Income Taxes - Deferred Tax Assets Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Employee and retiree benefit plans	$ 26,872	$ 28,097
Capital loss and other carryforwards	16,316	16,035
Operating lease assets	24,705	20,036
Operating lease liabilities	(23,945)	(19,530)
Depreciation and amortization	(188,993)	(175,904)
Inventories	8,780	7,699
Allowances and accruals	7,343	7,765
Interest rate exchange agreement	745	2,113
Other	(16,946)	(14,998)
Total gross deferred tax (liabilities)	(145,123)	(128,687)
Valuation allowance	(16,316)	(16,035)
Total deferred tax (liabilities), net of valuation allowances	$ (161,439)	$ (144,722)