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Asset Retirement Obligations (Narrative) (Details) - USD ($)
$ in Thousands
1 Months Ended 12 Months Ended
Dec. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Asset Retirement Obligations [Abstract]      
Additions   $ 359 $ 595
Revisions $ (400) $ 238 $ (379)