Types and Classifications of Derivative Instruments Designated as Hedges (Detail) (Asset And Liability Management, USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Notional Value	$ 6,884.8	$ 6,545.8
Fair Value Asset	251.7	135.1
Fair Value Liability	48.7	136.5
FAIR VALUE HEDGES | Senior Notes and Long- Term Subordinated Debt | Interest Rate Swaps
Derivative [Line Items]
Notional Value	1,250.0	1,250.0
Fair Value Asset	112.8	83.6
Fair Value Liability	2.0	33.4
FAIR VALUE HEDGES | Available for Sale Investment Securities | Interest Rate Swaps
Derivative [Line Items]
Notional Value	2,859.5	3,296.9
Fair Value Asset	12.7	31.5
Fair Value Liability	28.5	44.8
CASH FLOW HEDGES | Forecasted Foreign Currency Denominated Transactions | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	344.9	314.0
Fair Value Asset	6.0	10.2
Fair Value Liability	14.8	5.5
CASH FLOW HEDGES | Available for Sale Investment Securities | Interest Rate Swaps
Derivative [Line Items]
Notional Value	10.0
CASH FLOW HEDGES | Available for Sale Investment Securities | Interest Rate Option Contracts
Derivative [Line Items]
Notional Value	625.0
Fair Value Asset	1.3
Net Investment Hedges | Net Investments in Non-U.S. Affiliates | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	1,795.4	1,684.9
Fair Value Asset	118.9	9.8
Fair Value Liability	$ 3.4	$ 52.8