Income Taxes - Components of (Loss) Income Before Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components Of Income Tax Expense Benefit Continuing Operations [Abstract]
U.S.	$ (123.8)	$ (65.1)	$ (83.4)
Foreign	107.9	115.7	84.7
(Loss) income from continuing operations before income taxes	$ (15.9)	$ 50.6	$ 1.3