Reconciliation of Level 3 Fair Value Measurements (Details) - Derivative Financial Instrument Net Assets - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Roll-forward of Level 3 Assets
Fair Value, net assets (liabilities), beginning of period	$ 26,958	$ 22,504	$ 8,414	$ 58,329
Fair Value, net assets (liabilities), end of period	(9,215)	30,905	(9,215)	30,905
Commodity Price Risk Management (loss), net
Roll-forward of Level 3 Assets
Changes in fair value included in statement of operations line item:	(21,521)	10,846	32,840	(22,077)
Settlements included in statement of operations line items:	(14,652)	(2,445)	(50,469)	(5,347)
Net change in fair value of unsettled derivatives included in statement of operations line item	$ (13,171)	$ 6,787	$ 9,466	$ (11,620)