Derivative Instruments - Location and Fair Value of Commodity Derivatives (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Offsetting Derivative Assets [Abstract]
Derivative assets, gross amounts of recognized assets	$ 467	$ 3,928
Derivative assets, gross amounts offset in the balance sheet	0	(2,754)
Derivative assets	467	1,174
Offsetting Derivative Liabilities [Abstract]
Derivative liabilities, gross amounts of recognized liabilities	97,688	34,498
Derivative liabilities, gross amounts offset in the balance sheet	(3,130)	(14,683)
Derivative liabilities	94,558	19,815
Current assets | Commodity derivative instruments
Offsetting Derivative Assets [Abstract]
Derivative assets, gross amounts of recognized assets	467	633
Derivative assets, gross amounts offset in the balance sheet	0	(98)
Derivative assets	467	535
Non-current assets | Commodity derivative instruments
Offsetting Derivative Assets [Abstract]
Derivative assets, gross amounts of recognized assets	0	3,295
Derivative assets, gross amounts offset in the balance sheet	0	(2,656)
Derivative assets	0	639
Current liabilities | Commodity derivative instruments
Offsetting Derivative Liabilities [Abstract]
Derivative liabilities, gross amounts of recognized liabilities	59,262	33,812
Derivative liabilities, gross amounts offset in the balance sheet	(2,318)	(14,117)
Derivative liabilities	56,944	19,695
Non-current liabilities | Commodity derivative instruments
Offsetting Derivative Liabilities [Abstract]
Derivative liabilities, gross amounts of recognized liabilities	38,426	686
Derivative liabilities, gross amounts offset in the balance sheet	(812)	(566)
Derivative liabilities	$ 37,614	$ 120