Income Taxes - Components of Comprehensive Provision for Income Taxes Allocation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule Of Income Tax [Line Items]
Expected tax expense, at U.S. federal statutory income tax rate of 21%	$ 14.9	$ 1.7	$ 30.3	$ 15.6
Incremental net tax benefit on earnings and losses of non-U.S., U.S. and non-tax group companies	(0.7)	(3.9)	(2.6)	(7.8)
Non-U.S. tax rates	1.3	(0.2)	3.1	0.8
Valuation allowance	(0.7)	(2.1)	0.8	4.9
Adjustment to the reserve for uncertain tax positions, net	0.3	(0.5)	0.1	0.7
Global intangible low-tax income, net	0.9	(6.8)	1.9	6.3
Nondeductible expenses	0.3	(0.5)	0.7	1.3
U.S. state income taxes and other, net	0.6	0.9	0.9	(0.6)
Income tax expense (benefit)	16.9	(11.4)	35.2	21.2
Comprehensive provision (benefit) for income taxes allocable to:
Net income	16.9	(11.4)	35.2	21.2
Other comprehensive income (loss):
Currency translation	(0.8)	1.2	(0.4)	(1.5)
Total	18.0	(8.4)	40.8	25.0
OPEB
Other comprehensive income (loss):
Defined benefit plans	(0.1)	(0.1)	(0.2)	(0.2)
Pension Plans
Other comprehensive income (loss):
Defined benefit plans	$ 2.0	$ 1.9	$ 6.2	$ 5.5