Income taxes - Components of Comprehensive Provision for Income Taxes Allocation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Schedule Of Income Tax [Line Items]
Income from continuing operations before income taxes	$ (9.8)	$ 83.3
Expected tax expense, at U.S. federal statutory income tax rate of 21%	(2.1)	17.5
Non-U.S. tax rates		2.1
Incremental net tax benefit on earnings and losses of U.S. and non-U.S. tax group companies	0.4	(0.9)
Valuation allowance	(0.9)	0.6
Global intangible low-tax income, net	(1.5)	0.7
U.S. state income taxes and other, net	0.3	0.2
Adjustment to the reserve for uncertain tax positions, net	(1.4)	(0.7)
Adjustment of prior year taxes, net	(0.4)
Nondeductible expenses	(0.5)	0.4
Income tax expense	(6.1)	19.9
Comprehensive provision for income taxes allocable to:
Net income	(6.1)	19.9
Other comprehensive income (loss):
Currency translation	(0.8)	0.7
Other	(0.2)	0.2
Total	(6.8)	22.2
Pension Plans
Other comprehensive income (loss):
Defined benefit plans	$ 0.3	$ 1.4