Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Commodity Derivative Positions (Detail) bbl in Thousands, MMBTU in Thousands, $ in Thousands	Jun. 30, 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	1,745	2,416
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	1,135	415
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 7,880	$ 24,332
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (3,812)	$ (646)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	10,197	5,745
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	3,066	9,314
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 1,861	$ 417
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (248)	$ (1,272)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	1,205	415
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	1,675	2,416
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 3,919	$ 646
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (7,662)	$ (24,009)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	3,066	10,236
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	10,197	4,823
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 248	$ 1,373
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (1,768)	$ (393)