Income Taxes - Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Postretirement and other employee benefits	$ 191,099	$ 197,657
Product liability	67,528	61,456
Net operating loss, capital loss, and tax credit carryforwards	15,274	11,187
All other items	48,718	45,747
Total deferred tax assets	322,619	316,047
Deferred tax liabilities:
Property, plant and equipment	(160,075)	(156,520)
All other items	(9,685)	(10,399)
Total deferred tax liabilities	(169,760)	(166,919)
Deferred tax assets (liabilities), Net, Total	152,859	149,128
Valuation allowances	(20,228)	(15,103)
Net deferred tax asset	$ 132,631	$ 134,025