v2.4.0.6
Document and Entity Information (USD $)
12 Months Ended
Dec. 31, 2010
Feb. 18, 2011
Entity Registrant Name WILLIS GROUP HOLDINGS PLC  
Entity Central Index Key 0001140536  
Document Type 10-K  
Document Period End Date Dec. 31, 2010  
Amendment Flag false  
Document Fiscal Year Focus 2010  
Document Fiscal Period Focus FY  
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
Euro [Member]
   
Entity Common Stock, Shares Outstanding   40,000
United States of America, Dollars [Member]
   
Entity Common Stock, Shares Outstanding   171,257,649