Income Taxes - Schedule of Transactions Affecting Valuation Allowance on Deferred Tax Assets (Detail) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation Allowance [Line Items]
Balance, beginning of year	$ 237.5	$ 255.9	$ 238.3
Current year expense-net	(44.8)	34.5	29.1
Write-offs		(50.1)	(0.2)
Foreign exchange and other	3.0	(2.8)	(11.3)
Balance, end of year	$ 195.7	$ 237.5	$ 255.9