Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions (Detail) bbl in Thousands, MMBTU in Thousands, $ in Thousands	Mar. 31, 2019 USD ($) MMBTU bbl	Dec. 31, 2018 USD ($) MMBTU bbl
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	1,520	2,416
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	1,546	415
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 5,495	$ 24,332
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (6,882)	$ (646)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	4,061	5,745
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	10,630	9,314
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 438	$ 417
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (910)	$ (1,272)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	1,650	415
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	1,416	2,416
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 7,044	$ 646
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (5,377)	$ (24,009)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	10,660	10,236
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	4,031	4,823
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 1,025	$ 1,373
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (433)	$ (393)