v3.4.0.3
Document and Entity Information Document - shares
3 Months Ended
Mar. 31, 2016
Apr. 30, 2016
Document and Entity Information [Abstract]    
Entity Registrant Name Willis Towers Watson Plc.  
Entity Central Index Key 0001140536  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Mar. 31, 2016  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   138,440,802