Cumulative Amount of Unrecognized Hedge Losses Recorded in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	$ (9.8)	$ (0.3)
Net Investment Hedging [Member]
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	(12.1)	(1.2)
Net Investment Hedging [Member] | Foreign Exchange Forward [Member]
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	23.5	23.5
Net Investment Hedging [Member] | Long-Term Debt [Member]
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	(35.6)	(24.7)
Cash Flow Hedging [Member]
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	2.3	0.9
Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	(0.4)	(0.4)
Cash Flow Hedging [Member] | Cross-Currency Swap [Member]
Derivative [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI	$ 2.7	$ 1.3