v2.4.0.6
Document and Entity Information (USD $)
9 Months Ended
Sep. 30, 2010
Feb. 22, 2010
Oct. 29, 2010
Euro [Member]
Oct. 29, 2010
United States of America, Dollars [Member]
Entity Registrant Name WILLIS GROUP HOLDINGS PLC      
Entity Central Index Key 0001140536      
Document Type 10-Q      
Document Period End Date Sep. 30, 2010      
Amendment Flag false      
Document Fiscal Year Focus 2010      
Document Fiscal Period Focus Q3      
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   $ 4,787,610,612    
Entity Common Stock, Shares Outstanding     40,000 170,624,279