Contingencies - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended					123 Months Ended	254 Months Ended
	Jan. 31, 2019	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2021	Feb. 14, 2014
Loss Contingencies [Line Items]
Other current liabilities		$ 17,936		$ 19,628	$ 17,936				$ 19,628
Other liabilities		14,373		13,086	14,373				13,086
New Idria Mercury Mine [Member]
Loss Contingencies [Line Items]
Financial assurance required to be provided to EPA to secure performance			$ 2,000
Prepayment amount	$ 200
New Almaden Mine (Formerly Referred to as Guadalupe River Watershed) [Member] | Natural Resource Damage Claim [Member]
Loss Contingencies [Line Items]
Total reserve				1,500					1,500
Other current liabilities				300					300
Other liabilities				1,200					1,200
Revised estimated project costs, Low Estimate							$ 3,300
Revised estimated project costs, High Estimate							$ 4,400
Pending Litigation [Member] | New Idria Mercury Mine [Member] | EPA Notice Letter [Member]
Loss Contingencies [Line Items]
Loss contingency, Loss in period		$ 500		700	$ 500	$ 4,000		$ 1,300	11,100	$ 1,600
Loss contingencies, payments									2,900
Total reserve				8,200					8,200
Other current liabilities				1,100					1,100
Other liabilities				$ 7,100					$ 7,100