Types of Risk Management Derivative Instruments Not Formally Designated as Hedges and Their Notional Amounts and Fair Values (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Fair Value Asset	$ 3,047.6	$ 1,864.5
Fair Value Liability	2,767.6	2,261.8
Nondesignated
Derivative [Line Items]
Notional Value	559.6	397.4
Fair Value Asset	0.8	0.2
Fair Value Liability	27.0	14.6
Nondesignated | Foreign Exchange Contracts
Derivative [Line Items]
Notional Value	289.6	244.6
Fair Value Asset	0.8	0.2
Fair Value Liability	1.8	3.7
Nondesignated | Other Financial Derivatives
Derivative [Line Items]
Notional Value	270.0	152.8
Fair Value Asset	0.0	0.0
Fair Value Liability	$ 25.2	$ 10.9