Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Revenues	$ 147,416	$ 234,382	$ 371,704	$ 450,720
Number of segments | segment			2
Realized gain on derivatives	44,110	1,165	$ 54,977	4,435
Unrealized (loss) gain on derivatives	(132,668)	6,157	3,762	(39,562)
Expenses	498,230	164,915	676,283	331,264
Operating (loss) income	(435,310)	76,789	(241,778)	84,329
Total assets	4,001,133	3,751,451	4,001,133	3,751,451	$ 4,069,676
Capital expenditures	195,959	209,639	474,554	437,488
Depletion, depreciation and amortization	93,350	80,132	184,057	156,999
Full-cost ceiling impairment	324,001	0	324,001	0
Lease bonus - mineral acreage	4,062	0	4,062	0
Corporate
Segment Reporting Information [Line Items]
Realized gain on derivatives	0	0	0	0
Unrealized (loss) gain on derivatives	0	0	0	0
Expenses	12,409	17,783	26,726	34,734
Operating (loss) income	(12,409)	(17,783)	(26,726)	(34,734)
Total assets	76,571	87,800	76,571	87,800
Capital expenditures	594	1,400	1,381	2,206
Depletion, depreciation and amortization	700	600	1,400	1,200
Lease bonus - mineral acreage	0		0
Consolidations and Eliminations
Segment Reporting Information [Line Items]
Realized gain on derivatives	0	0	0	0
Unrealized (loss) gain on derivatives	0	0	0	0
Expenses	(21,566)	(17,807)	(43,485)	(36,223)
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
Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Realized gain on derivatives	44,110	1,165	54,977	4,435
Unrealized (loss) gain on derivatives	(132,668)	6,157	3,762	(39,562)
Expenses	483,812	141,514	645,137	283,493
Operating (loss) income	(441,723)	75,371	(255,361)	82,606
Total assets	3,159,528	3,155,577	3,159,528	3,155,577
Capital expenditures	130,709	166,532	340,444	364,143
Depletion, depreciation and amortization	87,800	75,700	172,900	148,300
Capital expenditures attributable to land and seismic acquisition expenditures	9,600	8,200	49,300	31,300
Full-cost ceiling impairment			324,000
Lease bonus - mineral acreage	4,062		4,062
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Realized gain on derivatives	0	0	0	0
Unrealized (loss) gain on derivatives	0	0	0	0
Expenses	23,575	23,425	47,905	49,260
Operating (loss) income	18,822	19,201	40,309	36,457
Total assets	765,034	508,074	765,034	508,074
Capital expenditures	64,656	41,707	132,729	71,139
Depletion, depreciation and amortization	5,000	3,800	9,800	7,500
Net income attributable to non-controlling interest in subsidiaries		(8,300)	(16,800)	(15,800)
Capital expenditures attributable to non-controlling interest	31,900	24,200	79,400	37,900
Lease bonus - mineral acreage	0		0
Operating Income (Loss) | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Net income attributable to non-controlling interest in subsidiaries	(7,500)
Oil and natural gas revenues
Segment Reporting Information [Line Items]
Revenues	118,767	211,060	316,681	404,329
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	118,258	209,563	315,053	401,226
Oil and natural gas revenues | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	509	1,497	1,628	3,103
Third-party midstream services revenues
Segment Reporting Information [Line Items]
Revenues	14,668	14,359	30,498	26,197
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	(21,566)	(17,807)	(43,485)	(36,223)
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	36,234	32,166	73,983	62,420
Sales of purchased natural gas
Segment Reporting Information [Line Items]
Revenues	13,981	8,963	24,525	20,194
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	8,327	0	11,922	0
Sales of purchased natural gas | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	$ 5,654	$ 8,963	$ 12,603	$ 20,194