Cash-Based Compensation Plans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Based Compensation Plan Expense [Line Items]
Cash based compensation expense	$ 212.4	$ 192.4	$ 186.8

Amount of commitment made to pay deferred cash remuneration.

No definition available.

Name:	us-gaap_DeferredCompensationArrangementWithIndividualCashAwardGrantedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant