Types and Classifications of Derivative Instruments Designated as Hedges (Detail) (Asset And Liability Management, USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Notional Value	$ 6,669.3	$ 6,545.8
Fair Value Asset	184.0	135.1
Fair Value Liability	40.2	136.5
FAIR VALUE HEDGES | Senior Notes and Long- Term Subordinated Debt | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	1,250.0	1,250.0
Fair Value Asset	92.4	83.6
Fair Value Liability	2.0	33.4
FAIR VALUE HEDGES | Available for Sale Investment Securities | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	2,939.7	3,296.9
Fair Value Asset	20.8	31.5
Fair Value Liability	24.9	44.8
CASH FLOW HEDGES | Forecasted Foreign Currency Denominated Transactions | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	341.0	314.0
Fair Value Asset	5.2	10.2
Fair Value Liability	9.5	5.5
CASH FLOW HEDGES | Available for Sale Investment Securities | Interest Rate Swap Contracts
Derivative [Line Items]
Notional Value	10.0
CASH FLOW HEDGES | Available for Sale Investment Securities | Interest Rate Option Contracts
Derivative [Line Items]
Notional Value	375.0
Fair Value Asset	0.1
Fair Value Liability	0.7
Net Investment Hedges | Net Investments in Non-U.S. Affiliates | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	1,753.6	1,684.9
Fair Value Asset	65.5	9.8
Fair Value Liability	$ 3.1	$ 52.8