Annual report pursuant to Section 13 and 15(d)

Asset Retirement Obligations (Details)

v3.20.4
Asset Retirement Obligations (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Asset Retirement Obligations      
Beginning of period $ 30,972 $ 30,384 $ 27,036
Change in estimated reclamation costs (1,583) 11 2,840
Accretion expense 576 577 508
End of period $ 29,965 $ 30,972 $ 30,384