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Derivative Instruments - Schedule of Outstanding Commodity Derivative Instruments (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) MMBTU $ / bbl $ / MMBTU bbl
Derivative [Line Items]
Fair value asset (liability) | $	$ (135,214)
Crude oil | 2018 Swaps
Derivative [Line Items]
Total notional amount of oil barrels (in bbl) | bbl	13,675,000
Average swap price (in dollars per barrel / dollars per btu)	51.25
Fair value asset (liability) | $	$ (109,129)
Crude oil | 2018 Two-way Collar
Derivative [Line Items]
Total notional amount of oil barrels (in bbl) | bbl	1,250,000
Average floor price (in dollars per barrel / dollars per btu)	48.19
Average ceiling price (in dollars per barrel / dollars per btu)	53.33
Fair value asset (liability) | $	$ (7,785)
Crude oil | 2018 Three-way Collar
Derivative [Line Items]
Total notional amount of oil barrels (in bbl) | bbl	186,000
Average sub-floor price (in dollars per barrel / dollars per btu)	31.67
Average floor price (in dollars per barrel / dollars per btu)	45.83
Average ceiling price (in dollars per barrel / dollars per btu)	59.94
Fair value asset (liability) | $	$ (107)
Crude oil | 2019 Swaps
Derivative [Line Items]
Total notional amount of oil barrels (in bbl) | bbl	4,091,000
Average swap price (in dollars per barrel / dollars per btu)	51.52
Fair value asset (liability) | $	$ (18,635)
Crude oil | 2019 Two-way Collar
Derivative [Line Items]
Total notional amount of oil barrels (in bbl) | bbl	93,000
Average floor price (in dollars per barrel / dollars per btu)	48.67
Average ceiling price (in dollars per barrel / dollars per btu)	53.07
Fair value asset (liability) | $	$ (513)
Crude oil | 2020 Swaps
Derivative [Line Items]
Total notional amount of oil barrels (in bbl) | bbl	279,000
Average swap price (in dollars per barrel / dollars per btu)	51.76
Fair value asset (liability) | $	$ (728)
Natural gas | 2018 Swaps
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	7,665,000
Average swap price (in dollars per barrel / dollars per btu) | $ / MMBTU	3.05
Fair value asset (liability) | $	$ 1,683

X

- Definition

Derivative, Sub-Floor Price

+ References

No definition available.

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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.

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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.

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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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611

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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

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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