Derivative Instruments - Fair value gains (losses) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 29, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary of realized and unrealized gains (losses) on derivative instruments
Commodity derivative fair value gains (losses)		$ (168,015)	$ 328,427	$ 397,818	$ 251,059
Subsequent event
Summary of realized and unrealized gains (losses) on derivative instruments
Proceeds from derivative	$ 29,000
Revenue
Summary of realized and unrealized gains (losses) on derivative instruments
Commodity derivative fair value gains (losses)		$ (168,015)	$ 328,427	$ 397,818	$ 251,059