Net Investment Hedge Gains and Losses Recognized in AOCI (Detail) (NET INVESTMENT HEDGES, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative [Line Items]
Hedging Instrument Gain/(Loss) Recognized in AOCI (Before Tax)	$ (44.8)	$ 81.3	$ (17.4)	$ (4.1)
Foreign Exchange Contracts
Derivative [Line Items]
Hedging Instrument Gain/(Loss) Recognized in AOCI (Before Tax)	(35.4)	75.6	(8.1)	(1.9)
Sterling Denominated Subordinated Debt
Derivative [Line Items]
Hedging Instrument Gain/(Loss) Recognized in AOCI (Before Tax)	$ (9.4)	$ 5.7	$ (9.3)	$ (2.2)