Derivative Instruments - Summary of Outstanding Contracts with Respect to Natural Gas (Detail) (Natural Gas [Member])	9 Months Ended
	Sep. 30, 2014 MMBTU
October 2014 to December 2014 Swaps [Member]
Derivative [Line Items]
Natural Gas Production Derivative Volume, MMBtus	30,820,000
Swaps Weighted Average Price	4.20
January 2015 - December 2015 Swaps [Member]
Derivative [Line Items]
Natural Gas Production Derivative Volume, MMBtus	24,500,000
Swaps Weighted Average Price	4.27
January 2015 to December 2015 Collars [Member]
Derivative [Line Items]
Natural Gas Production Derivative Volume, MMBtus	29,200,000
Floors, Weighted Average Price	3.69
Ceilings, Weighted Average Price	5.04
January 2016 to December 2016 Swaps [Member]
Derivative [Line Items]
Natural Gas Production Derivative Volume, MMBtus	4,550,000
Swaps Weighted Average Price	4.27
Minimum [Member] | January 2015 to December 2015 Collars [Member]
Derivative [Line Items]
Derivative, Floor Price	3.50
Derivative, Cap Price	4.89
Maximum [Member] | January 2015 to December 2015 Collars [Member]
Derivative [Line Items]
Derivative, Floor Price	3.75
Derivative, Cap Price	5.48