v2.4.0.6
Document and Entity Information
6 Months Ended
Jun. 30, 2012
Aug. 03, 2012
Document and Entity Information [Abstract]    
Entity Registrant Name WILLIS GROUP HOLDINGS PLC  
Entity Central Index Key 0001140536  
Document Period End Date Jun. 30, 2012  
Amendment Flag false  
Document Fiscal Year Focus 2012  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
Document Type 10-Q  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   173,136,128