Reconciliation of Level 3 Fair Value Measurements (Details) - Derivative Financial Instrument Net Assets - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Roll-forward of Level 3 Assets
Fair Value, net assets (liabilities), beginning of period	$ 67,240	$ 12,990	$ 8,414	$ 58,329
Fair Value, net assets (liabilities), end of period	26,958	22,504	26,958	22,504
Commodity Price Risk Management (loss), net
Roll-forward of Level 3 Assets
Changes in fair value included in statement of operations line item:	(13,169)	10,597	54,361	(32,923)
Settlements included in statement of operations line items:	(27,113)	(1,083)	(35,817)	(2,902)
Net change in fair value of unsettled derivatives included in statement of operations line item	$ (13,675)	$ 6,200	$ 21,989	$ (26,641)