Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Reserves	$ 3,145	$ 4,625
Environmental	11,189	20,868
Compensation	6,782	8,950
Post-retirement benefits	12,570	18,318
Research & development expenses	6,787	6,949
Inventories	1,891	1,464
Tax carryforwards	21,988	14,438
Other	2,106	993
Deferred tax assets	66,458	76,605
Valuation allowance	(7,405)	(4,066)
Net deferred tax assets	59,053	72,539
Property	(98,809)	(81,837)
Intangible assets	(17,647)	(16,561)
Pension	(21,941)	(29,041)
Other	(4,110)
Deferred tax liabilities	(142,507)	(127,439)
Net deferred tax liabilities	$ (83,454)	$ (54,900)