Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Balance at the beginning of the period	$ 94,508
Additions charged to expense	21
Payments, net	(696)
Balance at the end of the period	93,833
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	3,132	$ 3,065
Noncurrent liability	$ 90,701	$ 91,443