v2.4.0.6
Document and Entity Information (USD $)
6 Months Ended
Jun. 30, 2011
Jul. 29, 2011
Feb. 18, 2011
Document and Entity Information [Abstract]      
Entity Registrant Name WILLIS GROUP HOLDINGS PLC    
Entity Central Index Key 0001140536    
Document Type 10-Q    
Document Period End Date Jun. 30, 2011    
Amendment Flag false    
Document Fiscal Year Focus 2011    
Document Fiscal Period Focus Q2    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 6,651,075,613
Entity Common Stock, Shares Outstanding   173,040,762