Derivative Instruments and Hedging Activities - Net Investment Hedge Gains (Losses) Recognized on Condensed Consolidated Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	$ (31.0)	$ 91.1	$ 23.6	$ 64.7
Euro Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	(16.0)	62.3	4.4	33.3
Cross-currency Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	$ (15.0)	$ 28.8	$ 19.2	$ 31.4