Derivative Instruments and Hedging Activities - Net Investment Hedge Gains (Losses) Recognized on Condensed Consolidated Statements of Comprehensive Income (Loss) (Detail) - 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 [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	$ 56.9	$ (158.2)	$ 150.9	$ (131.0)
Euro Notes [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	40.5	(74.1)	96.9	(75.0)
Cross-currency Interest Rate Swaps [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of Gain / (Loss) Recognized in AOCI	$ 16.4	$ (84.1)	$ 54.0	$ (56.0)