Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Balance at the beginning of the period	$ 98,211
Additions charged (credited) to expense, net	(579)
Payments, net	(2,656)
Balance at the end of the period	94,976
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	3,168	$ 5,027
Noncurrent liability	$ 91,808	$ 93,184