Commodity Derivative Positions (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2016 USD ($) bbl $ / bbl	Dec. 31, 2015 USD ($)
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative Liability	$ 15,179	$ 0
Crude Oil
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.62
Crude Oil \| Fourth quarter 2016
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	5,940
Derivative, Swap Type, Average Fixed Price \| $ / bbl	47.69
Fair Value Asset	$ 0
Fair Value Liability	$ 709
Crude Oil \| First Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,408
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.62
Fair Value Asset	$ 0
Fair Value Liability	$ 737
Crude Oil \| Second Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,408
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.62
Fair Value Asset	$ 0
Fair Value Liability	$ 1,106
Crude Oil \| Third Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,408
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.62
Fair Value Asset	$ 0
Fair Value Liability	$ 1,335
Crude Oil \| Fourth Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,408
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.62
Fair Value Asset	$ 0
Fair Value Liability	$ 1,518
Crude Oil \| First Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.12
Fair Value Asset	$ 0
Fair Value Liability	$ 1,131
Crude Oil \| Second Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.12
Fair Value Asset	$ 0
Fair Value Liability	$ 1,244
Crude Oil \| Third Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.12
Fair Value Asset	$ 0
Fair Value Liability	$ 1,353
Crude Oil \| Fourth Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.12
Fair Value Asset	$ 0
Fair Value Liability	$ 1,451
Crude Oil \| First Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.90
Fair Value Asset	$ 0
Fair Value Liability	$ 1,051
Crude Oil \| Second Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.90
Fair Value Asset	$ 0
Fair Value Liability	$ 1,117
Crude Oil \| Fourth Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.90
Fair Value Asset	$ 0
Fair Value Liability	$ 1,247
Crude Oil \| Third Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.90
Fair Value Asset	$ 0
Fair Value Liability	$ 1,179

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

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-Name Accounting Standards Codification
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-SubTopic 10
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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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Average fixed price related to the group of price risk swap derivatives.

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

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