Derivative Instruments - Financial Instruments for Hedging Volume (Detail)	Dec. 31, 2018 MMBTU USD ($) $ / unit bbl
2019 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Oil (Bbls) | bbl	6,704,184
Weighted Average Price, Hedge Backed Oil Volumes | $	58.85
Natural Gas (MMbtu) | MMBTU	3,050,000
Weighted Average Price, Hedge Backed Gas Volumes | $	2.46
2020 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Oil (Bbls) | bbl	2,469,000
Weighted Average Price, Hedge Backed Oil Volumes | $	60.79
Natural Gas (MMbtu) | MMBTU	0
Weighted Average Price, Hedge Backed Gas Volumes | $	0.00
Crude Oil [Member] | Cashless Collars [Domain] | 2019 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Oil (Bbls) | bbl	552,000
Derivative, Average Floor Price | $ / unit	55.00
Derivative, Average Ceiling Price | $ / unit	77.56
Natural Gas [Member] | Cashless Collars [Domain] | 2019 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Natural Gas (MMbtu) | MMBTU	225,000
Derivative, Average Floor Price | $ / unit	3.25
Derivative, Average Ceiling Price | $ / unit	4.45