Non-cash restructuring charges Restructuring and Related Cost, Accelerated Depreciation Entity Address, City or Town Entity Address, City or Town Schedule of Other Current Assets [Table Text Block] Schedule of Prepaid and Other Current Asset Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for both operating lease and finance lease. Lease Liability Undiscounted Excess Amount Total Lease, Interest Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Reconciliation between US federal income taxes at the statutory rate and the Company's provision for income taxes on continuing operations FRANCE France [Member] Fair Value Disclosures [Abstract] Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block] Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets Defined Benefit Plan, Plan Assets, Target Allocation, Percentage Pension plan asset target allocations Earnings Per Share [Abstract] EARNINGS PER SHARE Fair Value, Inputs, Level 1 [Member] Level 1 [Member] Process Optimization [Member] Process Optimization Member Process Optimization Member Depreciation, not including integration component. Depreciation Not Including Integration Component Depreciation Finance Lease, 2025 Finance Lease, Liability, to be Paid, Year Three Disposal group including discontinued operation notes payable interest rate. Disposal Group Including Discontinued Operation Notes Payable Interest Rate Disposal group including discontinued operation notes payable interest rate Domestic Tax Authority [Member] Domestic Tax Authority [Member] U.S. - Federal [Member] Term for renewal commissions expected. Term For Renewal Commissions Expected Term for renewal commissions expected Net Cash Provided by (Used in) Financing Activities [Abstract] CASH FLOWS (USED IN)/FROM FINANCING ACTIVITIES (DECREASE)/INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH Increase/(decrease) in cash, cash equivalents and other restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Amount payable from option. Amount Payable From Option Amount payable from option Defined contribution plan tranches. Defined Contribution Plan Tranches [Domain] Defined Contribution Plan Tranches Fair Value Measurement [Domain] Fair Value Measurement Capitalized Contract Cost, Net, Current Deferred contract costs Defined benefit plan net assets held in investments. Defined Benefit Plan Net Assets Held In Investments Net assets held in investments Senior notes due 2021, 03500. Senior Notes Due202103500 [Member] 3.500% senior notes due 2021 [Member] Contract with Customer, Performance Obligation Satisfied in Previous Period Contract with Customer, Performance Obligation Satisfied in Previous Period Amendment Flag Amendment Flag Commingled funds. Commingled Funds [Member] Pooled / commingled funds [Member] Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Defined pension and post-retirement benefits Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax, Total 2026 Long-Term Debt, Maturity, Year Four Mergers, Acquisitions and Dispositions Disclosures [Text Block] Acquisitions and Divestitures Effective Income Tax Reconciliation, Foreign Statutory Income Tax Rate Effective Income Tax Reconciliation Foreign Statutory Income Tax Rate Foreign statutory income tax rate U.K. tax rate Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Finite-Lived Intangible Assets, Accumulated Amortization Finite-lived intangible assets, accumulated amortization Her Majesty's Revenue and Customs (HMRC) [Member] Her Majesty's Revenue and Customs (HMRC) [Member] Effective Income Tax Rate Reconciliation, Disposition of Business, Amount Benefit from tax-exempt gain on sale Sale/(purchase) of investments Sale/(purchase) of investments Payments for (Proceeds from) Investments, Total Payments for (Proceeds from) Investments Rest of world. Rest Of World [Member] Rest of World [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items] Goodwill Goodwill, net, ending balance Goodwill, net, beginning balance Goodwill Goodwill, Total Deferred Income Tax Assets, Net Deferred tax assets Deferred Income Tax Assets, Net, Total Operating Lease, Right-of-Use Asset Right-of-use assets Defined benefit plan fair value of plan assets liabilities, net. Defined Benefit Plan Fair Value Of Plan Assets Liabilities Net Fair value of plan assets\(liabilities) Net assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Changes in the Net Carrying Amount of the Components of Finite-Lived Intangible Assets Other Comprehensive Income Location [Axis] Other Comprehensive Income Location Disposal Group Name [Axis] Disposal Group Name Debt instrument maturity year. Debt Instrument Maturity Year Debt instrument maturity year Fixed Income Securities [Member] Other fixed income [Member] Schedule of Long-Term Debt Instruments [Table] Debt Instrument [Table] Payments for Repurchase of Common Stock Repurchase of shares Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Foreign currency translation [Member] Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration Operating loss carryforwards, not subject to expiration SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves Lessee, Operating Lease, Liability, Undiscounted Excess Amount Operating Lease, Interest Cash and Cash Equivalents [Domain] Schedule of finance leased assets. Schedule Of Finance Leased Assets Table [Text Block] Finance Leases Statement [Table] Statement [Table] Operating Lease, Liability, Noncurrent Long-term lease liabilities Operating Lease, Long-term lease liabilities Finance Lease, 2023 Finance Lease, Liability, to be Paid, Year One Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax, Total Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax Plan (disposal)/addition Finance Lease, Interest Expense Interest on lease liabilities Other comprehensive (loss)/income, tax Other Comprehensive Income (Loss), Tax Other Comprehensive Income (Loss), Tax, Total Unrecognized Tax Benefits that Would Impact Effective Tax Rate Reduction in liability for unrecognized tax benefits Income tax reconciliation base erosion anti-abuse tax. Income Tax Reconciliation Base Erosion Anti Abuse Tax Base Erosion Anti-Abuse Tax (BEAT) Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, Accumulated Depreciation and Amortization Accumulated depreciation Other Postretirement Benefits Plan [Member] PRW [Member] Litigation Status [Axis] Litigation Status Operating Lease, Payments Operating leases Tax Year 2023 Through 2042 [Member] Tax Year 2023 Through 2042 [Member] Tax year 2023 through 2042. Remeasurement of Deferred Tax Assets and Liabilities. Remeasurement of Deferred Tax Assets and Liabilities [Member] Number of Operating Segments Number of operating segments London Interbank Offered Rate (LIBOR) [Member] LIBOR [Member] Service [Member] Service Business Acquisition [Axis] Business Acquisition Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income Loss [Table] Restructuring Charges Restructuring costs Restructuring costs Restructuring Charges, Total Charges incurred Payments of Ordinary Dividends, Common Stock Dividends paid Auditor Firm ID Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Balance, Weighted Average Grant Date Fair Value (in dollars per share) Balance, Weighted Average Grant Date Fair Value (in dollars per share) Grant date fair value,per share Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Vested, Weighted Average Grant Date Fair Value (in dollars per share) Restructuring, Expected future effects Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract] Senior notes due 2021, 05750. Senior Notes Due202105750 [Member] 5.750% senior notes due 2021 [Member] Net loss/(gain) on disposal of operations (Loss)/gain on disposal of Willis Re Tax exempt gain on sale Preliminary pre-tax gain on sale Nature of Operations [Text Block] Nature of Operations Property Lease Guarantee [Member] Property Lease Guarantee [Member] One-year term loan. One Year Term Loan [Member] One Year Term Loan [Member] Other Current Liabilities [Table Text Block] Schedule of Other Current Liabilities Income Tax Authority [Domain] Income Tax Authority 2026 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Share-Based Payment Arrangement, Expense, Tax Benefit Tax benefit from compensation expense Hedging Relationship [Domain] Hedging Relationship Product and Service [Axis] Product and Service Disposal group including discontinued operation fiduciary assets. Disposal Group Including Discontinued Operation Fiduciary Assets Fiduciary assets Benefits delivery and administration. Benefits Delivery And Administration [Member] BDA [Member] Business Combination, Contingent Consideration, Liability Contingent consideration estimated fair value Business Combination, Contingent Consideration, Liability, Total Non-cash consideration received Other Significant Noncash Transaction, Consideration Received Cumulative Effect, Period of Adoption, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax) Other Investments [Member] Other [Member] Finite-Lived Intangible Asset, Useful Life Weighted average remaining life of amortizable intangible assets and liabilities Amount of lessee's undiscounted obligation for lease payments for both operating lease and finance lease. Lease Liability Payments Due Total Lease, Total future lease payments Retirement Plan Tax Status [Axis] Retirement Plan Tax Status One Year Term Loan Facility Due 2016, Tranche Two [Member] One Year Term Loan Facility Due2016 Tranche Two [Member] 1-year Term Loan Facility Matures 2016, Tranche two [Member] Share-Based Payment Arrangement, Option [Member] Stock Options [Member] Concentration Risk Type [Axis] Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Issuance of shares under employee stock compensation plans (in shares) Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture, Total Accounts receivable, net balances excluded from held-for-sale. Accounts Receivable Net Balances Excluded From Held For Sale Accounts receivable, net balances excluded from held-for-sale Operating Lease, Weighted Average Remaining Lease Term Operating Leases, Weighted-average remaining term (in years) Debt instrument additional basis spread on variable rate1. Debt Instrument Additional Basis Spread On Variable Rate1 Debt Instrument Additional Basis Spread On Variable Rate1 Gain (Loss) on Contract Termination Termination payment Liabilities and Equity TOTAL LIABILITIES AND EQUITY Tax Period [Axis] Tax Period AOCI Including Portion Attributable to Noncontrolling Interest [Member] AOCL [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Plan Name [Domain] Plan Name Gain/(loss) reclassified from Accumulated OCL into income (effective element) Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net, Total Assets for Plan Benefits, Defined Benefit Plan Pension benefits assets Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] Derivative instruments [Member] Other Liabilities, Current Other current liabilities Total other current liabilities Goodwill, Impaired, Accumulated Impairment Loss Accumulated impairment losses, ending balance Accumulated impairment losses, beginning balance Equity Method Investments [Policy Text Block] Investments in Associates Unbilled Receivables, Current Unbilled Receivable, Current SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Movement in Valuation Allowances and Reserves [Roll Forward] Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, interest cost on projected benefit obligation. Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Interest Cost On Projected Benefit Obligation Discount rate - interest cost on PBO Time based stock options. Time Based Stock Options [Member] Time-based Stock Options [Member] Deferred Foreign Income Tax Expense (Benefit) U.K. corporation tax Derivative Liability, Current Derivatives Measurement Input, Discount Rate [Member] Fair Value Inputs, Discount Rate [Member] Willis Towers Watson merger-related securities litigation. Willis Towers Watson Merger Related Securities Litigation [Member] Merger-Related Securities Litigation [Member] Long-Term Investments and Receivables, Net Long-term note receivable Long-term Investments and Receivables, Net, Total Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Income Statement [Abstract] Obligations, Fair Value Disclosure Contingent consideration Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Other items, net Non-US [Member] Non-US [Member] Continuing Operation [Member] Continuing Operation [Member] Continuing operation. Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Table Text Block] Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets Finance Lease, Weighted Average Remaining Lease Term Finance Leases, Weighted-average remaining term (in years) Derivative liability, fair values Derivative Liability Derivative financial instruments Derivative Liability, Total Repurchase Agreements [Member] Repurchase agreements [Member] Operating Segments [Member] Operating Segments [Member] Finance Lease, Liability, Current Finance Lease, Current lease liabilities Newly-eligible employees. Newly Eligible Employees [Member] Newly-eligible employees [Member] Labor and Related Expense Salaries and benefits Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward] Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward] Liabilities, Current Total current liabilities Contract with Customer, Asset, after Allowance for Credit Loss, Current Contract asset, Current Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total Summary of entities. Summary of Entities [Table Text Block] Summary of Entities Operating Lease, 2025 Lessee, Operating Lease, Liability, to be Paid, Year Three Loss Contingency Nature [Axis] Loss Contingency Nature Non-current contract assets Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent Non-current contract assets Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent, Total Other Income [Member] Other Income, Net [Member] 2027 Long-Term Debt, Maturity, Year Five Cash Acquired from Acquisition Cash acquired Liabilities of disposal group including discontinued operation current fiduciary liabilities. Liabilities Of Disposal Group Including Discontinued Operation Current Fiduciary Liabilities Fiduciary liabilities Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income attributable to non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest, Total Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree Fair Value, Recurring [Member] Recurring [Member] Interest Expense Interest expense Interest expense Interest Expense, Total Accounts Receivable, Allowance for Credit Loss Allowance for doubtful debts Accounts Receivable, Allowance for Credit Loss, Beginning Balance Accounts Receivable, Allowance for Credit Loss, Ending Balance Acquired renewal commissions receivable non current. Acquired Renewal Commissions Receivable Non Current Acquired renewal commissions receivable Real estate rationalization. Real estate rationalization [Member] Real Estate Rationalization [Member] Short-Term Lease, Cost Short-term lease cost Income Tax, Policy [Policy Text Block] Income Taxes Willis Towers Watson public limited company. Willis Towers Watson Public Limited Company [Member] Willis Towers Watson Public Limited Company [Member] Redeemable noncontrolling interest. Redeemable Noncontrolling Interest [Member] Redeemable Non-controlling interest [Member] Deferred Tax Liabilities, Derivatives Financial derivative transactions Preferred Stock, Shares Authorized Preference shares, shares authorized Other Noncurrent Assets [Member] Other Non-current Assets [Member] Reclassification from AOCI, Current Period, Tax Reclassification from AOCI, Current Period, Tax Reclassification from AOCI, Current Period, Tax, Total Deferred Tax Liabilities, Net Net deferred tax liabilities Fiduciary liabilities, current. Fiduciary Liabilities Current Fiduciary liabilities Employee status. Employee Status [Domain] Employee Status Liability, Defined Benefit Plan, Current Current liability for pension benefits Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent Income from continuing operations attributable to Willis Towers Watson Lease payments for both operating lease and finance lease. Lease Payment Total lease payments Senior notes due 2024, 03600. Senior Notes Due202403600 [Member] 3.600% senior notes due 2024 [Member] Treasury Stock, Shares Treasury shares Treasury Stock, Shares, Total Treasury Stock, Shares, Beginning Balance Treasury Stock, Shares, Ending Balance Hedge Funds [Member] Hedge funds [Member] Derivative Asset Derivative Asset, Total Derivative asset, fair values Restricted Cash and Cash Equivalents Items [Line Items] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption Provision for benefit from income taxes from continuing operations Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Operating Lease, Weighted Average Discount Rate, Percent Operating Leases, Weighted-average discount rate Deferred Tax Assets, Capital Loss Carryforwards Capital loss carryforwards Corporate, Non-Segment [Member] Corporate, Non-Segment Variable Rate [Axis] Variable Rate Entity Small Business Entity Small Business Number of Reportable Segments Number of reportable segments Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents CASH, CASH EQUIVALENTS AND RESTRICTED CASH, END OF YEAR CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF YEAR Total cash, cash equivalents and restricted cash Cash, cash equivalents and restricted cash Payroll and other benefits-related liabilities. Payroll and other benefits-related liabilities Collaborative Arrangement and Arrangement Other than Collaborative [Axis] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Valuation And Qualifying Accounts Disclosure [Line Items] Hedging Relationship [Axis] Hedging Relationship Operating Activities [Axis] Restructuring and Related Activities [Abstract] Restructuring Reserve, Total Restructuring Reserve Beginning Balance Ending Balance Divested businesses Divested businesses Divested Businesses Divested businesses Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Revenue and Tangible Long-lived Assets by Geographical Areas Compensation and retirement disclosure. Compensation And Retirement Disclosure [Table] Compensation And Retirement Disclosure [Table] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Obligations assumed Consulting. Consulting [Member] Consulting [Member] Assets, Current Total current assets Property, Plant and Equipment [Line Items] Property,Plant and Equipment [LineItems] Schedule of Allocation of Plan Assets [Table Text Block] Schedule of Allocation of Plan Assets Trademarks and Trade Names [Member] Trademark and trade name [Member] PerformanceBasedStockOptionsMember Performance Based Stock Options [Member] Performance-based Stock Options [Member] Increase (Decrease) in Other Operating Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities, Total Effect on Future Earnings, Amount Annual cost savings of program Weighted Average Number of Shares Outstanding, Basic Basic weighted-average number of shares outstanding (shares) Weighted Average Number of Shares Outstanding, Basic, Total Repayment of principal and interest outstanding. Repayment of principal and interest outstanding Property plant and equipment foreign exchange. Property Plant And Equipment Increase Decrease Due To Foreign Exchange Foreign exchange Unrecognized tax benefits associated with discontinued operations Discontinued Operation, Tax Effect of Gain (Loss) from Disposal of Discontinued Operation HWC [Member] Health Wealth Career Segment [Member] Health Wealth Career Segment . Other Noncurrent Liabilities [Table Text Block] Schedule of Other Non-current Liabilities Finance Lease, Liability Finance Lease, Total lease liabilities Finance Lease, Liability, Total City Area Code City Area Code Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value End of period, Aggregate Intrinsic Value Schedule of Debt [Table Text Block] Schedule of Current and Long-term Debt Schedule of Net Benefit Costs [Table Text Block] Schedule of Net Periodic Benefit Cost Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net (Loss)/gain recognized in income Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Total Defined benefit plan fair value of plan assets liabilities reconciliation. Defined Benefit Plan Fair Value Of Plan Assets Liabilities Reconciliation Fair value of plan assets, end of year Fair value of plan assets, beginning of year Fair value of plan assets Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Commitment fee percentage Tax Year 2019 and 2020 [Member] Tax Year 2019 and 2020 [Member] Tax Year 2019 and 2020. Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Cancelled, Outstanding (in shares) Cancelled, Outstanding (in shares) CARES. C A R E S [Member] CARES [Member] Comprehensive Income (Loss) Note [Text Block] Accumulated Other Comprehensive Loss Defined Benefit Plan, Funded (Unfunded) Status of Plan Funded status at end of year Defined Benefit Plan, Funded (Unfunded) Status of Plan, Total Share-Based Payment Arrangement [Abstract] Schedule of Other Nonoperating Income (Expense) [Table Text Block] Schedule of Other Nonoperating Income Liabilities TOTAL LIABILITIES Document Period End Date Document Period End Date Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests Temporary equity, ending balance Temporary equity, beginning balance Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests, Total SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] Valuation And Qualifying Accounts Disclosure [Table] Schedule of Finite-Lived Intangible Assets [Table] Schedule Of Finite Lived Intangible Assets [Table] Funds Held for Clients Fiduciary assets Entity Number of Employees Number of employees employed (more than 44,000) Delaware Action. Delaware Action [Member] Delaware Action [Member] Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-Based Compensation Cost Stock options Product and Service, Other [Member] Other [Member] Total Lease, 2024 Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due in second fiscal year following latest fiscal year. Lease Liability Payments Due Year Two Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Net periodic benefit (income)/cost Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment Finite-lived intangible assets disposed. Finite Lived Intangible Assets Disposed Intangible asset disposals Software and Software Development Costs [Member] Software [Member] 2023 Finite-Lived Intangible Asset, Expected Amortization, Year One Cash and fiduciary funds transferred in sale of operations Cash Divested from Deconsolidation Statistical Measurement [Axis] Statistical Measurement Human capital and benefits. Human Capital And Benefits [Member] HCB [Member] Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation Accumulated benefit obligation at end of year Adjustments to additional paid in capital, foreign currency translation gain (loss). Adjustments To Additional Paid In Capital Foreign Currency Translation Gain Loss Foreign currency translation Other Assets, Current Other current assets Payments to acquire fixed assets and software for internal use. Payments To Acquire Fixed Assets And Software For Internal Use Additions to fixed assets and software for internal use 2023 Defined Benefit Plan, Expected Future Benefit Payment, Year One Interest income Interest Income, Other Lessee Lease Liabilities Payments Due [Abstract] Leases Liabilities Due [Abstract] Restructuring Costs, Total Restructuring Costs Total Stockholders' Equity Attributable to Noncontrolling Interest Non-controlling interests Stockholders' Equity Attributable to Noncontrolling Interest, Total Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Finance Lease, Interest Payment on Liability Finance leases Finite-Lived Intangible Asset, Expected Amortization, after Year Five Thereafter Balance sheet date. Balance Sheet Date [Domain] Balance Sheet Date Assets TOTAL ASSETS Noncontrolling Interest [Line Items] Minority Interest [Line Items] Derivative Contract [Domain] Derivative Contract GERMANY Germany [Member] Revolving 1.25 billion dollar credit facility. Revolving125 Billion Dollar Credit Facility [Member] Revolving 1.25 Billion Dollar Credit Facility [Member] Previously Reported [Member] State and Local Jurisdiction [Member] State and Local [Member] Costs and Expenses [Abstract] Costs of providing services Derivative [Line Items] Derivative [Line Items] Europe [Member] Western Europe. Western Europe [Member] Software Development [Member] Internally developed software [Member] Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Accumulated other comprehensive loss/(income) Going concern. Going Concern Policy [Text Block] Going Concern Proceeds from Issuance of Senior Long-Term Debt Senior notes issued Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Maximum annual contributions per employee, percent Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Rate of increase in compensation levels Long-Term Debt, Excluding Current Maturities Long-term debt Long-term debt, excluding current maturities Long-term Debt, Excluding Current Maturities, Total Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment Curtailments Curtailments Earnings Per Share, Diluted — Diluted: income from continuing operations Diluted earnings per share Retirement Plan Type [Axis] Retirement Plan Type Deferred tax liabilities operating lease right of use assets. Deferred Tax Liabilities Operating Lease Right Of Use Assets Operating lease right-of-use assets Accounts Receivable [Policy Text Block] Accounts Receivable Income Taxes Receivable, Current Corporate income and other taxes Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Valuation allowances and reserves foreign exchange differences. Valuation Allowances And Reserves Foreign Exchange Differences Foreign exchange Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Balance as of end of period Balance as of beginning of period Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Rate of increase in compensation levels Discontinued Operations [Member] Discontinued Operations [Member] Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change Other Entity Address, Postal Zip Code Entity Address, Postal Zip Code Disposal group including discontinued operation costs of providing services. Disposal Group Including Discontinued Operation Costs Of Providing Services Total costs of providing services Earnings Per Share, Basic [Abstract] Basic earnings per share: Effective Income Tax Rate Reconciliation, Deduction, Other, Amount Net tax effect on intra-group items Other comprehensive (loss)/income, tax Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest, Total Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest Revision of Prior Period [Axis] Document Fiscal Period Focus Document Fiscal Period Focus Accounts Payable, Other, Current Accounts payable, accrued liabilities and deferred income Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table] Finite Lived Intangible Assets Acquired As Part Of Business Combination [Table] Current Income Tax Expense (Benefit) Total current tax expense Current Income Tax Expense (Benefit), Total Increase (Decrease) in Accounts Receivable Accounts receivable Pension Plan [Member] Pension Plan [Member] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Deferred Tax Assets, Valuation Allowance Valuation allowance Less: valuation allowance Deferred Tax Assets, Valuation Allowance, Total Derivative [Table] Derivative [Table] Goodwill, Written off Related to Sale of Business Unit Goodwill disposals Finance Lease, 2027 Finance Lease, Liability, to be Paid, Year Five Payments for (Proceeds from) Other Investing Activities Other, net Other Income and Other Expense Disclosure [Text Block] Other Income, Net Counterparty Name [Domain] Counterparty Name Other Legislation Other Legislation [Policy Text Block] Other legislation Operating Lease, Liability Operating Lease, Total lease liabilities Operating Lease, Liability, Total Payments to Develop Software Capitalized software costs Rollforward of liability associated with cash-based charges. Rollforward of liability associated with cash-based charges [Table Text Block] Rollforward of Liability Associated with Cash-based Charges Net Cash Provided by (Used in) Financing Activities Net cash (used in)/from financing activities Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant Employee contributions Deferred Tax Liabilities, Property, Plant and Equipment Cost of tangible assets, net of related depreciation Short-Term Debt, Type [Axis] Short-term Debt, Type Statement of Financial Position [Abstract] Realized and unrealized gains Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Notes Payable to Banks [Member] Notes Payable [Member] Term Loan Government bonds [Member] Debt Security, Government, Non-US [Member] Entity File Number Securities Act File Number Untaxable manner. Untaxable Manner [Member] Untaxable Manner [Member] Scenario [Domain] Disposal Groups, Including Discontinued Operations [Table Text Block] Schedule of Selected Financial Information and Summary of Total Assets and Liabilities Relates to the Operations of Willis Re Finance Lease, Liability, to be Paid Finance Lease, Total future lease payments Capital lease obligations Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share Income from discontinued operations per share Statement of Cash Flows [Abstract] Additional non-controlling interests Noncontrolling Interest, Increase from Business Combination Lessee, Operating Lease, Liability, to be Paid, after Year Five Operating Lease, Thereafter Willis Re. Willis Re [Member] Willis Re [Member] Sublease Income Sublease income Capitalized Contract Cost, Foreign Exchange Translation Gain (Loss) Capitalized Contract Cost Foreign Exchange Translation Gain Loss Capitalized Contract Cost, Foreign Exchange Translation Gain (Loss) Prepaid expense and accrued revenue receivable noncurrent. Prepaid Expense And Accrued Revenue Receivable Noncurrent Prepayments and accrued income Retirement Benefits [Text Block] Retirement Benefits Business combination payments for deferred consideration payable Business Combination Payment for Deferred Consideration Financing Activities Business combination payment for deferred consideration financing activities. Error Corrections and Prior Period Adjustments Restatement [Line Items] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type Geographical [Domain] Geographical Other Operating Income (Expense), Net Unallocated, net Statistical Measurement [Domain] Statistical Measurement Statement of Stockholders' Equity [Abstract] Dilutive securities effect on basic earnings per share continuing operations. Dilutive Securities Effect On Basic Earnings Per Share Continuing Operations Dilutive effect of potentially issuable shares, continuing operations (USD per share) Auditor Location Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets Fair value of plan assets at end of year Fed Funds Effective Rate Overnight Index Swap Rate [Member] Federal Funds Effective Swap Rate [Member] Class of Stock [Domain] Class of Stock Disclosure of accounting policy for fiduciary assets and liabilities i.e. balances that have been or are due to be collected or remitted to insurers and/or insured in the Company's capacity as an insurance broker or agent. Fiduciary Assets And Fiduciary Liabilities Policy [Text Block] Fiduciary Assets and Liabilities Revenue Benchmark [Member] SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Additions charged to costs and expenses Deferred compensation plan assets current. Deferred Compensation Plan Assets Current Deferred compensation plan assets Revenue from Contract with Customer [Policy Text Block] Revenue Recognition Legal Entity Legal Entity [Axis] Stock Repurchased and Retired During Period, Shares Shares repurchased (in shares) Lease, Cost [Table Text Block] Schedule of Amount Recorded in Consolidated Statements of Comprehensive Income Equity Method Investment, Ownership Percentage Equity ownership voting percentage Willis. Willis [Member] Willis [Member] Fair Value Disclosures [Text Block] Fair Value Measurements Termination of proposed combination with AON Plc. Termination Of Proposed Combination With A O N Plc [Member] Termination of Proposed Combination with AON Plc [Member] Disposal Group, Including Discontinued Operation, Liabilities, Current Current liabilities held for sale Total liabilities held for sale Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Net of Forfeitures Options granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures, Total Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Options exercisable at end of period, Weighted Average Remaining Contractual Term Proceeds from Stock Options Exercised Cash received from exercise of stock options Proceeds from Issuance of Common Stock Proceeds from issuance of shares Long-Term Debt, Type [Axis] Long-term Debt, Type Liabilities of disposal group including discontinued operation current other liabilities. Liabilities Of Disposal Group Including Discontinued Operation Current Other Liabilities Other liabilities Years 2028 - 2032 Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years (Benefit from)/provision for deferred income taxes Deferred Income Tax Expense (Benefit) Deferred income tax benefit Total deferred tax (expense)/benefit Deferred Income Tax Expense (Benefit), Total Tabular disclosure of undiscounted cash flows of lessee's operating lease liability and finance lease liability. includes, but is not limited to, reconciliation of undiscounted cash flows to lease liabilities recognized in statement of financial position. Lessee Operating And Finance Lease Liability Maturity Table [Text Block] Schedule of Maturity of Operating and Finance Leases Liabilities U.S. state. U.S. State [Member] Accounting Standards Update 2018-02 [Member] Accounting Standards Update 2018-02 [Member] Revenue member. Revenue [Member] Revenue [Member] Weighted Average Number of Shares Outstanding, Diluted, Adjustment Dilutive effect of potentially issuable shares (shares) Weighted Average Number Diluted Shares Outstanding Adjustment, Total Deferred Income Tax Liabilities, Net Deferred tax liabilities Deferred Income Tax Liabilities, Net, Total Property, Plant and Equipment [Table Text Block] Property, Plant and Equipment SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Deductions/other movements Deductions Proceeds from (Payments for) Other Financing Activities Other, net Revenue from Contract with Customer [Text Block] Revenue Unusual Risk or Uncertainty, Nature [Axis] Unusual Risk or Uncertainty, Nature Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Amortization of unrecognized actuarial loss Antidilutive Securities [Axis] Antidilutive Securities Disposal Group, Including Discontinued Operation, Revenue Revenue from discontinued operations Derivative, Remaining Maturity Longest outstanding maturity Line of Credit Facility, Maximum Borrowing Capacity Maximum borrowing capacity Business combination contingent consideration liability and deferred consideration current. Business Combination Contingent Consideration Liability And Deferred Consideration Current Contingent and deferred consideration on acquisitions Pension and Other Postretirement Plans, Pensions, Policy [Policy Text Block] Pensions Sale of non-controlling interests Noncontrolling Interest, Increase from Sale of Parent Equity Interest Preferred Stock, Par or Stated Value Per Share Preference shares, nominal value (USD per share) Insurance contracts. Insurance Contracts [Member] Insurance contracts [Member] Loss Contingency, Nature [Domain] Loss Contingency, Nature Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Net book value Capitalized Contract Cost, Amortization Capitalized Contract Cost, Amortization Lessee, Lease, Description [Line Items] 4.650% senior notes due 2027 [Member] Senior Notes Due 202704650 [Member] Senior notes due 202704650 [Member]. Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss) Foreign currency changes Foreign currency changes Movement in Property, Plant and Equipment [Roll Forward] Movement in Property, Plant and Equipment [Roll Forward] Supplemental Balance Sheet Disclosures [Text Block] Supplementary Information for Certain Balance Sheet Accounts Credit Facility [Domain] Credit Facility Not Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument [Member] Nondesignated [Member] Weighted Average Number of Shares Outstanding, Diluted Diluted weighted-average number of shares outstanding (shares) Retirement Plan Sponsor Location [Domain] Retirement Plan Sponsor Location Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Impact of U.S. state and local taxes Credit Facility [Axis] Credit Facility Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Table] Defined Benefit Plan, Plan Assets, Amount Fair value of plan assets, end of year Fair value of plan assets, beginning of year Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount, Total Corporate Debt Securities [Member] Corporate bonds [Member] Portion at Fair Value Measurement [Member] Fair Value Disclosure Item Amounts [Default] Portion at Fair Value Measurement [Member] [Default] SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Balance at end of year Balance at beginning of year Broking. Broking [Member] Broking [Member] Earnout receivable in cash not recognized as an asset on balance sheet. Earnout Receivable In Cash Earnout receivable in cash in 2025 Gain on disposal Gain (Loss) on Disposition of Assets Gain (Loss) on Disposition of Assets, Total Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Supplemental Disclosures Regarding Cash Flow Information and Non-cash Flow Investing and Financing Activities Aon plc. Aon Plc [Member] Aon Plc [Member] Other acquisitions. Other Acquisitions [Member] Other Acquisitions [Member] Current Fiscal Year End Date Current Fiscal Year End Date Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax Reclassifications of foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax, Total Derivative Instruments and Hedging Activities Disclosure [Abstract] Liability Class [Axis] Liability Class (Loss)/gain recognized in OCL (effective element) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax, Total Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Derivative instruments Depreciation Depreciation Depreciation expense Depreciation, Total Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment Curtailment gain Trinity Acquisition plc. Trinity Acquisition Plc [Member] Trinity Acquisition plc [Member] Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Beginning Balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Ending Balance Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Total cash, cash equivalents and restricted cash Stock Repurchased and Retired During Period, Value Shares repurchased Capitalized Contract Cost [Table Text Block] Capitalized Contract Cost Other Assets, Noncurrent Other non-current assets Total other non-current assets Portion Of Revenue Portion Of Revenue Portion of Revenue Effective income tax rate reconciliation, effect of foreign exchange and other differences. Effective Income Tax Rate Reconciliation Effect Of Foreign Exchange And Other Differences Effect of foreign exchange and other differences Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Equity, ending balance Equity, beginning balance Total equity Entity Address, Address Line One Entity Address, Address Line One Repayments of Long-Term Debt Repayments of debt Repayments of Long-term Debt, Total Deferred Tax Liabilities, Intangible Assets Cost of intangible assets, net of related amortization Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of Derivative Instruments Designated/Nondesignated As Hedging Instrument Effect on Condensed Consolidated Statements of Comprehensive Income Noncontrolling Interest [Member] Non-controlling interests [Member] Document Annual Report Document Annual Report Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Quarterly Financial Information Disclosure [Abstract] Disposal Groups, Including Discontinued Operations [Table] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class Schedule of cash paid for amount in the measurement of lease liabilities. Schedule Of Cash Paid For Amount In Measurement Of Lease Liabilities Table [Text Block] Schedule of Cash Paid in the Measurement of Lease Liabilities Supplemental Cash Flow Information [Abstract] Supplemental disclosures of cash flow information: Loss Contingency Accrual, Provision Provision for litigation losses Provision for significant litigation Components of Deferred Tax Assets [Abstract] Deferred tax assets: Common Stock Including Additional Paid in Capital [Member] Ordinary shares and APIC [Member] (Loss)/income from discontinued operations per share Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share Income Tax Expense (Benefit) Income Tax Expense Benefit Provision for income taxes Total provision for income taxes Income Tax Expense (Benefit), Total Obligations [Member] Contingent consideration [Member] Defined Benefit Plan, Accumulated Benefit Obligation Accumulated Benefit Obligation Defined benefit plan, average remaining service period. Defined Benefit Plan Average Remaining Service Period Average remaining service period Fiduciary liabilities excluded from held for sale. Fiduciary liabilities excluded from held for sale Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Changes in valuation allowances Senior Notes [Member] Senior Notes [Member] Finance Lease, Liability, to be Paid [Abstract] Finance Leases [Abstract] Income Tax Disclosure [Text Block] Income Taxes Preferred Stock, Shares Issued Preference shares, shares issued Preferred Stock, Shares Issued, Total Balance Sheet Location [Domain] Balance Sheet Location Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items] Foreign Exchange Contract [Member] Foreign exchange contracts [Member] Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax Settlement Other Sundry Liabilities, Noncurrent Other non-current liabilities Derivative [Member] Derivatives [Member] Revenue, Remaining Performance Obligation, Amount Revenue, Remaining Performance Obligation Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, before Accumulated Depreciation and Amortization Finance leases Income Tax Disclosure [Abstract] Disposal Group, Including Discontinued Operation, Assets, Noncurrent Non-current assets held for sale Disposal Group, Including Discontinued Operation, Assets, Noncurrent, Total Contract Termination [Member] Termination Agreement Termination Agreement [Member] Fair Value Measurements, Nonrecurring [Table Text Block] Schedule of Assets and Liabilities Whose Carrying Values Differ From the Fair Value and are Not Measured on a Recurring Basis Dilutive securities effect on basic earnings per share discontinued operations. Dilutive Securities Effect On Basic Earnings Per Share Discontinued Operations Dilutive effect of potentially issuable shares Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation Projected benefit obligation at end of year Disposal group including discontinued operation right of use assets. Disposal Group Including Discontinued Operation Right Of Use Assets Right-of-use assets Cash proceeds from other disposal Proceeds from Divestiture of Businesses, Net of Cash Divested Proceeds from Divestiture of Businesses, Net of Cash Divested, Total Non-Fiduciary. Non-Fiduciary [Member] Non-Fiduciary [Member] Deferred Tax Liabilities, Tax Deferred Income Accrued revenue not currently taxable Schedule​ of share ​based ​payment​ award​ restricted stock units valuation ​assumptions​. Schedule Of Share Based Payment Award Restricted Stock Units Valuation Assumptions Table [Text Block] Schedule of Assumptions Reported Value Measurement [Member] Carrying Value [Member] Assets, Fair Value Disclosure [Abstract] Assets: Defined Benefit Plan, Roll Forwards [Abstract] Number of Reporting Units Number of reporting units Costs and Expenses Total costs of providing services Total costs of providing services Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV Senior notes due 2026, 04400. Senior Notes Due202604400 [Member] 4.400% senior notes due 2026 [Member] Senior notes due 2023, 04625. Senior Notes Due202304625 [Member] 4.625% senior notes due 2023 [Member] Goodwill and Intangible Assets Disclosure [Abstract] Share-Based Payment Arrangement [Policy Text Block] Share-Based Compensation Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of unrecognized prior service (credit)/cost Certificates of deposit and term deposits. Certificates of Deposit And Term Deposits [Member] Certificates of Deposit and Term Deposits [Member] Auditor Name Transaction and transformation, net Business combination integration related transaction costs. Business Combination Integration Related Transaction Costs Transaction and integration, net Equity [Abstract] Finance Lease, 2026 Finance Lease, Liability, to be Paid, Year Four Deferred other jurisdictions tax expense benefit. Deferred Other Jurisdictions Tax Expense Benefit Other jurisdictions Contract with Customer, Liability, Revenue Recognized Contract with Customer, Liability, Revenue Recognized Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax Gain on sale of discontinued operations before income taxes Income from discontinued operations before income taxes Other foreign plans. Other Foreign Plans [Member] Other Foreign Plans [Member] Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Cancelled Weighted Average Exercise Price (in dollars per share) Operating Income (Loss) Income/(loss) from operations Income from operations Income from operations Debt Instrument, Interest Rate, Stated Percentage Stated interest rate Building [Member] Buildings [Member] Liabilities, Noncurrent Total non-current liabilities Additional Paid in Capital, Common Stock Additional paid-in capital Additional Paid in Capital, Common Stock, Beginning Balance Additional Paid in Capital, Common Stock, Ending Balance Finance Lease, Liability, to be Paid, after Year Five Finance Lease, Thereafter Reimbursable expenses and other. Reimbursable Expenses And Other Reimbursable expenses and other Payments to Acquire Businesses, Net of Cash Acquired Acquisitions of operations, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired, Total Scenario [Axis] Concentration Risk Benchmark [Domain] Entity Filer Category Entity Filer Category Comprehensive Income (Loss) [Table Text Block] Comprehensive Income (Loss) Cumulative Costs [Member] Cumulative costs. Restructuring Plan [Domain] Derivative Asset, Statement of Financial Position [Extensible Enumeration] Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Plan amendments Non-cash Revaluation Gain Related to Acquisition [Member] Non-cash revaluation gain related to acquisition. Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Amortization of unrecognized prior service credit Loans and Leases Receivable, Net of Deferred Income, Total Loans and Leases Receivable, Net of Deferred Income Net losses receivable from Gallagher on Deferred Closing Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Net other comprehensive income/(loss) Senior Notes Due 2016 [Member] Senior Notes Due2016 [Member] 4.125% Senior Notes Due 2016 [Member] Percent of minimum tax for taxable income adjusted. Percent Of Minimum Tax For Taxable Income Adjusted Percent of minimum tax for taxable income adjusted Fair Value by Liability Class [Domain] Fair Value by Liability Class Entity Current Reporting Status Entity Current Reporting Status Goodwill, Foreign Currency Translation Gain (Loss) Foreign exchange Asset Class [Domain] Current State and Local Tax Expense (Benefit) U.S. state and local taxes ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Line of Credit [Member] Line of Credit [Member] Disposal Group, Including Discontinued Operation, Goodwill, Current Goodwill Book of business settlements. Book of Business Settlements [Member] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Deferred Revenue and Accrued Expenses Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Options exercisable at end of period, Aggregate Intrinsic Value Impairment Impairment Asset Impairment Charges Asset Impairment Charges, Total Insurance Settlements Receivable, Noncurrent Insurance recovery receivables Derivatives and investments current. Derivatives And Investments Current Derivatives and investments Business Combinations [Abstract] Finite-Lived Intangible Assets, Net Finite-lived intangible assets, net amount Total Finite-Lived Intangible Assets, Net, Beginning Balance Finite-Lived Intangible Assets, Net, Ending Balance Earnings Per Share, Diluted [Abstract] Diluted earnings per share: Stockholders' Equity Attributable to Parent Stockholders' equity attributable to parent, ending balance Stockholders' equity attributable to parent, beginning balance Total WTW shareholders' equity Net proceeds/(payments) from fiduciary funds held for clients Net proceeds/(payments) from fiduciary funds held for clients Net (payments)/proceeds from fiduciary funds held for clients. Net Payments Proceeds from Fiduciary Funds Held for Clients AOCI Attributable to Parent [Member] AOCI Attributable to Parent [Member] Total [Member] Short-Term Investments [Member] Short-term securities [Member] Base Rate [Member] Bank Base Rate [Member] Schedule of Expected Benefit Payments [Table Text Block] Schedule of Expected Benefit Payments Commitments and Contingencies, Policy [Policy Text Block] Commitments, Contingencies and Accrued Liabilities Asset Class [Axis] 2024 Long-Term Debt, Maturity, Year Two Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Entity Tax Identification Number Entity Tax Identification Number Income Statement Location [Axis] Income Statement Location Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Forfeited (shares) Forfeited (shares) Consolidation Items [Axis] Consolidation Items Retained Earnings (Accumulated Deficit) Retained earnings Reclassification of tax effects per ASU 2018-02 Retained Earnings (Accumulated Deficit), Total Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Ending Balance Adjustment of retained earnings Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount Tax differentials of non-U.S. jurisdictions Equity Components [Axis] Equity Components Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Total Trident V parallel fund. Trident V Parallel Fund [Member] Trident V Parallel Fund [Member] Senior notes due 2043, 06125. Senior Notes Due204306125 [Member] 6.125% senior notes due 2043 [Member] Accounting Standards Update [Domain] Accounting Standards Update Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents Cash and cash equivalents Leases [Abstract] Contract with Customer, Liability Deferred revenue Contract with Customer, Liability, Total Customer Relationships [Member] Client relationships [Member] Disaggregation of Revenue [Table] Disaggregation Of Revenue [Table] Business Acquisition, Date of Acquisition Agreement Business acquisition, effective date of acquisition 2025 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Entity Emerging Growth Company Entity Emerging Growth Company Schedule of Business Acquisitions, by Acquisition [Table] Schedule Of Business Acquisitions By Acquisition [Table] Defined Benefit Plan, Interest Cost Interest cost Goodwill [Roll Forward] Goodwill [Roll Forward] Noncash or part Noncash acquisition fair value of deferred and contingent consideration Non Cash Or Part Non Cash Acquisition Fair Value Of Deferred And Contingent Consideration Fair value of deferred and contingent consideration related to acquisitions Income (Loss) from Continuing Operations, Per Diluted Share Income from continuing operations per share Diluted earnings per share from continuing operations attributable to WTW -- Diluted: income from continuing operations Gallagher. Gallagher [Member] Gallagher [Member] Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Change in Plan Assets Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax Net actuarial (gain)/loss Current Federal Tax Expense (Benefit) U.S. federal taxes Goodwill [Line Items] Goodwill [Line Items] Retirement Plan Type [Domain] Retirement Plan Type CANADA Canada - Federal [Member] Canada [Member] Disposal group including discontinued operation other expense (income) net. Disposal Group Including Discontinued Operation Other Expense Income Net Other income, net Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Contract with Customer, Asset and Liability Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share Diluted earnings per share from discontinued operations, net of tax Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category Reduction of non-controlling interests Noncontrolling Interest, Decrease from Deconsolidation Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term Expected life (years) Significant accounting policies and recent accounting pronouncements. Significant Accounting Policies And Recent Accounting Pronouncements [Line Items] Significant Accounting Policies And Recent Accounting Pronouncements [Line Items] Disposal Group, Including Discontinued Operation, Liabilities, Current [Abstract] Liabilities held for sale: Europe [Member] Europe [Member] Lessee, Operating Lease, Liability, to be Paid [Abstract] Operating Leases [Abstract] Defined Benefit Plan, Service Cost Service cost Corporate risk and broking. Corporate Risk And Broking [Member] CRB [Member] Entity Voluntary Filers Entity Voluntary Filers Deferred Federal Income Tax Expense (Benefit) U.S. federal taxes Divested Businesses [Member] Divested Businesses [Member] Divested Businesses Gain on disposal of operations Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Accumulated depreciation depletion and amortization foreign exchange. Accumulated Depreciation Depletion And Amortization Foreign Exchange Foreign exchange Retirement Benefits [Abstract] Deferred Tax Assets, Derivative Instruments Financial derivative transactions Maximum annual salary amount. Maximum Annual Salary Amount Increase in salary maximum amount Document Transition Report Document Transition Report Fiduciary assets. Fiduciary Assets [Member] Operating Leases, Rent Expense Rent expense, net of sublease income Operating Leases, Rent Expense, Total Operating Loss Carryforwards, Valuation Allowance Operating loss carryforwards, valuation allowance Operating Loss Carryforwards, Valuation Allowance, Total Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Net income Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest, Total Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Income from continuing operations before income taxes and interest in earnings of associates by location of taxing jurisdiction Termination Payment. Termination Payment [Member] 2025 Long-Term Debt, Maturity, Year Three Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Granted, Weighted Average Grant Date Fair Value (in dollars per share) Estimated Litigation Liability, Current Litigation settlements Liabilities of disposal group including discontinued operation current deferred revenue and accrued expenses. Liabilities Of Disposal Group Including Discontinued Operation Current Deferred Revenue And Accrued Expenses Deferred revenue and accrued expenses Schedule of Segment Reporting Information, by Segment [Table] Schedule Of Segment Reporting Information By Segment [Table] Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) Revenue from Rights Concentration Risk [Member] Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Outsourced administration. Outsourced Administration [Member] Outsourced administration [Member] Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Exercised, Weighted Average Exercise Price (in dollars per share) Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations Effect of exchange rate changes on cash, cash equivalents and restricted cash Risks and Uncertainties of the Economic Environment Risk and uncertainties. Risk And Uncertainties Policy [Text Block] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Tax Period [Domain] Tax Period Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable, net Accounts receivable, net Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year Expected future employer contributions, next fiscal year Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Deferred State and Local Income Tax Expense (Benefit) U.S. state and local taxes Other comprehensive (loss)/income, net of tax, before non-controlling interests Other Comprehensive Income (Loss), Net of Tax Other comprehensive income/(loss), total Cash Flow, Supplemental Disclosures [Text Block] Supplemental Disclosures of Cash Flow Information Revision of Prior Period [Domain] Prepaid bonuses current. Prepaid Bonuses Current Retention incentives Senior notes due 2028, 045. Senior Notes Due2028045 [Member] 4.500% senior notes due 2028 [Member] Private Equity Funds [Member] Private equity [Member] Net Income (Loss) Attributable to Parent Net income attributable to Willis Towers Watson NET INCOME ATTRIBUTABLE TO WTW Net income attributable to WTW Great Britain. Great Britain [Member] Great Britain [Member] Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation Projected benefit obligation at end of year Schedule of projected pension contributions. Schedule Of Projected Pension Contributions Table [Text Block] Schedule of Projected Pension Contributions Operating Lease, Liability, Current Current lease liabilities Operating Lease, Current lease liabilities Disposal Group, Including Discontinued Operation, Intangible Assets, Current Other intangible assets, net Intangible assets, net Internally-developed software asset. Internally Developed Software Asset [Member] Internally-developed Software Asset [Member] Disposal Group, Including Discontinued Operation, Property, Plant and Equipment, Current Fixed assets, net Deconsolidation gain or loss amount Deconsolidation, Gain (Loss), Amount Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis Decrease in Unrecognized Tax Benefits is Reasonably Possible Expected decrease in liability for uncertain tax position Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Revenue Commissioners, Ireland [Member] Revenue Commissioners, Ireland [Member] Payment, Tax Withholding, Share-Based Payment Arrangement Cash paid for employee taxes on withholding shares Income taxes payable Taxes Payable, Current Taxes Payable, Current, Total Line of Credit Facility, Expiration Date Line of credit maturity date Deferred Tax Assets, Operating Loss Carryforwards Net operating losses Deferred Tax Assets, Operating Loss Carryforwards, Total Defined contribution plan tranche two. Defined Contribution Plan Tranche Two [Member] Defined Contribution Plan Tranche Two [Member] Schedule of Maturities of Long-Term Debt [Table Text Block] Schedule of Maturities of Long-term Debt Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net Accounts receivable, net Property, Plant and Equipment, Additions Additions Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Impact of change in rate on deferred tax balances Restructuring Plan [Axis] Entity Registrant Name Entity Registrant Name Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Decreases related to lapse in statute of limitations Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Unencumbered and available funds required Cash and Cash Equivalents, at Carrying Value, Total Cash and Cash Equivalents, at Carrying Value, Beginning Balance Cash and Cash Equivalents, at Carrying Value, Ending Balance SWITZERLAND Switzerland Earnings Per Share [Text Block] Earnings Per Share Effective income tax rate reconciliation net adjustments on acquisition costs. Effective Income Tax Rate Reconciliation Net adjustments on Acquisition Costs Net adjustments on acquisition costs Net adjustments on acquisition costs Class of Stock [Axis] Class of Stock Debt Instrument, Maturity Date Maturity date Lessee, Lease, Description [Table] Revenues Revenue Total revenue Revenues Percentage of lease denominated in major currencies such as U.S. dollars, Pounds Sterling or Euros. Percentage Of Lease Denominated In Major Currencies Percentage of lease denominated in U.S. dollars, Pounds Sterling or Euros Share-Based Payment Arrangement, Noncash Expense Share-based compensation Share-based Payment Arrangement, Noncash Expense, Total Property, Plant and Equipment, Net Fixed assets, net Property, Plant and Equipment, Net, Total Property, Plant and Equipment, Net, Beginning Balance Property, Plant and Equipment, Net, Ending Balance Finance Lease, Right-of-Use Asset, Amortization Amortization of right-of-use assets Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Options vested or expected to vest at end of period, Weighted Average Remaining Contractual Term Award Type [Domain] Award Type Statement [Line Items] Statement [Line Items] AOCI, Derivative Qualifying as Hedge, Excluded Component, Parent [Member] Derivative instruments [Member] Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Issuance of shares under employee stock compensation plans Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture, Total Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement Settlements Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement, Total Other Long-Term Debt, Current Current portion of long term debt Income from continuing operations before income taxes and interest in earnings of associates. Income From Continuing Operations Before Income Taxes And Interest In Earnings Of Associates [Line Items] Income from Continuing Operations before Income Taxes and Interest in Earnings of Associates [Line Items] Liabilities, Fair Value Disclosure [Abstract] Liabilities: Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Options vested or expected to vest at end of period, Weighted Average Exercise Price (in dollars per share) (Loss)/income from discontinued operations, net of tax Income/(loss) from discontinued operations, net of tax INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX Goodwill, Purchase Accounting Adjustments Acquisition accounting adjustment Total Lease, 2023 Lease liability payments due next twelve months. Lease Liability Payments Due Next Twelve Months Title of 12(b) Security Title of 12(b) Security Finite-Lived Intangible Assets, Gross Finite-lived intangible assets, gross carrying amount Finite-Lived Intangible Assets, Gross, Total Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Current tax expense: Ownership [Domain] Ownership Restructuring Cost and Reserve [Line Items] Common Stock [Member] Shares outstanding [Member] Derivative, Notional Amount Derivative, notional amount Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, service cost. Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Service Cost Discount rate - service cost 2012 Equity Incentive Plan [Member] A2012 Equity Incentive Plan [Member] 2012 Equity Incentive Plan [Member] Net Cash Provided by (Used in) Operating Activities [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES Equity Component [Domain] Equity Component Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due after fifth fiscal year following latest fiscal year. Lease Liability Payments Due After Year Five Total Lease, Thereafter Revenue from Contract with Customer, Excluding Assessed Tax Revenue from Contract with Customer, Excluding Assessed Tax Revenue from Contract with Customer, Excluding Assessed Tax, Total Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES Finance Lease, Liability, Undiscounted Excess Amount Finance Lease, Interest Senior notes due 2049, 03875. Senior Notes Due204903875 [Member] 3.875% senior notes due 2049 [Member] Entity Address, State or Province Entity Address, State or Province Finite-Lived Intangible Assets [Roll Forward] Finite-lived Intangible Assets [Roll Forward] Operating Lease, 2026 Lessee, Operating Lease, Liability, to be Paid, Year Four Geographical [Axis] Geographical Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Share Price Sharebased Compensation Arrangementby Sharebased Payment Award Equity Instruments Otherthan Options Vestedin Period Weighted Average Grant Date Share Price Vested, Weighted Average Grant Date Fair Value (in dollars per share) Amount of unrecognized tax benefits including interest. Unrecognized Tax Benefits Including Interest Liabilities for uncertain tax positions Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration] Capitalized Contract Cost, Net Capitalized Contract Cost, Net Capitalized Contract Cost, Net Capitalized Contract Cost, Net, Total Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income before non-controlling interests Document Type Document Type Interest Paid, Excluding Capitalized Interest, Operating Activities Cash payments for interest Litigation Status [Domain] Litigation Status Global Intangible Low-Taxed Income (GILTI) Global Intangible Low-Taxed Income (GILTI) Effective Income Tax Rate Reconciliation, GILTI, Amount UNITED STATES United States [Member] UNITED STATES [Member] Significant accounting policies and recent accounting pronouncements. Significant Accounting Policies And Recent Accounting Pronouncements [Table] Significant Accounting Policies And Recent Accounting Pronouncements [Table] Adjustments to additional paid in capital, sharebased compensation and net settlements. Adjustments To Additional Paid In Capital Sharebased Compensation And Net Settlements Share-based compensation and net settlements Defined Benefit Plan, Amortization of Gain (Loss) Amortization of unrecognized actuarial loss Entity Shell Company Entity Shell Company Derivatives, Policy [Policy Text Block] Derivatives Net prior service loss/(gain) Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax December 31 2021 [Member] December 31 2021 [Member] December 31 2021 Member. Share-Based Payment Arrangement, Expense Share-based compensation Disposal Group, Including Discontinued Operation, Assets, Current [Abstract] Assets held for sale: Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Fair Value of Financial Instruments, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Effective income tax reconciliation foreign statutory tax rate. Effective Income Tax Reconciliation Foreign Statutory Tax Rate Foreign statutory tax rate Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate Health care cost trend - ultimate rate year Defined Benefit Plan, Benefit Obligation, Benefits Paid Benefits paid Fair Value, Recurring and Nonrecurring [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair value level one level two level or three transfers amount. Fair Value Level One Level Two Or Level Three Transfers Amount Fair value significant transfers between Levels 1, 2 or 3 Net receivable for investments purchased Defined benefit plan net (payable) receivable for Investments purchased. Defined Benefit Plan Net Payable Receivable For Investments Purchased Debt Securities [Member] Debt securities [Member] Defined Benefit Plan, Plan Assets, Benefits Paid Benefits paid Unrecognized Tax Benefits, Increase Resulting from Acquisition Increases related to acquisitions Unrecognized Tax Benefits, Interest on Income Taxes Accrued Interest on income taxes accrued North America [Member] North America [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Capital contribution obligation. Capital Contribution Obligation Capital contribution obligation Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] EQUITY Security Exchange Name Security Exchange Name Employee Services Share Based Compensation, Tax Benefit Realized From Vesting Of RSUs Employee Services Share Based Compensation Tax Benefit Realized From Vesting Of R S Us Employee Services Share Based Compensation, Tax Benefit Realized From Vesting Of RSUs Goodwill and Intangible Assets, Policy [Policy Text Block] Goodwill and Other Intangible Assets Revenue from Contract with Customer [Abstract] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss) Foreign exchange Willis Towers Watson. Willis Towers Watson [Member] Willis Towers Watson [Member] Finance Lease, Liability, Noncurrent Finance Lease, Long-term lease liabilities Finance leases Cash Flow, Operating Activities, Lessee [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities Net cash from operating activities Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Change in Benefit Obligation Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Compensation cost not yet recognized, period for recognition Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term End of period, Weighted Average Remaining Contractual Term Deferred Tax Liabilities, Prepaid Expenses Prepaid retirement benefits Debt Instrument, Interest Rate, Effective Percentage Effective interest rate (as a percent) Deferred tax liabilities. Deferred Tax Liabilities [Member] Deferred Tax Liabilities [Member] Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive (loss)/income, net of tax: Defined benefit plans, percentage of obligation from plans. Defined Benefit Plans Percentage Of Obligation From Plans Portion of pension and OPEB obligation attributed to disclosed plans (as a percent) cash payments totaling Payments to Acquire Businesses, Gross Consideration paid in cash Commitments and Contingencies Disclosure [Abstract] Net income (payable to)/receivable from Gallagher on Deferred Closing Gains (losses) accruing to acquirer. Gains Losses Accruing To Acquirer Disposal group including discontinued operation costs of providing services. Disposal Group Including Discontinued Operation Costs Of Providing Services [Abstract] Costs of providing services Operating Lease, Cost Operating lease cost Interest Payable, Current Interest payable Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Reconciliation Of Operating Profit Loss From Segments To Consolidated [Table] Restricted Stock Units (RSUs) [Member] Restricted Stock Units [Member] Restricted share units [Member] Acquired renewal commission receivable current. Acquired Renewal Commission Receivable Current Acquired renewal commissions receivable Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Discount rate Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Reconciliation of the beginning and ending amounts of unrecognized tax benefits Segment Reconciliation [Abstract] Revenue: Consolidation, Policy [Policy Text Block] Principles of Consolidation Finance Lease, 2024 Finance Lease, Liability, to be Paid, Year Two Actuarial gains Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Actuarial (gains)/losses Business combination, contingent consideration, liability and deferred consideration, noncurrent. Business Combination Contingent Consideration Liability And Deferred Consideration Noncurrent Contingent and deferred consideration on acquisitions Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Schedule of Share-based Compensation, Restricted Stock Units Award Activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Schedule of Share-based Compensation, Stock Options, Activity TRANZACT acquisition. T R A N Z A C T Acquisition [Member] TRANZACT Acquisition [Member] Max Matthiessen. Max Matthiessen [Member] Max Matthiessen [Member] New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Pronouncements Receivable [Policy Text Block] Acquired Accounts Receivable Schedule of Defined Benefit Plans Disclosures [Table] Schedule Of Defined Benefit Plans Disclosures [Table] Common Stock, Shares, Outstanding Ordinary shares, shares outstanding Common Stock, Shares, Outstanding, Beginning Balance Common Stock, Shares, Outstanding, Ending Balance Business Acquisition [Line Items] Business Acquisition [Line Items] Debt Disclosure [Text Block] Debt Entity Address, Country Entity Address, Country Fair Value, Inputs, Level 2 [Member] Level 2 [Member] Proceeds from Issuance of Long-Term Debt Proceeds from long-term debt issuance Proceeds from Issuance of Long-term Debt, Total Non-cash proceeds from other disposal Noncash or Part Noncash Divestiture, Amount of Consideration Received CASH FLOWS (USED IN)/FROM INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Present value of lessee's discounted obligation for lease payments from both operating lease and finance lease. Lease Liability Total Lease, Total lease liabilities Insurance Settlements Receivable, Current Insurance recovery receivables Insurance and other recovery receivables Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Schedule of Future Estimated Amortization Expense for Amortizable Intangible Assets Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held Unrealized loss Real Estate [Member] Real estate [Member] Total Lease, 2025 Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due in third fiscal year following latest fiscal year. Lease Liability Payments Due Year Three Senior notes due 2029, 02950. Senior Notes Due202902950 [Member] 2.950% senior notes due 2029 [Member] Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Increases related to current year tax positions Interest carryforwards Deferred Tax Asset, Interest Carryforward Commitments and Contingencies COMMITMENTS AND CONTINGENCIES Income Tax Authority, Name [Domain] Income Tax Authority, Name Common Stock, Shares, Issued Ordinary shares, shares issued Common Stock, Shares, Issued, Total Other Assets, Miscellaneous, Noncurrent Other non-current assets Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Financial Instruments Reimbursed Expenses [Member] Reimbursed Expenses [Member] Reimbursed Expenses [Member] Variable Rate [Domain] Variable Rate Minimum [Member] Minimum [Member] Hedging Designation [Axis] Hedging Designation Designated as Hedging Instrument [Member] Restructuring and Related Costs [Table Text Block] Summary of Total Restructuring Costs Tax Year 2019 [Member] Tax Year 2019 [Member] Income Tax Authority, Name [Axis] Income Tax Authority, Name Transition Services Agreement. Transition Services Agreement [Member] Marketable Securities Mutual funds / exchange traded funds Marketable Securities, Total Miscellaneous other non-operating income expense. Miscellaneous Other Non Operating Income Expense Other Abandonment of long-lived asset. Abandonment Of Long Lived Asset Abandonment Abandonment of long-lived asset Losses on derivatives to be reclassified within the next twelve months Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred Insurance Contract, Rights and Obligations [Member] Insurance contracts [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Segments [Domain] Segments Restricted Cash, Current Restricted cash Other restricted cash (included in prepaids and other current assets) Investment, risk and reinsurance. Investment Risk And Reinsurance [Member] IRR [Member] OCI, before Reclassifications, Net of Tax, Attributable to Parent Other comprehensive income/(loss) before reclassifications Proceeds from Debt, Net of Issuance Costs Proceeds from debt, net of issuance costs Lessee, Leases [Policy Text Block] Leases Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Options exercisable at end of period, Weighted Average Exercise Price (in dollars per share) Repayments of Lines of Credit Repayment of line of credit Net payments on revolving credit facility Accounting Standards Update [Axis] Accounting Standards Update Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Schedule of weighted average term and discount rates for operating and finance lease. Schedule Of Weighted Average Term And Discount Rates For Operating And Finance Lease Table [Text Block] Schedule of Weighted Average Term and Discount Rates Unrecognized Tax Benefits, Other Increase (Decrease). Unrecognized Tax Benefits Other Increase Decrease Cumulative translation adjustment and other adjustments Capitalized Contract Cost, Impairment Loss Capitalized Contract Cost, Impairment Loss Capitalized Contract Cost, Impairment Loss Quarterly Financial Data [Abstract] Debt Instrument [Axis] Debt Instrument Treasury Stock [Member] Treasury shares [Member] Non-cash foreign exchange gain Foreign Currency Transaction Gain (Loss), before Tax Foreign Currency Transaction Gain (Loss), before Tax, Total Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Income from continuing operations INCOME FROM CONTINUING OPERATIONS Counterparty Name [Axis] Counterparty Name Entity Address, Address Line Two Entity Address, Address Line Two Other Intangible Assets [Member] Other [Member] Segments [Axis] Segments Computer Software, Intangible Asset [Member] Software [Member] Current Foreign Tax Expense (Benefit) U.K. corporation tax Noncontrolling Interest [Table] Minority Interest [Table] Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Actual return on plan assets Foreign Currency Transactions and Translations Policy [Policy Text Block] Foreign Currency Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Forfeited, Weighted Average Grant Date Fair Value (in dollars per share) Restrictions on Cash and Cash Equivalents [Table] Amortization of Intangible Assets Amortization Amortization Amortization of Intangible Assets, Total Other Deferred Compensation Arrangements, Liability, Current Accrued vacation Award Type [Axis] Award Type Lease liability non current. Lease Liability Noncurrent Total Long-term lease liabilities Cash Flow, Financing Activities, Lessee [Abstract] Cash flows used in financing activities: Amortization Cost, Amortization Other Noncash Income (Expense) Other, net Other Noncash Income (Expense), Total Senior notes due 2022, 02125. Senior Notes Due202202125 [Member] 2.125% senior notes due 2022 [Member] Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Compensation cost not yet recognized Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total Employee status. Employee Status [Axis] Employee Status Basis of Presentation and Significant Accounting Policies [Text Block] Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements Capital Expenditures [Member] Capital Expenditures. Deferred Tax Assets, Gross Gross deferred tax assets Loss Contingencies [Table] Loss Contingencies [Table] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value Options, exercises in period, intrinsic value Other Nonoperating Income (Expense) Other income, net Income from operations Other income, net Towers Watson Co. Towers Watson Co [Member] Towers Watson & Co. [Member] Towers Watson & Co. [Member] Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount Non-deductible expenses and dividends Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount, Total Long-Term Debt, Current Maturities Current debt Long-term Debt, Current Maturities, Total Discontinued Operations and Disposal Groups [Abstract] 2024 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Finite-Lived Intangible Assets, Foreign Currency Translation Gain (Loss) Foreign exchange Contingent consideration fair value Other Significant Noncash Transaction, Value of Consideration Given Federal Funds Effective Rate [Member] Federal Funds Effective Rate [Member] Federal Funds Effective Rate. Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Defined pension and post-retirement benefits [Member] Acquisition Costs Adjustment. Acquisition Costs Adjustment [Member] Lessee, Operating Lease, Liability, to be Paid Operating Lease, Total future lease payments Operating leases Restructuring Type [Axis] Restructuring Type Defined Benefit Plan, Plan Assets, Contributions by Plan Participant Employee contributions Payments of deferred and contingent consideration related to acquisitions Payment for Contingent Consideration Liability, Financing Activities Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Decreases related to tax positions in prior years Lessee, Operating Lease, Term of Contract Real estate lease term Land and Building [Member] Land and Building [Member] Cash and Cash Equivalents [Member] Cash [Member] IRELAND Ireland [Member] Benefit from/(provision for) income tax expense Discontinued Operation, Tax Effect of Discontinued Operation, Total Discontinued Operation, Tax Effect of Discontinued Operation Provision for income tax expense Deferred tax expense with discontinued operations Defined benefit plan expected future benefit payments. Defined Benefit Plan Expected Future Benefit Payments Expected future benefit payments, total Entity Central Index Key Entity Central Index Key Other Income and Expenses [Abstract] Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Increase (decrease) in valuation allowance Payments for Restructuring Cash payments Cash payments Schedule of net plan investments reconciliation to total fair value of plan assets. Schedule Of Net Plan Investments Reconciliation To Total Fair Value Of Plan Assets Table [Text Block] Schedule of Net Plan Investments Reconciliation To Total Fair Value Of Plan Assets Finite-Lived Intangible Assets [Line Items] Finite Lived Intangible Assets [Line Items] Short-term Investments, Total Short-Term Investments Short-term investments Accounting Policies [Abstract] Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest Less: income attributable to non-controlling interests Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward] Movement in Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment [Roll Forward] Stockholders' Equity, Other Other Amount of lessee's right to use underlying asset under both operating lease and finance lease. Lease Right Of Use Asset Total Right-of-use assets Disaggregation of Revenue [Line Items] Disaggregation Of Revenue [Line Items] Finance Lease, Right-of-Use Asset, after Accumulated Amortization Finance Lease, Right-of-use assets Net book value Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Depreciation: at end of period Depreciation: at beginning of period Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Property, Plant and Equipment [Table] Schedule Of Property Plant And Equipment [Table] Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected volatility Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Net periodic pension and postretirement benefit credits Hedging Designation [Domain] Hedging Designation Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax Total recognized in other comprehensive loss/(income) Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date Finance Lease, Weighted Average Discount Rate, Percent Finance Leases, Weighted-average discount rate Long-Lived Assets Long-Lived Assets Measurement Frequency [Axis] Measurement Frequency Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration Operating loss carryforwards, subject to expiration Consolidation Items [Domain] Consolidation Items Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Number of shares available for grant Other current liabilities excluded from held for sale. Other current liabilities excluded from held for sale Share-based Compensation Share-Based Payment Arrangement [Text Block] Plan (disposal)/addition Defined Benefit Plan Plan Assets And Addition Disposal Defined benefit plan plan assets and addition disposal. Collateralized facility. Collateralized Facility [Member] Collateralized Facility [Member] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Options vested or expected to vest at end of period, Aggregate Intrinsic Value Projected annual cost savings by end of 2024. Projected Annual Cost Savings by End of 2024 [Member] Debt instrument commitment fee percentage. Debt Instrument Commitment Fee Percentage Debt Instrument Commitment Fee Percentage Deferred Compensation Plan Assets Deferred compensation plan assets Measurement Input Type [Domain] Measurement Input Type Organization, Consolidation and Presentation of Financial Statements [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Balance as of end of period, Weighted Average Exercise Price (in dollars per share) Balance as of beginning of period, Weighted Average Exercise Price (in dollars per share) Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Business combination, contingent consideration arrangements, range of outcomes, value, high Finance Lease, Principal Payments Finance leases Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position Components on the Consolidated Balance Sheet Fair Value, Nonrecurring [Member] Nonrecurring [Member] Disposal group including discontinued operation other operating expense. Disposal Group Including Discontinued Operation Other Operating Expense Other operating expenses Prepaid Expenses and Other Current Assets [Member] Prepaid Expenses and Other Current Assets [Member] Other comprehensive (loss)/income, before tax Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest, Total Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest Other comprehensive income/(loss), before tax Defined benefit plan required employee contribution rate. Defined Benefit Plan Required Employee Contribution Rate Defined benefit plan required employee contribution rate Capitalized Contract Cost, Additions Capitalized Contract Cost Additions Capitalized Contract Cost, Additions Lease, Cost Total lease cost, net Lease cost Transaction and transformation, net Business combination integration related costs credits. Business Combination Integration Related Costs Credits Transaction and integration expense Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Non-cash additions to operating lease ROU assets Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other Accrued expenses not currently deductible Other comprehensive income (loss) curtailment gain of pension and non pension postretirement plan valuation before tax. Other Comprehensive Income (Loss) Curtailment Gain Of Pension And Non Pension Postretirement Plan Valuation Before Tax Curtailment gain Curtailment gain Other Accrued Liabilities, Noncurrent Other provisions Fees earned under service agreement. Fees earned under service agreement Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to total net cash from operating activities: Defined Benefit Plan, Plan Assets, Payment for Settlement Settlements Defined contribution plan tranches. Defined Contribution Plan Tranches [Axis] Defined Contribution Plan Tranches Retained Earnings [Member] Retained earnings [Member] Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax Reclassifications of defined pension and post-retirement benefits costs Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax, Total Federal Action. Federal Action [Member] Federal Action [Member] Billed Contracts Receivable Billed Receivable, Current Income (Loss) from Equity Method Investments Interest in earnings of associates and other investments Income (Loss) from Equity Method Investments, Total Dividends attributable to redeemable non-controlling interest. Dividends Attributable To Redeemable Non Controlling Interest Dividends attributable to non-controlling interests, redeemable Designated as Hedging Instrument [Member] Designated as Hedging Instrument [Member] Designated [Member] Segment Reporting [Abstract] Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) Foreign currency adjustment Foreign exchange Foreign currency adjustment Measurement Input Type [Axis] Measurement Input Type Schedule of Goodwill [Table] Schedule Of Goodwill [Table] Notes Payable, Other Payables [Member] Other [Member] Total consideration received from sale of subsidiary Total upfront cash consideration received from sale of subsidiary Final total consideration received from sale of subsidiary Property, Plant and Equipment, Gross Cost: at end of period Cost: at beginning of period Property, Plant and Equipment, Gross, Total Percentage of voting rights. Percentage Of Voting Rights Percentage of entity voting rights Goodwill, Acquired During Period Goodwill acquired Financing Receivable, Current, Allowance for Credit Loss [Table Text Block] Schedule of Changes in Allowance for Doubtful Accounts Long-Term Debt, Maturity, after Year Five Thereafter One year term loan facility due 2016. One Year Term Loan Facility Due2016 [Member] 1-year Term Loan Facility Matures 2016 [Member] Carrying value as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to employees and directors or earned by them based on the terms of one or more relevant arrangements. Accrued Discretionary And Incentive Compensation Accrued discretionary and incentive compensation Finite-Lived Intangible Assets Acquired Intangible assets acquired Entity Interactive Data Current Entity Interactive Data Current Entity Public Float Entity Public Float Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Options vested or expected to vest at end of period, Outstanding (in shares) Tax exemption on gain on disposal of discontinued operations. Tax Exemption on Gain on Disposal of Discontinued Operations [Member] Tax Exemption on Gain on Disposal of Willis Re [Member] Estimated Litigation Liability, Noncurrent Claims, lawsuits and other proceedings Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental disclosures of non-cash investing and financing activities: Increase decrease in provision for liabilities. Increase Decrease In Provision For Liabilities Provisions Cash payments made on stock awards Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Share-Based Liabilities Paid Operating Activities [Domain] Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets Expected long-term rate of return on assets Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, interest cost on service cost. Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Interest Cost On Service Cost Discount rate - interest cost on service cost Operating Lease, 2023 Lessee, Operating Lease, Liability, to be Paid, Year One Deferred Compensation Liability, Current Deferred compensation plan liabilities Deferred Compensation Liability, Current, Total Defined Benefit Plan, Assumptions [Table Text Block] Schedule of Assumptions Used Proceeds from (Payments to) Noncontrolling Interests Acquisitions of and dividends paid to non-controlling interests Proceeds from (Payments to) Noncontrolling Interests, Total Accounts Receivable, Credit Loss Expense (Reversal) Provision for doubtful receivables from clients Leasehold Improvements [Member] Leasehold Improvements [Member] Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Deferred tax (expense)/benefit: Lease liability current. Lease Liability Current Total Current lease liabilities (Benefit from)/provision for deferred income taxes Deferred Income Tax Expense Benefit Including Discontinued Operations Deferred income tax expense benefit including discontinued operations. Total Lease, 2026 Amount of lessee's undiscounted obligation for lease payments for finance lease, due in fourth fiscal year following latest fiscal year. Lease Liability Payments Due Year Four Local Phone Number Local Phone Number Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent U.S. statutory tax rate U.S. federal statutory income tax rate Provision for liabilities non current. Provision For Liabilities Non Current Provision for liabilities Total provision for liabilities Unrecognized Tax Benefits Balance at end of year Balance at beginning of year Unrecognized tax benefits Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Basic and Diluted Earnings Per Share Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Disposal Group, Including Discontinued Operations, Beginning Balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Disposal Group, Including Discontinued Operations, Ending Balance Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Disposal Group, Including Discontinued Operations Cash and cash equivalents and fiduciary funds (included in current assets held for sale) Capitalized Contract Cost [Abstract] Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Share-based compensation, expected term Term Loan Due December 2019 [Member] Term Loan Due December2019 [Member] Term Loan Due 2019 [Member] AOCI Attributable to Noncontrolling Interest [Member] AOCI Attributable to Noncontrolling Interest [Member] Defined Benefit Plan, Benefit Obligation Benefit obligation, end of year Benefit obligation, beginning of year Debt Disclosure [Abstract] Share-Based Payment Arrangement, Exercise of Option, Tax Benefit Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options Net Income (Loss) Attributable to Noncontrolling Interest Income attributable to non-controlling interests Net Income (Loss) Attributable to Noncontrolling Interest, Total Quarterly Financial Information [Table Text Block] Summary of Retrospectively-adjusted Quarterly Financial Data Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Net tax effect on disposal of operations Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Options exercisable at end of period, Outstanding (in shares) RSU vested in prior year Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Prior Period Share based compensation arrangement by share based payment award equity instruments other than options vested in prior period. Gain on disposal of operations Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain Disaggregation of Revenue [Table Text Block] Disaggregation of Revenue Other Liabilities, Noncurrent Other non-current liabilities Total other non-current liabilities 2027 Defined Benefit Plan, Expected Future Benefit Payment, Year Five Components of Deferred Tax Liabilities [Abstract] Deferred tax liabilities: Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of Change in Fair Value of Level 3 Liabilities Summary of Valuation Allowance [Table Text Block] Summary of Valuation Allowance Derivative Liability, Statement of Financial Position [Extensible Enumeration] Income Statement Location [Domain] Income Statement Location Depreciation expense excluding abandonment of an internally-developed software asset. Depreciation Expense Excluding Abandonment Of Internally Developed Software Asset Depreciation expense 2023 Long-Term Debt, Maturity, Year One Other Comprehensive Income Location [Domain] Other Comprehensive Income Location Settled Litigation [Member] Settled Litigation [Member] Property, Plant and Equipment [Abstract] Fiduciary. Fiduciary [Member] Fiduciary [Member] Deferred revenue and accrued liabilities current. Deferred Revenue And Accrued Liabilities Current Deferred revenue and accrued expenses Total deferred revenue and accrued expenses Assets, Noncurrent Total non-current assets Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Balance (shares) Balance (shares) Restricted share units outstanding Pension and Other Postretirement Benefits Expense (Reversal of Expense), Noncash Net periodic benefit of defined benefit pension plans Pension and Other Postretirement Benefits Expense (Reversal of Expense), Noncash, Total Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Decreases related to settlements Long-Term Debt Total Borrowings Shares, Outstanding Equity, ending balance (in shares) Equity, beginning balance (in shares) Other Cost and Expense, Operating Other operating expenses Other Cost and Expense, Operating, Total Defined Benefit plan, fair value of plan assets, liabilities. Defined Benefit Plan Fair Value Of Plan Assets Liabilities Fair value of plan liabilities Liability, Defined Benefit Plan, Noncurrent Liability for pension benefits Non-current liability for pension benefits Liability, Defined Benefit Plan, Noncurrent, Total Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Quarterly Financial Information [Text Block] Quarterly Financial Data (Unaudited) Revolving 800 million dollar credit facility. Revolving800 Million Dollar Credit Facility [Member] Revolving $800 million Credit Facility [Member] Other comprehensive (loss)/income before tax Other Comprehensive Income (Loss), before Tax Other Comprehensive Income (Loss), before Tax, Total Disposal group including discontinued operation salaries and benefits. Disposal Group Including Discontinued Operation Salaries And Benefits Salaries and benefits Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Balance as of end of period, Outstanding (in shares) Balance as of beginning of period, Outstanding (in shares) Stock options outstanding Debt Instrument, Name [Domain] Debt Instrument, Name Document Fiscal Year Focus Document Fiscal Year Focus Intangible Assets, Net (Excluding Goodwill) Other intangible assets, net Intangible Assets, Net (Excluding Goodwill), Total Nature of Uncertainty [Axis] Nature of Uncertainty Repayments of Debt Repayment of debt Extinguishment of Debt, Amount Prepayment of outstanding debt Payments of Debt Issuance Costs Debt issuance costs Balance sheet date. Balance Sheet Date [Axis] Balance Sheet Date Other comprehensive income (loss), net of tax including portion attributable to nonredeemable noncontrolling interest. Other Comprehensive Income Loss Net Of Tax Including Portion Attributable To Nonredeemable Noncontrolling Interest Other comprehensive (loss)/income Property plant and equipment acquisitions. Property Plant And Equipment Acquisitions Acquisitions Operating Lease, 2024 Lessee, Operating Lease, Liability, to be Paid, Year Two Interest and Other Income Interest and other income Interest and Other Income, Total Earnings Per Share, Basic — Basic: income from continuing operations Basic earnings per share Senior notes due 2019, 0700. Senior Notes Due20190700 [Member] 7.000% senior notes due 2019 [Member] Income from continuing operations per share Income (Loss) from Continuing Operations, Per Outstanding Share, Total Basic earnings per share from continuing operations attributable to WTW -- Basic: income from continuing operations Common Stock, Dividends, Per Share, Declared Dividends declared per share Defined benefit plan employees covered percentage. Defined Benefit Plan Employees Covered Percentage Defined benefit plan employees covered percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Tax Credit Carryforward [Table] Tax Credit Carryforward [Table] Goodwill, Gross Goodwill, gross, ending balance Goodwill, gross, beginning balance Assets [Abstract] ASSETS Deferred Compensation Liability, Classified, Noncurrent Deferred compensation plan liability Deferred Compensation Liability, Classified, Noncurrent, Total Income Tax Contingency [Table] Income Tax Contingency [Table] Phantom restricted stock units. Phantom Restricted Stock Units [Member] Phantom RSUs [Member] Other Restricted Assets, Current Fiduciary funds (included in fiduciary assets) Prepaid Expense and Other Assets, Current Prepaid and other current assets Total prepaid and other current assets Foreign Countries [Member] Total Foreign Countries [Member] Treasury shares, at cost, 17,519 in 2022 and 2021 Treasury Stock, Value Treasury Stock, Value, Total Treasury Stock, Value, Beginning Balance Treasury Stock, Value, Ending Balance Tax year 2022 through 2041. Tax Year 2022 Through 2041 [Member] Debt Instrument, Face Amount Debt instrument, face amount Liabilities of disposal group including discontinued operation current provision for liabilities. Liabilities Of Disposal Group Including Discontinued Operation Current Provision For Liabilities Provision for liabilities Disposal Group, Including Discontinued Operation, Other Assets, Current Other assets Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset Depreciation and amortization Disposal Group, Including Discontinued Operation, Depreciation and Amortization Schedule of Restructuring and Related Costs [Table] Concentration Risk Benchmark [Axis] Transaction integration expense. Transaction Integration Expense [Member] Transaction and Integration Expense [Member] Revolving 15 Billion Dollar Credit Facility. Revolving15 Billion Dollar Credit Facility [Member] Revolving 1.5 Billion Dollar Credit Facility [Member] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Liabilities and Equity [Abstract] LIABILITIES AND EQUITY Summary of Income Tax Examinations [Table Text Block] Summary of Income Tax Examinations Interest on senior notes. Interest On Senior Notes [Member] Interest on Senior Notes [Member] Senior Notes [Member] Mutual Fund [Member] Mutual funds [Member] Accrued Employee Benefits, Current Accrued retirement benefits Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Deferred Rent Operating lease liabilities Income Taxes Paid, Net Cash payments for income taxes, net Income Taxes Paid, Net, Total Debt instrument interest accrual date description. Debt Instrument Interest Accrual Date Description Description of interest accrual date Technology modernization. Technology modernization [Member] Technology Modernization [Member] Senior Notes Due 2021 and 2026 [Member] Senior Notes Due2021and2026 [Member] Senior Notes Due 2021 and 2026 [Member] Property, Plant and Equipment, Policy [Policy Text Block] Fixed Assets Retirement Plan Tax Status [Domain] Retirement Plan Tax Status Antidilutive Securities, Name [Domain] Antidilutive Securities, Name Income Tax Authority [Axis] Income Tax Authority Type of Restructuring [Domain] Type of Restructuring Deferred Tax Assets, Net of Valuation Allowance Deferred Tax Assets, Net of Valuation Allowance Net deferred tax assets Other non-current assets NET INCOME NET INCOME Net income, total Net income Dividends, Common Stock Dividends declared Dividends, Common Stock, Total 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Four Total Lease, 2027 Amount of lessee's undiscounted obligation for lease payments for operating lease and finance lease, due in fifth fiscal year following latest fiscal year. Lease Liability Payments Due Year Five Term loan facility. Term Loan Facility [Member] Term Loan Facility [Member] 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Two Segment Reporting Disclosure [Text Block] Segment Information Tax exempt income on gain loss on sale of business. Tax Exempt Income On Gain Loss On Sale Of Business Tax exempt income on preliminary pre-tax gain on sale December 31,2021. December 31 2021 [Member] December312020 [Member] Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Schedule of Amounts Recognized in Other Comprehensive Income (Loss) Tranzact collateralized facility. Tranzact Collateralized Facility [Member] Tranzact Collateralized Facility [Member] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Significant components of deferred income tax assets and liabilities and their balance sheet classifications Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax Prior service cost/(credit) Schedule of Goodwill [Table Text Block] Components of Goodwill Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV Supplemental Cash Flow Elements [Abstract] Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Increases related to tax positions in prior years Measurement Frequency [Domain] Measurement Frequency Restructuring and Related Activities, Description Restructuring, description Capitalized Contract Cost, Net, Noncurrent Deferred contract costs Defined contribution plan employers matching contribution employee vesting period. Defined Contribution Plan Employers Matching Contribution Employee Vesting Period Vesting period Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities, net of effects from purchase of subsidiaries: International. International [Member] International [Member] Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Health care cost trend - Initial rate Accrued Sales Commission, Current Third-party commissions Lease, Cost [Abstract] Finance lease cost: SEC Schedule, 12-09, Allowance, Credit Loss [Member] Allowance for doubtful accounts [Member] Entity Entity [Domain] Open tax years. Open Tax Years Open Tax Years Restructuring and Related Activities Disclosure [Text Block] Restructuring Costs Property, Plant and Equipment, Disposals Disposals Schedule​ of finite​ lived ​intangible​ assets​ amortization basis and expected life. Schedule Of Finite Lived Intangible Assets Amortization Basis And Expected Life Table [Text Block] Schedule of Acquired Intangible Assets Amortized Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest INCOME FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total Transformation program. Transformation Program [Member] Transformation Program [Member] Defined Benefit Plan, Plan Assets, Contributions by Employer Employer contributions Qualified Plan [Member] Qualified Plan [Member] Cover [Abstract] Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location Accumulated Depreciation, Depletion and Amortization, Sale or Disposal of Property, Plant and Equipment Disposals Concentration risk percentage Concentration Risk, Percentage Product and Service [Domain] Product and Service Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase for Purchase Purchases Other Restructuring [Member] Other [Member] Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life Expected life Compensation and retirement disclosure. Compensation And Retirement Disclosure [Line Items] Compensation and Retirement Disclosure [Line Items] Measurement Basis [Axis] Measurement Basis The entire disclosure for operating lease and finance lease by the lessee. Lessee Operating And Finance Lease Disclosure [Text Block] Leases Net (payments)/proceeds from sale of operations Payments for (Proceeds from) Sale of Operations Payments for (Proceeds from) Sale of Operations Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Current other jurisdictions tax expense benefit. Current Other Jurisdictions Tax Expense Benefit Other jurisdictions Other jurisdictions, Tax expense Other jurisdictions, Tax expense Operating Lease, 2027 Lessee, Operating Lease, Liability, to be Paid, Year Five Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Vested (shares) Vested (shares) Undistributed Earnings, Basic, Total Undistributed Earnings, Basic Undistributed earnings Foreign exchange gain Foreign Currency Transaction Gain (Loss), Realized Senior notes due 2048, 0505. Senior Notes Due20480505 [Member] 5.050% senior notes due 2048 [Member] Foreign Plan [Member] UNITED KINGDOM [Member] Secured Long-Term Debt, Noncurrent Assumed debt related to borrowings Reinvested indefinitely. Reinvested Indefinitely [Member] Reinvested Indefinitely [Member] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite Lived Intangible Assets [Line Items] Accounts Receivable, after Allowance for Credit Loss, Noncurrent Accounts receivable, net Non-current accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Noncurrent, Total Plan (disposal)/addition Defined Benefit Plan Benefit Obligation And Addition Disposal Defined benefit plan benefit obligation and addition disposal. Defined Benefit Plan, Other Cost (Credit) Other Other Disposal Group Name [Domain] Disposal Group Name Maximum [Member] Maximum [Member] Maximum [Member] Defined Contribution Plan, Employer Matching Contribution, Percent of Match Employer matching contribution, percent of match Ordinary share one. Ordinary Share One [Member] Ordinary shares, $0.000304635 nominal value [Member] Base Erosion Anti Abuse Tax. Base Erosion Anti Abuse Tax [Member] BEAT [Member] Number of Countries in which Entity Operates Number of countries in which entity operates (more than 140) Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent Non-current liabilities held for sale Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent, Total Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Foreign currency translation [Member] Net cash (used in)/from investing activities Net Cash Provided by (Used in) Investing Activities Salaries and benefits. Salaries And Benefits [Member] Salaries and Benefits [Member] Furniture and Fixtures [Member] Furniture, equipment and software [Member] Unrecognized Tax Benefits, Interest on Income Taxes Expense Tax expense includes in interest expense Restructuring Charges [Member] Restructuring Charges [Member] Restructuring Costs [Member] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Exercised, Outstanding (in shares) Exercised, Outstanding (in shares) Goodwill and Intangible Assets Disclosure [Text Block] Goodwill and Other Intangible Assets Fair Value, Inputs, Level 3 [Member] Level 3 [Member] Financing Receivable, before Allowance for Credit Loss, Noncurrent Notes receivable repayable by purchaser Long-term note receivable Other Investments Other investments Other Investments, Total Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Defined pension and post-retirement benefit costs [Member] Use of Estimates, Policy [Policy Text Block] Use of Estimates Defined benefit plan, assumptions used calculating net periodic benefit cost, discount rate, projected benefit obligation. Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Projected Benefit Obligation Discount rate - PBO Debt Instrument, Basis Spread on Variable Rate Interest rate spread Dividends Payable, Current Dividends payable Deferred Tax Liabilities, Gross Deferred tax liabilities Deferred tax liabilities Capitalized contract cost disposals. Capitalized Contract Cost Disposals Capitalized Contract Cost, Disposals Capitalized Contract Cost, Disposals Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits Accrued retirement benefits Cash Unencumbered and available cash balance required Cash, Beginning Balance Cash, Ending Balance Provisions for liabilities. Provisions For Liabilities Table [Text Block] Provisions for Liabilities Other comprehensive (loss)/income, net of tax, before non-controlling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest, Total Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Other comprehensive income/(loss), net of tax, before non-controlling interests Willis limited. Willis Limited [Member] Willis Limited [Member] Income from continuing operations before income taxes and interest in earnings of associates. Income From Continuing Operations Before Income Taxes And Interest In Earnings Of Associates [Table] Income From Continuing Operations Before Income Taxes And Interest In Earnings Of Associates [Table] Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration] 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Five Fiduciary assets excluded from held-for-sale. Fiduciary Assets Excluded From Held For Sale Fiduciary assets excluded from held-for-sale Defined contribution plan tranche one. Defined Contribution Plan Tranche One [Member] Defined Contribution Plan Tranche One [Member] Long-term Investments, Total Long-Term Investments Long-term investments Segment Reconciling Items [Member] Segment Reconciling Items [Member] Property, Plant and Equipment, Useful Life Useful life Defined Contribution Plan, Cost Defined contribution plan expenses Foreign Tax Authority [Member] Foreign Tax Authority [Member] Impaired Assets to be Disposed of by Method Other than Sale, Carrying Value of Asset Cost Schedule of lease. Schedule Of Lease Table [Text Block] Schedule of Lease Alternative Investment, Measurement Input Fair value inputs, weighted-average discount rate Foreign exchange remeasurement on income tax account balances Foreign Exchange Remeasurement on Income Tax Account Balances [Member] Foreign exchange remeasurement on income tax account balances. 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Three Common Stock, Shares Authorized Ordinary shares, shares authorized Short-Term Debt, Type [Domain] Short-term Debt, Type Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Health care cost trend - Ultimate rate Prepaid expense and accrue revenue receivable current. Prepaid Expense And Accrued Revenue Receivable Current Prepayments and accrued income Other Expense [Member] Other income, net [Member] Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Settlement Trading Symbol Trading Symbol Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block] Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets Costs Recognized in Net Periodic Benefit Cost and Other Comprehensive Income Costs Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Total recognized in net periodic benefit (income)/cost and other comprehensive loss/(income) Ownership [Axis] Ownership Equity Securities [Member] Equity securities [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] Maximum expected service period. Maximum expected service period Parent [Member] Total WTW shareholders' equity [Member] Other Sundry Liabilities, Current Other current liabilities Schedule of Other Assets, Noncurrent [Table Text Block] Schedule of Other Non-current Assets Liabilities of disposal group including discontinued operation current lease liabilities. Liabilities Of Disposal Group Including Discontinued Operation Current Lease Liabilities Lease liabilities Non-cash lease expense Operating Lease, Right-of-Use Asset, Amortization Expense Performance Shares [Member] Performance-Based Stock Units [Member] Performance-based [Member] Debt Instrument, Interest Rate Terms Debt Instrument, Interest Rate Terms R&B [Member] Risk and Broking [Member] Risk and Broking. Balance Sheet Location [Axis] Balance Sheet Location Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Net actuarial loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income attributable to WTW Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Risk-free interest rate Miller. Miller [Member] Miller [Member] Liabilities of disposal group including discontinued operation current liability for pension benefits. Liabilities Of Disposal Group Including Discontinued Operation Current Liability For Pension Benefits Liability for pension benefits Unremitted earnings Deferred Tax Liabilities, Undistributed Foreign Earnings Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Other Operating Assets, Total Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Payments Domestic Plan [Member] UNITED STATES [Member] Plan Name [Axis] Plan Name EURO-denominated. E U R O Denominated [Member] EURO-Denominated [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Cash Flow Hedging [Member] Cash Flow Hedging [Member] Other Employee-related Liabilities, Current Other employee-related liabilities Internal Revenue Service (IRS) [Member] Internal Revenue Service (IRS) [Member] Concentration Risk Type [Domain] Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Income tax expense at U.S. federal tax rate Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Dividends attributable to non-controlling interests Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share Basic earnings per share from discontinued operations, net of tax Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share, Total Debt Instrument, Term Debt instrument, term Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block] Schedule of Changes in Projected Benefit Obligations Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty [Domain] Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty Disposal Group, Including Discontinued Operation, Assets, Current Current assets held for sale Total assets held for sale Common Stock, Par or Stated Value Per Share Ordinary shares, nominal value Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Federal and foreign tax authority. Federal And Foreign Tax Authority [Member] U.S. Federal and Non-U.S. [Member] Variable Lease, Cost Variable lease cost Tax on unremitted earnings Tax On Unremitted Earnings Net Of Foreign Tax Credits Tax on unremitted earnings net of foreign tax credits. Employee-related Liabilities Liability recognized Employee-related Liabilities, Total Investment in multiple employer pension plan. Investment in multiple employer pension plan [Member] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Granted (shares) Granted units Restricted Cash and Cash Equivalents [Axis] Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Derivative Instrument [Axis] Derivative Instrument Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets Fair value of plan assets at end of year Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Property, Plant and Equipment Disclosure [Text Block] Fixed Assets Estimate of Fair Value Measurement [Member] Fair Value [Member] SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] Valuation Allowance of Deferred Tax Assets [Member] Unusual Risk or Uncertainty, Nature [Domain] Unusual Risk or Uncertainty, Nature HWC [Member] Health, Wealth and Career [Member] Health, Wealth and Career Term loan. Term Loan [Member] Term Loan [Member] UNITED KINGDOM United Kingdom [Member] UNITED KINGDOM [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-Term Debt, Type [Domain] Long-term Debt, Type Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive securities excluded from computation of earnings per share Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] Interest Income and Interest Expense Disclosure [Table Text Block] Schedule of Debt Interest Expense Tax Credit Carryforward [Line Items] Tax Credit Carryforward [Line Items] Defined Benefit Plan, Expected Return (Loss) on Plan Assets Expected return on plan assets Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Net Operating Income of the Reported Segments