Income Taxes - Components of Income Taxes and Comprehensive Provision for Income Taxes Allocation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule Of Income Tax [Line Items]
Expected tax expense, at U.S. federal statutory income tax rate of 35% in 2017 and 21% in 2018	$ 20.9	$ 16.7
Non-U.S. tax rates	7.1	(2.4)
Incremental net tax expense (benefit) on earnings and losses of U.S. and non-U.S. companies	0.4	1.2
Valuation allowance		(5.0)
Adjustment to reserve for uncertain tax positions, net	1.4
Nondeductible expenses	0.3
U.S. state income tax and other, net	0.3	0.5
Income tax expense	29.0	11.0
Comprehensive provision for income taxes allocable to:
Net income	29.0	11.0
Other comprehensive income (loss):
Marketable securities		(0.1)
Interest rate swap		0.3
Total	30.1	11.4
Canada - Germany APA
Schedule Of Income Tax [Line Items]
Canada-Germany APA	(1.4)
Defined Benefit Pension Plans
Other comprehensive income (loss):
Benefit plans	$ 1.1	$ 0.2