Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Revenues	$ 223,091		$ 620,539
Number of segments | segment			2
Realized gain (loss) on derivatives	5,424	$ 485	$ (1,322)	$ (1,176)
Unrealized (loss) gain on derivatives	(21,337)	(12,372)	(9,492)	21,449
Expenses	139,325	99,730	394,517	270,887
Operating (loss) income	67,853	26,549	215,208	119,816
Total assets	3,154,202	1,848,537	3,154,202	1,848,537	$ 2,145,690
Capital expenditures	764,216	217,188	1,232,881	634,587
Depletion, depreciation and amortization	70,457	47,800	192,664	123,066
Impairment charges		0	0
Other (expense) income	(976)	(36)	(1,275)	1,956
Income before income taxes	25,115	17,979	155,676	95,566
Corporate
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives		0
Unrealized (loss) gain on derivatives		0
Expenses	19,041	15,447	55,338	47,055
Operating (loss) income	(19,041)	(15,447)	(55,338)	(47,055)
Total assets	65,194	35,586	65,194	35,586
Capital expenditures	312	1,494	1,570	4,710
Depletion, depreciation and amortization	600	400	1,800	1,100
Consolidations and Eliminations
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives		0
Unrealized (loss) gain on derivatives		0
Expenses	(18,141)	(8,043)	(47,374)	(25,373)
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	5,424	485	(1,322)	(1,176)
Unrealized (loss) gain on derivatives	(21,337)	(12,372)	(9,492)	21,449
Expenses	128,263	86,728	359,830	233,145
Operating (loss) income	71,072	35,873	232,093	149,168
Total assets	2,697,685	1,590,677	2,697,685	1,590,677
Capital expenditures	716,751	180,686	1,105,541	554,642
Depletion, depreciation and amortization	67,200	46,100	184,400	118,200
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Realized gain (loss) on derivatives		0
Unrealized (loss) gain on derivatives		0
Expenses	10,162	5,598	26,723	16,060
Operating (loss) income	15,822	6,123	38,453	17,703
Total assets	391,323	222,274	391,323	222,274
Capital expenditures	47,153	35,008	125,770	75,235
Depletion, depreciation and amortization	2,600	1,300	6,500	3,800
Net income attributable to non-controlling interest in subsidiaries		(2,900)	(18,200)	(8,000)
Capital expenditures attributable to non-controlling interest	23,100	17,200	61,600	35,800
Capital expenditures attributable to land and seismic acquisition expenditures	554,900		613,800
Operating Income (Loss) | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Net income attributable to non-controlling interest in subsidiaries	(7,300)
Oil and natural gas revenues
Segment Reporting Information [Line Items]
Revenues	216,282	134,948	607,255	363,559
Oil and natural gas revenues | Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Revenues	215,248	134,488	602,737	362,040
Oil and natural gas revenues | Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,034	460	4,518	1,519
Third-party midstream services revenues
Segment Reporting Information [Line Items]
Revenues	6,809	3,218	13,284	6,871
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	(18,141)	(8,043)	(47,374)	(25,373)
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	$ 24,950	$ 11,261	$ 60,658	$ 32,244