Derivative Activities - Derivative Volumes Hedged and Average Hedge Prices (Detail)	Dec. 31, 2017 MMBTU / d bbl / d $ / MMBTU $ / bbl $ / gal
2018 Commodity Contract | Swaps | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	794,822
Weighted Average Hedge Price | $ / MMBTU	3.13
2018 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged	8,995
Weighted Average Hedge Price | $ / bbl	53.30
2018 Commodity Contract | Swaps | NGLs (C2-Ethane)
Derivative [Line Items]
Volume Hedged	250
Weighted Average Hedge Price | $ / gal	0.29
2018 Commodity Contract | Swaps | NGLs (C3-Propane)
Derivative [Line Items]
Volume Hedged	10,362
Weighted Average Hedge Price | $ / gal	0.68
2018 Commodity Contract | Swaps | NGLs (NC4-Normal Butane)
Derivative [Line Items]
Volume Hedged	4,621
Weighted Average Hedge Price | $ / gal	0.81
2018 Commodity Contract | Swaps | NGLs (C5-Natural Gasoline)
Derivative [Line Items]
Volume Hedged	4,713
Weighted Average Hedge Price | $ / gal	1.19
2018 Commodity Contract | Collars | NGLs (C3-Propane)
Derivative [Line Items]
Volume Hedged	2,000
Weighted Average Floor Price | $ / gal	0.90
Weighted Average Cap Price | $ / gal	1.05
2019 Commodity Contract | Swaps | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	12,329
Weighted Average Hedge Price | $ / MMBTU	3.01
2019 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged	4,746
Weighted Average Hedge Price | $ / bbl	52.81
2019 Commodity Contract | Swaps | NGLs (C5-Natural Gasoline)
Derivative [Line Items]
Volume Hedged	1,000
Weighted Average Hedge Price | $ / gal	1.24
2019 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	85,000
Weighted Average Hedge Price | $ / MMBTU	2.97	[1]
January−March 2018 Commodity Contract | Collars | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	60,000
Weighted Average Floor Price | $ / MMBTU	3.40
Weighted Average Cap Price | $ / MMBTU	3.76
April-December 2018 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	307,500
Weighted Average Hedge Price | $ / MMBTU	2.98	[1]

[1] Contains a combined derivative instrument consisting of a fixed price swap and a sold option to extend or double the volume. For April through December 2018, we have swaps in place for 147,500 Mmbtu per day on which the counterparty can elect to double the volume at a weighted average price of $2.89. We also have swaps in place for 160,000 Mmbtu per day on which the counterparty can elect to extend the contract through December 2019 at a weighted average price of $3.07. In 2019, if the counterparty elects to double the volume, we would have additional swaps covering 85,000 Mmbtu per day at a weighted average price of $2.97.