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, 2017 USD ($) MMBTU bbl	Dec. 31, 2016 USD ($) MMBTU bbl
Financial Institution Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	977	227
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	1,082	944
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 1,530	$ 206
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (1,311)	$ (4,400)
Financial Institution Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	3,351	0
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	1,546	1,299
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 319	$ 0
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (81)	$ (1,357)
Customer Counterparties [Member] | Oil Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | bbl	1,096	944
Oil/Natural Gas Derivative Liabilities, Notional Amount | bbl	963	227
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 1,459	$ 4,580
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (1,327)	$ (206)
Customer Counterparties [Member] | Natural Gas Commodity Derivative [Member]
Derivative Instruments [Line Items]
Oil/Natural Gas Derivative Assets, Notional Amount | MMBTU	1,546	1,299
Oil/Natural Gas Derivative Liabilities, Notional Amount | MMBTU	3,351	0
Oil/Natural Gas Derivative Assets, Estimated Fair Value	$ 96	$ 1,393
Oil/Natural Gas Derivative Liabilities, Estimated Fair Value	$ (285)	$ 0