Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Balance at the beginning of the period	$ 93,416
Additions charged (credited) to expense, net	(90)
Payments, net	(311)
Balance at the end of the period	93,015
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	2,167	$ 2,027
Noncurrent liability	$ 90,848	$ 91,389