Derivative Instruments - Ineffectiveness Related to Derivatives and Hedging Relationships Recorded in Income (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships		$ (13.6)	$ (0.2)	$ (2.3)
Fair value hedges of securities
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships		(7.4)	1.3	1.4
Fair value hedges of long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships		(6.2)	(1.5)	(3.7)
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships		0.0	0.0	0.0
Other
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness related to derivatives and hedging relationships	[1]	$ 0.0	$ 0.0	$ 0.0

[1] Includes ineffectiveness recorded on foreign exchange hedges.