Other, Net - Summary of Pre-development, reclamation and other (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other Income and Expenses [Abstract]
Accretion Expense, Including Asset Retirement Obligations	$ 2,905	$ 2,847
Other Operating Income (Expense), Net	881	1,220
Gain (Loss) on Termination of Lease	0	(4,051)
Covid-19 Related Costs	3,005	272
Care and maintenance costs	6,921	2,608
Temporary Suspension Costs	0	3,659
Pre-development, reclamation, and other	$ 13,712	$ 6,555