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Asset Retirement Obligations (Tables) | 6 Months Ended
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Jun. 30, 2021
Asset Retirement Obligation Disclosure [Abstract] |
Schedule of asset retirement obligations | The following table describes the changes in our AROs (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | 2021 |  | 2020
AROs at January 1, | ​ | $ | 30,913 | ​ | $ | 28,258
Revisions in estimates | ​ |  | (2,631) | ​ |  | —
Accretion expense | ​ |  | 48 | ​ |  | 1,304
AROs at June 30, | ​ | $ | 28,330 | ​ | $ | 29,562

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- Definition Tabular disclosure of the carrying amount of a liability for asset retirement obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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