Commitments and contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Commitments and contingencies
Balance at the beginning of the period	$ 92,358
Additions charged to expense, net	65
Payments, net	(1,064)
Balance at the end of the period	91,359
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	1,850	$ 2,627
Noncurrent liability	$ 89,509	$ 89,731