Derivative Activities - Derivative Volumes Hedged and Average Hedge Prices (Detail)	Sep. 30, 2016 MMBTU / d bbl / d $ / MMBTU $ / bbl $ / gal
Natural Gas | Swaps | 2016
Derivative [Line Items]
Volume Hedged | MMBTU / d	901,739	[1]
Weighted Average Hedge Price | $ / MMBTU	3.32	[1]
Natural Gas | Swaps | 2017
Derivative [Line Items]
Volume Hedged | MMBTU / d	478,192	[1]
Weighted Average Hedge Price | $ / MMBTU	3.14	[1]
Natural Gas | Swaps | 2018
Derivative [Line Items]
Volume Hedged | MMBTU / d	70,000
Weighted Average Hedge Price | $ / MMBTU	2.92
Natural Gas | Collar | 2016
Derivative [Line Items]
Volume Hedged | MMBTU / d	32,609	[1]
Weighted Average Floor Price | $ / MMBTU	4.00	[1]
Weighted Average Cap Price | $ / MMBTU	4.71	[1]
Natural Gas | Collar | 2017
Derivative [Line Items]
Volume Hedged | MMBTU / d	34,521	[1]
Weighted Average Floor Price | $ / MMBTU	4.00	[1]
Weighted Average Cap Price | $ / MMBTU	5.06	[1]
Natural Gas | Purchased Put | 2016
Derivative [Line Items]
Volume Hedged | MMBTU / d	218,478	[1]
Weighted Average Hedge Price | $ / MMBTU	3.54	[1],[2]
Natural Gas | Purchased Put | 2017
Derivative [Line Items]
Volume Hedged | MMBTU / d	175,890	[1]
Weighted Average Hedge Price | $ / MMBTU	3.48	[1],[3]
Crude Oil | Swaps | 2016
Derivative [Line Items]
Volume Hedged	8,640	[1]
Weighted Average Hedge Price | $ / bbl	69.49	[1]
Crude Oil | Swaps | 2017
Derivative [Line Items]
Volume Hedged	5,416	[1]
Weighted Average Hedge Price | $ / bbl	57.18	[1]
Crude Oil | Swaps | 2018
Derivative [Line Items]
Volume Hedged	500
Weighted Average Hedge Price | $ / bbl	54.25
Crude Oil | Collar | 2016
Derivative [Line Items]
Volume Hedged	848	[1]
Weighted Average Floor Price | $ / bbl	80.00	[1]
Weighted Average Cap Price | $ / bbl	99.70	[1]
Commodity Contract NGLs (C2 - Ethane) | Swaps | 2016
Derivative [Line Items]
Volume Hedged	5,839	[1]
Weighted Average Hedge Price | $ / gal	0.46	[1]
Commodity Contract NGLs (C2 - Ethane) | Swaps | 2017
Derivative [Line Items]
Volume Hedged	3,000
Weighted Average Hedge Price | $ / gal	0.27
Commodity Contract NGLs (C3 - Propane) | Swaps | 2016
Derivative [Line Items]
Volume Hedged	11,142	[1]
Weighted Average Hedge Price | $ / gal	0.75	[1]
Commodity Contract NGLs (C3 - Propane) | Swaps | 2017
Derivative [Line Items]
Volume Hedged	6,966
Weighted Average Hedge Price | $ / gal	0.52
Commodity Contract NGLs (iC4-isobutane) | Swaps | 2016
Derivative [Line Items]
Volume Hedged	1,969	[1]
Weighted Average Hedge Price | $ / gal	1.21	[1]
Commodity Contract NGLs (NC4 - Normal Butane) | Swaps | 2016
Derivative [Line Items]
Volume Hedged	6,071	[1]
Weighted Average Hedge Price | $ / gal	0.72	[1]
Commodity Contract NGLs (NC4 - Normal Butane) | Swaps | 2017
Derivative [Line Items]
Volume Hedged	1,500
Weighted Average Hedge Price | $ / gal	0.65
Commodity Contract NGLs (C5 - Natural Gasoline) | Swaps | 2016
Derivative [Line Items]
Volume Hedged	8,142	[1]
Weighted Average Hedge Price | $ / gal	1.36	[1]
Commodity Contract NGLs (C5 - Natural Gasoline) | Swaps | 2017
Derivative [Line Items]
Volume Hedged	2,000
Weighted Average Hedge Price | $ / gal	0.98

[1] Includes derivative instruments assumed in connection with the Memorial Merger.

[2] Weighted average deferred premium is ($0.34).

[3] Weighted average deferred premium is ($0.32).