Types and Classifications of Derivative Instruments Designated as Hedges (Detail) (Asset And Liability Management, USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Notional Value	$ 6,681.8	$ 5,759.6
Fair Value Asset	191.2	171.0
Fair Value Liability	93.8	76.0
FAIR VALUE HEDGES | Senior Notes and Long- Term Subordinated Debt | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	1,100.0	1,100.0
Fair Value Asset	140.7	147.0
Fair Value Liability	0.5	0.5
FAIR VALUE HEDGES | Available for Sale Investment Securities | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	3,234.3	2,172.0
Fair Value Asset	3.4	2.6
Fair Value Liability	65.9	46.8
CASH FLOW HEDGES | Forecasted Foreign Currency Denominated Transactions | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	937.9	932.9
Fair Value Asset	10.2	9.4
Fair Value Liability	24.7	27.2
NET INVESTMENT HEDGES | Net Investments in Non-U.S. Affiliates | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	1,409.6	1,554.7
Fair Value Asset	36.9	12.0
Fair Value Liability	$ 2.7	$ 1.5