Income Taxes - Components of Income Taxes and Comprehensive Provision for Income Taxes Allocation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule Of Income Tax [Line Items]
Expected tax expense, at U.S. federal statutory income tax rate of 21%	$ 5.4	$ 7.4
Non-U.S. tax rates	0.7	0.9
Incremental net tax benefit on earnings and losses of U.S. and non-U.S. companies	(0.7)	(1.3)
Global intangible low-tax income, net	0.5	1.2
Valuation allowance, net	0.5	(0.5)
Adjustment to the reserve for uncertain tax positions, net	(0.5)	0.4
Other, net	0.1	0.3
Income tax expense	6.0	8.4
Comprehensive provision for income taxes allocable to:
Net income	6.0	8.4
Total	7.6	9.8
Defined Benefit Pension Plans
Comprehensive provision for income taxes allocable to:
Other comprehensive income - pension plans	$ 1.6	$ 1.4