Types and Classifications of Derivative Instruments Designated as Hedges (Detail) (Asset And Liability Management, USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Derivative [Line Items]
Notional Value	$ 4,922.2	$ 4,285.4
Fair Value Asset	158.1	166.9
Fair Value Liability	54.6	48.8
Fair Value Hedges | Interest Rate Swap Contracts | Available for Sale Investment Securities
Derivative [Line Items]
Notional Value	1,425.0	860.0
Fair Value Asset	3.5	4.8
Fair Value Liability	24.7	14.9
Fair Value Hedges | Interest Rate Swap Contracts | Senior Notes and Long- Term Subordinated Debt
Derivative [Line Items]
Notional Value	1,100.0	1,100.0
Fair Value Asset	127.9	129.8
Fair Value Liability	0.3	0.4
Foreign Exchange Contracts | Cash Flow Hedges | Forecasted Foreign Currency Denominated Transactions
Derivative [Line Items]
Notional Value	922.1	935.3
Fair Value Asset	25.9	19.3
Fair Value Liability	14.3	15.2
Foreign Exchange Contracts | Net Investment Hedges | Net Investments in Non-U.S. Affiliates
Derivative [Line Items]
Notional Value	1,475.1	1,390.1
Fair Value Asset	0.8	13.0
Fair Value Liability	$ 15.3	$ 18.3