Net Investment Hedge Gains and Losses Recognized in AOCI (Detail) (NET INVESTMENT HEDGES, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Derivative [Line Items]
Hedging Instrument Gain/(Loss) Recognized in AOCI (Before Tax)	$ (45.2)	$ (66.8)
Foreign Exchange Contracts
Derivative [Line Items]
Hedging Instrument Gain/(Loss) Recognized in AOCI (Before Tax)	(36.3)	(57.0)
Sterling Denominated Subordinated Debt
Derivative [Line Items]
Hedging Instrument Gain/(Loss) Recognized in AOCI (Before Tax)	$ (8.9)	$ (9.8)