Income Taxes - Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Pension and postretirement benefits	$ 855	$ 1,208
Deferred compensation	446	973
Restructuring related and other reserves		6
Operating lease liabilities	7,706	10,314
Alternative minimum tax and net operating loss carryforward	27,458	19,529
Inventory	3,831	4,161
Intangible assets and goodwill	4,217	4,744
Other, net	2,764	1,741
Deferred tax assets before valuation allowance	47,277	42,676
Valuation allowance	(30,165)	(14,344)
Total deferred tax assets	17,112	28,332
Deferred tax liabilities:
Depreciation	3,674	4,394
Operating right-of-use asset	7,664	10,300
Excess of book basis over tax basis in investments	312	318
Convertible debt discount	4,604	15,140
Other, net	178	421
Total deferred tax liabilities	16,432	30,573
Net deferred tax assets	$ 680
Net deferred tax liabilities		$ (2,241)