Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Parenthetical) (Detail) - Foreign Exchange Contracts [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Call Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	$ 354.7	$ 342.0
Put Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	354.7	342.0
Forward Contracts [Member] | Call Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	57.6	43.8
Forward Contracts [Member] | Put Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	$ 9.0	$ 12.1