Derivative Instruments- Ineffectiveness Related to Derivatives and Hedging Relationships Recorded in Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	$ (7.7)		$ 3.6		$ 4.3
Fair value hedges of securities
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	(4.9)		3.7		4.6
Fair value hedges of deposits and long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	(2.8)		(0.1)		(0.3)
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	0.1		0		0.1
Other
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	$ (0.1)	[1]	$ 0	[1]	$ (0.1)	[1]

[1] Includes ineffectiveness recorded on foreign exchange hedges.