Cumulative Amount of Unrecognized Hedge Losses Recorded in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	$ (0.3)	$ 36.5
Net Investment Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	(1.2)	34.8
Net Investment Hedging [Member] | Foreign Exchange Forwards [Member]
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	23.5	22.3
Net Investment Hedging [Member] | Long-Term Debt [Member]
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	(24.7)	12.5
Cash Flow Hedging [Member]
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	0.9	1.7
Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	(0.4)	(1.1)
Cash Flow Hedging [Member] | Cross-Currency Swap [Member]
Derivative Instruments Gain Loss [Line Items]
Cumulative amount of unrecognized hedge losses recorded in AOCI of net investment hedges, net of tax	$ 1.3	$ 2.8