v2.4.0.6
Document and Entity Information (USD $)
6 Months Ended
Jun. 30, 2010
Feb. 22, 2010
Jul. 31, 2010
Euro Member
Jul. 31, 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 Jun. 30, 2010      
Amendment Flag false      
Document Fiscal Year Focus 2010      
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   $ 4,787,610,612    
Entity Common Stock, Shares Outstanding     40,000 170,276,062