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Significant Accounting Policies - Impairment of Proved and Unproved Properties (Details)
a in Thousands, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2019
USD ($)
a
well
Dec. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
a
well
Productive Wells [Line Items]        
Impairment of proved and unproved properties $ 327,400 $ 0 $ 61,849 $ 327,400
Impairment of unproved properties   0 0 119,429
Exploration and Production Related Other Costs        
Productive Wells [Line Items]        
Exploration expense   $ 20,626 $ 14,994 $ 44,380
Marcellus Shale | Central Pennsylvania        
Productive Wells [Line Items]        
Number of operated wells | well 56     56
Net acres of land | a 51     51