Gains and Losses Recorded in Consolidated Statement of Income Related to Fair Value Hedges (Detail) (Asset And Liability Management, FAIR VALUE HEDGES, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain/(Loss) Recognized in Income	$ 12.8	$ 22.8	$ 33.2	$ 25.5
Available for Sale Investment Securities | Interest Rate Swap Contracts | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain/(Loss) Recognized in Income	(14.9)	34.6	(27.0)	38.0
Senior Notes and Long- Term Subordinated Debt | Interest Rate Swap Contracts | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain/(Loss) Recognized in Income	$ 27.7	$ (11.8)	$ 60.2	$ (12.5)