Derivative Instruments- Ineffectiveness Related to Derivatives and Hedging Relationships Recorded in Income (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	$ 14.2		$ (9.0)
Fair Value Hedge of Securities
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	10.4		(1.7)
Fair Value Hedge of Deposits and Long-Term Debt
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	3.8		(7.3)
Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	(0.1)		0.1
Other
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	$ 0.1	[1]	$ (0.1)	[1]

[1] Includes ineffectiveness recorded on foreign exchange hedges.