Subsidiary Guarantor Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2016	Jun. 30, 2018	Jun. 30, 2017
Crude oil, natural gas and NGLs sales	$ 325,933	$ 213,602		$ 631,158	$ 403,294
Commodity price risk management gain (loss), net	(116,126)	57,932		(163,366)	138,636
Other income	2,724	3,624		5,339	6,935
Revenues	212,531	275,158		473,131	548,865
Lease operating expenses	32,260	20,028		61,896	39,817
Production taxes	22,604	15,042		42,773	27,441
Transportation, gathering and processing expenses	8,964	6,488		16,277	12,390
Exploration, geologic and geophysical expense	875	1,033		3,521	1,987
Impairment of properties and equipment	159,554	27,566		192,742	29,759
General and administrative expense	37,247	29,531		72,943	55,846
Results of Operations, Depreciation, Depletion, Amortization and Accretion	135,624	126,013		262,412	235,329
Accretion of asset retirement obligations	1,285	1,666		2,573	3,434
GainLossonSaleOfOilAndGasPropertyFromContinuingOperations	(351)	(532)		1,081	(692)
Provision for uncollectible note receivable	0	(40,203)	$ 44,000	0	(40,203)
Other Cost and Expense, Operating	2,708	3,890		5,476	7,418
Costs and Expenses	400,770	190,522		661,694	372,526
Operating Income (Loss)	(188,239)	84,636		(188,563)	176,339
Interest expense	(17,410)	(19,617)		(34,939)	(39,084)
Interest income	69	768		217	1,008
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(205,580)	65,787		(223,285)	138,263
Income tax (expense) benefit	45,323	(24,537)		49,889	(50,867)
Income (Loss) from Subsidiaries, Net of Tax	0	0		0	0
Net income (loss)	(160,257)	41,250		(173,396)	87,396
Corporate, Non-Segment [Member]
Crude oil, natural gas and NGLs sales	242,903	190,828		476,397	361,567
Commodity price risk management gain (loss), net	(116,126)	57,932		(163,366)	138,636
Other income	2,479	3,586		4,995	6,884
Revenues	129,256	252,346		318,026	507,087
Lease operating expenses	23,432	15,557		44,794	31,374
Production taxes	16,189	13,388		32,270	24,532
Transportation, gathering and processing expenses	3,610	5,767		6,841	10,982
Exploration, geologic and geophysical expense	296	256		609	527
Impairment of properties and equipment	86	531		92	1,134
General and administrative expense	33,152	26,617		64,711	50,146
Results of Operations, Depreciation, Depletion, Amortization and Accretion	93,217	108,727		187,593	210,465
Accretion of asset retirement obligations	1,177	1,589		2,377	3,274
GainLossonSaleOfOilAndGasPropertyFromContinuingOperations	(351)	(532)		1,081	(692)
Provision for uncollectible note receivable		(40,203)			(40,203)
Other Cost and Expense, Operating	2,708	3,890		5,476	7,418
Costs and Expenses	173,516	135,587		345,844	298,957
Operating Income (Loss)	(44,260)	116,759		(27,818)	208,130
Interest expense	(17,915)	(19,800)		(36,012)	(39,397)
Interest income	69	768		217	1,008
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(62,106)	97,727		(63,613)	169,741
Income tax (expense) benefit	13,348	(36,285)		13,925	(62,448)
Income (Loss) from Subsidiaries, Net of Tax	(111,499)	(20,192)		(123,708)	(19,897)
Net income (loss)	(160,257)	41,250		(173,396)	87,396
Reportable Legal Entities [Member]
Crude oil, natural gas and NGLs sales	83,030	22,774		154,761	41,727
Commodity price risk management gain (loss), net	0	0		0	0
Other income	245	38		344	51
Revenues	83,275	22,812		155,105	41,778
Lease operating expenses	8,828	4,471		17,102	8,443
Production taxes	6,415	1,654		10,503	2,909
Transportation, gathering and processing expenses	5,354	721		9,436	1,408
Exploration, geologic and geophysical expense	579	777		2,912	1,460
Impairment of properties and equipment	159,468	27,035		192,650	28,625
General and administrative expense	4,095	2,914		8,232	5,700
Results of Operations, Depreciation, Depletion, Amortization and Accretion	42,407	17,286		74,819	24,864
Accretion of asset retirement obligations	108	77		196	160
GainLossonSaleOfOilAndGasPropertyFromContinuingOperations	0	0		0	0
Provision for uncollectible note receivable		0			0
Other Cost and Expense, Operating	0	0		0	0
Costs and Expenses	227,254	54,935		315,850	73,569
Operating Income (Loss)	(143,979)	(32,123)		(160,745)	(31,791)
Interest expense	505	183		1,073	313
Interest income	0	0		0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(143,474)	(31,940)		(159,672)	(31,478)
Income tax (expense) benefit	31,975	11,748		35,964	11,581
Income (Loss) from Subsidiaries, Net of Tax	0	0		0	0
Net income (loss)	(111,499)	(20,192)		(123,708)	(19,897)
Consolidation, Eliminations [Member]
Crude oil, natural gas and NGLs sales	0	0		0	0
Commodity price risk management gain (loss), net	0	0		0	0
Other income	0	0		0	0
Revenues	0	0		0	0
Lease operating expenses	0	0		0	0
Production taxes	0	0		0	0
Transportation, gathering and processing expenses	0	0		0	0
Exploration, geologic and geophysical expense	0	0		0	0
Impairment of properties and equipment	0	0		0	0
General and administrative expense	0	0		0	0
Results of Operations, Depreciation, Depletion, Amortization and Accretion	0	0		0	0
Accretion of asset retirement obligations	0	0		0	0
GainLossonSaleOfOilAndGasPropertyFromContinuingOperations	0	0		0	0
Provision for uncollectible note receivable		0			0
Other Cost and Expense, Operating	0	0		0	0
Costs and Expenses	0	0		0	0
Operating Income (Loss)	0	0		0	0
Interest expense	0	0		0	0
Interest income	0	0		0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	0	0		0	0
Income tax (expense) benefit	0	0		0	0
Income (Loss) from Subsidiaries, Net of Tax	111,499	20,192		123,708	19,897
Net income (loss)	$ 111,499	$ 20,192		$ 123,708	$ 19,897