Derivative Instruments- Ineffectiveness Related to Derivatives and Hedging Relationships Recorded in Income (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	$ (19.7)		$ 14.2
Fair value hedges of securities
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	(7.7)		10.4
Fair value hedges of deposits and long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	(12.0)		3.8
Cash flow hedges
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.