Basis of Presentation and Significant Accounting Policies Offset between deferred tax assets and uncertain tax positions (Details) $ in Millions	Mar. 31, 2014 USD ($)
Offset between deferred tax assets and uncertain tax positions [Abstract]
Offset between deferred tax assets and uncertain tax positions	$ 21

Amount of an unrecognized tax benefit that is presented as a reduction of the related deferred tax asset in the balance sheet if that deferred tax asset is not used. This amount is presented separately from the deferred tax asset for a net operating loss carryforward if this unrelated tax benefit is associated with a different tax position

No definition available.

Name:	wsh_Offsetbetweendeferredtaxassetsanduncertaintaxpositions
Namespace Prefix:	wsh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant