, beginning of year	$	3,873		$	5,086		$	588		$	—		$	3,403		$	4,402		$	486		$	1
Actual return on plan assets		602			590			64			—			557			561			85			—
Employer contributions		71			66			35			7			89			77			31			5
Employee contributions		15			—			—			3			15			—			—			6
Settlements		(10	)		(27	)		(4	)		—			(6	)		(8	)		(3	)		—
Benefits paid		(194	)		(146	)		(32	)		(10	)		(185	)		(140	)		(26	)		(12	)
Transfers in		—			—			—			—			—			—			2			—
Other		—			—			1			—			—			—			—			—
Foreign currency adjustment		—			198			32			—			—			194			13			—
Fair value of plan assets, end of year	$	4,357		$	5,767		$	684		$	—		$	3,873		$	5,086		$	588		$	—
Funded status at end of year	$	(934	)	$	924		$	(271	)	$	(91	)	$	(895	)	$	827		$	(254	)	$	(90	)
Accumulated Benefit Obligation	$	5,291		$	4,841		$	918		$	91		$	4,768		$	4,259		$	810		$	90
Components on the Consolidated Balance Sheet
Pension benefits assets	$	—		$	932		$	28		$	—		$	—		$	835		$	22		$	—
Current liability for pension benefits	$	(31	)	$	(1	)	$	(5	)	$	(6	)	$	(33	)	$	(1	)	$	(6	)	$	(6	)
Non-current liability for pension benefits	$	(903	)	$	(7	)	$	(294	)	$	(85	)	$	(862	)	$	(7	)	$	(270	)	$	(84	)
	$	(934	)	$	924		$	(271	)	$	(91	)	$	(895	)	$	827		$	(254	)	$	(90	)

For both the years ended December 31, 2020 and 2019, bond yields continued to decline, which drove a decrease in the discount rates. This reduction, coupled with unfavorable foreign exchange effects for the U.K. and Other plans, was the most significant driver of the increase in benefit obligations for the plans. Additionally in 2019, the actuarial loss in the PRW plan driven by the discount rate reduction was partially offset by gains due to fewer retirees enrolling in medical coverage than had been assumed.

Amounts recognized in accumulated other comprehensive loss as of December 31, 2020 and 2019 consist of:

	2020										2019
	U.S.		U.K.			Other		PRW			U.S.		U.K.			Other		PRW
Net actuarial loss	$	1,143	$	1,304		$	169	$	24		$	982	$	1,133		$	128	$	20
Net prior service gain		—		(37	)		—		(23	)		—		(61	)		—		(27	)
Accumulated other comprehensive loss/(income)	$	1,143	$	1,267		$	169	$	1		$	982	$	1,072		$	128	$	(7	)

The following table presents the projected benefit obligation and fair value of plan assets for our plans that have a projected benefit obligation in excess of plan assets as of December 31, 2020 and 2019:

	2020						2019
	U.S.		U.K.		Other		U.S.		U.K.		Other
Projected benefit obligation at end of year	$	5,291	$	8	$	891	$	4,768	$	7	$	784
Fair value of plan assets at end of year	$	4,357	$	—	$	593	$	3,873	$	—	$	509

The following table presents the projected benefit obligation, accumulated benefit obligation and fair value of plan assets for our plans that have an accumulated benefit obligation in excess of plan assets as of December 31, 2020 and 2019.

	2020						2019
	U.S.		U.K.		Other		U.S.		U.K.		Other
Projected benefit obligation at end of year	$	5,291	$	8	$	477	$	4,768	$	7	$	784
Accumulated benefit obligation at end of year	$	5,291	$	8	$	457	$	4,768	$	7	$	752
Fair value of plan assets at end of year	$	4,357	$	—	$	193	$	3,873	$	—	$	509

The components of the net periodic benefit income and other amounts recognized in other comprehensive (income)/loss for the years ended December 31, 2020, 2019 and 2018 for the defined benefit pension and PRW plans are as follows:

	2020												2019												2018
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Components of net periodic benefit (income)/cost:
Service cost	$	72		$	15		$	21		$	1		$	65		$	14		$	20		$	1		$	66		$	18		$	21		$	1
Interest cost		131			73			15			2			157			93			18			3			140			95			18			4
Expected return on plan assets		(291	)		(247	)		(34	)		—			(254	)		(246	)		(29	)		—			(273	)		(298	)		(31	)		—
Amortization of unrecognized prior service credit		—			(17	)		—			(4	)		—			(16	)		—			(4	)		—			(19	)		—			—
Amortization of unrecognized actuarial loss		35			23			3			1			19			21			2			1			11			45			2			—
Settlement		2			3			1			—			—			—			1			—			1			41			2			—
Curtailment gain		—			—			—			—			—			—			—			—			—			—			(16	)		—
Net periodic benefit (income)/cost	$	(51	)	$	(150	)	$	6		$	—		$	(13	)	$	(134	)	$	12		$	1		$	(55	)	$	(118	)	$	(4	)	$	5
Other changes in plan assets and benefit obligations recognized in other comprehensive loss/(income):
Net actuarial loss/(gain)	$	198		$	151		$	35		$	5		$	232		$	157		$	32		$	5		$	117		$	191		$	13		$	(3	)
Amortization of unrecognized actuarial loss		(35	)		(23	)		(3	)		(1	)		(19	)		(21	)		(2	)		(1	)		(11	)		(45	)		(2	)		—
Prior service cost/(credit)		—			9			—			—			—			—			—			—			—			40			—			(31	)
Amortization of unrecognized prior service credit		—			17			—			4			—			16			—			4			—			19			—			—
Settlement		(2	)		(3	)		(1	)		—			—			—			(1	)		—			(1	)		(41	)		(2	)		—
Curtailment gain		—			—			—			—			—			—			—			—			—			—			16			—
Total recognized in other comprehensive loss/(income)		161			151			31			8			213			152			29			8			105			164			25			(34	)
Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income)	$	110		$	1		$	37		$	8		$	200		$	18		$	41		$	9		$	50		$	46		$	21		$	(29	)

During the year ended December 31, 2018, the Company terminated its Netherlands-based defined benefit plan, resulting in the recognition of a non-cash curtailment gain of $16 million.

During the year ended December 31, 2018, as a result of past changes in U.K. legislation and the low interest rate environment, the amount of transfer payments from the Legacy Willis U.K. pension plan exceeded the plan’s service and interest costs. This triggered settlement accounting which required immediate recognition of a portion of the obligations associated with the plan transfers. Consequently, the Company recognized a non-cash expense of $40 million for the year ended December 31, 2018.

Assumptions Used in the Valuations of the Defined Benefit Pension Plans and PRW Plan

The determination of the Company’s obligations and annual expense under the plans is based on a number of assumptions that, given the longevity of the plans, are long-term in focus. A change in one or a combination of these assumptions could have a material impact on our projected benefit obligation. However, certain of these changes, such as changes in the discount rate and actuarial assumptions, are not recognized immediately in net income, but are instead recorded in other comprehensive income. The accumulated gains and losses not yet recognized in net income are amortized into net income as a component of the net periodic benefit cost/(income) generally based on the average working life expectancy of each of the plan’s active participants to the extent that the net gains or losses as of the beginning of the year exceed 10% of the greater of the market-related value of plan assets or the projected benefit obligation. The average remaining service period of participants for the PRW plan is approximately 8.7 years.

The Company considers several factors prior to the start of each fiscal year when determining the appropriate annual assumptions, including economic forecasts, relevant benchmarks, historical trends, portfolio composition and peer company comparisons. These assumptions, used to determine our pension liabilities and pension expense, are reviewed annually by senior management and changed when appropriate. A discount rate will be changed annually if underlying rates have moved, whereas an expected long-term return on assets will be changed less frequently as longer-term trends in asset returns emerge or long-term target asset allocations are revised. To calculate the discount rate, we use the granular approach to determining service and interest costs. The expected rate of return assumptions for all plans are supported by an analysis of the weighted-average yield expected to be achieved based upon the anticipated makeup of the plans’ investments. Other material assumptions include rates of participant mortality, and the expected long-term rate of compensation and pension increases.

The following assumptions were used in the valuations of Willis Towers Watson’s defined benefit pension plans and PRW plan. The assumptions presented for the U.S. plans represent the weighted-average of rates for all U.S. plans. The assumptions presented for the U.K. plans represent the weighted-average of rates for the U.K. plans. The assumptions presented for the Other plans represent the weighted-average of rates for the Canada, France, Germany and Ireland plans.

The assumptions used to determine net periodic benefit cost for the fiscal years ended December 31, 2020, 2019 and 2018 were as follows:

	Years ended December 31,
	2020												2019												2018
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Discount rate - PBO		3.3	%		2.0	%		2.1	%		3.2	%		4.2	%		2.8	%		2.8	%		4.2	%		3.6	%		2.6	%		2.6	%		3.5	%
Discount rate - service cost		3.4	%		2.1	%		2.5	%		3.3	%		4.3	%		2.9	%		3.0	%		4.2	%		3.5	%		2.7	%		2.9	%		3.5	%
Discount rate - interest cost on service cost		2.8	%		1.9	%		2.4	%		2.8	%		3.8	%		2.8	%		2.9	%		3.9	%		3.1	%		2.5	%		2.7	%		3.2	%
Discount rate - interest cost on PBO		2.8	%		1.8	%		1.9	%		2.8	%		3.9	%		2.6	%		2.5	%		3.9	%		3.2	%		2.3	%		2.3	%		3.1	%
Expected long-term rate of return on assets		7.7	%		5.0	%		5.9	%	N/A				7.6	%		5.6	%		6.0	%		2.0	%		7.6	%		6.2	%		5.7	%		2.0	%
Rate of increase in compensation levels		4.3	%		3.0	%		2.3	%	N/A				4.3	%		3.0	%		2.3	%	N/A				4.3	%		3.0	%		2.3	%	N/A
Healthcare cost trend
Initial rate											6.5	%											6.0	%											6.5	%
Ultimate rate											5.0	%											5.0	%											5.0	%
Year reaching ultimate rate										2027												2022												2022

The following tables present the assumptions used in the valuation to determine the projected benefit obligation for the fiscal years ended December 31, 2020 and 2019:

	December 31, 2020												December 31, 2019
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Discount rate		2.5	%		1.5	%		1.7	%		2.4	%		3.3	%		2.0	%		2.1	%		3.2	%
Rate of increase in compensation levels		4.3	%		3.0	%		2.3	%	N/A				4.3	%		3.0	%		2.3	%	N/A

The expected return on plan assets was determined on the basis of the weighted-average of the expected future returns of the various asset classes, using the target allocations shown below. The Company’s pension plan asset target allocations as of December 31, 2020 were as follows:

	U.S.						U.K.									Canada			Germany			Ireland
Asset Category	Willis			Willis Towers Watson			Willis			Towers Watson			Miller			Towers Watson			Towers Watson			Willis			Towers Watson
Equity securities		30	%		23	%		—	%		1	%		19	%		40	%		36	%		29	%		40	%
Debt securities		33	%		33	%		30	%		24	%		21	%		50	%		57	%		29	%		30	%
Real estate		11	%		6	%		—	%		2	%		—	%		5	%		—	%		3	%		—	%
Other		26	%		38	%		70	%		73	%		60	%		5	%		7	%		39	%		30	%
Total		100	%		100	%		100	%		100	%		100	%		100	%		100	%		100	%		100	%

The Willis plan in Germany is invested in insurance contracts. Consequently, the asset allocations of the plans are managed by the respective insurer. The Gras Savoye plan in France is unfunded.

Our investment strategy is designed to generate returns that will reduce the interest rate risk inherent in each of the plan’s benefit obligations and enable the plans to meet their future obligations. The precise amount for which these obligations will be settled depends on future events, including the life expectancy of the plan participants and salary inflation. The obligations are estimated using actuarial assumptions based on the current economic environment.

Each pension plan seeks to achieve total returns sufficient to meet expected future obligations when considered in conjunction with expected future contributions and prudent levels of investment risk and diversification. Each plan’s targeted asset allocation is generally determined through a plan-specific asset-liability modeling study. These comprehensive studies provide an evaluation of the projected status of asset and benefit obligation measures for each plan under a range of both positive and negative factors. The studies include a number of different asset mixes, spanning a range of diversification and potential equity exposures.

In evaluating the strategic asset allocation choices, an emphasis is placed on the long-term characteristics of each individual asset class, such as expected return, volatility of returns and correlations with other asset classes within the portfolios. Consideration is also given to the proper long-term level of risk for each plan, the impact of the volatility and magnitude of plan contributions and costs, and the impact that certain actuarial techniques may have on the plan’s recognition of investment experience.

We monitor investment performance and portfolio characteristics on a quarterly basis to ensure that managers are meeting expectations with respect to their investment approach. There are also various restrictions and controls placed on managers, including prohibition from investing in our stock.

Fair Value of Plan Assets

The fair value hierarchy has three levels based on the reliability of the inputs used to determine fair value:

•

Level 1: refers to fair values determined based on quoted market prices in active markets for identical assets;

•

Level 2: refers to fair values estimated using observable market-based inputs or unobservable inputs that are corroborated by market data; and

•

Level 3: includes fair values estimated using unobservable inputs that are not corroborated by market data.

The fair values of our U.S. plan assets by asset category at December 31, 2020 and 2019 are as follows:

	December 31, 2020								December 31, 2019
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Asset category:
Cash ⁽ⁱ⁾	$	3	$	—	$	—	$	3	$	172	$	—	$	—	$	172
Short-term securities		—		106		—		106		—		99		—		99
Government bonds		—		—		—		—		4		—		—		4
Pooled / commingled funds		—		—		—		2,599		—		—		—		2,033
Private equity		—		—		—		415		—		—		—		487
Hedge funds		—		—		—		1,234		—		—		—		1,084
Total assets	$	3	$	106	$	—	$	4,357	$	176	$	99	$	—	$	3,879

(i)	At December 31, 2019, consists primarily of cash on deposit with the managers of the hedge funds due to the timing of purchases of units in the funds.

The fair values of our U.K. plan assets by asset category at December 31, 2020 and 2019 are as follows:

	December 31, 2020								December 31, 2019
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Asset category:
Cash	$	366	$	—	$	—	$	366	$	253	$	—	$	—	$	253
Government bonds		2,684		—		—		2,684		1,865		—		—		1,865
Corporate bonds		—		898		—		898		—		741		—		741
Other fixed income		—		458		—		458		—		350		—		350
Pooled / commingled funds		—		—		—		1,237		—		—		—		1,828
Mutual funds		—		—		—		59		—		—		—		34
Private equity		—		—		—		31		—		—		—		34
Derivatives		—		376		—		376		—		246		—		246
Real estate		—		—		—		159		—		—		—		161
Hedge funds		—		—		—		—		—		—		—		54
Insurance contracts		—		—		71		71		—		—		—		—
Total assets	$	3,050	$	1,732	$	71	$	6,339	$	2,118	$	1,337	$	—	$	5,566

Liability category:
Repurchase agreements		—		572		—		572		—		480		—		480
Net assets/(liabilities)	$	3,050	$	1,160	$	71	$	5,767	$	2,118	$	857	$	—	$	5,086

The fair values of our Other plan assets by asset category at December 31, 2020 and 2019 are as follows:

	December 31, 2020								December 31, 2019
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Asset category:
Cash	$	2	$	—	$	—	$	2	$	2	$	—	$	—	$	2
Pooled / commingled funds		—		—		—		635		—		—		—		444
Mutual funds		—		—		—		—		—		—		—		106
Hedge funds		—		—		—		39		—		—		—		34
Insurance contracts		—		—		8		8		—		—		2		2
Total assets	$	2	$	—	$	8	$	684	$	2	$	—	$	2	$	588

We evaluate the need to transfer between levels based upon the nature of the financial instrument and size of the transfer relative to the total net assets of the plans. There were no significant transfers between Levels 1, 2 or 3 in the fiscal years ended December 31, 2020 and 2019.

In accordance with Subtopic 820-10, Fair Value Measurement and Disclosures, certain investments that are measured at fair value using the net asset value per share practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in these tables are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of net assets.

Following is a description of the valuation methodologies used for investments at fair value:

Short-term securities: Valued at the net value of shares held by the Company at year end as reported by the sponsor of the funds.

Equity securities and mutual funds: Valued at the closing price reported on the active market on which the individual securities are traded. Exchange-traded mutual funds are included as Level 1 above.

Government bonds: Valued at the closing price reported in the active market in which the bond is traded.

Corporate bonds: Valued using pricing models maximizing the use of observable inputs for similar securities. This includes basing values on yields currently available on comparable securities of issuers with similar credit ratings.

Other fixed income: Foreign and municipal bonds are valued using pricing models maximizing the use of observable inputs for similar securities.

Pooled / commingled funds and mutual funds: Valued at the net value of shares held by the Company at year end as reported by the manager of the funds. These funds are not exchange-traded and are not reported by level in the tables above.

Derivative investments: Valued at the closing level of the relevant index or security and interest accrual through the valuation date.

Private equity funds, real estate funds, hedge funds: The fair values for these investments are estimated based on the net asset values derived from the latest audited financial statements or most recent capital account statements provided by the private equity fund’s investment manager or third-party administrator.

Insurance contracts: The fair values are determined using model-based techniques that include option-pricing models, discounted cash flow models and similar techniques.

Repurchase agreements: Valued as the repurchase obligation which includes an interest rate linked to the underlying fixed interest government bond portfolio. These agreements are short-term in nature (less than one year) and were entered into for the purpose of purchasing additional government bonds.

The following table reconciles the net plan investments to the total fair value of the plan assets:

	December 31,
	2020		2019
Net assets held in investments	$	10,808	$	9,553
Net receivable/(payable) for investments purchased		—		(7	)
Dividend and interest receivable		—		1
Fair value of plan assets	$	10,808	$	9,547

Level 3 investments

As a result of the inherent limitations related to the valuations of the Level 3 investments, due to the unobservable inputs of the underlying funds, the estimated fair values may differ significantly from the values that would have been used had a market for those investments existed.

The following table sets forth a summary of changes in the fair value of the plans’ Level 3 assets for the fiscal year ended December 31, 2020:

	Level 3 Roll Forward
Beginning balance at December 31, 2019	$	2
Purchases		64
Unrealized gains		7
Foreign exchange		6
Ending balance at December 31, 2020	$	79

Contributions and Benefit Payments

Funding is based on actuarially-determined contributions and is limited to amounts that are currently deductible for tax purposes. Since funding calculations are based on different measurements than those used for accounting purposes, pension contributions are not equal to net periodic pension costs.

The following table sets forth our projected pension contributions to our qualified plans for fiscal year 2020, as well as the pension contributions to our qualified plans in fiscal years 2020 and 2019:

	2021 (Projected)		2020 (Actual)		2019 (Actual)
U.S.	$	60	$	40	$	60
U.K.	$	47	$	65	$	76
Other	$	25	$	24	$	22

Expected benefit payments from our defined benefit pension plans to current plan participants, including the effects of their expected future service, as appropriate, are as follows:

	Benefit Payments
Fiscal Year	U.S.		U.K.		Other		PRW		Total
2021	$	248	$	128	$	32	$	10	$	418
2022		275		122		28		10		435
2023		265		131		29		10		435
2024		274		139		31		11		455
2025		277		143		32		11		463
Years 2026 – 2029		1,421		808		187		58		2,474
	$	2,760	$	1,471	$	339	$	110	$	4,680

Defined Contribution Plans

We have defined contribution plans covering eligible employees in many countries. The most significant plans are in the U.S. and U.K. and are described here.

We have a U.S. defined contribution plan (the ‘Plan’) covering all eligible employees of Willis Towers Watson. The Plan allows participants to make pre-tax and Roth after-tax contributions, and the Company provides a 100% match on the first 1% of employee contributions and a 50% match on the next 5% of employee contributions. Employees vest in the Company match upon 2 years of service. All investment assets of the plan are held in a trust account administered by independent trustees.

Our Legacy Towers Watson U.K. and Legacy Willis U.K. pension plans provide for a defined contribution component as part of a master trust. We make contributions to the plan, a portion of which represents matching contributions made by the participants up to a maximum rate.

We had defined contribution plan expense for the years ended December 31, 2020, 2019 and 2018 amounting to $160 million, $150 million and $150 million, respectively.

The entire disclosure for retirement benefits.

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Commitments And Contingencies Disclosure [Abstract]

Leases

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Leases

Note 13 — Leases

The following tables present amounts recorded on our consolidated balance sheets at December 31, 2020 and 2019, classified as either operating or finance leases. Operating leases are presented separately on our consolidated balance sheets. For the finance leases, the right-of-use (‘ROU’) assets are included in fixed assets, net, and the liabilities are classified within other current liabilities or other non-current liabilities.

	December 31, 2020						December 31, 2019
	Operating Leases		Finance Leases		Total Leases		Operating Leases		Finance Leases		Total Leases
Right-of-use assets	$	902	$	8	$	910	$	968	$	10	$	978
Current lease liabilities		152		3		155		164		3		167
Long-term lease liabilities		918		19		937		964		22		986

The following tables present amounts recorded on our consolidated statements of comprehensive income for the years ended December 31, 2020 and 2019:

	Years ended December 31,
	2020			2019
Finance lease cost:
Amortization of right-of-use assets	$	2		$	2
Interest on lease liabilities		3			3
Operating lease cost		181			191
Short-term lease cost		1			2
Variable lease cost		53			51
Sublease income		(21	)		(16	)
Total lease cost, net	$	219		$	233

The total lease cost is recognized in different locations in our consolidated statements of comprehensive income. Amortization of the finance lease ROU assets is included in depreciation, while the interest cost component of these finance leases is included in interest expense. All other costs are included in other operating expenses. The Company had rent expense for the year ended December 31, 2018 of $243 million, net of sublease income, related to operating leases classified within other operating expenses on our consolidated statement of comprehensive income.

Cash paid for amounts included in the measurement of lease liabilities for the years ended December 31, 2020 and 2019, as well as its location in the consolidated statements of cash flows, is as follows:

	Years ended December 31,
	2020		2019
Cash flows from operating activities:
Operating leases	$	190	$	205
Finance leases		3		3
Cash flows used in financing activities:
Finance leases		3		2
Total lease payments	$	196	$	210

Non-cash additions to our operating lease ROU assets were $70 million and $124 million during the years ended December 31, 2020 and 2019, respectively.

Our operating and finance leases have the following weighted-average terms and discount rates as of December 31, 2020 and 2019:

	December 31, 2020						December 31, 2019
	Operating Leases			Finance Leases			Operating Leases			Finance Leases
Weighted-average term (in years)		8.3			5.2			8.8			6.0
Weighted-average discount rate		3.4	%		12.9	%		3.6	%		12.9	%

The maturity of our lease liabilities on an undiscounted basis, including a reconciliation to the total lease liabilities reported on the consolidated balance sheet as of December 31, 2020, is as follows:

	Operating Leases			Finance Leases			Total Leases
2021	$	185		$	6		$	191
2022		172			6			178
2023		157			6			163
2024		138			6			144
2025		123			6			129
Thereafter		458			1			459
Total future lease payments		1,233			31			1,264
Interest		(163	)		(9	)		(172	)
Total lease liabilities	$	1,070		$	22		$	1,092

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies

Note 14 — Commitments and Contingencies

Guarantees

Guarantees issued by certain of Willis Towers Watson’s subsidiaries with respect to the senior notes and credit facilities are discussed in Note 10 — Debt.

Certain of Willis Towers Watson’s subsidiaries in the U.S. and the U.K. have given the landlords of some leased properties occupied by the Company guarantees with respect to the repayment of the lease obligations. The operating lease obligations subject to such guarantees amounted to $566 million and $536 million at December 31, 2020 and 2019, respectively. The capital lease obligations subject to such guarantees amounted to $5 million and $6 million at December 31, 2020 and 2019, respectively.

Acquisition liabilities

The Company has deferred and contingent consideration related to acquisition due to be paid until 2024 totaling $55 million at December 31, 2020. Total deferred and contingent consideration paid during the year ended December 31, 2020 was $12 million.

Other contractual obligations

For certain subsidiaries and associates, the Company has the right to purchase shares (a call option) from co-shareholders at various dates in the future. In addition, the co-shareholders of certain subsidiaries and associates have the right to sell their shares (a put option) to the Company at various dates in the future. Generally, the exercise price of such put options and call options is formula-based (using revenue and earnings) and is designed to reflect fair value. Based on current projections of profitability and exchange rates, and assuming the put options are exercised, the potential amount payable from these options is not expected to exceed $38 million.

Additionally, the Company has capital commitments with Trident V Parallel Fund, LP, an investment fund managed by Stone Point Capital, and Dowling Capital Partners I, LP. At December 31, 2020, the Company is obligated to make capital contributions of approximately $2 million, collectively, to these funds.

Indemnification Agreements

Willis Towers Watson has various agreements which provide that it may be obligated to indemnify the other party to the agreement with respect to certain matters. Generally, these indemnification provisions are included in contracts arising in the normal course of business and in connection with the purchase and sale of certain businesses. It is not possible to predict the maximum potential amount of future payments that may become due under these indemnification agreements because of the conditional nature of the Company’s obligations and the unique facts of each particular agreement. However, we do not believe that any potential liability that may arise from such indemnity provisions is probable or material.

Legal Proceedings

In the ordinary course of business, the Company is subject to various actual and potential claims, lawsuits and other proceedings. Some of the claims, lawsuits and other proceedings seek damages in amounts which could, if assessed, be significant. We expect the impact of claims or demands not described below to be immaterial to the Company’s consolidated financial statements. The Company also receives subpoenas in the ordinary course of business and, from time to time, receives requests for information in connection with governmental investigations.

Errors and omissions claims, lawsuits, and other proceedings arising in the ordinary course of business are covered in part by professional indemnity or other appropriate insurance. The terms of this insurance vary by policy year. Regarding self-insured risks, the Company has established provisions which are believed to be adequate in light of current information and legal advice, or, in certain cases, where a range of loss exists, the Company accrues the minimum amount in the range if no amount within the range is a better estimate than any other amount. The Company adjusts such provisions from time to time according to developments. See Note 15 — Supplementary Information for Certain Balance Sheet Accounts for the amounts accrued at December 31, 2020 and 2019 in the consolidated balance sheets.

On the basis of current information, the Company does not expect that the actual claims, lawsuits and other proceedings to which it is subject, or potential claims, lawsuits, and other proceedings relating to matters of which it is aware, will ultimately have a material adverse effect on its financial condition, results of operations or liquidity. Nonetheless, given the large or indeterminate amounts sought in certain of these actions, and the inherent unpredictability of litigation and disputes with insurance companies, it is possible that an adverse outcome or settlement in certain matters could, from time to time, have a material adverse effect on the Company’s results of operations or cash flows in particular quarterly or annual periods. In addition, given the early stages of some litigation or regulatory proceedings described below, it may not be possible to predict their outcomes or resolutions, and it is possible that any one or more of these events may have a material adverse effect on the Company.

The Company provides for contingent liabilities based on ASC 450, Contingencies, when it is determined that a liability, inclusive of defense costs, is probable and reasonably estimable. The contingent liabilities recorded are primarily developed actuarially. Litigation is subject to many factors which are difficult to predict so there can be no assurance that in the event of a material unfavorable result in one or more claims, we will not incur material costs.

Litigation Relating to the Proposed Combination with Aon plc

On May 11, 2020, a purported stockholder of the Company filed a complaint in the United States District Court for the Southern District of New York against the Company and the members of the Company’s board of directors, captioned Stein v. Willis Towers Watson Public Limited Company, et al., Case No. 1:20-cv-03656 (S.D.N.Y.), referred to as the ‘Stein Complaint.’ On May 14, 2020, a purported stockholder of the Company filed a putative class action in the United States District Court for the District of Delaware against the Company, the members of the Company’s board of directors, and Aon plc (‘Aon’), captioned Kent v. Willis Towers Watson Public Limited Company, et al., Case No. 1:20-cv-00641 (D. Del.), referred to as the ‘Kent Complaint.’ On May 19, 2020, a purported stockholder of the Company filed a putative class action in the United States District Court for the Southern District of New York against the Company and the members of the Company’s board of directors, captioned Carter v. Willis Towers Watson Public Limited Company, et al., Case No. 1:20-cv-03865 (S.D.N.Y.), referred to as the ‘Carter Complaint.’ On May 28, 2020, a purported stockholder of the Company filed a complaint in the United States District Court for the Southern District of California against the Company and the members of the Company’s board of directors, captioned Tang v. Willis Towers Watson Public Limited Company, et al., Case No. 3:20-cv-00986 (S.D. Cal.), referred to as the ‘Tang Complaint.’ On June 17, 2020, a purported stockholder of the Company filed a complaint in the United States District Court for the Southern District of California against the Company and the members of the Company’s board of directors, captioned Kuznik v. Willis Towers Watson Public Limited Company, et al., Case No. 3:20-cv-01097 (S.D. Cal.), referred to as the ‘Kuznik Complaint,’ and together with the Stein Complaint, the Kent Complaint, the Carter Complaint, and the Tang Complaint, referred to as the ‘Complaints.’

The Complaints assert claims against certain defendants under Section 14(a) of the Securities Exchange Act of 1934 (the ‘Exchange Act’) for allegedly false and misleading statements in the proxy statement; and against certain defendants under Section 20(a) of the Exchange Act for alleged ‘control person’ liability with respect to such allegedly false and misleading statements. The Stein Complaint, the Carter Complaint, and the Tang Complaint each seek, among other relief, an order enjoining the proposed combination with Aon unless and until corrective disclosures are made. The Kuznik Complaint and the Kent Complaint each seek, among other relief, an order enjoining the proposed combination with Aon and an order directing certain defendants to issue corrective disclosures. The Stein Complaint and the Carter Complaint also seek damages in an unspecified amount. The Company believes the allegations in the Complaints are without merit.

On August 4, 2020, certain plaintiffs voluntarily dismissed without prejudice the Kent Complaint, the Carter Complaint, and the Stein Complaint. On September 15, 2020, certain plaintiffs voluntarily dismissed without prejudice the Tang Complaint and the Kuznik Complaint.

Willis Towers Watson Merger-Related Securities Litigation

On November 21, 2017, a purported former stockholder of Legacy Towers Watson filed a putative class action complaint on behalf of a putative class consisting of all Legacy Towers Watson stockholders as of October 2, 2015 against the Company, Legacy Towers Watson, Legacy Willis, ValueAct Capital Management (‘ValueAct’), and certain current and former directors and officers of Legacy Towers Watson and Legacy Willis (John Haley, Dominic Casserley, and Jeffrey Ubben), in the United States District Court for the Eastern District of Virginia. The complaint asserted claims against certain defendants under Section 14(a) of the Securities Exchange Act of 1934 (the ‘Exchange Act’) for allegedly false and misleading statements in the proxy statement for the Merger; and against other defendants under Section 20(a) of the Exchange Act for alleged ‘control person’ liability with respect to such allegedly false and misleading statements. The complaint further contended that the allegedly false and misleading statements caused stockholders of Legacy Towers Watson to accept inadequate Merger consideration. The complaint sought damages in an unspecified amount. On February 20, 2018, the court appointed the Regents of the University of California (‘Regents’) as Lead Plaintiff and Bernstein Litowitz Berger & Grossman LLP (‘Bernstein’) as Lead Counsel for the putative class, consolidated all subsequently filed, removed, or transferred actions, and captioned the consolidated action ‘In re Willis Towers Watson plc Proxy Litigation,’ Master File No. 1:17-cv-1338-AJT-JFA (the ‘Federal Action’). On March 9, 2018, Lead Plaintiff filed an Amended Complaint. On April 13, 2018, the defendants filed motions to dismiss the Amended Complaint, and, on July 11, 2018, following briefing and argument, the court granted the motions and dismissed the Amended Complaint in its entirety. On July 30, 2018, Lead Plaintiff filed a notice of appeal from the court’s July 11, 2018 dismissal order to the United States Court of Appeals for the Fourth Circuit (the ‘Fourth Circuit’), and, on December 6, 2018, the parties completed briefing on the appeal. On May 8, 2019, the parties argued the appeal, and on August 30, 2019, the Fourth Circuit vacated the dismissal order and remanded the case to the Eastern District of Virginia for further proceedings consistent with its decision. On September 13, 2019, the defendants filed a petition for rehearing by the Fourth Circuit en banc, which the Fourth Circuit denied on September 27, 2019. On November 8, 2019, the defendants filed renewed motions to dismiss in the Eastern District of Virginia based upon certain arguments that were advanced in their original motions to dismiss, but undecided by both the district court and the Fourth Circuit. On December 18, 2019, the parties completed briefing on the defendants’ renewed motions, and, on December 20, 2019, the court heard argument on the motions. On January 31, 2020, the court denied the motions. On June 12, 2020, Lead Plaintiff filed a motion for class certification, in connection with which it indicated that it is seeking class-wide damages of approximately $456 million. On September 4, 2020, the court granted Lead Plaintiff’s motion for class certification, certified the putative class, and appointed Lead Plaintiff as the Class Representative for the certified class. On October 16, 2020, the defendants filed motions for summary judgment and to exclude Lead Plaintiff’s proposed experts. Also on October 16, 2020, Lead Plaintiff filed a motion to exclude certain of the defendants’ proposed experts.

On February 27, 2018 and March 8, 2018, two additional purported former stockholders of Legacy Towers Watson, City of Fort Myers General Employees’ Pension Fund (‘Fort Myers’) and Alaska Laborers-Employers Retirement Trust (‘Alaska’), filed putative class action complaints on behalf of a putative class of Legacy Towers Watson stockholders against the former members of the Legacy Towers Watson board of directors, Legacy Towers Watson, Legacy Willis and ValueAct, in the Delaware Court of Chancery, captioned City of Fort Myers General Employees’ Pension Fund v. Towers Watson & Co., et al., C.A. No. 2018-0132, and Alaska Laborers-Employers Retirement Trust v. Victor F. Ganzi, et al., C.A. No. 2018-0155, respectively. Based on similar allegations as the Eastern District of Virginia action described above, the complaints assert claims against the former directors of Legacy Towers Watson for breach of fiduciary duty and against Legacy Willis and ValueAct for aiding and abetting breach of fiduciary duty.

On March 9, 2018, Regents filed a putative class action complaint on behalf of a putative class of Legacy Towers Watson stockholders against the Company, Legacy Willis, ValueAct, and Messrs. Haley, Casserley, and Ubben, in the Delaware Court of Chancery, captioned The Regents of the University of California v. John J. Haley, et al., C.A. No. 2018-0166. Based on similar allegations as the Eastern District of Virginia action described above, the complaint asserts claims against Mr. Haley for breach of fiduciary duty and against all other defendants for aiding and abetting breach of fiduciary duty. Also on March 9, 2018, Regents filed a motion for consolidation of all pending and subsequently filed Delaware Court of Chancery actions, and for appointment as Lead Plaintiff and for the appointment of Bernstein as Lead Counsel for the putative class. On March 29, 2018, Fort Myers and Alaska responded to Regents’ motion and cross-moved for appointment as Co-Lead Plaintiffs and for the appointment of their counsel, Grant & Eisenhofer P.A. and Kessler Topaz Meltzer & Check, LLP as Co-Lead Counsel. On April 2, 2018, the court consolidated the Delaware Court of Chancery actions and all related actions subsequently filed in or transferred to the Delaware Court of Chancery. On June 5, 2018, the court denied Regents’ motion for appointment of Lead Plaintiff and Lead Counsel and granted Fort Myers’ and Alaska’s cross-motion. On June 20, 2018, Fort Myers and Alaska designated the complaint previously filed by Alaska (the ‘Alaska Complaint’) as the operative complaint in the consolidated action (the ‘Delaware Action’). On September 14, 2018, the defendants filed motions to dismiss the Alaska Complaint. On October 31, 2018, Fort Myers and Alaska filed an amended complaint, which, based on similar allegations, asserts claims against the former directors of legacy Towers Watson for breach of fiduciary duty and

against ValueAct and Mr. Ubben for aiding and abetting breach of fiduciary duty. On January 11, 2019, the defendants filed motions to dismiss the amended complaint, and on March 29, 2019, the parties completed briefing on the motions. The court heard argument on the motions on April 11, 2019 and, on July 25, 2019, dismissed the amended complaint in its entirety. On August 22, 2019, Fort Myers and Alaska filed a notice of appeal (only with respect to Messrs. Haley and Ubben and ValueAct) from the court’s July 25, 2019 dismissal order to the Supreme Court of the State of Delaware. On November 22, 2019, the parties completed briefing on the appeal, which was submitted on April 22, 2020 for decision in lieu of argument. On June 30, 2020, the Supreme Court of the State of Delaware reversed and remanded the case to the Court of Chancery for further proceedings consistent with its decision. On July 27, 2020, Fort Myers and Alaska filed a motion for class certification, which is currently pending. On September 14, 2020, Mr. Haley answered the amended complaint.

On October 18, 2018, three additional purported former stockholders of Legacy Towers Watson, Naya Master Fund LP, Naya 174 Fund Limited and Naya Lincoln Park Master Fund Limited (collectively, ‘Naya’), filed a complaint against the Company, Legacy Towers Watson, Legacy Willis and John Haley, in the Supreme Court of the State of New York, County of New York, captioned Naya Master Fund LP, et al. v. John J. Haley, et al., Index No. 654968/2018. Based on similar allegations as the Eastern District of Virginia and Delaware actions described above, the complaint asserts claims for common law fraud and negligent misrepresentation. On December 18, 2018, the defendants filed a motion to dismiss the complaint, and on March 21, 2019, the parties completed briefing on the motion. On April 23, 2019, the parties filed a Stipulation and Proposed Order Voluntarily Discontinuing Action providing for the dismissal of the action with prejudice, which the court entered on April 29, 2019.

On or about November 19, 2020, the parties to the Federal Action and the Delaware Action reached an agreement in principle to resolve the Federal Action and the Delaware Action for $75 million and $15 million, respectively. The Company agreed to the settlement and the payment of the settlement amounts to eliminate the distraction, burden, expense and uncertainty of further litigation. Further, in reaching the settlement, the parties understood and agreed that there is no admission of liability or wrongdoing by the Company or any of the other defendants in either the Federal Action or the Delaware Action. The Company and the other defendants expressly deny any liability or wrongdoing with respect to the matters alleged in the Federal Action and the Delaware Action.

On January 15, 2021, the parties to the Federal Action and the Delaware Action signed formal stipulations of settlement, which memorialized the terms of the agreement in principle, and which the plaintiffs in the Federal Action and the Delaware Action then filed with each of the respective courts. Also on January 15, 2021, the plaintiff in the Federal Action filed a motion to preliminarily approve the settlement. On January 21, 2021, the court in the Federal Action preliminarily approved the settlement, approved the form of notice to be disseminated to class members, and scheduled a final fairness hearing on the settlement for May 21, 2021. On January 25, 2021, the court in the Delaware Action approved the form of notice to be disseminated to class members and scheduled a final fairness hearing on the settlement for May 25, 2021. The settlement remains subject to notice to class members in the two actions. The settlement is contingent upon final approval by the courts in both the Federal Action and the Delaware Action. The Company will make the $90 million aggregate settlement payment in February 2021, but it will not be distributed to class members unless and until the settlement is finally approved by the courts in both the Federal Action and the Delaware Action and not subject to any further appeal.

During the three and twelve months ended December 31, 2020, the Company recognized $50 million and $65 million respectively, of expense, net of $25 million of insurance and other recoveries. Additional insurance recoveries are possible.

Stanford Financial Group

The Company was named as a defendant in 15 similar lawsuits relating to the collapse of The Stanford Financial Group (‘Stanford’), for which Willis of Colorado, Inc. acted as broker of record on certain lines of insurance. The complaints in these actions generally alleged that the defendants actively and materially aided Stanford’s alleged fraud by providing Stanford with certain letters regarding coverage that they knew would be used to help retain or attract actual or prospective Stanford client investors. The complaints further alleged that these letters, which contained statements about Stanford and the insurance policies that the defendants placed for Stanford, contained untruths and omitted material facts and were drafted in this manner to help Stanford promote and sell its allegedly fraudulent certificates of deposit. The plaintiffs in these actions sought overlapping damages, representing either the entirety or a portion of the approximately $4.6 billion in total alleged collective losses incurred by investors in Stanford certificates of deposit, notwithstanding the fact that Legacy Willis acted as broker of record for only a portion of time that Stanford issued certificates of deposit.

On March 31, 2016, the Company entered into a settlement in principle, as reflected in a Settlement Term Sheet, relating to the Stanford litigation. The Company agreed to the Settlement Term Sheet to eliminate the distraction, burden, expense and uncertainty of further litigation. In particular, the settlement and the related bar orders described below would enable the Company to conduct itself with the bar orders’ protection from the continued overhang of matters alleged to have occurred over a decade ago. Further, the

Settlement Term Sheet provided that the parties understood and agreed that there was no admission of liability or wrongdoing by the Company. The Company expressly denies any liability or wrongdoing with respect to the matters alleged in the Stanford litigation.

On or about August 31, 2016, the parties to the settlement signed a formal Settlement Agreement memorializing the terms of the settlement as originally set forth in the Settlement Term Sheet. The parties to the Settlement Agreement are Ralph S. Janvey (in his capacity as the Court-appointed receiver (the ‘Receiver’) for The Stanford Financial Group and its affiliated entities in receivership (collectively, ‘Stanford’)), the Official Stanford Investors Committee, Samuel Troice, Martha Diaz, Paula Gilly-Flores, Punga Punga Financial, Ltd., Manuel Canabal, Daniel Gomez Ferreiro and Promotora Villa Marina, C.A. (collectively, ‘Plaintiffs’), on the one hand, and Willis Towers Watson Public Limited Company (formerly Willis Group Holdings Public Limited Company), Willis Limited, Willis North America Inc., Willis of Colorado, Inc. and the Willis associate referenced above (collectively, ‘Defendants’), on the other hand. Under the terms of the Settlement Agreement, the parties agreed to settle and dismiss all current or future claims arising from or related to Stanford in exchange for a one-time cash payment to the Receiver by the Company of $120 million to be distributed to all Stanford investors who have claims recognized by the Receiver pursuant to the distribution plan in place at the time the payment was made.

The Settlement Agreement also provided the parties’ agreement to seek the Court’s entry of bar orders prohibiting any continued or future litigation against the Defendants and their related parties of claims relating to Stanford, whether asserted or not. The terms of the bar orders therefore would prohibit all Stanford-related litigation, and not just the filed actions, but including any pending matters and any actions that may be brought in the future. Final Court approval of these bar orders was a condition of the settlement.

On September 7, 2016, Plaintiffs filed with the Court a motion to approve the settlement. On October 19, 2016, the Court preliminarily approved the settlement. Several of the plaintiffs in the other actions above objected to the settlement, and a hearing to consider final approval of the settlement was held on January 20, 2017, after which the Court reserved decision. On August 23, 2017, the Court approved the settlement, including the bar orders. Several of the objectors appealed the settlement approval and bar orders to the Fifth Circuit. Oral argument on the appeals was heard on December 3, 2018, and, on July 22, 2019, the Fifth Circuit affirmed the approval of the settlement, including the bar orders. On August 5, 2019, certain of the plaintiff-appellants filed a petition for rehearing by the Fifth Circuit en banc (the ‘Petition’). On August 19, 2019, the Fifth Circuit requested a response to the Petition. On August 29, 2019, the Receiver filed a response to the Petition. On December 19, 2019, the Fifth Circuit granted the Petition (treating it as a petition for panel rehearing), withdrew its July 22, 2019 opinion, and substituted a new opinion that also affirmed the approval of the settlement, including the bar orders. On January 2, 2020, certain of the plaintiff-appellants filed another petition for rehearing by the Fifth Circuit en banc (the ‘Second Petition’), in which the other plaintiff-appellants joined. On January 21, 2020, the Fifth Circuit denied the Second Petition. On June 19, 2020, the plaintiff-appellants filed petitions for writ of certiorari with the United States Supreme Court. On September 10, 2020, the Supreme Court requested responses to the petitions for writ of certiorari, which were filed on November 6, 2020. On December 14, 2020, the Supreme Court denied the petitions. On January 12, 2021, the Company made the $120 million settlement payment. The terms of the bar orders that are a part of the settlement prohibit any claims or litigation related to this matter from being maintained or brought against the Company.

Aviation Broking Competition Investigations

In October 2017, the European Commission (‘Commission’) disclosed to us that it has initiated civil investigation proceedings in respect of a suspected infringement of E.U. competition rules involving several broking firms, including our principal U.K. broking subsidiary and one of its parent entities. In particular, the Commission has stated that the civil proceedings concern the exchange of commercially sensitive information between competitors in relation to aviation and aerospace insurance and reinsurance broking products and services in the European Economic Area, as well as possible coordination between competitors. In November 2020, the Commission advised us that it has decided to close the proceedings against us without taking further action.

Since 2017, we have become aware that other countries are conducting their own investigations of the same or similar alleged conduct, including, without limitation, Brazil. In January 2019, the Brazil Conselho Administrativo de Defesa Economica (‘CADE’) launched an administrative proceeding to investigate alleged sharing of competitive and commercially sensitive information in the insurance and reinsurance brokerage industry for aviation and aerospace and related ancillary services. The CADE identified 11 entities under investigation, including Willis Group Limited, one of our U.K. subsidiaries.

Given the status of the above-noted investigations, the Company is currently unable to assess the terms on which they will be resolved, or how any other regulatory matter or civil claims emanating from the conduct being investigated will be resolved, and thus is unable to provide an estimate of the reasonably possible loss or range of loss.

Supplementary Information for Certain Balance Sheet Accounts

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Supplementary Information for Certain Balance Sheet Accounts

Note 15 — Supplementary Information for Certain Balance Sheet Accounts

Additional details of specific balance sheet accounts are detailed below.

Prepaid and other current assets consist of the following:

	December 31, 2020		December 31, 2019
Prepayments and accrued income	$	124	$	145
Deferred contract costs		108		101
Derivatives and investments		42		49
Deferred compensation plan assets		14		18
Retention incentives		3		11
Corporate income and other taxes		83		56
Insurance and other recovery receivables		25		—
Restricted cash		7		8
Acquired renewal commissions receivable		16		25
Other current assets		75		112
Total prepaid and other current assets	$	497	$	525

Other non-current assets consist of the following:

	December 31, 2020		December 31, 2019
Prepayments and accrued income	$	13	$	12
Deferred contract costs		98		76
Deferred compensation plan assets		117		150
Deferred tax assets		95		72
Accounts receivable, net		34		30
Acquired renewal commissions receivable		84		125
Long-term note receivable		71		—
Other investments		24		23
Insurance recovery receivables		117		119
Non-current contract assets		329		105
Other non-current assets		114		123
Total other non-current assets	$	1,096	$	835

Deferred revenue and accrued expenses consist of the following:

	December 31, 2020		December 31, 2019
Accounts payable, accrued liabilities and deferred income	$	862	$	856
Accrued discretionary and incentive compensation		851		727
Litigation settlement		210		—
Accrued vacation		161		137
Other employee-related liabilities		77		64
Total deferred revenue and accrued expenses	$	2,161	$	1,784

Other current liabilities consist of the following:

	December 31, 2020		December 31, 2019
Dividends payable	$	103	$	100
Income and other taxes payable		102		138
Interest payable		68		65
Deferred compensation plan liabilities		57		14
Contingent and deferred consideration on acquisitions		39		12
Payroll-related liabilities		268		216
Derivatives		5		3
Third-party commissions		173		179
Other current liabilities		73		75
Total other current liabilities	$	888	$	802

Provision for liabilities consists of the following:

	December 31, 2020		December 31, 2019
Claims, lawsuits and other proceedings	$	325	$	456
Other provisions		82		81
Total provision for liabilities	$	407	$	537

Other non-current liabilities consist of the following:

	December 31, 2020		December 31, 2019
Deferred compensation plan liability	$	117	$	150
Contingent and deferred consideration on acquisitions		16		26
Liabilities for uncertain tax positions		49		48
Derivatives		2		—
Finance leases		19		22
Other non-current liabilities		109		89
Total other non-current liabilities	$	312	$	335

Other Income, Net

12 Months Ended

Dec. 31, 2020

Other Income And Expenses [Abstract]

Other Income, Net

Note 16 — Other Income, Net

Other income, net consists of the following:

	Years ended December 31,
	2020		2019			2018
Gain/(loss) on disposal of operations	$	81	$	(2	)	$	(9	)
Net periodic pension and postretirement benefit credits		304		234			280
Interest in earnings of associates and other investments		6		21			3
Foreign exchange gain/(loss)		6		(26	)		(24	)
Other		2		—			—
Other income, net	$	399	$	227		$	250

Accumulated Other Comprehensive Loss

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Accumulated Other Comprehensive Loss

Note 17 — Accumulated Other Comprehensive Loss

The components of other comprehensive (loss)/income are as follows:

	December 31, 2020								December 31, 2019									December 31, 2018
	Before tax amount			Tax		Net of tax amount			Before tax amount			Tax			Net of tax amount			Before tax amount			Tax			Net of tax amount
Other comprehensive income/(loss):
Foreign currency translation	$	139		$	—	$	139		$	78		$	—		$	78		$	(251	)	$	—		$	(251	)
Defined pension and post-retirement benefits		(342	)		76		(266	)		(412	)		83			(329	)		(258	)		59			(199	)
Derivative instruments		(5	)		1		(4	)		23			(2	)		21			5			(3	)		2
Other comprehensive loss		(208	)		77		(131	)		(311	)		81			(230	)		(504	)		56			(448	)
Less: Other comprehensive income attributable to non-controlling interests		(1	)		—		(1	)		—			—			—			—			—			—
Other comprehensive loss attributable to Willis Towers Watson	$	(209	)	$	77	$	(132	)	$	(311	)	$	81		$	(230	)	$	(504	)	$	56		$	(448	)

Changes in the components of accumulated other comprehensive loss, net of tax, are included in the following table. This table excludes amounts attributable to non-controlling interests, which are not material for further disclosure.

	Foreign currency translation ⁽ⁱ⁾			Derivative instruments ⁽ⁱ⁾			Defined pension and post- retirement benefit costs ⁽ⁱⁱ⁾			Total
Balance, January 1, 2018	$	(365	)	$	(10	)	$	(1,138	)	$	(1,513	)
Other comprehensive loss before reclassifications		(251	)		(22	)		(241	)		(514	)
Loss reclassified from accumulated other comprehensive loss (net of income tax benefit of $17)		—			24			42			66
Net other comprehensive (loss)/income		(251	)		2			(199	)		(448	)
Balance, December 31, 2018	$	(616	)	$	(8	)	$	(1,337	)	$	(1,961	)
Other comprehensive income/(loss) before reclassifications		78			12			(343	)		(253	)
Loss reclassified from accumulated other comprehensive loss (net of income tax benefit of $9)		—			9			14			23
Net other comprehensive income/(loss)		78			21			(329	)		(230	)
Reclassification of tax effects per ASU 2018-02 ⁽ⁱⁱⁱ⁾		—			—			(36	)		(36	)
Balance, December 31, 2019	$	(538	)	$	13		$	(1,702	)	$	(2,227	)
Other comprehensive income/(loss) before reclassifications		138			(12	)		(298	)		(172	)
Loss reclassified from accumulated other comprehensive loss (net of income tax benefit of $11)		—			8			32			40
Net other comprehensive income/(loss)		138			(4	)		(266	)		(132	)
Balance, December 31, 2020	$	(400	)	$	9		$	(1,968	)	$	(2,359	)

(i)

Reclassification adjustments from accumulated other comprehensive loss related to derivative instruments for the years ended December 31, 2020 and 2019 are included in Revenue and Salaries and benefits, and are included in Other income, net for the year ended December 31, 2018 in the accompanying consolidated statements of comprehensive income. See Note 9 — Derivative Financial Instruments for additional details regarding the reclassification adjustments for the derivative settlements.

(ii)	Reclassification adjustments from accumulated other comprehensive loss are included in the computation of net periodic pension cost (see Note 12 — Retirement Benefits). These components are included in Other income, net in the accompanying consolidated statements of comprehensive income.

(iii)

On January 1, 2019, in accordance with ASU 2018-02, we reclassified to Retained earnings $36 million of defined pension and postretirement costs, representing the ‘stranded’ tax effect of the change in the U.S. federal corporate tax rate resulting from U.S. Tax Reform.

Share-Based Compensation

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

Note 18 — Share-based Compensation

Plan Summaries

On December 31, 2020, the Company had a number of open share-based compensation plans, which provide for the granting of time-based and performance-based options, time-based and performance-based restricted stock units, and various other share-based grants to employees. All of the Company’s share-based compensation plans under which any options, restricted stock units (‘RSUs’) or other share-based grants are outstanding as of December 31, 2020 are described below. The compensation cost that has been recognized for

these plans for the years ended December 31, 2020, 2019 and 2018 was $90 million, $74 million and $50 million, respectively. The total income tax benefits recognized in the consolidated statements of comprehensive income for share-based compensation arrangements for the years ended December 31, 2020, 2019, and 2018 were $15 million, $11 million and $10 million, respectively.

2012 Equity Incentive Plan

This plan, established on April 25, 2012 and amended and restated on June 10, 2016, provides for the granting of incentive stock options, time-based or performance-based non-statutory stock options, share appreciation rights, restricted shares, time-based or performance-based RSUs, performance-based awards and other share-based grants or any combination thereof to employees, officers, non-employee directors and consultants of the Company (‘2012 Plan’). The board of directors also adopted a sub-plan under the 2012 Plan to provide an employee sharesave scheme in the U.K.

There were approximately 5 million shares remaining available for grant under this plan as of December 31, 2020. Options are exercisable on a variety of dates, including from the second, third, fourth or fifth anniversary of the grant date. The 2012 Plan shall continue in effect until terminated by the board of directors, except that no incentive stock option may be granted under the 2012 Plan after April 21, 2026 or after its expiration. That termination will not affect the validity of any grants outstanding at that date.

Towers Watson Share Plans

In January 2016, in connection with the Merger, we assumed the Towers Watson & Co. 2009 Long-Term Incentive Plan (‘2009 LTIP’) and converted the outstanding unvested restricted stock units and options into Willis Towers Watson RSUs and options using a conversion ratio stated in the Merger Agreement. We determined the fair value of the portion of the outstanding RSUs and options related to pre-acquisition employee service using the straight-line methodology from the date of grant to the acquisition date to be $37 million, which was added to the transaction consideration. The fair value of the remaining portion of RSUs and options related to the post-acquisition employee services was $45 million and was recorded over the subsequent vesting periods through 2018. For the year ended December 31, 2018, we recorded $3 million of non-cash stock-based compensation expense.

The acquired awards have vested in full, and the Company does not intend to grant future awards under the 2009 LTIP plan.

Options

There were no options granted during the years ended December 31, 2020, 2019 and 2018.

Award Activity

Classification of options as time-based or performance-based is dependent on the original terms of the award. Performance conditions on the options have been met. A summary of option activity under the plans at December 31, 2020, and changes during the year then ended is presented below:

	Options (thousands)		Weighted- Average Exercise Price ⁽ⁱ⁾		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Time-based stock options
Balance as of December 31, 2019		260	$	105.38
Exercised		163	$	101.09
Cancelled		12	$	95.56
Balance as of December 31, 2020		85	$	114.92	1.5 years	$	8
Options vested or expected to vest at December 31, 2020		85	$	114.92	1.5 years	$	8
Options exercisable at December 31, 2020		57	$	107.72	1.4 years	$	6
Performance-based stock options
Balance as of December 31, 2019		287	$	110.58
Exercised		3	$	110.58
Balance as of December 31, 2020		284	$	110.58	1.7 years	$	28
Options vested or expected to vest at December 31, 2020		284	$	110.58	1.7 years	$	28
Options exercisable at December 31, 2020		284	$	110.58	1.7 years	$	28

(i)	Certain options are exercisable in Pounds sterling and are converted to dollars using the exchange rate at December 31, 2020.

The total intrinsic values of time-based options exercised during the years ended December 31, 2020, 2019 and 2018 were $17 million, $16 million and $12 million, respectively. At December 31, 2020, there was less than $1 million of total unrecognized compensation cost under the time-based stock option plans; that cost is expected to be recognized over a weighted-average period of 1.4 years.

The total intrinsic values of performance-based options exercised during the year ended December 31, 2020 was less than $1 million, and was $16 million and $8 million for the years ended December 31, 2019 and 2018, respectively. At December 31, 2020, there is no unrecognized compensation cost related to the performance-based stock option plans.

Cash received from option exercises under all share-based payment arrangements for the years ended December 31, 2020, 2019 and 2018 was $16 million, $45 million and $45 million, respectively. The actual tax benefit recognized for the tax deductions from option exercises of the share-based payment arrangements totaled $5 million, $6 million and $4 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Equity-settled RSUs

Valuation Assumptions

The fair value of each time-based RSU is based on the grant date fair value, or the fair value on the acquisition date in the case of acquired awards. The fair value of each performance-based RSU is estimated on the grant date using a Monte-Carlo simulation that uses the assumptions noted in the following table. The awards also contain a market-based performance target. For the awards granted in 2020, 2019 and 2018, the performance measure is entirely based on this market target. Expected volatility is based on the historical volatility of the Company’s shares. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of the grant. The assumptions noted in the table below represent the weighted average of each assumption for each grant during the year.

	Years ended December 31,
	2020			2019			2018
Expected volatility		24.2	%		25.6	%		17.9	%
Expected dividend yield		—	%		—	%		—	%
Expected life (years)		2.9			2.7			2.5
Risk-free interest rate		0.4	%		2.1	%		2.6	%

Award Activity

A summary of time-based and performance-based RSU activity under the plans at December 31, 2020, and changes during the year then ended, is presented below:

	Shares (thousands)		Weighted- Average Grant Date Fair Value
Nonvested shares (time-based RSUs)
Balance as of December 31, 2019		11	$	172.25
Granted		13	$	193.25
Vested		13	$	178.54
Forfeited		—	$	160.48
Balance as of December 31, 2020		11	$	190.09
Nonvested shares (performance-based RSUs)
Balance as of December 31, 2019		507	$	150.22
Granted		356	$	230.24
Vested		416	$	117.01
Forfeited		8	$	216.64
Balance as of December 31, 2020		439	$	245.49

Time-based RSUs totaling 12,586, 21,025 and 164,728 vested during the years ended December 31, 2020, 2019 and 2018, respectively, with average share prices of $195.69, $189.42 and $156.14, respectively. At December 31, 2020 there was $1 million of total unrecognized compensation cost related to the time-based RSU plan; that cost is expected to be recognized over a weighted-average period of 0.6 years.

Performance-based RSUs totaling 416,349, 178,346 and 249,901 vested during the years ended December 31, 2020, 2019 and 2018, respectively, with average share prices of $185.30, $175.01 and $154.99, respectively. At December 31, 2020 there was $42 million of total unrecognized compensation cost related to the performance-based RSU plan; that cost is expected to be recognized over a weighted-average period of 2.3 years.

The actual tax benefit recognized for the tax deductions from RSUs that vested totaled $7 million, $7 million and $12 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Phantom RSUs

The Company granted 204,269 and 268,956 units of phantom stock with a market-performance feature during the years ended December 31, 2019 and 2018, respectively, and did not grant phantom stock during 2020. These are cash-settled awards with final payout based on the performance of the Company’s stock. The grant date fair value of the awards was $105.97 and $83.57 per share for the 2019 and 2018 awards, respectively. The fair value of each phantom RSU is estimated using a Monte Carlo simulation. The Company’s stock price as of the last day of the period is one of the inputs used in the simulation. Expected volatility is based on the historical volatility of the Company’s shares. The expected term of each plan is three years, based on the vesting terms of the awards. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant.

Since the awards are cash-settled, they are considered a liability. Expense is recognized over the service period. The liability is remeasured at the end of each reporting period, and changes in fair value are recognized as compensation cost. For both plans, as of December 31, 2020, the liability recognized is $61 million and the estimated unrecognized compensation cost is $17 million.

Earnings Per Share

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Earnings Per Share

Note 19 — Earnings Per Share

Basic and diluted earnings per share are calculated by dividing net income attributable to Willis Towers Watson by the average number of ordinary shares outstanding during each period. The computation of diluted earnings per share reflects the potential dilution that could occur if dilutive securities and other contracts to issue shares were exercised or converted into shares or resulted in the issuance of shares that then shared in the net income of the Company.

At December 31, 2020, 2019 and 2018, there were 0.1 million, 0.3 million and 0.4 million time-based share options; 0.3 million, 0.3 million and 0.5 million performance-based options; and 0.4 million, 0.5 million and 0.8 million performance-based RSUs outstanding, respectively. The Company’s time-based RSUs were immaterial at December 31, 2020, 2019 and 2018.

Basic and diluted earnings per share are as follows:

	Years ended December 31,
	2020			2019			2018
Net income attributable to Willis Towers Watson	$	996		$	1,044		$	695

Basic weighted-average number of shares outstanding		130			130			131
Dilutive effect of potentially issuable shares		—			—			1
Diluted weighted-average number of shares outstanding		130			130			132

Basic earnings per share	$	7.68		$	8.05		$	5.29
Dilutive effect of potentially issuable shares		(0.03	)		(0.03	)		(0.02	)
Diluted earnings per share	$	7.65		$	8.02		$	5.27

There were no anti-dilutive options for the years ended December 31, 2020, 2019 and 2018. For the years ended December 31, 2020 and 2018, 0.1 million and 0.2 million RSUs, respectively, were not included in the computation of the dilutive effect of potentially issuable shares because their effect was anti-dilutive. Anti-dilutive RSUs were immaterial for the year ended December 31, 2019.

Supplemental Disclosures of Cash Flow Information

12 Months Ended

Dec. 31, 2020

Supplemental Cash Flow Elements [Abstract]

Supplemental Disclosures of Cash Flow Information

Note 20 — Supplemental Disclosures of Cash Flow Information

Supplemental disclosures regarding cash flow information and non-cash investing and financing activities are as follows:

	Years Ended December 31,
	2020		2019		2018
Supplemental disclosures of cash flow information:
Cash payments for income taxes, net	$	310	$	299	$	178
Cash payments for interest	$	229	$	210	$	176
Cash acquired	$	10	$	11	$	13
Supplemental disclosures of non-cash investing and financing activities:
Fair value of deferred and contingent consideration related to acquisitions	$	9	$	13	$	36

Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements (Policies)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation

Risks and Uncertainties Related to the COVID-19 Pandemic

CARES Act

Principles of Consolidation

Use of Estimates

Going Concern

Fair Value of Financial Instruments

•

Level 1: refers to fair values determined based on quoted market prices in active markets for identical assets;

•

Level 2: refers to fair values estimated using observable market-based inputs or unobservable inputs that are corroborated by market data; and

•

Level 3: includes fair values estimated using unobservable inputs that are not corroborated by market data.

The following methods and assumptions were used by the Company in estimating its fair value disclosure for financial instruments:

•

Available-for-sale securities are classified as Level 1 because we use quoted market prices in determining the fair value of these securities.

•

Investments in Associates

Cash and Cash Equivalents

Fiduciary Assets and Liabilities

Fiduciary assets on the consolidated balance sheets are comprised of both fiduciary funds and fiduciary receivables:

Fiduciary liabilities on the consolidated balance sheets represent the obligations to remit all fiduciary funds and fiduciary receivables to insurers or insureds.

Accounts Receivable

Acquired Accounts Receivable

Income Taxes

The Company recognizes interest and penalties relating to unrecognized tax benefits within income taxes. See Note 6 — Income Taxes for additional information regarding the Company’s income taxes.

Foreign Currency

Derivatives

Commitments, Contingencies and Accrued Liabilities

Share-Based Compensation

See Note 18 — Share-based Compensation for additional information about the Company’s share-based compensation.

Fixed Assets

Leases

inception by reference to the lease term and lease currency. Over 90% of our leases are denominated in U.S. dollars, Pounds sterling or Euros.

Our leases generally do not subject us to restrictive covenants and contain no residual value guarantees.

See Note 13 — Leases for additional information about our operating leases.

Goodwill and Other Intangible Assets

Acquired intangible assets are amortized over the following periods:



	Amortization basis	Expected life (years)
Client relationships	In line with underlying cash flows	5 to 20
Software	In line with underlying cash flows or straight-line basis	4 to 7
Trademark and trade name	Straight-line basis	14 to 25
Other	In line with underlying cash flows or straight-line basis	3 to 20

Pensions

Revenue Recognition

Company and the insurance carriers. As such, the estimate of these renewal commissions receivables has not been discounted to reflect a significant financing component.

We have engagement letters with our clients that specify the terms and conditions upon which the engagements are based. These terms and conditions can only be changed upon agreement by both parties.

We use different progress measures to determine our revenue depending on the nature of the engagement:

•

These contracts typically consist of an implementation phase and an ongoing administration phase:

•

Interest income — Interest income is recognized as earned.

For our broking business, the Company must estimate the fulfillment costs incurred during the pre-placement of the broking contracts. These judgments include:

•

which activities in the pre-placement process should be eligible for capitalization;

•

the amount of time and effort expended on those pre-placement activities;

•

the amount of payroll and related costs eligible for capitalization; and,

•

the monthly or quarterly timing of underlying insurance and reinsurance policy inception dates.

Recent Accounting Pronouncements

Not adopted for 2020

Adopted for 2020

Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Acquired Intangible Assets Amortized

Acquired intangible assets are amortized over the following periods:



	Amortization basis	Expected life (years)
Client relationships	In line with underlying cash flows	5 to 20
Software	In line with underlying cash flows or straight-line basis	4 to 7
Trademark and trade name	Straight-line basis	14 to 25
Other	In line with underlying cash flows or straight-line basis	3 to 20

Acquisitions and Divestures (Tables)

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Summary of Fair Values of Identifiable Assets Acquired and Liabilities Assumed

A summary of the fair values of the identifiable assets acquired, and liabilities assumed, of TRANZACT at July 30, 2019 are summarized in the following table.

Cash and cash equivalents	$	7
Restricted cash		2
Accounts receivable, net		3
Renewal commissions receivable, current ⁽ⁱ⁾		36
Prepaid and other current assets		22
Renewal commissions receivable, non-current ⁽ⁱ⁾		130
Fixed assets		9
Intangible assets		646
Goodwill		718
Right-of-use assets		19
Other non-current assets		2
Collateralized facility ⁽ⁱⁱ⁾		(91	)
Other current liabilities		(55	)
Deferred tax liabilities, net		(100	)
Lease liabilities		(19	)
Net assets acquired	$	1,329

______________

(i)

(ii)	See Note 10 — Debt for a description of the acquired collateralized facility debt.

Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Revenue From Contract With Customer [Abstract]

Disaggregation of Revenue

The following table presents revenue by service offering and segment, as well as a reconciliation to total revenue for the years ended December 31, 2020, 2019 and 2018. Along with reimbursable expenses and other, total revenue by service offering represents our revenue from customer contracts.

Year Ended December 31,	Broking		Consulting		Outsourced Administration		Other		Total revenue by service offering		Reimbursable expenses and other ⁽ⁱ⁾		Total revenue from customer contracts		Interest and other income ⁽ⁱⁱ⁾		Total revenue
HCB
2020	$	302	$	2,215	$	503	$	241	$	3,261	$	50	$	3,311	$	17	$	3,328
2019		278		2,269		466		262		3,275		61		3,336		23		3,359
2018		266		2,224		484		235		3,209		62		3,271		24		3,295
CRB
2020		2,707		154		66		11		2,938		2		2,940		39		2,979
2019		2,692		132		71		5		2,900		1		2,901		46		2,947
2018		2,578		163		65		9		2,815		—		2,815		37		2,852
IRR
2020		1,006		393		15		231		1,645		8		1,653		6		1,659
2019		975		421		10		205		1,611		9		1,620		26		1,646
2018		905		430		—		185		1,520		8		1,528		36		1,564
BDA
2020		834		—		525		—		1,359		12		1,371		—		1,371
2019		514		—		521		—		1,035		12		1,047		—		1,047
2018		272		—		486		—		758		7		765		—		765
Corporate ⁽ⁱ⁾
2020		1		5		—		3		9		2		11		4		15
2019		—		11		—		4		15		22		37		3		40
2018		—		13		—		4		17		17		34		3		37
Total
2020	$	4,850	$	2,767	$	1,109	$	486	$	9,212	$	74	$	9,286	$	66	$	9,352
2019	$	4,459	$	2,833	$	1,068	$	476	$	8,836	$	105	$	8,941	$	98	$	9,039
2018	$	4,021	$	2,830	$	1,035	$	433	$	8,319	$	94	$	8,413	$	100	$	8,513

_______

(i)	Reimbursable expenses and other, as well as Corporate revenue, are excluded from segment revenue, but included in total revenue on the consolidated statements of comprehensive income.

(ii)	Interest and other income is included in segment revenue and total revenue, however it has been presented separately in the above tables because it does not arise directly from contracts with customers.

Individual revenue streams aggregating to 5% of total revenue for the years ended December 31, 2020, 2019 and 2018 have been included within the Other column in the table above.

Year Ended December 31,	North America		Great Britain		Western Europe		International		Total revenue by geography
HCB
2020	$	1,859	$	491	$	584	$	327	$	3,261
2019		1,901		475		566		333		3,275
2018		1,849		481		562		317		3,209
CRB
2020		1,176		630		679		453		2,938
2019		1,112		656		661		471		2,900
2018		1,044		648		631		492		2,815
IRR
2020		474		824		193		154		1,645
2019		449		788		216		158		1,611
2018		416		732		218		154		1,520
BDA
2020		1,351		—		—		8		1,359
2019		1,033		—		—		2		1,035
2018		758		—		—		—		758
Corporate
2020		7		—		2		—		9
2019		13		—		1		1		15
2018		16		—		1		—		17
Total
2020	$	4,867	$	1,945	$	1,458	$	942	$	9,212
2019	$	4,508	$	1,919	$	1,444	$	965	$	8,836
2018	$	4,083	$	1,861	$	1,412	$	963	$	8,319

Contract with Customer, Asset and Liability

	December 31, 2020		December 31, 2019
Billed receivables, net of allowance for doubtful accounts of $41 million and $37 million	$	1,697	$	1,831
Unbilled receivables		445		434
Current contract assets		413		356
Accounts receivable, net	$	2,555	$	2,621
Non-current accounts receivable, net	$	34	$	30
Non-current contract assets	$	329	$	105
Deferred revenue	$	549	$	538

Schedule of Changes in Allowance for Doubtful Accounts

	December 31, 2020			December 31, 2019			December 31, 2018
Balance at beginning of year	$	37		$	40		$	45
Additions charged to costs and expenses		29			9			9
Deductions/other movements		(29	)		(10	)		(15	)
Foreign exchange		4			(2	)		1
Balance at end of year	$	41		$	37		$	40

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction

In addition, in accordance with ASC 606, the Company has elected not to disclose the remaining performance obligations when one or both of the following circumstances apply:

•

Performance obligations which are part of a contract that has an original expected duration of less than one year, and

•

Performance obligations satisfied in accordance with ASC 606-10-55-18 (‘right to invoice’).

		2021				2022				2023 onward				Total
Revenue expected to be recognized on contracts as of December 31, 2020		$	540			$	392			$	497			$	1,429

Capitalized Contract Cost

The following table shows the categories of costs that are capitalized and deferred over the expected life of a contract.

	Costs to fulfill
	December 31, 2020			December 31, 2019			December 31, 2018
Balance at beginning of the year	$	177		$	148		$	126
New capitalized costs		493			488			465
Amortization		(465	)		(460	)		(442	)
Impairments		(1	)		—			—
Foreign currency translation		2			1			(1	)
Balance at end of the year	$	206		$	177		$	148

Segment Information (Tables)

12 Months Ended

Dec. 31, 2020

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

The following table presents segment revenue and segment operating income for our reportable segments for the years ended December 31, 2020, 2019 and 2018.

	Segment revenue						Segment operating income
	Years ended December 31						Years ended December 31
	2020		2019		2018		2020		2019		2018
HCB	$	3,278	$	3,298	$	3,233	$	853	$	848	$	789
CRB		2,977		2,946		2,852		630		578		528
IRR		1,651		1,637		1,556		457		420		384
BDA		1,359		1,035		758		320		244		144
Total	$	9,265	$	8,916	$	8,399	$	2,260	$	2,090	$	1,845

Net Operating Income of the Reported Segments

The following table presents reconciliations of the information reported by segment to the Company’s consolidated amounts reported for the years ended December 31, 2020, 2019 and 2018.

	Years ended December 31,
	2020			2019			2018
Revenue:
Total segment revenue	$	9,265		$	8,916		$	8,399
Reimbursable expenses and other		87			123			114
Revenue	$	9,352		$	9,039		$	8,513

Total segment operating income	$	2,260		$	2,090		$	1,845
Amortization		(462	)		(489	)		(534	)
Restructuring costs ⁽ⁱ⁾		(24	)		—			—
Transaction and integration expenses ⁽ⁱⁱ⁾		(110	)		(13	)		(202	)
Provision for significant litigation ⁽ⁱⁱⁱ⁾		(65	)		—			—
Unallocated, net ^(iv)		(416	)		(259	)		(300	)
Income from operations		1,183			1,329			809
Interest expense		(244	)		(234	)		(208	)
Other income, net		399			227			250
Income from operations before income taxes	$	1,338		$	1,322		$	851

(i)	Restructuring costs relate to minor restructuring activities carried out by various business lines throughout the Company.

(ii)	Includes transaction costs related to the proposed Aon combination in 2020, the TRANZACT acquisition in 2019, and transaction and integration expenses related to the Merger and the acquisition of Gras Savoye in 2018.

(iii)

For additional information, see the disclosure under Willis Towers Watson Merger-Related Securities Litigation in Note 14 — Commitments and Contingencies.

(iv)	Includes certain costs, primarily related to corporate functions which are not directly related to the segments, and certain differences between budgeted expenses determined at the beginning of the year and actual expenses that we report for U.S. GAAP purposes.

Revenue and Long-lived Assets by Geographical Areas

	Revenue						Long-Lived Assets ⁽ⁱ⁾
	2020		2019		2018		2020		2019		2018
Ireland	$	157	$	144	$	138	$	110	$	103	$	78

United States		4,650		4,370		3,970		12,652		12,786		11,068
United Kingdom		1,920		1,934		1,926		2,840		2,901		2,349
Rest of World		2,625		2,591		2,479		2,533		2,527		2,411
Total Foreign Countries		9,195		8,895		8,375		18,025		18,214		15,828
	$	9,352	$	9,039	$	8,513	$	18,135	$	18,317	$	15,906

(i)	Long-lived assets do not include deferred tax assets.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income from continuing operations before income taxes and interest in earnings of associates by location of taxing jurisdiction

An analysis of income from operations before income taxes by taxing jurisdiction is shown below:

	Years ended December 31,
	2020			2019			2018
Ireland	$	(5	)	$	(11	)	$	(16	)
U.S.		25			178			(101	)
U.K.		332			337			182
Rest of World		986			818			786
Total	$	1,338		$	1,322		$	851

Provision for benefit from income taxes

The components of the provision for income taxes include:

	Years ended December 31,
	2020			2019			2018
Current tax expense:
U.S. federal taxes	$	(27	)	$	(108	)	$	(98	)
U.S. state and local taxes		(5	)		(43	)		(25	)
U.K. corporation tax		(45	)		(43	)		(16	)
Other jurisdictions		(142	)		(127	)		(112	)
Total current tax expense		(219	)		(321	)		(251	)
Deferred tax (expense)/benefit:
U.S. federal taxes		(78	)		56			79
U.S. state and local taxes		1			14			12
U.K. corporation tax		(48	)		(15	)		(6	)
Other jurisdictions		26			17			30
Total deferred tax (expense)/benefit		(99	)		72			115
Total provision for income taxes	$	(318	)	$	(249	)	$	(136	)

Reconciliation between US federal income taxes at the statutory rate and the Company's provision for income taxes on continuing operations

	Years ended December 31,
	2020			2019			2018
INCOME FROM OPERATIONS BEFORE INCOME TAXES	$	1,338		$	1,322		$	851
U.S. federal statutory income tax rate		21	%		21	%		21	%
Income tax expense at U.S. federal tax rate		(281	)		(278	)		(179	)
Adjustments to derive effective tax rate:
Non-deductible expenses and dividends		(20	)		(34	)		(44	)
Non-deductible acquisition costs		(15	)		(2	)		(2	)
Disposal of non-deductible goodwill		—			—			1
Impact of change in rate on deferred tax balances		(7	)		—			7
Effect of foreign exchange and other differences		(3	)		1			1
Changes in valuation allowances		(8	)		6			80
Net tax effect of intra-group items		90			93			99
Tax on disposal of operations		16			—			—
Tax differentials of non-U.S. jurisdictions		3			(2	)		(2	)
Tax differentials of U.S. state taxes and local taxes		(3	)		(21	)		(77	)
Global Intangible Low-Taxed Income (GILTI)		(3	)		(7	)		(15	)
Base Erosion Anti-Abuse Tax (BEAT)		(81	)		—			—
Other items, net		(6	)		(5	)		(5	)
Provision for income taxes	$	(318	)	$	(249	)	$	(136	)

Significant components of deferred income tax assets and liabilities and their balance sheet classifications

Deferred income tax assets and liabilities included in the consolidated balance sheets at December 31, 2020 and 2019 are comprised of the following:

	December 31,
	2020			2019
Deferred tax assets:
Accrued expenses not currently deductible	$	212		$	201
Net operating losses		92			116
Capital loss carryforwards		40			33
Accrued retirement benefits		334			326
Operating lease liabilities		165			181
Deferred compensation		90			86
Stock options		25			18
Financial derivative transactions		1			—
Gross deferred tax assets		959			961
Less: valuation allowance		(84	)		(76	)
Net deferred tax assets	$	875		$	885
Deferred tax liabilities:
Cost of intangible assets, net of related amortization	$	788		$	865
Operating lease right-of-use assets		159			177
Cost of tangible assets, net of related depreciation		78			53
Prepaid retirement benefits		152			121
Financial derivative transactions		1			3
Accrued revenue not currently taxable		163			120
Deferred tax liabilities	$	1,341		$	1,339
Net deferred tax liabilities	$	466		$	454

The net deferred income tax assets are included in other non-current assets and the net deferred tax liabilities are included in deferred tax liabilities in our consolidated balance sheets.

	December 31,
	2020		2019
Balance sheet classifications:
Other non-current assets	$	95	$	72
Deferred tax liabilities		561		526
Net deferred tax liability	$	466	$	454

Summary of Valuation Allowance

An analysis of our valuation allowance is shown below.

	Years ended December 31,
	2020			2019			2018
Balance at beginning of year	$	76		$	81		$	162
Additions charged to costs and expenses		17			7			18
Deductions		(9	)		(12	)		(99	)
Balance at end of year	$	84		$	76		$	81

Reconciliation of the beginning and ending amounts of unrecognized tax benefits

A reconciliation of the beginning and ending balances of the liability for unrecognized tax benefits is as follows:

	2020			2019			2018
Balance at beginning of year	$	49		$	49		$	59
Increases related to acquisitions		4			—			—
Increases related to tax positions in prior years		1			2			2
Decreases related to tax positions in prior years		—			(1	)		(4	)
Decreases related to settlements		(3	)		—			(4	)
Decreases related to lapse in statute of limitations		(2	)		(1	)		(5	)
Increases related to current year tax positions		—			—			3
Cumulative translation adjustment and other adjustments		1			—			(2	)
Balance at end of year	$	50		$	49		$	49

Summary of Income Tax Examinations



	Open Tax Years (fiscal year ending in)
U.S. — federal	2017 and forward
U.S. — various states	2014 and forward
U.K.	2010 and forward
Ireland	2016 and forward
France	2010 and forward
Germany	2010 and forward
Canada - federal	2013 and forward

Fixed Assets (Tables)

12 Months Ended

Dec. 31, 2020

Property Plant And Equipment [Abstract]

Property, Plant and Equipment

The following table reflects changes in the net carrying amount of the components of fixed assets for the years ended December 31, 2020 and 2019:

	Furniture, equipment and software			Leasehold improvements			Land and buildings			Total
Cost: at January 1, 2019	$	1,130		$	488		$	92		$	1,710
Additions		268			68			—			336
Acquisitions		7			3			—			10
Disposals		(117	)		(15	)		—			(132	)
Reclassification due to ASC 842 ⁽ⁱ⁾		—			—			(3	)		(3	)
Foreign exchange		14			6			1			21
Cost: at December 31, 2019		1,302			550			90			1,942
Additions		238			31			—			269
Acquisitions		1			—			—			1
Disposals		(64	)		(12	)		(1	)		(77	)
Abandonment of long-lived asset ⁽ⁱⁱ⁾		(35	)		—			—			(35	)
Foreign exchange		31			9			1			41
Cost: at December 31, 2020	$	1,473		$	578		$	90		$	2,141

Depreciation: at January 1, 2019	$	(519	)	$	(197	)	$	(52	)	$	(768	)
Depreciation expense		(179	)		(57	)		(4	)		(240	)
Disposals		109			11			—			120
Foreign exchange		(5	)		(2	)		(1	)		(8	)
Depreciation: at December 31, 2019		(594	)		(245	)		(57	)		(896	)
Depreciation expense ⁽ⁱⁱ⁾		(214	)		(55	)		(4	)		(273	)
Disposals		56			10			—			66
Foreign exchange		(17	)		(6	)		(1	)		(24	)
Depreciation: at December 31, 2020	$	(769	)	$	(296	)	$	(62	)	$	(1,127	)

Net book value:
At December 31, 2019	$	708		$	305		$	33		$	1,046

At December 31, 2020	$	704		$	282		$	28		$	1,014

(i)	Pertains to certain lease incentives which have been included within right-of-use assets upon the adoption of ASC 842. See Note 2 — Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements for further information.

(ii)	Depreciation expense on the statement of comprehensive income for the year ended December 31, 2020 includes both the depreciation expense presented here as well as the abandonment of an internally-developed software asset of $35 million prior to being placed in service.

Finance Leases

Included within land and buildings are the following assets held under finance leases:

	December 31,
	2020			2019
Finance leases	$	28		$	29
Accumulated depreciation		(20	)		(19	)
	$	8		$	10

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Components of Goodwill

The components of goodwill are outlined below for the years ended December 31, 2020 and 2019:

	HCB			CRB			IRR			BDA			Total
Balance at December 31, 2018
Goodwill, gross	$	4,300		$	2,308		$	1,792		$	2,557		$	10,957
Accumulated impairment losses		(130	)		(362	)		—			—			(492	)
Goodwill, net - December 31, 2018		4,170			1,946			1,792			2,557			10,465
Goodwill acquired		—			10			—			727			737
Goodwill disposals		—			(6	)		—			—			(6	)
Foreign exchange		(2	)		(3	)		3			—			(2	)
Balance at December 31, 2019
Goodwill, gross		4,298			2,309			1,795			3,284			11,686
Accumulated impairment losses		(130	)		(362	)		—			—			(492	)
Goodwill, net - December 31, 2019		4,168			1,947			1,795			3,284			11,194
Goodwill acquired		15			30			2			3			50
Goodwill disposals		(12	)		(1	)		(117	)		—			(130	)
Acquisition accounting adjustment		—			—			—			(9	)		(9	)
Foreign exchange		45			40			14			—			99
Balance at December 31, 2020
Goodwill, gross		4,346			2,378			1,694			3,278			11,696
Accumulated impairment losses		(130	)		(362	)		—			—			(492	)
Goodwill, net - December 31, 2020	$	4,216		$	2,016		$	1,694		$	3,278		$	11,204

Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets

The following table reflects changes in the net carrying amounts of the components of finite-lived intangible assets for the year ended December 31, 2020 and 2019:

	Client relationships			Software			Trademark and trade name			Favorable agreements ⁽ⁱ⁾			Other			Total
Balance at December 31, 2018:
Intangible assets, gross	$	3,401		$	749		$	1,052		$	14		$	102		$	5,318
Accumulated amortization		(1,415	)		(421	)		(132	)		(5	)		(27	)		(2,000	)
Intangible assets, net - December 31, 2018		1,986			328			920			9			75			3,318
ASC 842 reclassification ⁽ⁱ⁾		—			—			—			(9	)		—			(9	)
Intangible assets acquired ⁽ⁱⁱ⁾		626			—			—			—			34			660
Intangible asset disposals		(9	)		(1	)		—			—			—			(10	)
Amortization		(313	)		(125	)		(45	)		—			(6	)		(489	)
Foreign exchange		8			—			—			—			—			8
Balance at December 31, 2019:
Intangible assets, gross		4,029			753			1,051			—			134			5,967
Accumulated amortization		(1,731	)		(551	)		(176	)		—			(31	)		(2,489	)
Intangible assets, net - December 31, 2019		2,298			202			875			—			103			3,478
Intangible assets acquired		30			—			—			—			32			62
Intangible asset disposals		(19	)		—			—			—			(48	)		(67	)
Amortization		(301	)		(103	)		(43	)		—			(15	)		(462	)
Foreign exchange		26			3			2			—			1			32
Balance at December 31, 2020:
Intangible assets, gross		4,065			761			1,054			—			108			5,988
Accumulated amortization		(2,031	)		(659	)		(220	)		—			(35	)		(2,945	)
Intangible assets, net - December 31, 2020	$	2,034		$	102		$	834		$	—		$	73		$	3,043

(i)	On January 1, 2019, in accordance with ASC 842, we reclassified our favorable lease agreement assets to right-of-use assets within our consolidated balance sheet.

(ii)	Includes $612 million and $34 million of client relationship and domain name intangible assets, respectively, associated with our acquisition of TRANZACT.

Schedule of Future Estimated Amortization Expense for Amortizable Intangible Assets

The table below reflects the future estimated amortization expense for amortizable intangible assets for the next five years and thereafter:

Years ended December 31,	Amortization
2021	$	389
2022		328
2023		274
2024		239
2025		217
Thereafter		1,596
Total	$	3,043

Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2020

Designated [Member]

Schedule of Derivative Instruments Designated/Nondesignated As Hedging Instrument Effect on Condensed Consolidated Statements of Comprehensive Income

	Loss/(gain) recognized in OCI (effective element)
	2020			2019		2018
Foreign exchange contracts	$	(13	)	$	15	$	(22	)

Location of loss reclassified from Accumulated OCL into income (effective element)	Loss reclassified from Accumulated OCL into income (effective element)
	2020			2019			2018
Revenue	$	(5	)	$	(5	)	$	—
Salaries and benefits		(4	)		(4	)		—
Other income, net		—			—			(28	)
	$	(9	)	$	(9	)	$	(28	)

Nondesignated [Member]

Schedule of Derivative Instruments Designated/Nondesignated As Hedging Instrument Effect on Condensed Consolidated Statements of Comprehensive Income

	Location of (loss)/gain	(Loss)/gain recognized in income
Derivatives not designated as hedging instruments:	recognized in income	2020			2019		2018
Foreign exchange contracts	Other income, net	$	(3	)	$	18	$	—

Debt (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Current and Long-term Debt

Current debt consists of the following:

	December 31,
	2020		2019
5.750% senior notes due 2021	$	500	$	—
3.500% senior notes due 2021		449		—
Current portion of collateralized facility		22		24
Term loan due 2020		—		292
	$	971	$	316

Long-term debt consists of the following:

	December 31,
	2020		2019
Revolving $1.25 billion credit facility	$	—	$	—
Collateralized facility ⁽ⁱ⁾		33		60
5.750% senior notes due 2021		—		499
3.500% senior notes due 2021		—		448
2.125% senior notes due 2022 ⁽ⁱⁱ⁾		659		604
4.625% senior notes due 2023		249		249
3.600% senior notes due 2024		647		646
4.400% senior notes due 2026		546		546
4.500% senior notes due 2028		596		595
2.950% senior notes due 2029		726		446
6.125% senior notes due 2043		271		271
5.050% senior notes due 2048		395		395
3.875% senior notes due 2049		542		542
	$	4,664	$	5,301

(i)	At December 31, 2020 and 2019, the Company had $98 million and $127 million, respectively, of renewal commissions receivables pledged as collateral for this facility (see below for additional information).

(ii)	Notes issued in Euro (€540 million).

Schedule of Maturities of Long-term Debt

The following table summarizes the maturity of our debt and interest on senior notes and excludes any reduction for debt issuance costs:

	2021		2022		2023		2024		2025		Thereafter		Total
Senior notes	$	950	$	660	$	250	$	650	$	—	$	3,100	$	5,610
Interest on senior notes		197		171		162		140		131		1,418		2,219
RCF		—		—		—		—		—		—		—
Collateralized facility		22		17		13		3		—		—		55
Total	$	1,169	$	848	$	425	$	793	$	131	$	4,518	$	7,884

Schedule of Debt Interest Expense

The following table shows an analysis of the interest expense for the years ended December 31, 2020, 2019 and 2018:

	Years ended December 31,
	2020		2019		2018
Senior notes	$	227	$	206	$	166
Term loans		6		9		4
RCF		4		8		26
Collateralized facility		3		1		—
Other⁽ⁱ⁾		4		10		12
Total interest expense	$	244	$	234	$	208

(i)	Other primarily includes debt issuance costs, interest expense on financing leases and accretion on deferred and contingent consideration.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables present our assets and liabilities measured at fair value on a recurring basis at December 31, 2020 and December 31, 2019:

		Fair Value Measurements on a Recurring Basis at December 31, 2020
	Balance Sheet Location	Level 1		Level 2		Level 3		Total
Assets:
Available-for-sale securities:
Mutual funds / exchange traded funds	Prepaid and other current assets and other non-current assets	$	8	$	—	$	—	$	8
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Prepaid and other current assets and other non-current assets	$	—	$	27	$	—	$	27
Liabilities:
Contingent consideration:
Contingent consideration ⁽ⁱⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	—	$	45	$	45
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	7	$	—	$	7

		Fair Value Measurements on a Recurring Basis at December 31, 2019
	Balance Sheet Location	Level 1		Level 2		Level 3		Total
Assets:
Available-for-sale securities:
Mutual funds / exchange traded funds	Prepaid and other current assets and other non-current assets	$	20	$	—	$	—	$	20
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Prepaid and other current assets and other non-current assets	$	—	$	32	$	—	$	32
Liabilities:
Contingent consideration:
Contingent consideration ⁽ⁱⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	—	$	17	$	17
Derivatives:
Derivative financial instruments ⁽ⁱ⁾	Other current liabilities and other non-current liabilities	$	—	$	3	$	—	$	3

(i)	See Note 9 — Derivative Financial Instruments for further information on our derivative instruments.

(ii)

Schedule of Change in Fair Value of Level 3 Liabilities

The following table summarizes the change in fair value of the Level 3 liabilities:

Fair Value Measurements Using Significant Unobservable Inputs (Level 3)	December 31, 2020
Balance at December 31, 2019	$	17
Obligations assumed		9
Payments		—
Realized and unrealized gains		18
Foreign exchange		1
Balance at December 31, 2020	$	45

Schedule of Assets and Liabilities Whose Carrying Values Differ From the Fair Value and are Not Measured on a Recurring Basis

The following tables present our assets and liabilities not measured at fair value on a recurring basis at December 31, 2020 and 2019:

	December 31, 2020				December 31, 2019
	Carrying Value		Fair Value		Carrying Value		Fair Value
Assets:
Long-term note receivable	$	71	$	73	$	—	$	—
Liabilities:
Current debt	$	971	$	985	$	316	$	319
Long-term debt	$	4,664	$	5,488	$	5,301	$	5,694

Retirement Benefits (Tables)

12 Months Ended

Dec. 31, 2020

Compensation And Retirement Disclosure [Abstract]

Schedule of Changes in Projected Benefit Obligations

The following schedules provide information concerning the defined benefit pension plans and PRW plan as of and for the years ended December 31, 2020 and 2019:

	2020												2019
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Change in Benefit Obligation
Benefit obligation, beginning of year	$	4,768		$	4,259		$	842		$	90		$	4,187		$	3,666		$	728		$	87
Service cost		72			15			21			1			65			14			20			1
Interest cost		131			73			15			2			157			93			18			3
Employee contributions		15			—			—			3			15			—			—			6
Actuarial losses		509			494			65			5			535			472			88			5
Settlements		(10	)		(27	)		(4	)		—			(6	)		(8	)		(3	)		—
Benefits paid		(194	)		(146	)		(32	)		(10	)		(185	)		(140	)		(26	)		(12	)
Plan amendments		—			9			—			—			—			—			—			—
Business disposal		—			—			(1	)		—			—			—			—			—
Transfers in		—			—			—			—			—			—			2			—
Other		—			—			1			—			—			—			—			—
Foreign currency changes		—			166			48			—			—			162			15			—
Benefit obligation, end of year	$	5,291		$	4,843		$	955		$	91		$	4,768		$	4,259		$	842		$	90
Change in Plan Assets
Fair value of plan assets, beginning of year	$	3,873		$	5,086		$	588		$	—		$	3,403		$	4,402		$	486		$	1
Actual return on plan assets		602			590			64			—			557			561			85			—
Employer contributions		71			66			35			7			89			77			31			5
Employee contributions		15			—			—			3			15			—			—			6
Settlements		(10	)		(27	)		(4	)		—			(6	)		(8	)		(3	)		—
Benefits paid		(194	)		(146	)		(32	)		(10	)		(185	)		(140	)		(26	)		(12	)
Transfers in		—			—			—			—			—			—			2			—
Other		—			—			1			—			—			—			—			—
Foreign currency adjustment		—			198			32			—			—			194			13			—
Fair value of plan assets, end of year	$	4,357		$	5,767		$	684		$	—		$	3,873		$	5,086		$	588		$	—
Funded status at end of year	$	(934	)	$	924		$	(271	)	$	(91	)	$	(895	)	$	827		$	(254	)	$	(90	)
Accumulated Benefit Obligation	$	5,291		$	4,841		$	918		$	91		$	4,768		$	4,259		$	810		$	90
Components on the Consolidated Balance Sheet
Pension benefits assets	$	—		$	932		$	28		$	—		$	—		$	835		$	22		$	—
Current liability for pension benefits	$	(31	)	$	(1	)	$	(5	)	$	(6	)	$	(33	)	$	(1	)	$	(6	)	$	(6	)
Non-current liability for pension benefits	$	(903	)	$	(7	)	$	(294	)	$	(85	)	$	(862	)	$	(7	)	$	(270	)	$	(84	)
	$	(934	)	$	924		$	(271	)	$	(91	)	$	(895	)	$	827		$	(254	)	$	(90	)

Schedule of Amounts Recognized in Other Comprehensive Income (Loss)

Amounts recognized in accumulated other comprehensive loss as of December 31, 2020 and 2019 consist of:

	2020										2019
	U.S.		U.K.			Other		PRW			U.S.		U.K.			Other		PRW
Net actuarial loss	$	1,143	$	1,304		$	169	$	24		$	982	$	1,133		$	128	$	20
Net prior service gain		—		(37	)		—		(23	)		—		(61	)		—		(27	)
Accumulated other comprehensive loss/(income)	$	1,143	$	1,267		$	169	$	1		$	982	$	1,072		$	128	$	(7	)

Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets

	2020						2019
	U.S.		U.K.		Other		U.S.		U.K.		Other
Projected benefit obligation at end of year	$	5,291	$	8	$	891	$	4,768	$	7	$	784
Fair value of plan assets at end of year	$	4,357	$	—	$	593	$	3,873	$	—	$	509

Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets

	2020						2019
	U.S.		U.K.		Other		U.S.		U.K.		Other
Projected benefit obligation at end of year	$	5,291	$	8	$	477	$	4,768	$	7	$	784
Accumulated benefit obligation at end of year	$	5,291	$	8	$	457	$	4,768	$	7	$	752
Fair value of plan assets at end of year	$	4,357	$	—	$	193	$	3,873	$	—	$	509

Schedule of Net Periodic Benefit Cost

	2020												2019												2018
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Components of net periodic benefit (income)/cost:
Service cost	$	72		$	15		$	21		$	1		$	65		$	14		$	20		$	1		$	66		$	18		$	21		$	1
Interest cost		131			73			15			2			157			93			18			3			140			95			18			4
Expected return on plan assets		(291	)		(247	)		(34	)		—			(254	)		(246	)		(29	)		—			(273	)		(298	)		(31	)		—
Amortization of unrecognized prior service credit		—			(17	)		—			(4	)		—			(16	)		—			(4	)		—			(19	)		—			—
Amortization of unrecognized actuarial loss		35			23			3			1			19			21			2			1			11			45			2			—
Settlement		2			3			1			—			—			—			1			—			1			41			2			—
Curtailment gain		—			—			—			—			—			—			—			—			—			—			(16	)		—
Net periodic benefit (income)/cost	$	(51	)	$	(150	)	$	6		$	—		$	(13	)	$	(134	)	$	12		$	1		$	(55	)	$	(118	)	$	(4	)	$	5
Other changes in plan assets and benefit obligations recognized in other comprehensive loss/(income):
Net actuarial loss/(gain)	$	198		$	151		$	35		$	5		$	232		$	157		$	32		$	5		$	117		$	191		$	13		$	(3	)
Amortization of unrecognized actuarial loss		(35	)		(23	)		(3	)		(1	)		(19	)		(21	)		(2	)		(1	)		(11	)		(45	)		(2	)		—
Prior service cost/(credit)		—			9			—			—			—			—			—			—			—			40			—			(31	)
Amortization of unrecognized prior service credit		—			17			—			4			—			16			—			4			—			19			—			—
Settlement		(2	)		(3	)		(1	)		—			—			—			(1	)		—			(1	)		(41	)		(2	)		—
Curtailment gain		—			—			—			—			—			—			—			—			—			—			16			—
Total recognized in other comprehensive loss/(income)		161			151			31			8			213			152			29			8			105			164			25			(34	)
Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income)	$	110		$	1		$	37		$	8		$	200		$	18		$	41		$	9		$	50		$	46		$	21		$	(29	)

Schedule of Assumptions Used

The assumptions used to determine net periodic benefit cost for the fiscal years ended December 31, 2020, 2019 and 2018 were as follows:

	Years ended December 31,
	2020												2019												2018
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Discount rate - PBO		3.3	%		2.0	%		2.1	%		3.2	%		4.2	%		2.8	%		2.8	%		4.2	%		3.6	%		2.6	%		2.6	%		3.5	%
Discount rate - service cost		3.4	%		2.1	%		2.5	%		3.3	%		4.3	%		2.9	%		3.0	%		4.2	%		3.5	%		2.7	%		2.9	%		3.5	%
Discount rate - interest cost on service cost		2.8	%		1.9	%		2.4	%		2.8	%		3.8	%		2.8	%		2.9	%		3.9	%		3.1	%		2.5	%		2.7	%		3.2	%
Discount rate - interest cost on PBO		2.8	%		1.8	%		1.9	%		2.8	%		3.9	%		2.6	%		2.5	%		3.9	%		3.2	%		2.3	%		2.3	%		3.1	%
Expected long-term rate of return on assets		7.7	%		5.0	%		5.9	%	N/A				7.6	%		5.6	%		6.0	%		2.0	%		7.6	%		6.2	%		5.7	%		2.0	%
Rate of increase in compensation levels		4.3	%		3.0	%		2.3	%	N/A				4.3	%		3.0	%		2.3	%	N/A				4.3	%		3.0	%		2.3	%	N/A
Healthcare cost trend
Initial rate											6.5	%											6.0	%											6.5	%
Ultimate rate											5.0	%											5.0	%											5.0	%
Year reaching ultimate rate										2027												2022												2022

The following tables present the assumptions used in the valuation to determine the projected benefit obligation for the fiscal years ended December 31, 2020 and 2019:

	December 31, 2020												December 31, 2019
	U.S.			U.K.			Other			PRW			U.S.			U.K.			Other			PRW
Discount rate		2.5	%		1.5	%		1.7	%		2.4	%		3.3	%		2.0	%		2.1	%		3.2	%
Rate of increase in compensation levels		4.3	%		3.0	%		2.3	%	N/A				4.3	%		3.0	%		2.3	%	N/A

Schedule of Allocation of Plan Assets

The Company’s pension plan asset target allocations as of December 31, 2020 were as follows:

	U.S.						U.K.									Canada			Germany			Ireland
Asset Category	Willis			Willis Towers Watson			Willis			Towers Watson			Miller			Towers Watson			Towers Watson			Willis			Towers Watson
Equity securities		30	%		23	%		—	%		1	%		19	%		40	%		36	%		29	%		40	%
Debt securities		33	%		33	%		30	%		24	%		21	%		50	%		57	%		29	%		30	%
Real estate		11	%		6	%		—	%		2	%		—	%		5	%		—	%		3	%		—	%
Other		26	%		38	%		70	%		73	%		60	%		5	%		7	%		39	%		30	%
Total		100	%		100	%		100	%		100	%		100	%		100	%		100	%		100	%		100	%

The fair values of our U.S. plan assets by asset category at December 31, 2020 and 2019 are as follows:

	December 31, 2020								December 31, 2019
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Asset category:
Cash ⁽ⁱ⁾	$	3	$	—	$	—	$	3	$	172	$	—	$	—	$	172
Short-term securities		—		106		—		106		—		99		—		99
Government bonds		—		—		—		—		4		—		—		4
Pooled / commingled funds		—		—		—		2,599		—		—		—		2,033
Private equity		—		—		—		415		—		—		—		487
Hedge funds		—		—		—		1,234		—		—		—		1,084
Total assets	$	3	$	106	$	—	$	4,357	$	176	$	99	$	—	$	3,879

(i)	At December 31, 2019, consists primarily of cash on deposit with the managers of the hedge funds due to the timing of purchases of units in the funds.

The fair values of our U.K. plan assets by asset category at December 31, 2020 and 2019 are as follows:

	December 31, 2020								December 31, 2019
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Asset category:
Cash	$	366	$	—	$	—	$	366	$	253	$	—	$	—	$	253
Government bonds		2,684		—		—		2,684		1,865		—		—		1,865
Corporate bonds		—		898		—		898		—		741		—		741
Other fixed income		—		458		—		458		—		350		—		350
Pooled / commingled funds		—		—		—		1,237		—		—		—		1,828
Mutual funds		—		—		—		59		—		—		—		34
Private equity		—		—		—		31		—		—		—		34
Derivatives		—		376		—		376		—		246		—		246
Real estate		—		—		—		159		—		—		—		161
Hedge funds		—		—		—		—		—		—		—		54
Insurance contracts		—		—		71		71		—		—		—		—
Total assets	$	3,050	$	1,732	$	71	$	6,339	$	2,118	$	1,337	$	—	$	5,566

Liability category:
Repurchase agreements		—		572		—		572		—		480		—		480
Net assets/(liabilities)	$	3,050	$	1,160	$	71	$	5,767	$	2,118	$	857	$	—	$	5,086

The fair values of our Other plan assets by asset category at December 31, 2020 and 2019 are as follows:

	December 31, 2020								December 31, 2019
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Asset category:
Cash	$	2	$	—	$	—	$	2	$	2	$	—	$	—	$	2
Pooled / commingled funds		—		—		—		635		—		—		—		444
Mutual funds		—		—		—		—		—		—		—		106
Hedge funds		—		—		—		39		—		—		—		34
Insurance contracts		—		—		8		8		—		—		2		2
Total assets	$	2	$	—	$	8	$	684	$	2	$	—	$	2	$	588

Schedule of Net Plan Investments Reconciliation To Total Fair Value Of Plan Assets

The following table reconciles the net plan investments to the total fair value of the plan assets:

	December 31,
	2020		2019
Net assets held in investments	$	10,808	$	9,553
Net receivable/(payable) for investments purchased		—		(7	)
Dividend and interest receivable		—		1
Fair value of plan assets	$	10,808	$	9,547

Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets

The following table sets forth a summary of changes in the fair value of the plans’ Level 3 assets for the fiscal year ended December 31, 2020:

	Level 3 Roll Forward
Beginning balance at December 31, 2019	$	2
Purchases		64
Unrealized gains		7
Foreign exchange		6
Ending balance at December 31, 2020	$	79

Schedule of Projected Pension Contributions

	2021 (Projected)		2020 (Actual)		2019 (Actual)
U.S.	$	60	$	40	$	60
U.K.	$	47	$	65	$	76
Other	$	25	$	24	$	22

Schedule of Expected Benefit Payments

Expected benefit payments from our defined benefit pension plans to current plan participants, including the effects of their expected future service, as appropriate, are as follows:

	Benefit Payments
Fiscal Year	U.S.		U.K.		Other		PRW		Total
2021	$	248	$	128	$	32	$	10	$	418
2022		275		122		28		10		435
2023		265		131		29		10		435
2024		274		139		31		11		455
2025		277		143		32		11		463
Years 2026 – 2029		1,421		808		187		58		2,474
	$	2,760	$	1,471	$	339	$	110	$	4,680

Leases (Tables)

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Schedule of Lease

	December 31, 2020						December 31, 2019
	Operating Leases		Finance Leases		Total Leases		Operating Leases		Finance Leases		Total Leases
Right-of-use assets	$	902	$	8	$	910	$	968	$	10	$	978
Current lease liabilities		152		3		155		164		3		167
Long-term lease liabilities		918		19		937		964		22		986

Schedule of Amount Recorded in Condensed Consolidated Statements of Comprehensive Income

The following tables present amounts recorded on our consolidated statements of comprehensive income for the years ended December 31, 2020 and 2019:

	Years ended December 31,
	2020			2019
Finance lease cost:
Amortization of right-of-use assets	$	2		$	2
Interest on lease liabilities		3			3
Operating lease cost		181			191
Short-term lease cost		1			2
Variable lease cost		53			51
Sublease income		(21	)		(16	)
Total lease cost, net	$	219		$	233

Schedule of Cash Paid in the Measurement of Lease Liabilities

	Years ended December 31,
	2020		2019
Cash flows from operating activities:
Operating leases	$	190	$	205
Finance leases		3		3
Cash flows used in financing activities:
Finance leases		3		2
Total lease payments	$	196	$	210

Schedule of Weighted Average Term and Discount Rates

Our operating and finance leases have the following weighted-average terms and discount rates as of December 31, 2020 and 2019:

	December 31, 2020						December 31, 2019
	Operating Leases			Finance Leases			Operating Leases			Finance Leases
Weighted-average term (in years)		8.3			5.2			8.8			6.0
Weighted-average discount rate		3.4	%		12.9	%		3.6	%		12.9	%

Schedule of Maturity of Operating and Finance Leases Liabilities

	Operating Leases			Finance Leases			Total Leases
2021	$	185		$	6		$	191
2022		172			6			178
2023		157			6			163
2024		138			6			144
2025		123			6			129
Thereafter		458			1			459
Total future lease payments		1,233			31			1,264
Interest		(163	)		(9	)		(172	)
Total lease liabilities	$	1,070		$	22		$	1,092

Supplementary Information for Certain Balance Sheet Accounts (Tables)

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Prepaid and Other Current Asset

Prepaid and other current assets consist of the following:

	December 31, 2020		December 31, 2019
Prepayments and accrued income	$	124	$	145
Deferred contract costs		108		101
Derivatives and investments		42		49
Deferred compensation plan assets		14		18
Retention incentives		3		11
Corporate income and other taxes		83		56
Insurance and other recovery receivables		25		—
Restricted cash		7		8
Acquired renewal commissions receivable		16		25
Other current assets		75		112
Total prepaid and other current assets	$	497	$	525

Schedule of Other Non-current Assets

Other non-current assets consist of the following:

	December 31, 2020		December 31, 2019
Prepayments and accrued income	$	13	$	12
Deferred contract costs		98		76
Deferred compensation plan assets		117		150
Deferred tax assets		95		72
Accounts receivable, net		34		30
Acquired renewal commissions receivable		84		125
Long-term note receivable		71		—
Other investments		24		23
Insurance recovery receivables		117		119
Non-current contract assets		329		105
Other non-current assets		114		123
Total other non-current assets	$	1,096	$	835

Deferred Revenue and Accrued Liabilities

Deferred revenue and accrued expenses consist of the following:

	December 31, 2020		December 31, 2019
Accounts payable, accrued liabilities and deferred income	$	862	$	856
Accrued discretionary and incentive compensation		851		727
Litigation settlement		210		—
Accrued vacation		161		137
Other employee-related liabilities		77		64
Total deferred revenue and accrued expenses	$	2,161	$	1,784

Schedule of Other Current Liabilities

Other current liabilities consist of the following:

	December 31, 2020		December 31, 2019
Dividends payable	$	103	$	100
Income and other taxes payable		102		138
Interest payable		68		65
Deferred compensation plan liabilities		57		14
Contingent and deferred consideration on acquisitions		39		12
Payroll-related liabilities		268		216
Derivatives		5		3
Third-party commissions		173		179
Other current liabilities		73		75
Total other current liabilities	$	888	$	802

Provisions for Liabilities

Provision for liabilities consists of the following:

	December 31, 2020		December 31, 2019
Claims, lawsuits and other proceedings	$	325	$	456
Other provisions		82		81
Total provision for liabilities	$	407	$	537

Schedule of Other Non-current Liabilities

Other non-current liabilities consist of the following:

	December 31, 2020		December 31, 2019
Deferred compensation plan liability	$	117	$	150
Contingent and deferred consideration on acquisitions		16		26
Liabilities for uncertain tax positions		49		48
Derivatives		2		—
Finance leases		19		22
Other non-current liabilities		109		89
Total other non-current liabilities	$	312	$	335

Other Income, Net (Tables)

12 Months Ended

Dec. 31, 2020

Other Income And Expenses [Abstract]

Schedule of Other Nonoperating Income

Other income, net consists of the following:

	Years ended December 31,
	2020		2019			2018
Gain/(loss) on disposal of operations	$	81	$	(2	)	$	(9	)
Net periodic pension and postretirement benefit credits		304		234			280
Interest in earnings of associates and other investments		6		21			3
Foreign exchange gain/(loss)		6		(26	)		(24	)
Other		2		—			—
Other income, net	$	399	$	227		$	250

Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Comprehensive Income (Loss)

The components of other comprehensive (loss)/income are as follows:

	December 31, 2020								December 31, 2019									December 31, 2018
	Before tax amount			Tax		Net of tax amount			Before tax amount			Tax			Net of tax amount			Before tax amount			Tax			Net of tax amount
Other comprehensive income/(loss):
Foreign currency translation	$	139		$	—	$	139		$	78		$	—		$	78		$	(251	)	$	—		$	(251	)
Defined pension and post-retirement benefits		(342	)		76		(266	)		(412	)		83			(329	)		(258	)		59			(199	)
Derivative instruments		(5	)		1		(4	)		23			(2	)		21			5			(3	)		2
Other comprehensive loss		(208	)		77		(131	)		(311	)		81			(230	)		(504	)		56			(448	)
Less: Other comprehensive income attributable to non-controlling interests		(1	)		—		(1	)		—			—			—			—			—			—
Other comprehensive loss attributable to Willis Towers Watson	$	(209	)	$	77	$	(132	)	$	(311	)	$	81		$	(230	)	$	(504	)	$	56		$	(448	)

Schedule of Accumulated Other Comprehensive Income (Loss)

	Foreign currency translation ⁽ⁱ⁾			Derivative instruments ⁽ⁱ⁾			Defined pension and post- retirement benefit costs ⁽ⁱⁱ⁾			Total
Balance, January 1, 2018	$	(365	)	$	(10	)	$	(1,138	)	$	(1,513	)
Other comprehensive loss before reclassifications		(251	)		(22	)		(241	)		(514	)
Loss reclassified from accumulated other comprehensive loss (net of income tax benefit of $17)		—			24			42			66
Net other comprehensive (loss)/income		(251	)		2			(199	)		(448	)
Balance, December 31, 2018	$	(616	)	$	(8	)	$	(1,337	)	$	(1,961	)
Other comprehensive income/(loss) before reclassifications		78			12			(343	)		(253	)
Loss reclassified from accumulated other comprehensive loss (net of income tax benefit of $9)		—			9			14			23
Net other comprehensive income/(loss)		78			21			(329	)		(230	)
Reclassification of tax effects per ASU 2018-02 ⁽ⁱⁱⁱ⁾		—			—			(36	)		(36	)
Balance, December 31, 2019	$	(538	)	$	13		$	(1,702	)	$	(2,227	)
Other comprehensive income/(loss) before reclassifications		138			(12	)		(298	)		(172	)
Loss reclassified from accumulated other comprehensive loss (net of income tax benefit of $11)		—			8			32			40
Net other comprehensive income/(loss)		138			(4	)		(266	)		(132	)
Balance, December 31, 2020	$	(400	)	$	9		$	(1,968	)	$	(2,359	)

(i)

(ii)	Reclassification adjustments from accumulated other comprehensive loss are included in the computation of net periodic pension cost (see Note 12 — Retirement Benefits). These components are included in Other income, net in the accompanying consolidated statements of comprehensive income.

(iii)

Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity

A summary of option activity under the plans at December 31, 2020, and changes during the year then ended is presented below:

	Options (thousands)		Weighted- Average Exercise Price ⁽ⁱ⁾		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Time-based stock options
Balance as of December 31, 2019		260	$	105.38
Exercised		163	$	101.09
Cancelled		12	$	95.56
Balance as of December 31, 2020		85	$	114.92	1.5 years	$	8
Options vested or expected to vest at December 31, 2020		85	$	114.92	1.5 years	$	8
Options exercisable at December 31, 2020		57	$	107.72	1.4 years	$	6
Performance-based stock options
Balance as of December 31, 2019		287	$	110.58
Exercised		3	$	110.58
Balance as of December 31, 2020		284	$	110.58	1.7 years	$	28
Options vested or expected to vest at December 31, 2020		284	$	110.58	1.7 years	$	28
Options exercisable at December 31, 2020		284	$	110.58	1.7 years	$	28

(i)	Certain options are exercisable in Pounds sterling and are converted to dollars using the exchange rate at December 31, 2020.

Schedule of Assumptions

The assumptions noted in the table below represent the weighted average of each assumption for each grant during the year.

	Years ended December 31,
	2020			2019			2018
Expected volatility		24.2	%		25.6	%		17.9	%
Expected dividend yield		—	%		—	%		—	%
Expected life (years)		2.9			2.7			2.5
Risk-free interest rate		0.4	%		2.1	%		2.6	%

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

Award Activity

A summary of time-based and performance-based RSU activity under the plans at December 31, 2020, and changes during the year then ended, is presented below:

	Shares (thousands)		Weighted- Average Grant Date Fair Value
Nonvested shares (time-based RSUs)
Balance as of December 31, 2019		11	$	172.25
Granted		13	$	193.25
Vested		13	$	178.54
Forfeited		—	$	160.48
Balance as of December 31, 2020		11	$	190.09
Nonvested shares (performance-based RSUs)
Balance as of December 31, 2019		507	$	150.22
Granted		356	$	230.24
Vested		416	$	117.01
Forfeited		8	$	216.64
Balance as of December 31, 2020		439	$	245.49

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Earnings Per Share

Basic and diluted earnings per share are as follows:

	Years ended December 31,
	2020			2019			2018
Net income attributable to Willis Towers Watson	$	996		$	1,044		$	695

Basic weighted-average number of shares outstanding		130			130			131
Dilutive effect of potentially issuable shares		—			—			1
Diluted weighted-average number of shares outstanding		130			130			132

Basic earnings per share	$	7.68		$	8.05		$	5.29
Dilutive effect of potentially issuable shares		(0.03	)		(0.03	)		(0.02	)
Diluted earnings per share	$	7.65		$	8.02		$	5.27

Supplemental Disclosures of Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2020

Supplemental Cash Flow Elements [Abstract]

Supplemental Disclosures Regarding Cash Flow Information and Non-cash Flow Investing and Financing Activities

Supplemental disclosures regarding cash flow information and non-cash investing and financing activities are as follows:

	Years Ended December 31,
	2020		2019		2018
Supplemental disclosures of cash flow information:
Cash payments for income taxes, net	$	310	$	299	$	178
Cash payments for interest	$	229	$	210	$	176
Cash acquired	$	10	$	11	$	13
Supplemental disclosures of non-cash investing and financing activities:
Fair value of deferred and contingent consideration related to acquisitions	$	9	$	13	$	36

Nature of Operations (Details)	Dec. 31, 2020 Employee Country
Minority Interest [Line Items]
Number of employees employed (more than 00,000) \| Employee	46,000
Number of countries in which entity operates (more than 140) \| Country	140
Proposed Combination with AON Plc [Member]
Minority Interest [Line Items]
Number of shares receivable upon acquisition	1.08
Proposed Combination with AON Plc [Member] \| Aon Plc [Member]
Minority Interest [Line Items]
Percentage of ownership by parent	63.00%
Proposed Combination with AON Plc [Member] \| Willis Towers Watson Public Limited Company [Member]
Minority Interest [Line Items]
Percentage of ownership by non-controlling owner	37.00%

Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Narrative (Details)			3 Months Ended	12 Months Ended
	Mar. 27, 2020	Mar. 26, 2020	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) Unit	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Business interest deductions percentage		30.00%
Realized cash tax benefit				$ 83,000,000	$ 56,000,000
Income tax expense				318,000,000	249,000,000	$ 136,000,000
Unencumbered and available funds required				2,089,000,000	887,000,000
Restricted cash				$ 7,000,000	$ 8,000,000	$ 0	$ 0
Percentage of lease denominated in U.S. dollars, Pounds Sterling or Euros				90.00%
Number of reporting units \| Unit				8
Other [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Portion of Revenue				5.00%	5.00%	5.00%
Broking [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Portion of Revenue				52.00%	50.00%	48.00%
Consulting [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Portion of Revenue				30.00%	32.00%	34.00%
Outsourced administration [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Portion of Revenue				12.00%	12.00%	12.00%
Reimbursed Expenses [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Portion of Revenue				1.00%	1.00%	1.00%
Buildings [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Useful life				50 years
Tranzact Collateralized Facility [Member] \| Prepaid Expenses and Other Current Assets [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Restricted cash				$ 7,000,000	$ 8,000,000
Minimum [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Percentage of entity voting rights				50.00%
Equity ownership voting percentage				20.00%
Real estate lease term				5 years
Minimum [Member] \| Internally developed software [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Useful life				3 years
Minimum [Member] \| Furniture, equipment and software [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Useful life				3 years
Minimum [Member] \| Willis Limited [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Unencumbered and available funds required				$ 140,000,000
Unencumbered and available cash balance required				$ 51,000,000
Maximum [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Equity ownership voting percentage				50.00%
Real estate lease term				15 years
Term for renewal commissions expected				25 years
Maximum [Member] \| Internally developed software [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Useful life				10 years
Maximum [Member] \| Furniture, equipment and software [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Useful life				10 years
CARES [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Business interest deductions percentage	50.00%
Tax Year2019 And2020 [Member] \| CARES [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Business interest deductions percentage			50.00%
Realized cash tax benefit			$ 38,000,000
BEAT [Member] \| Tax Year 2019 [Member] \| CARES [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Income tax expense			$ 29,000,000	$ 29,000,000
BEAT [Member] \| Tax Year 2020 [Member] \| CARES [Member]
Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Income tax expense				$ 32,000,000

Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Acquired Intangible Assets Amortized (Details)	12 Months Ended
	Dec. 31, 2020
Minimum [Member] \| Client relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	5 years
Minimum [Member] \| Software [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	4 years
Minimum [Member] \| Trademark and trade name [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	14 years
Minimum [Member] \| Other [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	3 years
Maximum [Member] \| Client relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	20 years
Maximum [Member] \| Software [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	7 years
Maximum [Member] \| Trademark and trade name [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	25 years
Maximum [Member] \| Other [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Expected life	20 years

Acquisitions and Divestitures - Narrative (Details) - USD ($)

12 Months Ended

Jul. 30, 2019

Dec. 21, 2018

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Other intangible assets, net

1 year

Intangible assets

$ 62,000,000

$ 660,000,000

^[1]

3,043,000,000

3,478,000,000

Customer Relationships [Member]

11,204,000,000

11,194,000,000

$ 10,465,000,000

Maximum [Member] | Customer Relationships [Member]

Intangible assets

$ 30,000,000

626,000,000

^[1]

Intangible assets expected life

20 years

Minimum [Member] | Customer Relationships [Member]

Intangible assets expected life

5 years

TRANZACT Acquisition [Member]

Business acquisition, effective date of acquisition

Jul. 30, 2019

Consideration paid in cash

$ 1,300,000,000

Business combination, contingent consideration arrangements, range of outcomes, value, high

17,000,000

TRANZACT Acquisition [Member] | Customer Relationships [Member]

718,000,000

Intangible assets expected life

Intangible assets

$ 612,000,000

15 years 4 months 24 days

TRANZACT Acquisition [Member] | Term Loan [Member]

TRANZACT Acquisition [Member] | Term Loan [Member] | Maximum [Member]

1 year

Alston Gayler Acquisition [Member]

$ 1,100,000,000

Consideration paid in cash

$ 35,000,000

Total consideration

67,000,000

Deferred consideration

32,000,000

Other intangible assets, net

36,000,000

Other Acquisitions [Member]

$ 24,000,000

Consideration paid in cash

$ 79,000,000

Contingent consideration estimated fair value

$ 9,000,000

[1]	Includes $612 million and $34 million of client relationship and domain name intangible assets, respectively, associated with our acquisition of TRANZACT.

Acquisitions and Divestitures - Summary of Fair Values of Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($)
$ in Millions

Dec. 31, 2020

Dec. 31, 2019

Jul. 30, 2019

Dec. 31, 2018

TRANZACT Acquisition [Member]

$ 11,204

$ 11,194

$ 10,465

Cash and cash equivalents

$ 7

Restricted cash

Accounts receivable, net

Renewal commissions receivable, current

^[1]

Prepaid and other current assets

Renewal commissions receivable, non-current

^[1]

130

646

718

Other non-current assets

Collateralized facility

^[2]

(91)

Other current liabilities

(55)

Deferred tax liabilities, net

(100)

Lease liabilities

(19)

Net assets acquired

$ 1,329

[1]

[2]

See Note 10 — Debt for a description of the acquired collateralized facility debt.

Acquisitions and Divestitures - Summary of Preliminary Fair Values of Identifiable Assets Acquired and Liabilities Assumed (Parenthetical) (Details) $ in Millions	Jul. 30, 2019 USD ($)
TRANZACT Acquisition [Member]
Business Acquisition [Line Items]
Receivables prior to fair value adjustment	$ 231

Acquisitions and Divestitures - Max Matthiessen Divestiture (Details) kr in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2020 SEK (kr)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Tax exempt gain on sale		$ 81	$ (2)	$ (9)
Max Matthiessen [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Total consideration received from sale of subsidiary	$ 262				kr 2,300
Notes receivable repayable by purchaser	68				kr 600
Max Matthiessen [Member] \| Other Income, Net [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Tax exempt gain on sale	$ 86
Minimum [Member] \| Max Matthiessen [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Disposal group including discontinued operation notes payable interest rate	5.00%
Maximum [Member] \| Max Matthiessen [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Disposal group including discontinued operation notes payable interest rate	10.00%

Acquisitions and Divestitures - Miller Divestiture (Details) - Miller [Member] £ in Millions, $ in Millions	Mar. 31, 2021 USD ($)	Mar. 31, 2021 GBP (£)	Dec. 31, 2020 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net assets			$ 350
Scenario Forecast [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Total consideration received from sale of subsidiary	$ 808	£ 591

Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Revenue from Contract with Customer, Excluding Assessed Tax

$ 9,286

$ 8,941

$ 8,413

^[1]

100

9,352

9,039

8,513

Broking [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

4,850

4,459

4,021

Consulting [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

2,767

2,833

2,830

Outsourced administration [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

1,109

1,068

1,035

Other [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

486

476

433

Operating Segments [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

9,212

8,836

8,319

Segment Reconciling Items [Member]

9,265

8,916

8,399

Revenue from Contract with Customer, Excluding Assessed Tax

^[2]

105

123

114

HCB [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

3,311

3,336

3,271

^[1]

HCB [Member] | Broking [Member]

3,328

3,359

3,295

Revenue from Contract with Customer, Excluding Assessed Tax

302

278

266

HCB [Member] | Consulting [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

2,215

2,269

2,224

HCB [Member] | Outsourced administration [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

503

466

484

HCB [Member] | Other [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

241

262

235

HCB [Member] | Operating Segments [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

3,261

3,275

3,209

HCB [Member] | Segment Reconciling Items [Member]

3,278

3,298

3,233

Revenue from Contract with Customer, Excluding Assessed Tax

^[2]

CRB [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

2,940

2,901

2,815

^[1]

CRB [Member] | Broking [Member]

2,979

2,947

2,852

Revenue from Contract with Customer, Excluding Assessed Tax

2,707

2,692

2,578

CRB [Member] | Consulting [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

154

132

163

CRB [Member] | Outsourced administration [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

CRB [Member] | Other [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

CRB [Member] | Operating Segments [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

2,938

2,900

2,815

CRB [Member] | Segment Reconciling Items [Member]

2,977

2,946

2,852

Revenue from Contract with Customer, Excluding Assessed Tax

^[2]

IRR [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

1,653

1,620

1,528

^[1]

IRR [Member] | Broking [Member]

1,659

1,646

1,564

Revenue from Contract with Customer, Excluding Assessed Tax

1,006

975

905

IRR [Member] | Consulting [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

393

421

430

IRR [Member] | Outsourced administration [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

IRR [Member] | Other [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

231

205

185

IRR [Member] | Operating Segments [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

1,645

1,611

1,520

IRR [Member] | Segment Reconciling Items [Member]

1,651

1,637

1,556

Revenue from Contract with Customer, Excluding Assessed Tax

^[2]

BDA [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

1,371

1,047

765

BDA [Member] | Broking [Member]

1,371

1,047

765

Revenue from Contract with Customer, Excluding Assessed Tax

834

514

272

BDA [Member] | Outsourced administration [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

525

521

486

BDA [Member] | Operating Segments [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

1,359

1,035

758

BDA [Member] | Segment Reconciling Items [Member]

1,359

1,035

758

Revenue from Contract with Customer, Excluding Assessed Tax

^[2]

Corporate, Non-Segment [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

^[1]

Corporate, Non-Segment [Member] | Broking [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

Corporate, Non-Segment [Member] | Consulting [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

Corporate, Non-Segment [Member] | Other [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

Corporate, Non-Segment [Member] | Operating Segments [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

Corporate, Non-Segment [Member] | Segment Reconciling Items [Member]

Revenue from Contract with Customer, Excluding Assessed Tax

^[2]

$ 2

$ 22

$ 17

[1]	Interest and other income is included in segment revenue and total revenue, however it has been presented separately in the above tables because it does not arise directly from contracts with customers.
[2]	Reimbursable expenses and other, as well as Corporate revenue, are excluded from segment revenue, but included in total revenue on the consolidated statements of comprehensive income.

Revenue - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Revenue - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 37
December 31 2019 [Member]
Disaggregation Of Revenue [Line Items]
Contract with Customer, Liability, Revenue Recognized	$ 497
Maximum [Member] \| Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue, Percentage of Total Revenue	5.00%	5.00%	5.00%

Revenue - Schedule of Revenue by Geography (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 9,286	$ 8,941	$ 8,413
Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9,212	8,836	8,319
Corporate, Non-Segment [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9	15	17
North America [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,867	4,508	4,083
North America [Member] \| Corporate, Non-Segment [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	7	13	16
Great Britain [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,945	1,919	1,861
Western Europe [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,458	1,444	1,412
Western Europe [Member] \| Corporate, Non-Segment [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2	1	1
International [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	942	965	963
International [Member] \| Corporate, Non-Segment [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1
HCB [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,311	3,336	3,271
HCB [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,261	3,275	3,209
HCB [Member] \| North America [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,859	1,901	1,849
HCB [Member] \| Great Britain [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	491	475	481
HCB [Member] \| Western Europe [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	584	566	562
HCB [Member] \| International [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	327	333	317
CRB [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,940	2,901	2,815
CRB [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,938	2,900	2,815
CRB [Member] \| North America [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,176	1,112	1,044
CRB [Member] \| Great Britain [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	630	656	648
CRB [Member] \| Western Europe [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	679	661	631
CRB [Member] \| International [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	453	471	492
IRR [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,653	1,620	1,528
IRR [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,645	1,611	1,520
IRR [Member] \| North America [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	474	449	416
IRR [Member] \| Great Britain [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	824	788	732
IRR [Member] \| Western Europe [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	193	216	218
IRR [Member] \| International [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	154	158	154
BDA [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,371	1,047	765
BDA [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,359	1,035	758
BDA [Member] \| North America [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,351	1,033	$ 758
BDA [Member] \| International [Member] \| Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 8	$ 2

Revenue - Schedule of Contract Balances (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Revenue From Contract With Customer [Abstract]
Billed Receivable, Current	$ 1,697	$ 1,831
Unbilled Receivable, Current	445	434
Contract asset, Current	413	356
Accounts receivable, net	2,555	2,621
Non-current accounts receivable, net	34	30
Contract asset, Noncurrent	329	105
Deferred revenue	$ 549	$ 538

Revenue - Schedule of Contract Balances (Parenthetical) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Revenue From Contract With Customer [Abstract]
Allowance for doubtful debts	$ 41	$ 37

Revenue - Schedule of Changes in Allowance for Doubtful Accounts (Details) - Allowance for doubtful accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 37	$ 40	$ 45
Additions charged to costs and expenses	29	9	9
Deductions/other movements	(29)	(10)	(15)
Foreign exchange	4	(2)	1
Balance at end of year	$ 41	$ 37	$ 40

Revenue - Schedule of Remaining Performance Obligations (Details) $ in Millions	Dec. 31, 2020 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 1,429
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 540
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 392
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 497
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period

Revenue - Schedule of Remaining Performance Obligations (Details1) $ in Millions	Dec. 31, 2020 USD ($)
Revenue From Contract With Customer [Abstract]
Revenue, Remaining Performance Obligation	$ 1,429

Revenue - Schedule of Capitalized and Deferred Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Capitalized Contract Cost [Abstract]
Capitalized Contract Cost, Net	$ 177	$ 148	$ 126
Capitalized Contract Cost, Additions	493	488	465
Capitalized Contract Cost, Amortization	(465)	(460)	(442)
Capitalized Contract Cost, Impairment Loss	(1)	0	0
Capitalized Contract Cost, Foreign Exchange Translation Gain (Loss)	2	1	(1)
Capitalized Contract Cost, Net	$ 206	$ 177	$ 148

Segment Information - Narrative (Details)	12 Months Ended
Segment Information - Narrative (Details)	Dec. 31, 2020 segment
Segment Reporting [Abstract]
Number of operating segments	4
Number of reportable segments	4

Segment Information - Revenue (Net of Reimbursable Expenses) of the Reported Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 9,352	$ 9,039	$ 8,513
Income from operations	1,183	1,329	809
HCB [Member]
Segment Reporting Information [Line Items]
Revenues	3,328	3,359	3,295
CRB [Member]
Segment Reporting Information [Line Items]
Revenues	2,979	2,947	2,852
IRR [Member]
Segment Reporting Information [Line Items]
Revenues	1,659	1,646	1,564
BDA [Member]
Segment Reporting Information [Line Items]
Revenues	1,371	1,047	765
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	9,265	8,916	8,399
Income from operations	2,260	2,090	1,845
Operating Segments [Member] \| HCB [Member]
Segment Reporting Information [Line Items]
Revenues	3,278	3,298	3,233
Income from operations	853	848	789
Operating Segments [Member] \| CRB [Member]
Segment Reporting Information [Line Items]
Revenues	2,977	2,946	2,852
Income from operations	630	578	528
Operating Segments [Member] \| IRR [Member]
Segment Reporting Information [Line Items]
Revenues	1,651	1,637	1,556
Income from operations	457	420	384
Operating Segments [Member] \| BDA [Member]
Segment Reporting Information [Line Items]
Revenues	1,359	1,035	758
Income from operations	$ 320	$ 244	$ 144

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
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Segment Information - Reconciliation of Information Reported by Segment to Consolidated Amounts (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Revenue:

Income/(loss) from operations

$ 9,352

$ 9,039

$ 8,513

1,183

1,329

809

(462)

(489)

(534)

Restructuring costs

(24)

Income from operations before income taxes

(244)

(234)

(208)

Other income, net

399

227

250

1,338

1,322

851

Operating Segments [Member]

Revenue:

Income/(loss) from operations

9,265

8,916

8,399

2,260

2,090

1,845

Segment Reconciling Items [Member]

Revenue:

Income/(loss) from operations

123

114

1,183

1,329

809

Transaction and integration expenses

(462)

(489)

(534)

Restructuring costs

^[1]

(24)

^[2]

(110)

(13)

(202)

Provision for significant litigation

^[3]

(65)

Unallocated, net

^[4]

(416)

(259)

(300)

(244)

(234)

(208)

Other income, net

$ 399

$ 227

$ 250

[1]	Restructuring costs relate to minor restructuring activities carried out by various business lines throughout the Company.
[2]	Includes transaction costs related to the proposed Aon combination in 2020, the TRANZACT acquisition in 2019, and transaction and integration expenses related to the Merger and the acquisition of Gras Savoye in 2018.
[3]	For additional information, see the disclosure under Willis Towers Watson Merger-Related Securities Litigation in Note 14 — Commitments and Contingencies
[4]	Includes certain costs, primarily related to corporate functions which are not directly related to the segments, and certain differences between budgeted expenses determined at the beginning of the year and actual expenses that we report for U.S. GAAP purposes.

Segment Information - Revenue and Long-Lived Assets by Geographical Areas (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

$ 9,352

$ 9,039

$ 8,513

^[1]

18,135

18,317

15,906

Ireland [Member]

157

144

138

^[1]

110

103

United States [Member]

4,650

4,370

3,970

^[1]

12,652

12,786

11,068

United Kingdom [Member]

1,920

1,934

1,926

^[1]

2,840

2,901

2,349

Rest of World [Member]

2,625

2,591

2,479

Total Foreign Countries [Member]

^[1]

2,533

2,527

2,411

9,195

8,895

8,375

^[1]

$ 18,025

$ 18,214

$ 15,828

[1]	Long-lived assets do not include deferred tax assets.

Movement in Property, Plant and Equipment [Roll Forward]

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Income Tax Expense Benefit		$ 318	$ 249	$ 136
Deferred income tax benefit		$ 99	$ (72)	$ (115)
U.S. statutory tax rate		21.00%	21.00%	21.00%
Net operating losses		$ 92	$ 116
Deferred Tax Assets, Net of Valuation Allowance		875	885
Increase (decrease) in valuation allowance		8	(5)	$ (81)
Valuation allowance		84	76
Additional repatriation, amount previously deemed indefinitely reinvested				2,100
Permanently reinvested		8,900
Unrecognized tax benefits		50	49	49	$ 59
Decrease in unrecognized tax benefits is reasonably possible		3	3	2
Interest on income taxes accrued		5	4
Interest Expense [Member]
Operating Loss Carryforwards [Line Items]
Tax expense includes in interest expense		1	$ 1
Internal Restructuring [Member]
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance				(80)
Foreign earnings that could have been repatriated		2,100
Permanently reinvested		$ 1,400
Valuation Allowance of Deferred Tax Assets [Member]
Operating Loss Carryforwards [Line Items]
Deferred income tax benefit				$ (71)
CARES [Member] \| BEAT [Member]
Operating Loss Carryforwards [Line Items]
Percent of minimum tax for taxable income adjusted		10.00%
CARES [Member] \| BEAT [Member] \| Tax Year 2019 [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Expense Benefit	$ 29	$ 29
State and Local [Member] \| United States [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses		621
Operating loss carryforwards, not subject to expiration		97
State and Local [Member] \| United States [Member] \| Tax Year 2021 Through 2040 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, subject to expiration		524
U.S. Federal and Non-U.S. [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses		258
Operating loss carryforwards, not subject to expiration		209
U.S. Federal and Non-U.S. [Member] \| Tax Year 2021 Through 2040 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, subject to expiration		49
UK Tax [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance		26
US State and Non-US [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance		$ 19
Revenue Commissioners, Ireland [Member] \| Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Foreign statutory income tax rate		25.00%
Her Majesty's Revenue and Customs (HMRC) [Member] \| Foreign Tax Authority [Member] \| Capital Loss Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance		$ 39
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit		4
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit		$ 8

Income Taxes - Income (Loss) from Operations Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items]
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES	$ 1,338	$ 1,322	$ 851
Revenue Commissioners, Ireland [Member] \| Domestic Tax Authority [Member]
Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items]
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES	(5)	(11)	(16)
Internal Revenue Service (IRS) [Member] \| Foreign Tax Authority [Member]
Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items]
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES	25	178	(101)
Her Majesty's Revenue and Customs (HMRC) [Member] \| Foreign Tax Authority [Member]
Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items]
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES	332	337	182
Rest of World [Member] \| Foreign Tax Authority [Member]
Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items]
INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES	$ 986	$ 818	$ 786

Income Taxes - (Provision for) Benefit from Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current tax expense:
U.S. federal taxes	$ (27)	$ (108)	$ (98)
U.S. state and local taxes	(5)	(43)	(25)
U.K. corporation tax	(45)	(43)	(16)
Other jurisdictions	(142)	(127)	(112)
Total current tax expense	(219)	(321)	(251)
Deferred tax (expense)/benefit:
U.S. federal taxes	(78)	56	79
U.S. state and local taxes	1	14	12
U.K. corporation tax	(48)	(15)	(6)
Other jurisdictions	26	17	30
Total deferred tax (expense)/benefit	(99)	72	115
Total provision for income taxes	$ (318)	$ (249)	$ (136)

Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
INCOME FROM OPERATIONS BEFORE INCOME TAXES	$ 1,338	$ 1,322	$ 851
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%
Income tax expense at U.S. federal tax rate	$ (281)	$ (278)	$ (179)
Non-deductible expenses and dividends	(20)	(34)	(44)
Non-deductible acquisition costs	(15)	(2)	(2)
Disposal of non-deductible goodwill	0	0	1
Impact of change in rate on deferred tax balances	(7)	0	7
Effect of foreign exchange and other differences	(3)	1	1
Changes in valuation allowances	(8)	6	80
Net tax effect of intra-group items	90	93	99
Tax on disposal of operations	16	0	0
Tax differentials of non-U.S. jurisdictions	3	(2)	(2)
Tax differentials of U.S. state taxes and local taxes	(3)	(21)	(77)
Global Intangible Low-Taxed Income (GILTI)	(3)	(7)	(15)
Base Erosion Anti-Abuse Tax (BEAT)	(81)	0	0
Other items, net	(6)	(5)	(5)
Total provision for income taxes	$ (318)	$ (249)	$ (136)

Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Accrued expenses not currently deductible	$ 212	$ 201
Net operating losses	92	116
Capital loss carryforwards	40	33
Accrued retirement benefits	334	326
Operating lease liabilities	165	181
Deferred compensation	90	86
Stock options	25	18
Financial derivative transactions	1	0
Gross deferred tax assets	959	961
Less: valuation allowance	(84)	(76)
Net deferred tax assets	875	885
Deferred tax liabilities:
Cost of intangible assets, net of related amortization	788	865
Operating lease right-of-use assets	159	177
Cost of tangible assets, net of related depreciation	78	53
Prepaid retirement benefits	152	121
Financial derivative transactions	1	3
Accrued revenue not currently taxable	163	120
Deferred tax liabilities	1,341	1,339
Net deferred tax liabilities	$ 466	$ 454

Income Taxes - Deferred Tax Liabilities, Balance Sheet Classification (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Tax Credit Carryforward [Line Items]
Other non-current assets	$ 875	$ 885
Deferred tax liabilities	1,341	1,339
Net deferred tax liabilities	466	454
Other Non-current Assets [Member]
Tax Credit Carryforward [Line Items]
Other non-current assets	95	72
Deferred Tax Liabilities [Member]
Tax Credit Carryforward [Line Items]
Deferred tax liabilities	$ 561	$ 526

Income Taxes - Valuation Allowance (Details) - Valuation Allowance of Deferred Tax Assets [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 76	$ 81	$ 162
Additions charged to costs and expenses	17	7	18
Deductions	(9)	(12)	(99)
Balance at end of year	$ 84	$ 76	$ 81

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 49	$ 49	$ 59
Increases related to acquisitions	4	0	0
Increases related to tax positions in prior years	1	2	2
Decreases related to tax positions in prior years	0	(1)	(4)
Decreases related to settlements	(3)	0	(4)
Decreases related to lapse in statute of limitations	(2)	(1)	(5)
Increases related to current year tax positions	0	0	3
Cumulative translation adjustment and other adjustments	1	0	(2)
Balance at end of year	$ 50	$ 49	$ 49

Income Taxes - Summary of Tax Years that Remain Open to Tax Examination in Major Tax Jurisdictions (Details)	12 Months Ended
	Dec. 31, 2020
U.S. - Federal [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2017 and forward
State and Local [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2014 and forward
Foreign Tax Authority [Member] \| United Kingdom [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2010 and forward
Foreign Tax Authority [Member] \| Ireland [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2016 and forward
Foreign Tax Authority [Member] \| France [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2010 and forward
Foreign Tax Authority [Member] \| Germany [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2010 and forward
Foreign Tax Authority [Member] \| Canada - Federal [Member]
Income Tax Contingency [Line Items]
Open Tax Years	2013 and forward

Fixed Assets - Components of Fixed Assets (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

$ 1,942

$ 1,710

Additions

269

336

Acquisitions

Reclassification due to ASC 842

(77)

(132)

^[1]

(3)

Abandonment of long-lived asset

^[2]

(35)

Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward]

2,141

1,942

$ 1,710

(896)

(768)

^[2]

(273)

(308)

(240)

(213)

120

(24)

(8)

(1,127)

(896)

(768)

Furniture, equipment and software [Member]

1,014

1,046

Movement in Property, Plant and Equipment [Roll Forward]

1,302

1,130

Additions

238

268

Acquisitions

Abandonment of long-lived asset

(64)

(117)

^[2]

(35)

Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward]

1,473

1,302

1,130

(594)

(519)

^[2]

(214)

(179)

109

(17)

(5)

(769)

(594)

(519)

Leasehold Improvements [Member]

704

708

Movement in Property, Plant and Equipment [Roll Forward]

550

488

Additions

Acquisitions

(12)

(15)

Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward]

578

550

488

(245)

(197)

^[2]

(55)

(57)

(6)

(2)

(296)

(245)

(197)

Land and Building [Member]

282

305

Movement in Property, Plant and Equipment [Roll Forward]

Reclassification due to ASC 842

(1)

^[1]

(3)

Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward]

(57)

(52)

^[2]

(4)

(4)

(1)

(62)

(57)

$ (52)

Property,Plant and Equipment [LineItems]

$ 28

$ 33

[1]	Pertains to certain lease incentives which have been included within right-of-use assets upon the adoption of ASC 842. See Note 2 — Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements for further information.
[2]	Depreciation expense on the statement of comprehensive income for the year ended December 31, 2020 includes both the depreciation expense presented here as well as the abandonment of an internally-developed software asset of $35 million prior to being placed in service.

Fixed Assets - Components of Fixed Assets (Parenthetical) (Details)
$ in Millions

12 Months Ended

Dec. 31, 2020

USD ($)

Abandonment

$ 35

^[1]

Internally-developed Software Asset [Member]

Property,Plant and Equipment [LineItems]

Abandonment

$ 35

[1]	Depreciation expense on the statement of comprehensive income for the year ended December 31, 2020 includes both the depreciation expense presented here as well as the abandonment of an internally-developed software asset of $35 million prior to being placed in service.

Fixed Assets - Assets Held Under Finance Leases (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Finance leases	$ 28	$ 29
Accumulated depreciation	(20)	(19)
Net book value	$ 8	$ 10

Goodwill and Other Intangible Assets - Components of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	$ 11,686	$ 10,957
Accumulated impairment losses, beginning balance	(492)	(492)
Goodwill, net, beginning balance	11,194	10,465
Goodwill acquired	50	737
Goodwill disposals	(130)	(6)
Acquisition accounting adjustment	(9)
Foreign exchange	99	(2)
Goodwill, gross, ending balance	11,696	11,686
Accumulated impairment losses, ending balance	(492)	(492)
Goodwill, net, ending balance	11,204	11,194
HCB [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	4,298	4,300
Accumulated impairment losses, beginning balance	(130)	(130)
Goodwill, net, beginning balance	4,168	4,170
Goodwill acquired	15	0
Goodwill disposals	(12)	0
Acquisition accounting adjustment	0
Foreign exchange	45	(2)
Goodwill, gross, ending balance	4,346	4,298
Accumulated impairment losses, ending balance	(130)	(130)
Goodwill, net, ending balance	4,216	4,168
CRB [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	2,309	2,308
Accumulated impairment losses, beginning balance	(362)	(362)
Goodwill, net, beginning balance	1,947	1,946
Goodwill acquired	30	10
Goodwill disposals	(1)	(6)
Acquisition accounting adjustment	0
Foreign exchange	40	(3)
Goodwill, gross, ending balance	2,378	2,309
Accumulated impairment losses, ending balance	(362)	(362)
Goodwill, net, ending balance	2,016	1,947
IRR [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	1,795	1,792
Accumulated impairment losses, beginning balance	0	0
Goodwill, net, beginning balance	1,795	1,792
Goodwill acquired	2	0
Goodwill disposals	(117)	0
Acquisition accounting adjustment	0
Foreign exchange	14	3
Goodwill, gross, ending balance	1,694	1,795
Accumulated impairment losses, ending balance	0	0
Goodwill, net, ending balance	1,694	1,795
BDA [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	3,284	2,557
Accumulated impairment losses, beginning balance	0	0
Goodwill, net, beginning balance	3,284	2,557
Goodwill acquired	3	727
Goodwill disposals	0	0
Acquisition accounting adjustment	(9)
Foreign exchange	0	0
Goodwill, gross, ending balance	3,278	3,284
Accumulated impairment losses, ending balance	0	0
Goodwill, net, ending balance	$ 3,278	$ 3,284

Goodwill and Other Intangible Assets - Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Finite-lived intangible assets, gross carrying amount

$ 5,988

$ 5,967

$ 5,318

Finite-lived intangible assets, accumulated amortization

(2,945)

(2,489)

(2,000)

3,043

3,478

3,318

ASC 842 reclassification

^[1]

(9)

660

^[2]

(67)

(10)

(462)

(489)

(534)

Client relationships [Member]

Finite-lived intangible assets, gross carrying amount

4,065

4,029

3,401

Finite-lived intangible assets, accumulated amortization

(2,031)

(1,731)

(1,415)

2,034

2,298

1,986

626

^[2]

(19)

(9)

(301)

(313)

Software [Member]

Finite-lived intangible assets, gross carrying amount

761

753

749

Finite-lived intangible assets, accumulated amortization

(659)

(551)

(421)

102

202

328

(1)

(103)

(125)

Trademark and trade name [Member]

Finite-lived intangible assets, gross carrying amount

1,054

1,051

1,052

Finite-lived intangible assets, accumulated amortization

(220)

(176)

(132)

834

875

920

(43)

(45)

Favorable agreements [Member]

Finite-lived intangible assets, gross carrying amount

^[1]

Finite-lived intangible assets, accumulated amortization

^[1]

(5)

^[1]

ASC 842 reclassification

^[1]

(9)

Other [Member]

Finite-lived intangible assets, gross carrying amount

108

134

102

Finite-lived intangible assets, accumulated amortization

(35)

(31)

(27)

103

$ 75

^[2]

(48)

(15)

$ (6)

$ 1

[1]	On January 1, 2019, in accordance with ASC 842, we reclassified our favorable lease agreement assets to right-of-use assets within our consolidated balance sheet.
[2]	Includes $612 million and $34 million of client relationship and domain name intangible assets, respectively, associated with our acquisition of TRANZACT.

Goodwill and Other Intangible Assets - Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets (Parenthetical) (Details) - USD ($)
$ in Millions

12 Months Ended

Jul. 30, 2019

Dec. 31, 2020

Dec. 31, 2019

Client relationships [Member]

$ 62

$ 660

^[1]

Client relationships [Member] | TRANZACT Acquisition [Member]

$ 30

626

^[1]

Product and domain name [Member] | TRANZACT Acquisition [Member]

$ 612

612

$ 34

[1]	Includes $612 million and $34 million of client relationship and domain name intangible assets, respectively, associated with our acquisition of TRANZACT.

Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Amortization	$ (462)	$ (489)	$ (534)
Acquired unfavorable lease agreement liabilities, net			$ 21
Weighted average remaining life of amortizable intangible assets and liabilities	13 years 3 months 18 days

Goodwill and Other Intangible Assets - Schedule of Future Estimated Amortization Expense for Amortizable Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2021	$ 389
2022	328
2023	274
2024	239
2025	217
Thereafter	1,596
Total	$ 3,043	$ 3,478	$ 3,318

Derivative Financial Instruments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Jun. 10, 2020	Dec. 31, 2019
Derivative [Line Items]
Gains on derivatives to be reclassified within the next twelve months	$ 3
Max Matthiessen [Member]
Derivative [Line Items]
Loss on settlement of hedging instruments	$ 1
Maximum [Member]
Derivative [Line Items]
Longest outstanding maturity	1 year 8 months 12 days
Foreign exchange contracts [Member] \| Max Matthiessen [Member]
Derivative [Line Items]
Derivative, notional amount		$ 273
Designated as Hedging Instrument [Member] \| Foreign exchange contracts [Member] \| Max Matthiessen [Member]
Derivative [Line Items]
Derivative, notional amount		$ 181
Not Designated as Hedging Instrument [Member] \| Foreign exchange contracts [Member]
Derivative [Line Items]
Derivative, notional amount	$ 1,500		$ 931
Derivative assets, fair value	15		21
Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member] \| Foreign exchange contracts [Member]
Derivative [Line Items]
Derivative, notional amount	340		499
Derivative assets, fair value	$ 5		$ 8

Derivative Financial Instruments - Schedule of Derivative Instruments Designated As Hedging Instrument Effect on Condensed Consolidated Statements of Comprehensive Income (Details) - Cash Flow Hedging [Member] - Designated as Hedging Instrument [Member] - Foreign exchange contracts [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Loss/(gain) recognized in OCI (effective element)	$ (13)	$ 15	$ (22)
Loss reclassified from Accumulated OCL into income (effective element)	(9)	(9)	(28)
Revenue [Member]
Derivative [Line Items]
Loss reclassified from Accumulated OCL into income (effective element)	(5)	(5)	0
Salaries and Benefits [Member]
Derivative [Line Items]
Loss reclassified from Accumulated OCL into income (effective element)	(4)	(4)	0
Other Income, Net [Member]
Derivative [Line Items]
Loss reclassified from Accumulated OCL into income (effective element)	$ 0	$ 0	$ (28)

Derivative Financial Instruments - Schedule Of Derivative Instruments, Effect on Condensed Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Foreign exchange contracts [Member] \| Not Designated as Hedging Instrument [Member] \| Other income, net [Member]
Derivative [Line Items]
(Loss)/gain recognized in income	$ (3)	$ 18	$ 0

Debt - Schedule of Current and Long-term Debt (Details)
€ in Millions

12 Months Ended

Dec. 31, 2020

USD ($)

Dec. 31, 2019

USD ($)

Dec. 31, 2020

EUR (€)

Sep. 10, 2018

$ 971,000,000

$ 316,000,000

Term loan due 2020 [Member]

4,664,000,000

5,301,000,000

Collateralized Facility [Member]

292,000,000

Current portion of long term debt

22,000,000

24,000,000

Renewal commissions receivables pledged as collateral

^[1]

33,000,000

60,000,000

98,000,000

127,000,000

Revolving 1.25 Billion Dollar Credit Facility [Member] | Revolving Credit Facility [Member]

5.750% senior notes due 2021 [Member]

1,250,000,000

$ 500,000,000

$ 499,000,000

5.75%

3.500% senior notes due 2021 [Member]

2021

$ 449,000,000

$ 448,000,000

3.50%

2.125% senior notes due 2022 [Member]

2021

$ 659,000,000

^[2]

$ 604,000,000

^[2]

€ 540

^[2]

2.125%

4.625% senior notes due 2023 [Member]

^[2]

2022

$ 249,000,000

4.625%

3.600% senior notes due 2024 [Member]

2023

$ 647,000,000

$ 646,000,000

3.60%

4.400% senior notes due 2026 [Member]

2024

$ 546,000,000

4.40%

4.500% senior notes due 2028 [Member]

2026

$ 596,000,000

$ 595,000,000

4.50%

2.950% senior notes due 2029 [Member]

2028

$ 726,000,000

$ 446,000,000

2.95%

6.125% senior notes due 2043 [Member]

2029

$ 271,000,000

6.125%

5.050% senior notes due 2048 [Member]

2043

$ 395,000,000

5.05%

3.875% senior notes due 2049 [Member]

2048

$ 542,000,000

3.875%

2049

[1]	At December 31, 2020 and 2019, the Company had $98 million and $127 million, respectively, of renewal commissions receivables pledged as collateral for this facility (see below for additional information).
[2]	Notes issued in Euro (€540 million)

Debt - Narrative (Details)
€ in Millions

1 Months Ended

12 Months Ended

May 29, 2020

USD ($)

Sep. 10, 2019

USD ($)

Jul. 30, 2019

USD ($)

Sep. 10, 2018

USD ($)

May 16, 2017

USD ($)

Mar. 07, 2017

USD ($)

May 26, 2016

USD ($)

May 26, 2016

EUR (€)

Mar. 22, 2016

USD ($)

Dec. 28, 2015

USD ($)

Nov. 20, 2015

USD ($)

Aug. 15, 2013

USD ($)

Mar. 11, 2011

USD ($)

Sep. 30, 2019

USD ($)

Aug. 31, 2013

USD ($)

Dec. 31, 2020

USD ($)

Dec. 31, 2019

USD ($)

Dec. 31, 2018

USD ($)

May 26, 2016

EUR (€)

Mar. 15, 2016

Jan. 04, 2016

USD ($)

Sep. 30, 2009

USD ($)

Proceeds from debt, net of issuance costs

Interest has accrued on both the 2028 senior notes and 2048 senior notes from September 10, 2018 and is paid in cash on March 15 and September 15 of each year.

$ 989,000,000

Repayment of line of credit

1 year

$ 0

$ 131,000,000

$ 754,000,000

Borrowings

7,884,000,000

Term Loan Facility [Member]

Line of credit maturity date

Jul. 31, 2020

Repayment of debt

$ 175,000,000

Term Loan Due 2019 [Member]

Prepayment of outstanding debt

$ 127,000,000

Senior Notes [Member]

Proceeds from debt, net of issuance costs

Interest on the 2019 senior notes offering has accrued from September 10, 2019 and is paid in cash on March 15 and September 15 of each year.

$ 988,000,000

Borrowings

$ 5,610,000,000

5.750% senior notes due 2021 [Member]

5.750% senior notes due 2021 [Member] | Senior Notes [Member]

5.75%

5.75%

$ 500,000,000

5.871%

3.600% senior notes due 2024 [Member]

Mar. 15, 2021

4.500% senior notes due 2028 [Member]

3.60%

4.50%

$ 600,000,000

4.504%

2.950% senior notes due 2029 [Member]

Sep. 15, 2028

2.950% senior notes due 2029 [Member] | Senior Notes [Member]

2.95%

2.95%

$ 275,000,000

$ 450,000,000

2.697%

2.971%

Sep. 15, 2029

5.050% senior notes due 2048 [Member]

Interest on the additional 2029 senior notes has accrued from March 15, 2020 and is paid in cash on March 15 and September 15 of each year.

5.05%

$ 400,000,000

5.073%

3.875% senior notes due 2049 [Member]

Sep. 15, 2048

3.875% senior notes due 2049 [Member] | Senior Notes [Member]

3.875%

3.875%

$ 550,000,000

3.898%

4.625% senior notes due 2023 [Member]

Sep. 15, 2049

4.625% senior notes due 2023 [Member] | Senior Notes [Member]

4.625%

4.625%

$ 250,000,000

4.696%

6.125% senior notes due 2043 [Member]

Aug. 15, 2023

6.125% senior notes due 2043 [Member] | Senior Notes [Member]

6.125%

6.125%

$ 275,000,000

6.154%

3.500% senior notes due 2021 [Member]

Aug. 15, 2043

3.500% senior notes due 2021 [Member] | Senior Notes [Member]

3.50%

3.50%

$ 450,000,000

3.707%

4.400% senior notes due 2026 [Member]

Sep. 15, 2021

4.400% senior notes due 2026 [Member] | Senior Notes [Member]

4.40%

4.40%

$ 550,000,000

4.572%

2.125% senior notes due 2022 [Member]

Mar. 15, 2026

2.125% senior notes due 2022 [Member] | Senior Notes [Member]

^[1]

2.125%

2.125%

2.154%

May 26, 2022

Proceeds from long-term debt issuance

Interest has accrued on the notes from May 26, 2016 and will be paid in cash on May 26 of each year.

$ 600,000,000

€ 535

2.125% senior notes due 2022 [Member] | Senior Notes [Member] | Trinity Acquisition plc [Member]

Revolving 1.25 Billion Dollar Credit Facility [Member] | Revolving Credit Facility [Member]

$ 609,000,000

€ 540

Revolving 1.25 Billion Dollar Credit Facility [Member] | Line of Credit [Member] | Revolving Credit Facility [Member]

$ 1,250,000,000

Repayment of debt

$ 105,000,000

Line of credit maturity date

$ 1,250,000,000

Mar. 07, 2022

Revolving 1.25 Billion Dollar Credit Facility [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] | LIBOR [Member] | Minimum [Member]

Revolving 1.25 Billion Dollar Credit Facility [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] | LIBOR [Member] | Maximum [Member]

1.00%

Revolving 1.25 Billion Dollar Credit Facility [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] | Bank Base Rate [Member] | Minimum [Member]

1.75%

Revolving 1.25 Billion Dollar Credit Facility [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] | Bank Base Rate [Member] | Maximum [Member]

0.00%

3.600% senior notes due 2024 [Member] | Senior Notes [Member]

0.75%

3.60%

$ 650,000,000

3.614%

May 15, 2024

Proceeds from debt, net of issuance costs

interest has accrued on the 2024 senior notes from May 16, 2017 and is paid in cash on May 15 and November 15 of each year.

$ 644,000,000

Senior Notes Due 2021 and 2026 [Member] | Senior Notes [Member]

Proceeds from long-term debt issuance

$ 988,000,000

Revolving $800 million Credit Facility [Member] | Line of Credit [Member] | Revolving Credit Facility [Member]

Repayment of line of credit

$ 800,000,000

300,000,000

4.125% Senior Notes Due 2016 [Member] | Senior Notes [Member]

1-year Term Loan Facility Matures 2016, Tranche two [Member] | Line of Credit [Member] | Notes Payable [Member]

4.125%

Repayment of line of credit

$ 400,000,000

1-year Term Loan Facility Matures 2016 [Member] | Line of Credit [Member] | Notes Payable [Member]

Tranzact Collateralized Facility [Member]

1 year

Assumed debt related to borrowings

Jan. 31, 2033

$ 91,000,000

Borrowings

$ 0

Tranzact Collateralized Facility [Member] | LIBOR [Member]

7.000% senior notes due 2019 [Member] | Senior Notes [Member]

3.95%

7.00%

$ 300,000,000

Term Loan Due 2019 [Member] | Notes Payable [Member]

7.081%

Repayment of debt

$ 187,000,000

$ 113,000,000

$ 340,000,000

Prepayment of outstanding debt

4 years

$ 127,000,000

Proceeds from long-term debt issuance

$ 340,000,000

One Year Term Loan [Member]

Debt Instrument, Interest Rate Terms

1 year

Debt Instrument Commitment Fee Percentage

0.15%

One Year Term Loan [Member] | Maximum [Member]

One Year Term Loan [Member] | LIBOR [Member]

$ 1,100,000,000

One Year Term Loan [Member] | LIBOR [Member] | Minimum [Member]

1.00%

Debt Instrument Additional Basis Spread On Variable Rate1

0.00%

One Year Term Loan [Member] | LIBOR [Member] | Maximum [Member]

Debt Instrument Additional Basis Spread On Variable Rate1

0.375%

One Year Term Loan [Member] | EURO-Denominated [Member] | Minimum [Member]

One Year Term Loan [Member] | EURO-Denominated [Member] | Maximum [Member]

0.75%

One Year Term Loan [Member] | Federal Funds Effective Swap Rate [Member]

1.375%

0.50%

[1]	Notes issued in Euro (€540 million)

Debt - Maturities of Long Term Debt (Details) $ in Millions	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
2021	$ 1,169
2022	848
2023	425
2024	793
2025	131
Thereafter	4,518
Total	7,884
Senior Notes [Member]
Debt Instrument [Line Items]
2021	950
2022	660
2023	250
2024	650
Thereafter	3,100
Total	5,610
Interest on Senior Notes [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
2021	197
2022	171
2023	162
2024	140
2025	131
Thereafter	1,418
Total	2,219
Collateralized Facility [Member]
Debt Instrument [Line Items]
2021	22
2022	17
2023	13
2024	3
Total	$ 55

Debt - Interest Expense (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Collateralized Facility [Member]

$ 244

$ 234

$ 208

Senior Notes [Member]

227

206

166

Term Loan

Other [Member]

Revolving Credit Facility [Member] | Line of Credit [Member] | Revolving 1.25 Billion Dollar Credit Facility [Member]

^[1]

Contingent consideration [Member] | Fair Value Inputs, Discount Rate [Member]

$ 4

$ 8

$ 26

[1]	Other primarily includes debt issuance costs, interest expense on financing leases and accretion on deferred and contingent consideration.

Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details)
$ in Millions

Dec. 31, 2020

USD ($)

Dec. 31, 2019

USD ($)

Fair value inputs, weighted-average discount rate

0.0946

0.1016

Contingent consideration [Member] | Fair Value Inputs, Discount Rate [Member] | Minimum [Member]

Fair value inputs, weighted-average discount rate

0.0353

Contingent consideration [Member] | Fair Value Inputs, Discount Rate [Member] | Maximum [Member]

Fair value inputs, weighted-average discount rate

0.1300

Recurring [Member]

Assets:

$ 8

$ 20

^[1]

^[2]

Recurring [Member] | Level 1 [Member]

^[1]

Assets:

^[1]

^[2]

Recurring [Member] | Level 2 [Member]

^[1]

Assets:

^[1]

^[2]

Recurring [Member] | Level 3 [Member]

^[1]

Assets:

^[1]

^[2]

^[1]

$ 0

[1]

See Note 9 — Derivative Financial Instruments for further information on our derivative instruments.

[2]

Fair Value Measurements - Fair Value Liabilities Measured Using Significant Unobservable Inputs Level 3 (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of beginning of period	$ 17
Obligations assumed	9
Payments	0
Realized and unrealized gains	18
Foreign exchange	1
Balance as of end of period	$ 45

Fair Value Measurements - Narrative (Details) - USD ($)	12 Months Ended
Fair Value Measurements - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair value significant transfers between Levels 1, 2 or 3	$ 0	$ 0

Fair Value Measurements - Schedule of Assets and Liabilities Whose Carrying Values Differ From the Fair Value and are Not Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current debt	$ 971	$ 316
Long-term debt	4,664	5,301
Carrying Value [Member] \| Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term note receivable	71	0
Current debt	971	316
Long-term debt	4,664	5,301
Fair Value [Member] \| Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term note receivable	73	0
Current debt	985	319
Long-term debt	$ 5,488	$ 5,694

Retirement Benefits - Narrative (Details) $ in Millions	6 Months Ended	12 Months Ended
Retirement Benefits - Narrative (Details) $ in Millions	Dec. 31, 2017	Dec. 31, 2020 USD ($)	Dec. 31, 2020 EUR (€)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Compensation and Retirement Disclosure [Line Items]
Portion of pension and OPEB obligation attributed to disclosed plans (as a percent)		99.00%	99.00%
Defined contribution plan expenses		$ 160		$ 150	$ 150
PRW [Member]
Compensation and Retirement Disclosure [Line Items]
Curtailment		0		0	0
Settlement		$ 0		0	0
Average remaining service period		8 years 8 months 12 days	8 years 8 months 12 days
United States [Member]
Compensation and Retirement Disclosure [Line Items]
Vesting period		2 years	2 years
United States [Member] \| Defined Contribution Plan Tranche One [Member]
Compensation and Retirement Disclosure [Line Items]
Employer matching contribution, percent of match		100.00%	100.00%
Maximum annual contributions per employee, percent		1.00%	1.00%
United States [Member] \| Defined Contribution Plan Tranche Two [Member]
Compensation and Retirement Disclosure [Line Items]
Employer matching contribution, percent of match		50.00%	50.00%
Maximum annual contributions per employee, percent		5.00%	5.00%
United States [Member] \| Pension Plan [Member]
Compensation and Retirement Disclosure [Line Items]
Curtailment		$ 0		0	0
Settlement		(2)		0	(1)
United Kingdom [Member] \| Pension Plan [Member]
Compensation and Retirement Disclosure [Line Items]
Curtailment		0		0	0
Settlement		(3)		0	(41)
United Kingdom [Member] \| Pension Plan [Member] \| Pension Costs [Member]
Compensation and Retirement Disclosure [Line Items]
Settlement					(40)
Other Foreign Plans [Member] \| Pension Plan [Member]
Compensation and Retirement Disclosure [Line Items]
Curtailment		0		0	16
Settlement		$ (1)		$ (1)	(2)
Ireland [Member] \| Pension Plan [Member]
Compensation and Retirement Disclosure [Line Items]
Increase in salary maximum amount \| €			€ 150,000
Netherlands [Member] \| Pension Plan [Member]
Compensation and Retirement Disclosure [Line Items]
Curtailment					$ 16
Newly-eligible employees [Member] \| United States [Member]
Compensation and Retirement Disclosure [Line Items]
Defined benefit plan required employee contribution rate	0.02

Retirement Benefits - Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Plan Assets
Fair value of plan assets, beginning of year	$ 9,547
Fair value of plan assets, end of year	10,808	$ 9,547
Pension benefits assets	971	868
Non-current liability for pension benefits	(1,405)	(1,324)
Pension Plan [Member] \| United States [Member]
Change in Benefit Obligation
Benefit obligation, beginning of year	4,768	4,187
Service cost	72	65	$ 66
Interest cost	131	157	140
Employee contributions	15	15
Actuarial losses	509	535
Settlements	(10)	(6)
Benefits paid	(194)	(185)
Plan amendments	0	0
Business disposal	0	0
Transfers in	0	0
Other	0	0
Foreign currency changes	0	0
Benefit obligation, end of year	5,291	4,768	4,187
Change in Plan Assets
Fair value of plan assets, beginning of year	3,873	3,403
Actual return on plan assets	602	557
Employer contributions	71	89
Employee contributions	15	15
Settlements	(10)	(6)
Benefits paid	(194)	(185)
Transfers in	0	0
Other	0	0
Foreign currency adjustment	0	0
Fair value of plan assets, end of year	4,357	3,873	3,403
Funded status at end of year	(934)	(895)
Accumulated Benefit Obligation	5,291	4,768
Pension benefits assets	0	0
Current liability for pension benefits	(31)	(33)
Non-current liability for pension benefits	(903)	(862)
Components on the Consolidated Balance Sheet	(934)	(895)
Pension Plan [Member] \| United Kingdom [Member]
Change in Benefit Obligation
Benefit obligation, beginning of year	4,259	3,666
Service cost	15	14	18
Interest cost	73	93	95
Employee contributions	0	0
Actuarial losses	494	472
Settlements	(27)	(8)
Benefits paid	(146)	(140)
Plan amendments	9	0
Business disposal	0	0
Transfers in	0	0
Other	0	0
Foreign currency changes	166	162
Benefit obligation, end of year	4,843	4,259	3,666
Change in Plan Assets
Fair value of plan assets, beginning of year	5,086	4,402
Actual return on plan assets	590	561
Employer contributions	66	77
Employee contributions	0	0
Settlements	(27)	(8)
Benefits paid	(146)	(140)
Transfers in	0	0
Other	0	0
Foreign currency adjustment	198	194
Fair value of plan assets, end of year	5,767	5,086	4,402
Funded status at end of year	924	827
Accumulated Benefit Obligation	4,841	4,259
Pension benefits assets	932	835
Current liability for pension benefits	(1)	(1)
Non-current liability for pension benefits	(7)	(7)
Components on the Consolidated Balance Sheet	924	827
Pension Plan [Member] \| Other Foreign Plans [Member]
Change in Benefit Obligation
Benefit obligation, beginning of year	842	728
Service cost	21	20	21
Interest cost	15	18	18
Employee contributions	0	0
Actuarial losses	65	88
Settlements	(4)	(3)
Benefits paid	(32)	(26)
Plan amendments	0	0
Business disposal	(1)	0
Transfers in	0	2
Other	1	0
Foreign currency changes	48	15
Benefit obligation, end of year	955	842	728
Change in Plan Assets
Fair value of plan assets, beginning of year	588	486
Actual return on plan assets	64	85
Employer contributions	35	31
Employee contributions	0	0
Settlements	(4)	(3)
Benefits paid	(32)	(26)
Transfers in	0	2
Other	1	0
Foreign currency adjustment	32	13
Fair value of plan assets, end of year	684	588	486
Funded status at end of year	(271)	(254)
Accumulated Benefit Obligation	918	810
Pension benefits assets	28	22
Current liability for pension benefits	(5)	(6)
Non-current liability for pension benefits	(294)	(270)
Components on the Consolidated Balance Sheet	(271)	(254)
PRW [Member]
Change in Benefit Obligation
Benefit obligation, beginning of year	90	87
Service cost	1	1	1
Interest cost	2	3	4
Employee contributions	3	6
Actuarial losses	5	5
Settlements	0	0
Benefits paid	(10)	(12)
Plan amendments	0	0
Business disposal	0	0
Transfers in	0	0
Other	0	0
Foreign currency changes	0	0
Benefit obligation, end of year	91	90	87
Change in Plan Assets
Fair value of plan assets, beginning of year	0	1
Actual return on plan assets	0	0
Employer contributions	7	5
Employee contributions	3	6
Settlements	0	0
Benefits paid	(10)	(12)
Transfers in	0	0
Other	0	0
Foreign currency adjustment	0	0
Fair value of plan assets, end of year	0	0	$ 1
Funded status at end of year	(91)	(90)
Accumulated Benefit Obligation	91	90
Pension benefits assets	0	0
Current liability for pension benefits	(6)	(6)
Non-current liability for pension benefits	(85)	(84)
Components on the Consolidated Balance Sheet	$ (91)	$ (90)

Retirement Benefits - Amounts Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Plan [Member] \| United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 1,143	$ 982
Net prior service gain	0	0
Accumulated other comprehensive loss/(income)	1,143	982
Pension Plan [Member] \| United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	1,304	1,133
Net prior service gain	(37)	(61)
Accumulated other comprehensive loss/(income)	1,267	1,072
Pension Plan [Member] \| Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	169	128
Net prior service gain	0	0
Accumulated other comprehensive loss/(income)	169	128
PRW [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	24	20
Net prior service gain	(23)	(27)
Accumulated other comprehensive loss/(income)	$ 1	$ (7)

Retirement Benefits - Benefit Obligation In Excess Of Plan Assets (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	$ 5,291	$ 4,768
Fair value of plan assets at end of year	4,357	3,873
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	8	7
Fair value of plan assets at end of year	0	0
Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	891	784
Fair value of plan assets at end of year	$ 593	$ 509

Retirement Benefits - Accumulated Benefit Obligation In Excess of Plan Assets (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	$ 5,291	$ 4,768
Accumulated benefit obligation at end of year	5,291	4,768
Fair value of plan assets at end of year	4,357	3,873
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	8	7
Accumulated benefit obligation at end of year	8	7
Fair value of plan assets at end of year	0	0
Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	477	784
Accumulated benefit obligation at end of year	457	752
Fair value of plan assets at end of year	$ 193	$ 509

Retirement Benefits - Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member] \| United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 72	$ 65	$ 66
Interest cost	131	157	140
Expected return on plan assets	(291)	(254)	(273)
Amortization of unrecognized prior service credit	0	0	0
Amortization of unrecognized actuarial loss	35	19	11
Settlement	2	0	1
Curtailment gain	0	0	0
Net periodic benefit (income)/cost	(51)	(13)	(55)
Net actuarial loss/(gain)	198	232	117
Amortization of unrecognized actuarial loss	(35)	(19)	(11)
Prior service cost/(credit)	0	0	0
Amortization of unrecognized prior service credit	0	0	0
Settlement	(2)	0	(1)
Curtailment gain	0	0	0
Total recognized in other comprehensive loss/(income)	161	213	105
Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income)	110	200	50
Pension Plan [Member] \| United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	15	14	18
Interest cost	73	93	95
Expected return on plan assets	(247)	(246)	(298)
Amortization of unrecognized prior service credit	(17)	(16)	(19)
Amortization of unrecognized actuarial loss	23	21	45
Settlement	3	0	41
Curtailment gain	0	0	0
Net periodic benefit (income)/cost	(150)	(134)	(118)
Net actuarial loss/(gain)	151	157	191
Amortization of unrecognized actuarial loss	(23)	(21)	(45)
Prior service cost/(credit)	9	0	40
Amortization of unrecognized prior service credit	17	16	19
Settlement	(3)	0	(41)
Curtailment gain	0	0	0
Total recognized in other comprehensive loss/(income)	151	152	164
Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income)	1	18	46
Pension Plan [Member] \| Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	21	20	21
Interest cost	15	18	18
Expected return on plan assets	(34)	(29)	(31)
Amortization of unrecognized prior service credit	0	0	0
Amortization of unrecognized actuarial loss	3	2	2
Settlement	1	1	2
Curtailment gain	0	0	(16)
Net periodic benefit (income)/cost	6	12	(4)
Net actuarial loss/(gain)	35	32	13
Amortization of unrecognized actuarial loss	(3)	(2)	(2)
Prior service cost/(credit)	0	0	0
Amortization of unrecognized prior service credit	0	0	0
Settlement	(1)	(1)	(2)
Curtailment gain	0	0	16
Total recognized in other comprehensive loss/(income)	31	29	25
Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income)	37	41	21
PRW [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1
Interest cost	2	3	4
Expected return on plan assets	0	0	0
Amortization of unrecognized prior service credit	(4)	(4)	0
Amortization of unrecognized actuarial loss	1	1	0
Settlement	0	0	0
Curtailment gain	0	0	0
Net periodic benefit (income)/cost	0	1	5
Net actuarial loss/(gain)	5	5	(3)
Amortization of unrecognized actuarial loss	(1)	(1)	0
Prior service cost/(credit)	0	0	(31)
Amortization of unrecognized prior service credit	4	4	0
Settlement	0	0	0
Curtailment gain	0	0	0
Total recognized in other comprehensive loss/(income)	8	8	(34)
Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income)	$ 8	$ 9	$ (29)

Retirement Benefits - Assumptions Used (Details)	12 Months Ended
Retirement Benefits - Assumptions Used (Details)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member] \| United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - PBO	3.30%	4.20%	3.60%
Discount rate - service cost	3.40%	4.30%	3.50%
Discount rate - interest cost on service cost	2.80%	3.80%	3.10%
Discount rate - interest cost on PBO	2.80%	3.90%	3.20%
Expected long-term rate of return on assets	7.70%	7.60%	7.60%
Rate of increase in compensation levels	4.30%	4.30%	4.30%
Discount rate	2.50%	3.30%
Rate of increase in compensation levels	4.30%	4.30%
Pension Plan [Member] \| United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - PBO	2.00%	2.80%	2.60%
Discount rate - service cost	2.10%	2.90%	2.70%
Discount rate - interest cost on service cost	1.90%	2.80%	2.50%
Discount rate - interest cost on PBO	1.80%	2.60%	2.30%
Expected long-term rate of return on assets	5.00%	5.60%	6.20%
Rate of increase in compensation levels	3.00%	3.00%	3.00%
Discount rate	1.50%	2.00%
Rate of increase in compensation levels	3.00%	3.00%
Pension Plan [Member] \| Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - PBO	2.10%	2.80%	2.60%
Discount rate - service cost	2.50%	3.00%	2.90%
Discount rate - interest cost on service cost	2.40%	2.90%	2.70%
Discount rate - interest cost on PBO	1.90%	2.50%	2.30%
Expected long-term rate of return on assets	5.90%	6.00%	5.70%
Rate of increase in compensation levels	2.30%	2.30%	2.30%
Discount rate	1.70%	2.10%
Rate of increase in compensation levels	2.30%	2.30%
PRW [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate - PBO	3.20%	4.20%	3.50%
Discount rate - service cost	3.30%	4.20%	3.50%
Discount rate - interest cost on service cost	2.80%	3.90%	3.20%
Discount rate - interest cost on PBO	2.80%	3.90%	3.10%
Expected long-term rate of return on assets	0.00%	2.00%	2.00%
Rate of increase in compensation levels	0.00%
Health care cost trend - Initial rate	6.50%	6.00%	6.50%
Health care cost trend - Ultimate rate	5.00%	5.00%	5.00%
Health care cost trend - ultimate rate year	2027	2022	2022
Discount rate	2.40%	3.20%
Rate of increase in compensation levels	0.00%

Retirement Benefits - Fair Value Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Net assets held in investments	$ 10,808	$ 9,553
Net receivable/(payable) for investments purchased	0	(7)
Dividend and interest receivable	0	1
Fair value of plan assets	$ 10,808	$ 9,547

Retirement Benefits - Significant Unobservable Input Reconciliation (Details) - Level 3 [Member] $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plan assets, beginning of year	$ 2
Purchases	64
Unrealized gains	7
Foreign currency adjustment	6
Fair value of plan assets, end of year	$ 79

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

Retirement Benefits - Projected Benefit Obligation (Details) - Pension Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2021
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 71	$ 89
United States [Member] \| Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, next fiscal year			$ 60
Employer contributions	40	60
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	66	77
United Kingdom [Member] \| Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, next fiscal year			47
Employer contributions	65	76
Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	35	31
Other Foreign Plans [Member] \| Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, next fiscal year			$ 25
Employer contributions	$ 24	$ 22

Amount of contribution received by defined benefit plan from employer which increases plan assets.

Retirement Benefits - Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
2021	$ 418
2022	435
2023	435
2024	455
2025	463
Years 2026 – 2029	2,474
Expected future benefit payments, total	4,680
Pension Plan [Member] \| UNITED STATES [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	248
2022	275
2023	265
2024	274
2025	277
Years 2026 – 2029	1,421
Expected future benefit payments, total	2,760
Pension Plan [Member] \| UNITED KINGDOM [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	128
2022	122
2023	131
2024	139
2025	143
Years 2026 – 2029	808
Expected future benefit payments, total	1,471
Pension Plan [Member] \| Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	32
2022	28
2023	29
2024	31
2025	32
Years 2026 – 2029	187
Expected future benefit payments, total	339
PRW [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	10
2022	10
2023	10
2024	11
2025	11
Years 2026 – 2029	58
Expected future benefit payments, total	$ 110

Leases - Schedule of Lease (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Right-of-use assets	$ 902	$ 968
Operating Lease, Current lease liabilities	152	164
Operating Lease, Long-term lease liabilities	918	964
Finance Lease, Right-of-use assets	8	10
Finance Lease, Current lease liabilities	3	3
Finance Lease, Long-term lease liabilities	19	22
Total Right-of-use assets	910	978
Total Current lease liabilities	155	167
Total Long-term lease liabilities	$ 937	$ 986

Leases - Schedule of Amount Recorded in Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finance lease cost:
Amortization of right-of-use assets	$ 2	$ 2
Interest on lease liabilities	3	3
Operating lease cost	181	191
Short-term lease cost	1	2
Variable lease cost	53	51
Sublease income	(21)	(16)
Total lease cost, net	$ 219	$ 233

Leases - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Leases - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Rent expense, net of sublease income			$ 243
Non-cash additions to operating lease ROU assets	$ 70	$ 124

Leases -Schedule of Cash Paid in the Measurement of Lease Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Operating leases	$ 190	$ 205
Finance leases	3	3
Cash flows used in financing activities:
Finance leases	3	2
Total lease payments	$ 196	$ 210

Leases - Schedule of Weighted Average Term and Discount Rates (Details)	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating Leases, Weighted-average remaining term (in years)	8 years 3 months 18 days	8 years 9 months 18 days
Operating Leases, Weighted-average discount rate	3.40%	3.60%
Finance Leases, Weighted-average remaining term (in years)	5 years 2 months 12 days	6 years
Finance Leases, Weighted-average discount rate	12.90%	12.90%

Leases - Schedule of Maturity of Operating and Finance Leases Liabilities (Details) $ in Millions	Dec. 31, 2020 USD ($)
Operating Leases [Abstract]
Operating Lease, 2021	$ 185
Operating Lease, 2022	172
Operating Lease, 2023	157
Operating Lease, 2024	138
Operating Lease, 2025	123
Operating Lease, Thereafter	458
Operating Lease, Total future lease payments	1,233
Operating Lease, Interest	(163)
Operating Lease, Total lease liabilities	1,070
Finance Leases [Abstract]
Finance Lease, 2021	6
Finance Lease, 2022	6
Finance Lease, 2023	6
Finance Lease, 2024	6
Finance Lease, 2025	6
Finance Lease, Thereafter	1
Finance Lease, Total future lease payments	31
Finance Lease, Interest	(9)
Finance Lease, Total lease liabilities	22
Leases Liabilities Due [Abstract]
Total Lease, 2021	191
Total Lease, 2022	178
Total Lease, 2023	163
Total Lease, 2024	144
Total Lease, 2025	129
Total Lease, Thereafter	459
Total Lease, Total future lease payments	1,264
Total Lease, Interest	(172)
Total Lease, Total lease liabilities	$ 1,092

Commitments and Contingencies - Narrative (Details) $ in Millions															1 Months Ended	3 Months Ended	12 Months Ended			86 Months Ended
	Jan. 15, 2021 USD ($)	Jan. 12, 2021 USD ($)	Nov. 19, 2020 USD ($)	Jun. 17, 2020 lawsuit	Jun. 12, 2020 USD ($)	May 28, 2020 lawsuit	May 19, 2020 lawsuit	May 14, 2020 lawsuit	May 11, 2020 lawsuit	Oct. 18, 2018 lawsuit	Mar. 09, 2018 lawsuit	Mar. 08, 2018 lawsuit	Feb. 27, 2018 lawsuit	Nov. 21, 2017 lawsuit	Aug. 31, 2016 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 12, 2016 USD ($) lawsuit
Loss Contingencies [Line Items]
Business combination, deferred and contingent consideration																$ 55	$ 55
Payments for deferred contingent consideration, financing activities																	12	$ 57	$ 50
Amount payable from option																	38
Insurance recovery receivables																25	25
Settled Litigation [Member] \| Stanford Financial Group [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit																				15
Damages sought (in excess of)																				$ 4,600
Litigation settlement amount															$ 120
Settled Litigation [Member] \| Stanford Financial Group [Member] \| Subsequent Event [Member]
Loss Contingencies [Line Items]
Litigation settlement amount		$ 120
Trident V Parallel Fund [Member]
Loss Contingencies [Line Items]
Capital contribution obligation																2	2
Property Lease Guarantee [Member]
Loss Contingencies [Line Items]
Operating leases																566	566	536
Capital lease obligations																5	5	$ 6
Stein v. Willis Towers Watson Public Limited Company, et al [Member] \| Dismissed Litigation [Member] \| Aon Plc [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit									1
Kent v. Willis Towers Watson Public Limited Company, et al. [Member] \| Dismissed Litigation [Member] \| Aon Plc [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit								1
Carter v. Willis Towers Watson Public Limited Company, et al. [Member] \| Dismissed Litigation [Member] \| Aon Plc [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit							1
Tang v. Willis Towers Watson Public Limited Company, et al. [Member] \| Dismissed Litigation [Member] \| Aon Plc [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit						1
Kuznik v. Willis Towers Watson Public Limited Company, et al. [Member] \| Dismissed Litigation [Member] \| Aon Plc [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit				1
Merger-Related Securities Litigation [Member] \| Dismissed Litigation [Member] \| Legacy Towers Watson, Naya Master Fund LP, Naya 174 Fund Limited and Naya Lincoln Park Master Fund Limited (collectively, Naya) [Member] [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit										3
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member]
Loss Contingencies [Line Items]
Provision for litigation losses																50	65
Insurance recovery receivables																$ 25	$ 25
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Subsequent Event [Member]
Loss Contingencies [Line Items]
Litigation settlement amount	$ 90
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Legacy Towers Watson Stockholders [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit														1
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Lead Plaintiff [Member]
Loss Contingencies [Line Items]
Damages sought (in excess of)					$ 456
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Legacy Towers Watson, City of Fort Myers General Employees Pension Fund (Fort Myers) [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit													1
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Alaska Laborers-Employers Retirement Trust (Alaska) [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit												1
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Regents [Member]
Loss Contingencies [Line Items]
Number of complaints filed \| lawsuit											1
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Federal Action [Member]
Loss Contingencies [Line Items]
Litigation settlement amount			$ 75
Merger-Related Securities Litigation [Member] \| Settled Litigation [Member] \| Delaware Action [Member]
Loss Contingencies [Line Items]
Litigation settlement amount			$ 15

Supplementary Information for Certain Balance Sheet Accounts - Prepaid and Other Current Assets (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Prepayments and accrued income	$ 124,000,000	$ 145,000,000
Deferred contract costs	108,000,000	101,000,000
Derivatives and investments	42,000,000	49,000,000
Deferred compensation plan assets	14,000,000	18,000,000
Retention incentives	3,000,000	11,000,000
Corporate income and other taxes	83,000,000	56,000,000
Insurance and other recovery receivables	25,000,000
Restricted cash	7,000,000	8,000,000	$ 0	$ 0
Acquired renewal commissions receivable	16,000,000	25,000,000
Other current assets	75,000,000	112,000,000
Total prepaid and other current assets	$ 497,000,000	$ 525,000,000

Supplementary Information for Certain Balance Sheet Accounts - Other Non-current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Prepayments and accrued income	$ 13	$ 12
Deferred contract costs	98	76
Deferred compensation plan assets	117	150
Deferred tax assets	95	72
Accounts receivable, net	34	30
Acquired renewal commissions receivable	84	125
Long-term note receivable	71
Other investments	24	23
Insurance recovery receivables	117	119
Non-current contract assets	329	105
Other non-current assets	114	123
Total other non-current assets	$ 1,096	$ 835

Supplementary Information for Certain Balance Sheet Accounts - Deferred Revenue and Accrued Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accounts payable, accrued liabilities and deferred income	$ 862	$ 856
Accrued discretionary and incentive compensation	851	727
Litigation settlement	210
Accrued vacation	161	137
Other employee-related liabilities	77	64
Total deferred revenue and accrued expenses	$ 2,161	$ 1,784

Supplementary Information for Certain Balance Sheet Accounts - Other Current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Dividends payable	$ 103	$ 100
Income and other taxes payable	102	138
Interest payable	68	65
Deferred compensation plan liabilities	57	14
Contingent and deferred consideration on acquisitions	39	12
Payroll-related liabilities	268	216
Derivatives	5	3
Third-party commissions	173	179
Other current liabilities	73	75
Total other current liabilities	$ 888	$ 802

Supplementary Information for Certain Balance Sheet Accounts - Provision For Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Claims, lawsuits and other proceedings	$ 325	$ 456
Other provisions	82	81
Total provision for liabilities	$ 407	$ 537

Supplementary Information for Certain Balance Sheet Accounts - Other Non-current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Deferred compensation plan liability	$ 117	$ 150
Contingent and deferred consideration on acquisitions	16	26
Liabilities for uncertain tax positions	49	48
Derivatives	2
Finance leases	19	22
Other non-current liabilities	109	89
Total other non-current liabilities	$ 312	$ 335

Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
Other Income, Net (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Income And Expenses [Abstract]
Gain/(loss) on disposal of operations	$ 81	$ (2)	$ (9)
Net periodic pension and postretirement benefit credits	304	234	280
Interest in earnings of associates and other investments	6	21	3
Foreign exchange gain/(loss)	6	(26)	(24)
Other	2
Other income, net	$ 399	$ 227	$ 250

Accumulated Other Comprehensive Loss - Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)before tax	$ (208)	$ (311)	$ (504)
Other comprehensive income/(loss), tax	77	81	56
Other comprehensive income/(loss), net of tax, before non-controlling interests	(131)	(230)	(448)
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)before tax	139	78	(251)
Other comprehensive income/(loss), tax	0	0	0
Other comprehensive income/(loss), net of tax, before non-controlling interests	139	78	(251)
Defined pension and post-retirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)before tax	(342)	(412)	(258)
Other comprehensive income/(loss), tax	76	83	59
Other comprehensive income/(loss), net of tax, before non-controlling interests	(266)	(329)	(199)
Derivative instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)before tax	(5)	23	5
Other comprehensive income/(loss), tax	1	(2)	(3)
Other comprehensive income/(loss), net of tax, before non-controlling interests	(4)	21	2
AOCI Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)before tax	1	0	0
Other comprehensive income/(loss), tax	0	0	0
Other comprehensive income/(loss), net of tax, before non-controlling interests	1	0	0
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)before tax	(209)	(311)	(504)
Other comprehensive income/(loss), tax	77	81	56
Other comprehensive income/(loss), net of tax, before non-controlling interests	$ (132)	$ (230)	$ (448)

Amount before tax, after reclassification adjustments of other comprehensive income (loss).

Amount after tax and reclassification adjustments of other comprehensive income (loss).

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120385591&loc=d3e39076-109324

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32136-110900

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 20
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=120385591&loc=d3e38679-109324

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
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Time-based Stock Options [Member]

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	$ 10,249
Reclassification of tax effects per ASU 2018-02	(2,434)	$ (1,792)
Stockholders' equity attributable to parent, ending balance	10,820	10,249
Foreign currency translation [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(538)	(616)	$ (365)
Other comprehensive income/(loss) before reclassifications	138	78	(251)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	0	0	0
Net other comprehensive income/(loss)	138	78	(251)
Stockholders' equity attributable to parent, ending balance	(400)	(538)	(616)
Foreign currency translation [Member] \| Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02		0
Derivative instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	13	(8)	(10)
Other comprehensive income/(loss) before reclassifications	(12)	12	(22)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	8	9	24
Net other comprehensive income/(loss)	(4)	21	2
Stockholders' equity attributable to parent, ending balance	9	13	(8)
Derivative instruments [Member] \| Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02		0
Defined pension and post-retirement benefit costs [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(1,702)	(1,337)	(1,138)
Other comprehensive income/(loss) before reclassifications	(298)	(343)	(241)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	32	14	42
Net other comprehensive income/(loss)	(266)	(329)	(199)
Stockholders' equity attributable to parent, ending balance	(1,968)	(1,702)	(1,337)
Defined pension and post-retirement benefit costs [Member] \| Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02		(36)		$ (36)
Total [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(2,227)	(1,961)	(1,513)
Other comprehensive income/(loss) before reclassifications	(172)	(253)	(514)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	40	23	66
Net other comprehensive income/(loss)	(132)	(230)	(448)
Stockholders' equity attributable to parent, ending balance	$ (2,359)	(2,227)	$ (1,961)
Total [Member] \| Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02		$ (36)

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, Current Period, Tax	$ 11	$ 9	$ 17
Adjustment of retained earnings	$ 2,434	1,792
Accounting Standards Update 2018-02 [Member] \| Defined pension and post-retirement benefit costs [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Adjustment of retained earnings		$ 36		$ 36

Share-Based Compensation - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 90,000,000	$ 74,000,000	$ 50,000,000
Tax benefit from compensation expense	15,000,000	11,000,000	10,000,000
Cash received from exercise of stock options	16,000,000	45,000,000	45,000,000
Employee Services Share Based Compensation, Tax Benefit Realized From Vesting Of RSUs	$ 7,000,000	$ 7,000,000	$ 12,000,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	0	0	0
Time-based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, exercises in period, intrinsic value	$ 17,000,000	$ 16,000,000	$ 12,000,000
Compensation cost not yet recognized, period for recognition	1 year 4 months 24 days
Time-based Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized	$ 1,000,000
Performance-based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, exercises in period, intrinsic value		16,000,000	8,000,000
Compensation cost not yet recognized	0
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	5,000,000	$ 6,000,000	$ 4,000,000
Performance-based Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, exercises in period, intrinsic value	1,000,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized	$ 1,000,000
Compensation cost not yet recognized, period for recognition	7 months 6 days
Vested (shares)	12,586	21,025	164,728
Vested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 195.69	$ 189.42	$ 156.14
Granted units	13,000
Grant date fair value,per share	$ 190.09	$ 172.25
Performance-Based Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized	$ 42,000,000
Compensation cost not yet recognized, period for recognition	2 years 3 months 18 days
Vested (shares)	416,349	178,346	249,901
Vested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 185.30	$ 175.01	$ 154.99
Granted units	356,000
Grant date fair value,per share	$ 245.49	$ 150.22
Phantom RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized	$ 17,000,000
Granted units	0	204,269	268,956
Grant date fair value,per share		$ 105.97	$ 83.57
Share-based compensation, expected term	3 years
Liability recognized	$ 61,000,000
2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	5,000,000
Towers Watson & Co. 2009 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation			$ 3,000,000
Towers Watson & Co. 2009 Long Term Incentive Plan [Member] \| Restricted Stock Units (RSU) and Options [Member] \| Pre-acquisition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the outstanding units				$ 37,000,000
Towers Watson & Co. 2009 Long Term Incentive Plan [Member] \| Restricted Stock Units (RSU) and Options [Member] \| Post-acquisition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the outstanding units				$ 45,000,000

Share-Based Compensation - Options Activity (Details)
$ / shares in Units, shares in Thousands, $ in Millions

12 Months Ended

Dec. 31, 2020

USD ($)

$ / shares

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]

Balance as of beginning of period, Outstanding (in shares) | shares

260

Exercised, Outstanding (in shares) | shares

163

Cancelled, Outstanding (in shares) | shares

Balance as of end of period, Outstanding (in shares) | shares

Options vested or expected to vest at end of period, Outstanding (in shares) | shares

Options exercisable at end of period, Outstanding (in shares) | shares

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]

Balance as of beginning of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

$ 105.38

^[1]

Exercised, Weighted Average Exercise Price (in dollars per share) | $ / shares

101.09

^[1]

Cancelled Weighted Average Exercise Price (in dollars per share) | $ / shares

95.56

^[1]

Balance as of end of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

114.92

^[1]

Options vested or expected to vest at end of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

114.92

^[1]

Options exercisable at end of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

$ 107.72

^[1]

End of period, Weighted Average Remaining Contractual Term

1 year 6 months

Options vested or expected to vest at end of period, Weighted Average Remaining Contractual Term

1 year 6 months

Options exercisable at end of period, Weighted Average Remaining Contractual Term

1 year 4 months 24 days

End of period, Aggregate Intrinsic Value | $

$ 8

Options vested or expected to vest at end of period, Aggregate Intrinsic Value | $

Options exercisable at end of period, Aggregate Intrinsic Value | $

$ 6

Performance-based Stock Options [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]

Balance as of beginning of period, Outstanding (in shares) | shares

287

Exercised, Outstanding (in shares) | shares

Balance as of end of period, Outstanding (in shares) | shares

284

Options vested or expected to vest at end of period, Outstanding (in shares) | shares

284

Options exercisable at end of period, Outstanding (in shares) | shares

284

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]

Balance as of beginning of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

$ 110.58

^[1]

Exercised, Weighted Average Exercise Price (in dollars per share) | $ / shares

110.58

^[1]

Balance as of end of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

110.58

^[1]

Options vested or expected to vest at end of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

110.58

^[1]

Options exercisable at end of period, Weighted Average Exercise Price (in dollars per share) | $ / shares

$ 110.58

^[1]

End of period, Weighted Average Remaining Contractual Term

1 year 8 months 12 days

Options vested or expected to vest at end of period, Weighted Average Remaining Contractual Term

1 year 8 months 12 days

Options exercisable at end of period, Weighted Average Remaining Contractual Term

1 year 8 months 12 days

End of period, Aggregate Intrinsic Value | $

$ 28

Options vested or expected to vest at end of period, Aggregate Intrinsic Value | $

Options exercisable at end of period, Aggregate Intrinsic Value | $

$ 28

[1]	Certain options are exercisable in Pounds sterling and are converted to dollars using the exchange rate at December 31, 2020.

Share-Based Compensation - Assumptions (Details) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	24.20%	25.60%	17.90%
Expected life (years)	2 years 10 months 24 days	2 years 8 months 12 days	2 years 6 months
Risk-free interest rate	0.40%	2.10%	2.60%

Share-Based Compensation - Nonvested Restricted Stock Units and Performance Based Stock Units Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Balance (shares)	11,000
Granted (shares)	13,000
Vested (shares)	12,586	21,025	164,728
Forfeited (shares)	0
Balance (shares)	11,000	11,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Balance, Weighted Average Grant Date Fair Value (in dollars per share)	$ 172.25
Granted, Weighted Average Grant Date Fair Value (in dollars per share)	193.25
Vested, Weighted Average Grant Date Fair Value (in dollars per share)	178.54
Forfeited, Weighted Average Grant Date Fair Value (in dollars per share)	160.48
Balance, Weighted Average Grant Date Fair Value (in dollars per share)	$ 190.09	$ 172.25
Performance-Based Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Balance (shares)	507,000	800,000
Granted (shares)	356,000
Vested (shares)	416,349	178,346	249,901
Forfeited (shares)	8,000
Balance (shares)	439,000	507,000	800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Balance, Weighted Average Grant Date Fair Value (in dollars per share)	$ 150.22
Granted, Weighted Average Grant Date Fair Value (in dollars per share)	230.24
Vested, Weighted Average Grant Date Fair Value (in dollars per share)	117.01
Forfeited, Weighted Average Grant Date Fair Value (in dollars per share)	216.64
Balance, Weighted Average Grant Date Fair Value (in dollars per share)	$ 245.49	$ 150.22

Earnings Per Share - Narrative (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Antidilutive securities excluded from computation of earnings per share	0	0	0
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Antidilutive securities excluded from computation of earnings per share	100		200
Time-based award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding	100	300	400
Performance-Based Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding	300	300	500
Restricted share units outstanding	439	507	800

Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to Willis Towers Watson	$ 996	$ 1,044	$ 695
Basic weighted-average number of shares outstanding (shares)	130	130	131
Dilutive effect of potentially issuable shares (shares)	0	0	1
Diluted weighted-average number of shares outstanding (shares)	130	130	132
Basic earnings per share	$ 7.68	$ 8.05	$ 5.29
Dilutive effect of potentially issuable shares (USD per share)	(0.03)	(0.03)	(0.02)
Diluted earnings per share	$ 7.65	$ 8.02	$ 5.27

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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