Derivative Activities - Derivative Volumes Hedged and Average Hedge Prices (Detail)	Sep. 30, 2014 MMBTU
Natural Gas | Collars | 2014
Derivative [Line Items]
Volume Hedged	447,500
Average floor price	3.84
Average cap price	4.48
Natural Gas | Collars | 2015
Derivative [Line Items]
Volume Hedged	145,000
Average floor price	4.07
Average cap price	4.56
Natural Gas | Swaps | 2014
Derivative [Line Items]
Volume Hedged	260,000
Average hedge price	4.18
Natural Gas | Swaps | 2015
Derivative [Line Items]
Volume Hedged	307,432
Average hedge price	4.21
Natural Gas | Swaps | 2016
Derivative [Line Items]
Volume Hedged	90,000
Average hedge price	4.21
Crude Oil | Collars | 2014
Derivative [Line Items]
Volume Hedged	2,000
Average floor price	85.55
Average cap price	100.00
Crude Oil | Swaps | 2014
Derivative [Line Items]
Volume Hedged	9,500
Average hedge price	94.35
Crude Oil | Swaps | 2015
Derivative [Line Items]
Volume Hedged	9,626
Average hedge price	90.57
Crude Oil | Swaps | 2016
Derivative [Line Items]
Volume Hedged	1,000
Average hedge price	91.43
Commodity Contract NGLs (C3 - Propane) | Swaps | 2014
Derivative [Line Items]
Volume Hedged	12,000
Average hedge price	1.02
Commodity Contract NGLs (C3 - Propane) | Swaps | 2015 - first six months
Derivative [Line Items]
Volume Hedged	1,000
Average hedge price	1.10
Commodity Contract NGLs (NC4 - Normal Butane) | Swaps | 2014
Derivative [Line Items]
Volume Hedged	4,000
Average hedge price	1.34
Commodity Contract NGLs (C5 - Natural Gasoline) | Swaps | 2014
Derivative [Line Items]
Volume Hedged	3,500
Average hedge price	2.17
Commodity Contract NGLs (C5 - Natural Gasoline) | Swaps | 2015 - first quarter
Derivative [Line Items]
Volume Hedged	500
Average hedge price	2.14