Valuation Allowance Against Deferred Tax Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Allowances at beginning of year	$ 60.7	$ 71.0	$ 110.6
Benefits reserved current year	13.9	3.9	6.4
Benefits recognized current year	(1.1)	(10.5)	(36.9)
Translation difference	(5.6)	(3.7)	(9.1)
Allowances at end of year	$ 67.9	$ 60.7	$ 71.0