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ASSET RETIREMENT OBLIGATIONS AND RESTRICTED CASH - Schedule of Restricted Cash and Cash Equivalents (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Mar. 31, 2022
Jun. 30, 2021
Restricted Cash And Cash Equivalents [Roll Forward]    
Restricted cash, beginning of period $ 20,305 $ 20,817
Additional collateral posted 11 48
Refunds of collateral 0 $ (560)
Restricted cash, end of period $ 20,316