Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Balance at the beginning of the period	$ 113,133
Additions charged to expense, net	5,090
Payments, net	(1,412)
Balance at the end of the period	116,811
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability		$ 13,361	$ 8,668
Noncurrent liability		103,450	104,465
Balance at the end of the period	$ 113,133	$ 116,811	$ 113,133