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Summary of Significant Accounting Policies - Schedule of Gains and Losses from Derivative Financial Instruments (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Derivative [Line Items]        
Gain (loss) from derivative financial instruments $ (121,579) $ 24,858 $ (71,978) $ 31,945
Natural gas price derivatives        
Derivative [Line Items]        
Gain (loss) from derivative financial instruments (120,706) 22,664 (82,872) 37,722
Oil price derivatives        
Derivative [Line Items]        
Gain (loss) from derivative financial instruments (989) 2,194 13,529 (5,777)
Interest rate derivatives        
Derivative [Line Items]        
Gain (loss) from derivative financial instruments $ 116 $ 0 $ (2,635) $ 0