Commodity Derivative Positions (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) bbl $ / bbl
Settlement Agreement [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 1,721
Crude Oil \| Second Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,421
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.48
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 3,361
Crude Oil \| Third Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,397
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.50
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 3,430
Crude Oil \| Fourth Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,398
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.50
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 3,130
Crude Oil \| First Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.09
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 2,904
Crude Oil \| Second Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.09
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 2,369
Crude Oil \| Third Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.09
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 1,898
Crude Oil \| Fourth Quarter 2020 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-WTI
Derivative, Nonmonetary Notional Amount \| bbl	6,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	54.09
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 1,518
Louisiana Light Sweet [Member] \| Second Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-LLS
Derivative, Nonmonetary Notional Amount \| bbl	5,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	59.17
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 3,109
Louisiana Light Sweet [Member] \| Third Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-LLS
Derivative, Nonmonetary Notional Amount \| bbl	5,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	59.17
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 2,592
Louisiana Light Sweet [Member] \| Fourth Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative, Type of Instrument	Swaps-LLS
Derivative, Nonmonetary Notional Amount \| bbl	5,000
Derivative, Swap Type, Average Fixed Price \| $ / bbl	59.17
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 1,995

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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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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