Derivative and Hedging Financial Instruments - Summary of Volumes and Average Contract Prices of Contracts (Detail)	Mar. 31, 2016 MMBTU $ / MMBTU	Dec. 23, 2014 $ / MMBTU	Aug. 20, 2014 $ / MMBTU
Derivative [Line Items]
Commodity contracts, Basis Swap Fixed Price/mmbtu			(4.11)
Morgan Stanley Restrike [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	9,112,190
Commodity contracts, Basis Swap Fixed Price/mmbtu			(3.92)
Morgan Stanley Restrike [Member] | 2016 [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	3,321,358
Commodity contracts, Weighted- Average Fixed Price/mmbtu	3.27
Morgan Stanley Restrike [Member] | 2017 [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	3,248,187
Commodity contracts, Weighted- Average Fixed Price/mmbtu	3.27
Morgan Stanley Restrike [Member] | 2018 [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	2,542,645
Commodity contracts, Weighted- Average Fixed Price/mmbtu	3.27
Morgan Stanley Fixed III [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	4,238,034
Commodity contracts, Basis Swap Fixed Price/mmbtu		(1.12)
Morgan Stanley Fixed III [Member] | 2016 [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	1,509,895
Commodity contracts, Basis Swap Fixed Price/mmbtu	(1.12)
Morgan Stanley Fixed III [Member] | 2017 [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	1,518,648
Commodity contracts, Basis Swap Fixed Price/mmbtu	(1.12)
Morgan Stanley Fixed III [Member] | 2018 [Member]
Derivative [Line Items]
Volumes (MMBtu) | MMBTU	1,209,491
Commodity contracts, Basis Swap Fixed Price/mmbtu	(1.12)