Commodity Derivative Positions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015 bbl
Settlements to be received (paid) in subsequent period
Derivative Instruments Related to Oil and Gas Production [Line Items]
Fair Value Asset	$ 13,061
Fair Value Liability	0
Crude Oil \| Second quarter 2015
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Collars
Notional Volume, per day	4,000
Weighted Average Price, Floor/Swap	87.50
Weighted Average Price, Ceiling	94.66
Fair Value Asset	10,045
Fair Value Liability	0
Crude Oil \| Second quarter 2015 \| Short Put
Derivative Instruments Related to Oil and Gas Production [Line Items]
Strike price on put options	70.00
Notional Volume, per day	6,000
Crude Oil \| Third quarter 2015
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Collars
Notional Volume, per day	3,000
Weighted Average Price, Floor/Swap	86.67
Weighted Average Price, Ceiling	94.73
Fair Value Asset	6,063
Fair Value Liability	0
Crude Oil \| Fourth quarter 2015
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Collars
Notional Volume, per day	3,000
Weighted Average Price, Floor/Swap	86.67
Weighted Average Price, Ceiling	94.73
Fair Value Asset	5,738
Fair Value Liability	0
Crude Oil \| Second quarter 2015
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	9,000
Derivative, Swap Type, Average Fixed Price	91.81
Fair Value Asset	27,053
Fair Value Liability	0
Crude Oil \| Third and fourth quarters 2015 \| Short Put
Derivative Instruments Related to Oil and Gas Production [Line Items]
Strike price on put options	70.00
Notional Volume, per day	5,000
Crude Oil \| Third quarter 2015
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	8,000
Derivative, Swap Type, Average Fixed Price	91.06
Fair Value Asset	23,139
Fair Value Liability	0
Crude Oil \| Fourth quarter 2015
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	8,000
Derivative, Swap Type, Average Fixed Price	91.06
Fair Value Asset	21,918
Fair Value Liability	0
Crude Oil \| First quarter 2016
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	4,000
Derivative, Swap Type, Average Fixed Price	88.12
Fair Value Asset	11,392
Fair Value Liability	0
Crude Oil \| Second quarter 2016
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	4,000
Derivative, Swap Type, Average Fixed Price	88.12
Fair Value Asset	10,933
Fair Value Liability	0
Crude Oil \| Third quarter 2016
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	4,000
Derivative, Swap Type, Average Fixed Price	88.12
Fair Value Asset	10,649
Fair Value Liability	0
Crude Oil \| Fourth quarter 2016
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day	4,000
Derivative, Swap Type, Average Fixed Price	88.12
Fair Value Asset	10,262
Fair Value Liability	$ 0

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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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 as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624163-113959

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- Definition

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

+ References

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- Definition

The strike price on the price risk option contract such as a put option or a call option.

+ 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.

+ Details

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- Definition

Description of the type of derivative instrument, such as a swap, forward, and option. Excludes the underlying risk of the instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5579240-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(n)(2))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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