Income Taxes - Deferred Tax Assets Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Employee and retiree benefit plans	$ 27,615	$ 31,804
Capital loss carryforwards	12,754	12,853
Depreciation and amortization	(168,485)	(176,592)
Inventories	5,969	8,548
Allowances and accruals	11,540	4,572
Interest rate exchange agreement	3,543	5,007
Other	(6,388)	(8,019)
Total gross deferred tax (liabilities)	(113,452)	(121,827)
Capital loss valuation allowance	(12,754)	(12,853)
Total deferred tax (liabilities), net of valuation allowances	$ (126,206)	$ (134,680)