Derivative Instruments And Hedging Activities - Gains (Losses) Recognized in AOCI and Reclassified from AOCI on Derivatives (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Gains and Losses on Derivatives Designated as Hedging Instruments [Abstract]
Other Comprehensive Income (Loss), Amount of Gain (Loss) on Derivatives Arising During Period Net of Tax	$ (29.2)	$ 27.4	$ (5.7)	$ 18.0
Amount of Gain/(Loss) Reclassified from AOCI into Income, net of Tax	(0.1)	0.1	(0.1)	0.2
Gain/(Loss) Recognized in Income on Derivative (Amount Excluded from Effectiveness Testing)	13.5	2.1	21.8	2.1
Net Investment Hedging [Member]
Gains and Losses on Derivatives Designated as Hedging Instruments [Abstract]
Other Comprehensive Income (Loss), Amount of Gain (Loss) on Derivatives Arising During Period Net of Tax	(29.2)	27.4	(5.7)	16.5
Gain/(Loss) Recognized in Income on Derivative (Amount Excluded from Effectiveness Testing)	13.5	2.1	21.8	2.1
Cash Flow Hedging [Member]
Gains and Losses on Derivatives Designated as Hedging Instruments [Abstract]
Other Comprehensive Income (Loss), Amount of Gain (Loss) on Derivatives Arising During Period Net of Tax				1.5
Amount of Gain/(Loss) Reclassified from AOCI into Income, net of Tax	(0.1)	0.1	(0.1)	0.2
Cross-Currency Swap [Member] | Net Investment Hedging [Member]
Gains and Losses on Derivatives Designated as Hedging Instruments [Abstract]
Other Comprehensive Income (Loss), Amount of Gain (Loss) on Derivatives Arising During Period Net of Tax	(19.7)	4.0	(4.5)	4.0
Gain/(Loss) Recognized in Income on Derivative (Amount Excluded from Effectiveness Testing)	13.5	2.1	21.8	2.1
Cross-Currency Swap [Member] | Cash Flow Hedging [Member]
Gains and Losses on Derivatives Designated as Hedging Instruments [Abstract]
Other Comprehensive Income (Loss), Amount of Gain (Loss) on Derivatives Arising During Period Net of Tax				1.5
Amount of Gain/(Loss) Reclassified from AOCI into Income, net of Tax	0.0	0.1	(0.1)	0.2
Long Term Debt [Member] | Net Investment Hedging [Member]
Gains and Losses on Derivatives Designated as Hedging Instruments [Abstract]
Other Comprehensive Income (Loss), Amount of Gain (Loss) on Derivatives Arising During Period Net of Tax	$ (9.5)	$ 23.4	$ (1.2)	$ 12.5