Restricted Cash (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Reclamation and other surety bond cash collateral	$ 34,293	$ 39,677	$ 39,654
Decrease in restricted cash due to collateral requirements	5,400
Surety bond
Restricted Cash and Cash Equivalents Items [Line Items]
Guarantor obligations	$ 59,300