Condensed Consolidating Financial Information (Condensed Consolidating Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues:
Total revenues	$ 252,740	$ 323,953	$ 578,132	$ 656,957
Costs and expenses:
Lease operating expenses	22,912	20,721	41,818	40,024
Production taxes	7,659	5,139	14,513	9,045
Midstream gathering and processing	71,440	58,945	135,633	106,886
Depreciation, depletion and amortization	121,915	82,246	232,933	148,237
General and administrative	14,008	12,257	27,107	24,857
Accretion expense	1,015	410	2,019	692
Acquisition expense	0	1,060	0	2,358
Total costs and expenses	238,949	180,778	454,023	332,099
(LOSS) INCOME FROM OPERATIONS	13,791	143,175	124,109	324,858
OTHER (INCOME) EXPENSE:
Interest expense	33,704	24,188	67,669	47,667
Interest income	(33)	(48)	(70)	(890)
Insurance proceeds	(231)	0	(231)	0
Gain on sale of equity method investments	(122,035)	(12,523)	(122,035)	(12,523)
(Income) loss from equity method investments and investments in subsidiaries	(8,888)	25,824	(22,424)	30,731
Other income	(45)	(202)	(140)	(518)
INCOME (LOSS) BEFORE INCOME TAXES	111,319	105,936	201,340	260,391
INCOME TAX (EXPENSE) BENEFIT	0	0	(69)	0
NET INCOME (LOSS)	111,319	105,936	201,409	260,391
Parent
OTHER (INCOME) EXPENSE:
Insurance proceeds	(231)		(231)
Guarantors
OTHER (INCOME) EXPENSE:
Insurance proceeds	0		0
Non-Guarantor
OTHER (INCOME) EXPENSE:
Insurance proceeds	0		0
Reportable Legal Entities | Parent
Revenues:
Total revenues	146,774	249,353	360,335	521,794
Costs and expenses:
Lease operating expenses	16,593	16,423	30,424	33,872
Production taxes	4,793	3,645	8,804	6,747
Midstream gathering and processing	52,542	42,291	98,208	80,015
Depreciation, depletion and amortization	121,915	82,245	232,932	148,235
General and administrative	14,975	13,052	28,786	25,926
Accretion expense	795	291	1,585	573
Acquisition expense		5		5
Total costs and expenses	211,613	157,952	400,739	295,373
(LOSS) INCOME FROM OPERATIONS	(64,839)	91,401	(40,404)	226,421
OTHER (INCOME) EXPENSE:
Interest expense	34,663	26,133	69,056	51,181
Interest income	(27)	(42)	(58)	(884)
Gain on sale of equity method investments	(25,616)	(12,523)	(25,616)	12,523
(Income) loss from equity method investments and investments in subsidiaries	(183,901)	(27,952)	(283,765)	70,566
Other income	(1,046)	(151)	(1,130)	(1,178)
INCOME (LOSS) BEFORE INCOME TAXES	111,319	105,936	201,340	260,391
INCOME TAX (EXPENSE) BENEFIT	0	0	(69)	0
NET INCOME (LOSS)	111,319	105,936	201,409	260,391
Reportable Legal Entities | Guarantors
Revenues:
Total revenues	105,966	74,600	217,797	135,163
Costs and expenses:
Lease operating expenses	6,319	4,298	11,394	6,152
Production taxes	2,866	1,494	5,709	2,298
Midstream gathering and processing	18,898	16,654	37,425	26,871
Depreciation, depletion and amortization	0	1	1	2
General and administrative	(968)	(796)	(1,681)	(1,071)
Accretion expense	220	119	434	119
Acquisition expense		1,055		2,353
Total costs and expenses	27,335	22,825	53,282	36,724
(LOSS) INCOME FROM OPERATIONS	78,631	51,775	164,515	98,439
OTHER (INCOME) EXPENSE:
Interest expense	(959)	(1,945)	(1,387)	(3,514)
Interest income	(6)	(6)	(12)	(6)
Gain on sale of equity method investments	(96,419)	0	(96,419)	0
(Income) loss from equity method investments and investments in subsidiaries	(336)	(83)	(693)	2,458
Other income	1	(51)	(10)	(240)
INCOME (LOSS) BEFORE INCOME TAXES	176,350	53,860	263,036	99,741
INCOME TAX (EXPENSE) BENEFIT	0	0	0	0
NET INCOME (LOSS)	176,350	53,860	263,036	99,741
Reportable Legal Entities | Non-Guarantor
Revenues:
Total revenues	0	0	0	0
Costs and expenses:
Lease operating expenses	0	0	0	0
Production taxes	0	0	0	0
Midstream gathering and processing	0	0	0	0
Depreciation, depletion and amortization	0	0	0	0
General and administrative	1	1	2	2
Accretion expense	0	0	0	0
Acquisition expense		0		0
Total costs and expenses	1	1	2	2
(LOSS) INCOME FROM OPERATIONS	(1)	(1)	(2)	(2)
OTHER (INCOME) EXPENSE:
Interest expense	0	0	0	0
Interest income	0	0	0	0
Gain on sale of equity method investments	0	0	0	0
(Income) loss from equity method investments and investments in subsidiaries	228	208	558	573
Other income	0	0	0	0
INCOME (LOSS) BEFORE INCOME TAXES	(229)	(209)	(560)	(575)
INCOME TAX (EXPENSE) BENEFIT	0	0	0	0
NET INCOME (LOSS)	(229)	(209)	(560)	(575)
Eliminations
Revenues:
Total revenues	0	0	0	0
Costs and expenses:
Lease operating expenses	0	0	0	0
Production taxes	0	0	0	0
Midstream gathering and processing	0	0	0	0
Depreciation, depletion and amortization	0	0	0	0
General and administrative	0	0	0	0
Accretion expense	0	0	0	0
Acquisition expense		0		0
Total costs and expenses	0	0	0	0
(LOSS) INCOME FROM OPERATIONS	0	0	0	0
OTHER (INCOME) EXPENSE:
Interest expense	0	0	0	0
Interest income	0	0	0	0
Insurance proceeds	0		0
Gain on sale of equity method investments	0	0	0	0
(Income) loss from equity method investments and investments in subsidiaries	175,121	53,651	261,476	98,266
Other income	1,000	0	1,000	900
INCOME (LOSS) BEFORE INCOME TAXES	(176,121)	(53,651)	(262,476)	(99,166)
INCOME TAX (EXPENSE) BENEFIT	0	0	0	0
NET INCOME (LOSS)	$ (176,121)	$ (53,651)	$ (262,476)	$ (99,166)