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
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)