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Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Dec. 31, 2021
Asset Retirement Obligation      
Asset retirement obligation, beginning balance $ 4,700 $ 4,313 $ 4,313
Accretion expense 102 $ 93 387
Asset retirement obligation, ending balance 4,802   4,700
Legally restricted assets $ 0   $ 0