Annual report pursuant to Section 13 and 15(d)

Commodity Derivative Positions (Detail)

v3.10.0.1
Commodity Derivative Positions (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2018
USD ($)
bbl
Entity
$ / bbl
Fourth Quarter 2019 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,398
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.50
Fair Value Asset $ 3,498
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
Fourth Quarter 2019 [Member] | Louisiana Light Sweet [Member]  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 5,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 59.17
Fair Value Asset $ 3,015
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-LLS
Fourth Quarter 2020 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.09
Fair Value Asset $ 2,234
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
Third Quarter 2019 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,397
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.50
Fair Value Asset $ 3,821
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
Third Quarter 2019 [Member] | Louisiana Light Sweet [Member]  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 5,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 59.17
Fair Value Asset $ 3,092
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-LLS
Third Quarter 2020 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.09
Fair Value Asset $ 2,450
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
Second Quarter 2019 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,421
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.48
Fair Value Asset $ 4,307
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
Second Quarter 2019 [Member] | Louisiana Light Sweet [Member]  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 5,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 59.17
Fair Value Asset $ 3,203
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-LLS
Second Quarter 2020 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.09
Fair Value Asset $ 2,609
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
First Quarter 2019 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,446
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.46
Fair Value Asset $ 4,959
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
First Quarter 2019 [Member] | Louisiana Light Sweet [Member]  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 5,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 59.17
Fair Value Asset $ 3,684
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-LLS
First Quarter 2020 [Member] | Crude Oil  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Derivative, Nonmonetary Notional Amount | bbl 6,000
Derivative, Swap Type, Average Fixed Price | $ / bbl 54.09
Fair Value Asset $ 2,807
Fair Value Liability $ 0
Derivative, Type of Instrument Swaps-WTI
Commodity contracts  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Number Of Derivative Counterparty | Entity 8
Settlement Agreement [Member]  
Derivative Instruments Related to Oil and Gas Production [Line Items]  
Fair Value Asset $ 4,362