Commitments and contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Commitments and contingencies
Balance at the beginning of the period	$ 91,106
Additions charged to expense, net	1,428
Payments, net	(909)
Balance at the end of the period	91,625
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	2,462	$ 1,655
Noncurrent liability	$ 89,163	$ 89,451