Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments (Detail) - Designated as Hedging Instrument - Cash Flow Hedging - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	$ 4.4	$ (5.6)	$ 3.3	$ 6.0
Forwards
Derivative Instruments, Gain (Loss)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	(0.2)	0.0	(0.2)	0.0
Foreign Exchange Contracts
Derivative Instruments, Gain (Loss)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	$ 4.6	$ (5.6)	$ 3.5	$ 6.0