Royalty Obligation (Details) - USD ($) $ in Thousands		3 Months Ended
	May 29, 2020	Mar. 31, 2021	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Proceeds from royalty obligation	$ 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		$ 30
Payments for royalty obligations		400
Royalty obligation, current		$ 124	$ 124