Summary of Net Gain (Loss) on Foreign Exchange Forwards Not Designated as Hedging Instruments and on Interest Rate Swaps Designated as Fair Value Hedges (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivatives Designated as Accounting Hedges [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) recognized in income	$ (0.1)	$ 2.4
Derivatives Not Designated as Accounting Hedges [Member] | Foreign Exchange Forward [Member] | Other Nonoperating (Expense) Income [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) recognized in income	$ 27.6	$ (2.3)