Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Revenues	$ 264,498	$ 223,091	$ 715,218	$ 620,539
Lease bonus - mineral acreage	1,711	0	$ 1,711	0
Number of segments | segment			2
Realized gain (loss) on derivatives	3,346	5,424	$ 7,781	(1,322)
Unrealized gain (loss) on derivatives	9,847	(21,337)	(29,715)	(9,492)
Expenses	193,300	139,325	524,564	394,517
Operating (loss) income	86,102	67,853	170,431	215,208
Total assets	3,936,639	3,154,202	3,936,639	3,154,202	$ 3,455,518
Capital expenditures	269,466	764,216	706,954	1,232,881
Depletion, depreciation and amortization	92,498	70,457	249,497	192,664
Corporate
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives	0	0	0	0
Unrealized gain (loss) on derivatives	0	0	0	0
Expenses	18,613	19,041	53,349	55,338
Operating (loss) income	(18,613)	(19,041)	(53,349)	(55,338)
Total assets	37,178	65,194	37,178	65,194
Capital expenditures	1,705	312	3,911	1,570
Depletion, depreciation and amortization	700	600	1,900	1,800
Consolidations and Eliminations
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives	0	0	0	0
Unrealized gain (loss) on derivatives	0	0	0	0
Expenses	(20,276)	(18,141)	(56,499)	(47,374)
Operating (loss) income	0	0	0	0
Total assets	0	0	0	0
Capital expenditures	0	0	0	0
Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives	3,346	5,424	7,781	(1,322)
Unrealized gain (loss) on derivatives	9,847	(21,337)	(29,715)	(9,492)
Expenses	164,352	128,263	447,844	359,830
Operating (loss) income	81,820	71,072	164,427	232,093
Total assets	3,332,910	2,697,685	3,332,910	2,697,685
Capital expenditures	201,323	716,751	565,466	1,105,541
Depletion, depreciation and amortization	87,700	67,200	236,000	184,400
Capital expenditures attributable to land and seismic acquisition expenditures	6,500	554,900	37,800	613,800
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives	0	0	0	0
Unrealized gain (loss) on derivatives	0	0	0	0
Expenses	30,611	10,162	79,870	26,723
Operating (loss) income	22,895	15,822	59,353	38,453
Total assets	566,551	391,323	566,551	391,323
Capital expenditures	66,438	47,153	137,577	125,770
Depletion, depreciation and amortization	4,100	2,600	11,600	6,500
Net income attributable to non-controlling interest in subsidiaries		(7,300)
Capital expenditures attributable to non-controlling interest	47,200	23,100	85,100	61,600
Operating Income (Loss) | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Net income attributable to non-controlling interest in subsidiaries	(9,800)		(25,600)	(18,200)
Oil and natural gas revenues
Segment Reporting Information [Line Items]
Revenues	229,377	216,282	633,706	607,255
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	228,188	215,248	629,414	602,737
Oil and natural gas revenues | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,189	1,034	4,292	4,518
Third-party midstream services revenues
Segment Reporting Information [Line Items]
Revenues	15,257	6,809	41,454	13,284
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	(20,276)	(18,141)	(56,499)	(47,374)
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	35,533	24,950	97,953	60,658
Sales of purchased natural gas
Segment Reporting Information [Line Items]
Revenues	19,864	$ 0	40,058	$ 0
Lease bonus - mineral acreage	1,711		1,711
Sales of purchased natural gas | Corporate
Segment Reporting Information [Line Items]
Revenues	0		0
Lease bonus - mineral acreage	0		0
Sales of purchased natural gas | Consolidations and Eliminations
Segment Reporting Information [Line Items]
Revenues	0		0
Lease bonus - mineral acreage	0		0
Sales of purchased natural gas | Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Revenues	3,080		3,080
Lease bonus - mineral acreage	1,711		1,711
Sales of purchased natural gas | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	16,784		36,978
Lease bonus - mineral acreage	$ 0		$ 0