Derivative Activities - Derivative Volumes Hedged and Average Hedge Prices (Detail)	Dec. 31, 2018 MMBTU / d bbl / d $ / MMBTU $ / bbl $ / gal
2019 Commodity Contract | Swaps | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	1,318,041
Weighted Average Hedge Price | $ / MMBTU	2.86
2019 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged | bbl / d	7,000
Weighted Average Hedge Price | $ / bbl	55.26
2019 Commodity Contract | Swaps | NGLs (C5-Natural Gasoline)
Derivative [Line Items]
Volume Hedged | bbl / d	2,429
Weighted Average Hedge Price | $ / gal	1.44
2019 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	113,014
Weighted Average Hedge Price | $ / MMBTU	2.81	[1]
2019 Commodity Contract | Collars | Crude Oil
Derivative [Line Items]
Volume Hedged | bbl / d	1,000
2019 Commodity Contract | Collars | Crude Oil | Minimum
Derivative [Line Items]
Weighted Average Hedge Price | $ / gal	63.00
2019 Commodity Contract | Collars | Crude Oil | Maximum
Derivative [Line Items]
Weighted Average Hedge Price | $ / gal	73.03
2020 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged | bbl / d	1,562
Weighted Average Hedge Price | $ / bbl	61.05
2020 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	80,000
Weighted Average Hedge Price | $ / MMBTU	2.77	[1]
January-June, 2019 Commodity Contract | Swaps | NGLs (C3-Propane)
Derivative [Line Items]
Volume Hedged | bbl / d	8,500
Weighted Average Hedge Price | $ / gal	0.92
January-June, 2019 Commodity Contract | Collars | NGLs (C3-Propane)
Derivative [Line Items]
Volume Hedged | bbl / d	3,983
January-June, 2019 Commodity Contract | Collars | NGLs (C3-Propane) | Minimum
Derivative [Line Items]
Weighted Average Hedge Price | $ / gal	0.92
January-June, 2019 Commodity Contract | Collars | NGLs (C3-Propane) | Maximum
Derivative [Line Items]
Weighted Average Hedge Price | $ / gal	1.02
January-March, 2019 Commodity Contract | Swaps | NGLs (NC4-Normal Butane)
Derivative [Line Items]
Volume Hedged | bbl / d	2,250
Weighted Average Hedge Price | $ / gal	1.22

[1] Contains a combined derivative instrument consisting of a fixed price swap and a sold option to extend or double the volume. In 2019, we have swaps in place for 150,000 Mmbtu per day on which the counterparty can elect to extend the contract through December 2020 at a weighted average price of $2.81. In 2020, if the counterparty elects to double the volume, we would have additional swaps covering 80,000 Mmbtu per day at a weighted average price of $2.77.