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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	$ 124.2	$ 2.1	$ 147.8	$ 66.7
Euro Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	48.6	6.1	53.0	39.3
Cross-currency Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	$ 75.6	$ (4.0)	$ 94.8	$ 27.4