Cash-Based Compensation Plans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Based Compensation Plan Expense [Line Items]
Cash based compensation expense	$ 186.8	$ 176.7	$ 168.4

Amount of commitment made to pay deferred cash remuneration.

No definition available.

Name:	us-gaap_DeferredCompensationArrangementWithIndividualCashAwardsGrantedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration