Commitments and contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Commitments and contingencies.
Balance at the beginning of the period	$ 69,278
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]	Current liability, Noncurrent liability
Additions charged to expense, net	$ 578
Payments, net	(57,089)
Balance at the end of the period	$ 12,767
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]	Current liability, Noncurrent liability
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	$ 1,773	$ 58,135
Noncurrent liability	$ 10,994	$ 11,143