Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Oil production revenue	$ 266,150	$ 128,874	$ 527,210	$ 296,498
Gas production revenue	84,064	101,740	163,173	202,921
NGL production revenue	52,344	54,325	95,061	118,718
Total oil, gas, and NGL production revenue	402,558	284,939	785,444	618,137
Revenue, Remaining Performance Obligation	0		0
Permian
Segment Reporting Information [Line Items]
Oil production revenue	227,636	78,554	433,430	160,053
Gas production revenue	31,734	12,937	56,611	24,246
NGL production revenue	129	107	253	254
Total oil, gas, and NGL production revenue	259,499	91,598	490,294	184,553
South Texas & Gulf Coast
Segment Reporting Information [Line Items]
Oil production revenue	19,346	13,072	38,929	51,936
Gas production revenue	52,235	87,760	104,968	175,961
NGL production revenue	52,248	53,558	94,018	116,915
Total oil, gas, and NGL production revenue	123,829	154,390	237,915	344,812
Rocky Mountain
Segment Reporting Information [Line Items]
Oil production revenue	19,168	37,248	54,851	84,509
Gas production revenue	95	1,043	1,594	2,714
NGL production revenue	(33)	660	790	1,549
Total oil, gas, and NGL production revenue	$ 19,230	$ 38,951	$ 57,235	$ 88,772
Sales Revenue, Net \| Geographic Concentration Risk
Segment Reporting Information [Line Items]
Relative percentage	100.00%	100.00%	100.00%	100.00%
Sales Revenue, Net \| Geographic Concentration Risk \| Permian
Segment Reporting Information [Line Items]
Relative percentage	64.00%	32.00%	63.00%	30.00%
Sales Revenue, Net \| Geographic Concentration Risk \| South Texas & Gulf Coast
Segment Reporting Information [Line Items]
Relative percentage	31.00%	54.00%	30.00%	56.00%
Sales Revenue, Net \| Geographic Concentration Risk \| Rocky Mountain
Segment Reporting Information [Line Items]
Relative percentage	5.00%	14.00%	7.00%	14.00%

Oil Revenue

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Revenue from natural gas production during the reporting period. Natural gas consists largely of the hydrocarbon methane, and is found in underground formations either by itself or with crude oil.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
-Subparagraph (SX 210.5-03.1)
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Revenue from sale of residue oil and condensate, which normally exists in the reservoir as gas but condenses out as a liquid during production.

+ References

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Revenue from the sale of oil and gas during the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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