Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Pension, postretirement and other benefits	$ 51,736	$ 57,700
Capitalized expenditures	3,186	1,471
Deferred Tax Assets, Capital Loss Carryforwards	13,780	13,780
Net operating loss and tax credit carryforwards	157,319	145,528
Deferred Tax Assets, Goodwill and Intangible Assets	2,122	0
All other items	42,834	38,205
Total deferred tax assets	270,977	256,684
Deferred tax liabilities:
Property, plant and equipment	(23,312)	(28,899)
Intangibles	0	(2,273)
All other items	(15,793)	(11,834)
Total deferred tax liabilities	(39,105)	(43,006)
Valuation allowances	(170,098)	(189,355)
Net deferred tax assets	$ 61,774	$ 24,323