Derivative Instruments - Schedule of Outstanding Commodity Derivative Instruments (Details) $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($) MMBTU $ / bbl $ / MMBTU bbl	Jul. 31, 2018 $ / bbl
Derivative [Line Items]
Fair value asset \| $	$ (229,792)
Crude Oil [Member] \| 2018 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	7,745,000
Average swap price (in dollars per barrel)	53.02
Fair value asset \| $	$ (133,352)
Crude Oil [Member] \| 2018 Basis Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	153,000
Average swap price (in dollars per barrel)	10.50
Fair value asset \| $	$ 471
Crude Oil [Member] \| 2018 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	549,000
Average floor price (in dollars per barrel)	48.67
Average ceiling price (in dollars per barrel)	53.07
Fair value asset \| $	$ (9,479)
Crude Oil [Member] \| 2019 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	5,613,000
Average swap price (in dollars per barrel)	53.33
Fair value asset \| $	$ (69,121)
Crude Oil [Member] \| 2019 Basis Swaps [Member] [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	212,000
Average swap price (in dollars per barrel)	10.50
Fair value asset \| $	$ 353
Crude Oil [Member] \| 2019 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	761,000
Average floor price (in dollars per barrel)	52.03
Average ceiling price (in dollars per barrel)	69.03
Fair value asset \| $	$ (2,500)
Crude Oil [Member] \| 2019 Three-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	3,368,000
Average sub-floor price (in dollars per barrel)	40.54
Average floor price (in dollars per barrel)	51.03
Average ceiling price (in dollars per barrel)	68.68
Fair value asset \| $	$ (12,060)
Crude Oil [Member] \| 2020 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	403,000
Average swap price (in dollars per barrel)	53.47
Fair value asset \| $	$ (3,557)
Crude Oil [Member] \| 2020 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	62,000
Average floor price (in dollars per barrel)	52.50
Average ceiling price (in dollars per barrel)	71.25
Fair value asset \| $	$ (30)
Crude Oil [Member] \| 2020 Three-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) \| bbl	279,000
Average sub-floor price (in dollars per barrel)	40.00
Average floor price (in dollars per barrel)	50.56
Average ceiling price (in dollars per barrel)	67.80
Fair value asset \| $	$ (876)
Natural Gas [Member] \| 2018 Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) \| MMBTU	6,440,000
Average swap price (in dollars per barrel) \| $ / MMBTU	3.02
Fair value asset \| $	$ 403
Natural Gas [Member] \| 2018 Basis Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) \| MMBTU	1,220,000
Natural Gas [Member] \| 2019 Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) \| MMBTU	1,353,000
Average swap price (in dollars per barrel) \| $ / MMBTU	2.96
Fair value asset \| $	$ (44)
Natural Gas [Member] \| 2019 Basis Swaps [Member] [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) \| MMBTU	1,810,000
Subsequent Event [Member] \| Natural Gas [Member]
Derivative [Line Items]
Average swap price (in dollars per barrel)		0.06

Derivative, Sub-Floor Price

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- Definition

The average cap rate on a group of price risk derivatives such as caps or collars. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

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- Definition

The average floor rate on a group of price risk derivatives such as floors or collars. A payment or receipt is triggered if the market rate falls below the floor rate on the contract.

+ References

No definition available.

+ Details

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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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

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- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

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- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

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