Commitments and contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Balance at the beginning of the period	$ 91,106
Additions charged to expense, net	1,308
Payments, net	(623)
Balance at the end of the period	91,791
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	2,511	$ 1,655
Noncurrent liability	$ 89,280	$ 89,451