Segment Information (Details Textual)	12 Months Ended
Dec. 31, 2014
Segment information (Textual) [Abstract]
Commissions & fees and fixed assets from countries other than the UK and the US	10.00%

Commissions and Fees or Fixed Assets Exceed Ten Percent of the Company's Consolidated Commissions and Fees, Conduct Business, Percent

No definition available.

Name:	wsh_CommissionsAndFeesOrFixedAssetsExceedTenPercentOfCompanysConsolidatedCommissionsAndFeesConductBusinesPercent
Namespace Prefix:	wsh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration