Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Revenues	$ 221,825	$ 264,498		$ 593,529	$ 715,218
Number of segments | segment				2
Realized (loss) gain on derivatives	(5,406)	3,346		$ 49,571	7,781
Unrealized (loss) gain on derivatives	(13,033)	9,847		(9,271)	(29,715)
Expenses	424,527	193,300		1,100,810	524,564
Operating (loss) income	(221,141)	86,102		(462,919)	170,431
Total assets	3,786,230	3,936,639		3,786,230	3,936,639	$ 4,069,676
Capital expenditures	161,607	269,466		636,161	706,954
Depletion, depreciation and amortization	88,025	92,498		272,082	249,497
Full-cost ceiling impairment	251,163	0	$ 324,000	575,164	0
Lease bonus - mineral acreage	0	1,711		4,062	1,711
Corporate
Segment Reporting Information [Line Items]
Realized (loss) gain on derivatives	0	0		0	0
Unrealized (loss) gain on derivatives	0	0		0	0
Expenses	12,187	18,613		38,913	53,349
Operating (loss) income	(12,187)	(18,613)		(38,913)	(53,349)
Total assets	52,867	37,178		52,867	37,178
Capital expenditures	415	1,705		1,796	3,911
Depletion, depreciation and amortization	700	700		2,100	1,900
Lease bonus - mineral acreage		0		0	0
Consolidations and Eliminations
Segment Reporting Information [Line Items]
Realized (loss) gain on derivatives	0	0		0	0
Unrealized (loss) gain on derivatives	0	0		0	0
Expenses	(21,466)	(20,276)		(64,951)	(56,499)
Operating (loss) income	0	0		0	0
Total assets	0	0		0	0
Capital expenditures	0	0		0	0
Lease bonus - mineral acreage		0		0	0
Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Realized (loss) gain on derivatives	(5,406)	3,346		49,571	7,781
Unrealized (loss) gain on derivatives	(13,033)	9,847		(9,271)	(29,715)
Expenses	409,282	164,352		1,054,419	447,844
Operating (loss) income	(231,749)	81,820		(487,110)	164,427
Total assets	2,913,409	3,332,910		2,913,409	3,332,910
Capital expenditures	106,160	201,323		446,604	565,466
Depletion, depreciation and amortization	81,300	87,700		254,200	236,000
Capital expenditures attributable to land and seismic acquisition expenditures	13,700	6,500		63,000	37,800
Full-cost ceiling impairment				575,200
Lease bonus - mineral acreage		1,711		4,062	1,711
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Realized (loss) gain on derivatives	0	0		0	0
Unrealized (loss) gain on derivatives	0	0		0	0
Expenses	24,524	30,611		72,429	79,870
Operating (loss) income	22,795	22,895		63,104	59,353
Total assets	819,954	566,551		819,954	566,551
Capital expenditures	55,032	66,438		187,761	137,577
Depletion, depreciation and amortization	6,000	4,100		15,800	11,600
Net income attributable to non-controlling interest in subsidiaries		(9,800)		(26,800)	(25,600)
Capital expenditures attributable to non-controlling interest	26,600	47,200		106,000	85,100
Lease bonus - mineral acreage		0		0	0
Operating Income (Loss) | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Net income attributable to non-controlling interest in subsidiaries	(10,000)
Oil and natural gas revenues
Segment Reporting Information [Line Items]
Revenues	189,104	229,377		505,785	633,706
Oil and natural gas revenues | Corporate
Segment Reporting Information [Line Items]
Revenues	0	0		0	0
Oil and natural gas revenues | Consolidations and Eliminations
Segment Reporting Information [Line Items]
Revenues	0	0		0	0
Oil and natural gas revenues | Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Revenues	188,492	228,188		503,545	629,414
Oil and natural gas revenues | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	612	1,189		2,240	4,292
Third-party midstream services revenues
Segment Reporting Information [Line Items]
Revenues	19,363	15,257		49,861	41,454
Third-party midstream services revenues | Corporate
Segment Reporting Information [Line Items]
Revenues	0	0		0	0
Third-party midstream services revenues | Consolidations and Eliminations
Segment Reporting Information [Line Items]
Revenues	(21,466)	(20,276)		(64,951)	(56,499)
Third-party midstream services revenues | Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Revenues	0	0		0	0
Third-party midstream services revenues | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	40,829	35,533		114,812	97,953
Sales of purchased natural gas
Segment Reporting Information [Line Items]
Revenues	13,358	19,864		37,883	40,058
Sales of purchased natural gas | Corporate
Segment Reporting Information [Line Items]
Revenues	0	0		0	0
Sales of purchased natural gas | Consolidations and Eliminations
Segment Reporting Information [Line Items]
Revenues	0	0		0	0
Sales of purchased natural gas | Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Revenues	7,480	3,080		19,402	3,080
Sales of purchased natural gas | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	$ 5,878	$ 16,784		$ 18,481	$ 36,978