Royalty Obligation (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	May 29, 2020	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Proceeds from royalty obligation	$ 30,000		$ 0	$ 30,000
Smelter royalty obligation, percentage	1.50%
Smelter royalty obligation, right to repurchase percentage	33.30%
Smelter royalty obligation, right to repurchase percentage, net of returns	0.50%
Amortization of royalty obligation		$ 100	100
Payments for royalty obligations		600	1,000
Royalty obligation, current		$ 423	$ 423		$ 124