Derivative Activities - Derivative Volumes Hedged and Average Hedge Prices (Detail)	Jun. 30, 2018 MMBTU / d bbl / d $ / MMBTU $ / bbl $ / gal
2018 Commodity Contract | Swaps | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	1,246,739
Weighted Average Hedge Price | $ / MMBTU	2.96
2018 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged	8,500
Weighted Average Hedge Price | $ / bbl	53.20
2018 Commodity Contract | Swaps | NGLs (C3-Propane)
Derivative [Line Items]
Volume Hedged	10,918
Weighted Average Hedge Price | $ / gal	0.71
2018 Commodity Contract | Swaps | NGLs (NC4-Normal Butane)
Derivative [Line Items]
Volume Hedged	4,250
Weighted Average Hedge Price | $ / gal	0.81
2018 Commodity Contract | Swaps | NGLs (C5-Natural Gasoline)
Derivative [Line Items]
Volume Hedged	5,152
Weighted Average Hedge Price | $ / gal	1.23
2018 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	160,000
Weighted Average Hedge Price | $ / MMBTU	3.07	[1]
2019 Commodity Contract | Swaps | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	514,589
Weighted Average Hedge Price | $ / MMBTU	2.81
2019 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged	6,624
Weighted Average Hedge Price | $ / bbl	54.57
2019 Commodity Contract | Swaps | NGLs (C5-Natural Gasoline)
Derivative [Line Items]
Volume Hedged	1,244
Weighted Average Hedge Price | $ / gal	1.30
2019 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	317,945
Weighted Average Hedge Price | $ / MMBTU	2.86	[1]
October-December 2018 Commodity Contract | Calls | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	70,000
Weighted Average Hedge Price | $ / MMBTU	3.10	[2]
2020 Commodity Contract | Swaptions | Natural Gas
Derivative [Line Items]
Volume Hedged | MMBTU / d	10,000
Weighted Average Hedge Price | $ / MMBTU	2.75	[1]
July-September 2018 Commodity Contract | Swaps | NGLs (C2-Ethane)
Derivative [Line Items]
Volume Hedged	1,000
Weighted Average Hedge Price | $ / gal	0.30
January-March 2019 Commodity Contract | Collars | Crude Oil
Derivative [Line Items]
Volume Hedged	250
January-March 2019 Commodity Contract | Collars | Crude Oil | Minimum
Derivative [Line Items]
Weighted Average Hedge Price | $ / bbl	63.00
January-March 2019 Commodity Contract | Collars | Crude Oil | Maximum
Derivative [Line Items]
Weighted Average Hedge Price | $ / bbl	73.00
January-June 2020 Commodity Contract | Swaps | Crude Oil
Derivative [Line Items]
Volume Hedged	1,000
Weighted Average Hedge Price | $ / bbl	57.00

[1] Contains a combined derivative instrument consisting of a fixed price swap and a sold option to extend or double the volume. For July through December of 2018, we 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. We have swaps in place for 2019 for 220,000 Mmbtu/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 2019 for 130,000 Mmbtu per day on which the counterparty can elect to extend the contract through December 2020 at a weighted average price of $2.81. For 2020, we have swaps in place for 10,000 Mmbtu/day on which the counterparty can elect to double the volume at a weighted average price of $2.75.

[2] Weighted average deferred premium of $0.16.