Derivative Financial Instruments - Location of Gain (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative instruments, Location of Gain/(Loss)
Derivative, not designated as hedge, gain (loss)	$ (22,800)	$ (70,724)	$ 29,960
Commodity derivatives | Oil and gas revenue
Derivative instruments, Location of Gain/(Loss)
Derivative, not designated as hedge, gain (loss)	(5,620)	1,161	(1,963)
Commodity derivatives | Derivatives, net
Derivative instruments, Location of Gain/(Loss)
Derivative, not designated as hedge, gain (loss)	(17,180)	(71,885)	31,430
Interest rate contracts | Interest expense
Derivative instruments, Location of Gain/(Loss)
Derivative, not designated as hedge, gain (loss)	$ 0	$ 0	$ 493