Income and Mining Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities:
Inventory	$ 0	$ 5
Royalty and other long-term debt	1,495	1,094
Foreign subsidiaries - unremitted earnings	0	99
Gross deferred tax liabilities	1,495	1,198
Deferred tax assets:
Net operating loss carryforwards	267,944	241,985
Deferred Tax Assets, Mineral Properties	6,525	1,907
Property, plant, and equipment	13,161	10,841
Mining Royalty Tax	8,147	7,447
Capital loss carryforwards	15,404	17,341
Asset retirement obligation	39,262	38,761
Unrealized foreign currency loss and other	1,013	3,386
Accrued expenses	20,589	16,849
Tax credit carryforwards	26,594	29,809
Gross deferred tax assets	398,639	368,326
Valuation allowance	(430,053)	(401,304)
Deferred tax assets, net of valuation allowance	(31,414)	(32,978)
Net deferred tax liabilities	$ 32,909	$ 34,176