Commodity Derivative Positions (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($) bbl $ / bbl	Dec. 31, 2016 USD ($)
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative Liability	$ 18,557	$ 27,369
Settlement Agreement [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Fair Value Asset
Fair Value Liability	$ 172
Crude Oil \| Fourth Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,381
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.59
Fair Value Asset	$ 0
Fair Value Liability	$ 1,361
Crude Oil \| First Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps/Put option 1
Notional Volume, per day \| bbl	8,513
Derivative, Swap Type, Average Fixed Price \| $ / bbl	47.98
Fair Value Asset	$ 0
Fair Value Liability	$ 2,427
Crude Oil \| Second Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps/Put option 1
Notional Volume, per day \| bbl	8,484
Derivative, Swap Type, Average Fixed Price \| $ / bbl	47.98
Fair Value Asset	$ 0
Fair Value Liability	$ 1,971
Crude Oil \| Third Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps/Put option 1
Notional Volume, per day \| bbl	8,455
Derivative, Swap Type, Average Fixed Price \| $ / bbl	47.98
Fair Value Asset	$ 0
Fair Value Liability	$ 1,563
Crude Oil \| Fourth Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps/Put option 1
Notional Volume, per day \| bbl	8,455
Derivative, Swap Type, Average Fixed Price \| $ / bbl	47.98
Fair Value Asset	$ 0
Fair Value Liability	$ 1,251
Crude Oil \| First Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,946
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.87
Fair Value Asset	$ 0
Fair Value Liability	$ 356
Crude Oil \| Second Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,921
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.87
Fair Value Asset	$ 0
Fair Value Liability	$ 307
Crude Oil \| Third Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,897
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.87
Fair Value Asset	$ 0
Fair Value Liability	$ 258
Crude Oil \| Fourth Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,898
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.87
Fair Value Asset	$ 0
Fair Value Liability	$ 231

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.

+ References

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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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