Income Taxes - Deferred Income Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets:
Accrued liabilities	$ 54,971	$ 93,491
Retirement plans and postretirement benefits	10,379	34,777
Share-based compensation	3,886	13,322
Receivables and inventories	6,651	8,187
Derivative financial instruments	99	0
Net operating loss carryforwards	38,023	34,478
Tax credit carryforwards	9,965	8,890
Valuation allowances	(21,755)	(12,048)
Deferred income tax assets	102,219	181,097
Deferred income tax liabilities:
Property, plant and equipment	(124,185)	(208,559)
Intangible assets	(22,213)	(29,356)
Derivative financial instruments	0	(916)
Cancellation of debt	(1,708)	(5,576)
Other	(3,400)	(3,458)
Deferred income tax liabilities	(151,506)	(247,865)
Net deferred income tax asset (liability)	(49,287)	(66,768)
Deferred tax assets related to uncertain tax positions	$ 7,000	$ 8,800