Commitments and contingent liabilities - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
	Feb. 17, 2021	Dec. 31, 2020	Dec. 31, 2019
Pending Litigation | Subsequent Event
Loss Contingencies [Line Items]
Money damages sought	$ 66.9
Minimum
Loss Contingencies [Line Items]
Estimated time frame over which accrued amounts may be paid out		10 years
Minimum | China investigation, unpaid tariffs
Loss Contingencies [Line Items]
Loss contingency accrual, unpaid tariff, penalties percentage		30.00%
Loss contingency, estimate of possible loss		$ 3.0
Loss contingency accrual		$ 3.0
Maximum
Loss Contingencies [Line Items]
Estimated time frame over which accrued amounts may be paid out		15 years
Maximum | China investigation, unpaid tariffs
Loss Contingencies [Line Items]
Loss contingency accrual, unpaid tariff, penalties percentage		200.00%
Loss contingency, estimate of possible loss		$ 20.3
Accrued Liabilities
Loss Contingencies [Line Items]
Waste disposed accrued liability		1.6	$ 0.7
Contingency reserve for litigation		0.3	0.4
Other Liabilities
Loss Contingencies [Line Items]
Waste disposed accrued liability		$ 5.2	$ 6.2