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Asset Retirement Obligations - Schedule of Changes in Asset Retirement Obligations (Details)
$ in Thousands
6 Months Ended
Jun. 30, 2020
USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]  
Balance at beginning of period $ 56,784
Liabilities incurred during period 508
Liabilities settled during period (196)
Accretion expense during period 1,545
Balance at end of period $ 58,641