Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and the Amounts Reclassified to Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Asset And Liability Management | Foreign Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain/(Loss) Recognized in AOCI	$ 7.9	$ (1.2)	$ (9.4)
Net Gain/(Loss) Reclassified from AOCI to Earnings
Net Gain/(Loss) Reclassified from AOCI to Earnings	(0.9)	(9.9)	2.8
Asset And Liability Management | Interest Rate Option Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain/(Loss) Recognized in AOCI	(3.4)		0.7
Net Gain/(Loss) Reclassified from AOCI to Earnings
Net Gain/(Loss) Reclassified from AOCI to Earnings	2.8	5.2	1.2
Net Gain/(Loss) Reclassified from AOCI to Earnings | Foreign Exchange Contracts
Net Gain/(Loss) Reclassified from AOCI to Earnings
Interest Income	6.4
Net Gain/(Loss) Reclassified from AOCI to Earnings | Asset And Liability Management | Foreign Exchange Contracts
Net Gain/(Loss) Reclassified from AOCI to Earnings
Other Operating Income	(6.4)	(8.0)	3.3
Other Operating Expense	(0.9)	(1.9)	(0.5)
Net Gain/(Loss) Reclassified from AOCI to Earnings | Asset And Liability Management | Interest Rate Option Contracts
Net Gain/(Loss) Reclassified from AOCI to Earnings
Interest Income	$ 2.8	$ 5.2	$ 1.2