Other, Net - Summary of Pre-development, reclamation and other (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Income and Expenses [Abstract]
Accretion Expense, Including Asset Retirement Obligations	$ 2,965	$ 2,908	$ 5,870	$ 5,755
Other Operating Income (Expense), Net	1,011	647	1,893	2,016
Gain (Loss) on Termination of Lease	0	0	0	(4,051)
Covid-19 Related Costs	2,315	6,108	5,319	6,380
Care and maintenance costs	6,447	5,183	13,368	7,792
Temporary Suspension Costs	0	3,829	0	7,338
Pre-development, reclamation, and other	$ 12,738	$ 18,675	$ 26,450	$ 25,230