Commodity Derivative Positions (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2015 USD ($) bbl counterparty $ / bbl
Settlements to be received in subsequent period
Derivative Instruments Related to Oil and Gas Production [Line Items]
Fair Value Asset	$ 12,849
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 \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	80.41
Fair Value Asset	$ 22,894
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 \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	80.41
Fair Value Asset	$ 21,509
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 \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	80.41
Fair Value Asset	$ 20,767
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 \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	80.41
Fair Value Asset	$ 19,937
Fair Value Liability	$ 0
Commodity contracts
Derivative Instruments Related to Oil and Gas Production [Line Items]
Number Of Derivative Counterparty \| counterparty	7
Commodity contracts \| Credit Concentration Risk
Derivative Instruments Related to Oil and Gas Production [Line Items]
Number Of Derivative Counterparty \| counterparty	5

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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+ 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=56946850&loc=SL5624163-113959

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

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+ References

Reference 1: 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=56946850&loc=SL5580258-113959

Reference 2: 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

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
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