Other, Net - Summary of Pre-development, reclamation and other (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Income and Expenses [Abstract]
Accretion Expense, Including Asset Retirement Obligations	$ 3,027	$ 2,968	$ 8,898	$ 8,724
Other Operating Income (Expense), Net	1,273	1,345	3,164	3,359
Gain (Loss) on Termination of Lease	0	0	0	(4,051)
Covid-19 Related Costs	617	4,037	5,937	10,418
Care and maintenance costs	5,589	3,913	18,957	11,704
Temporary Suspension Costs	0	2,768	0	10,107
Pre-development, reclamation, and other	$ 10,506	$ 15,031	$ 36,956	$ 40,261