Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Asset (liability)
Post-employment benefits other than pensions	$ 1,230	$ 1,714
Other reserves	1,831	1,901
Deferred compensation	3,850	3,263
Environmental reserves	1,321	1,358
Inventory	6,118	0
Research expenditures	7,069	0
Revenue recognition	7,878	5,027
Lease liabilities	12,651	11,639
Interest expense carryforward	12,470	14,163
Pensions	0	1,393
Accrued compensation expense	5,477	6,410
Net operating loss and credit carryforwards	9,915	11,423
Subtotal	69,810	58,291
Valuation allowance	(4,935)	(4,957)
Total deferred tax assets	64,875	53,334
Depreciation	(42,481)	(24,484)
Lease assets	(12,078)	(11,184)
Inventory	0	(2,329)
Amortization	(32,925)	(35,542)
Mine development	0	(917)
Pensions	(400)	0
Unrealized gains	(1,940)	(663)
Total deferred tax liabilities	(89,824)	(75,119)
Net deferred tax liabilities	$ (24,949)	$ (21,785)