Income Taxes - Components of Deferred Income Tax Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax liabilities:
Plant, equipment, and intangibles	$ (96,254)	$ (98,141)
Deferred income tax assets:
Postretirement, pensions, and stock compensation	30,338	27,549
Reserves and accruals	16,371	20,641
Net operating loss and tax credit carryforwards	76,456	79,703
Valuation allowances	(50,420)	(39,402)
Deferred tax assets	72,745	88,491
Net deferred income tax asset	$ (23,509)	$ (9,650)