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Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions (Detail) bbl in Thousands, MMBTU in Thousands, $ in Thousands | Sep. 30, 2019 USD ($) MMBTU bbl | Dec. 31, 2018 USD ($) MMBTU bbl
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Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member] |  |
Derivative Instruments [Line Items] |  |
Oil/Natural Gas Derivative Assets, Notional Amount | bbl | 2,280 | 2,416
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl | 727 | 415
Oil/Natural Gas Derivative Assets, Estimated Fair Value | $ 12,884 | $ 24,332
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value | $ (1,363) | $ (646)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member] |  |
Derivative Instruments [Line Items] |  |
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU | 8,716 | 5,745
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU | 3,439 | 9,314
Oil/Natural Gas Derivative Assets, Estimated Fair Value | $ 2,053 | $ 417
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value | $ (191) | $ (1,272)
Customer Counterparties [Member] | Oil Commodity Derivative [Member] |  |
Derivative Instruments [Line Items] |  |
Oil/Natural Gas Derivative Assets, Notional Amount | bbl | 730 | 415
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl | 2,277 | 2,416
Oil/Natural Gas Derivative Assets, Estimated Fair Value | $ 1,392 | $ 646
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value | $ (12,572) | $ (24,009)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member] |  |
Derivative Instruments [Line Items] |  |
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU | 3,543 | 10,236
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU | 8,613 | 4,823
Oil/Natural Gas Derivative Assets, Estimated Fair Value | $ 205 | $ 1,373
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value | $ (1,960) | $ (393)

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