Supplementary Information on Oil and Gas Producing Activities (Unaudited) - Summary of the Proved Reserves (Detail)	12 Months Ended
	Dec. 31, 2014 bbl	Dec. 31, 2013 bbl
Reserve Quantities [Line Items]
Revisions of previous estimates	8.2
Oil [Member]
Reserve Quantities [Line Items]
Beginning of the period	19,073	133,735
Revisions of previous estimates	397	(1,808)
Extensions and discoveries	8	6,267
Production	(2,104)	(1,414)
Sales of minerals in place-leaseholds		(117,707)
End of period	17,374	19,073
Proved Developed Reserves, End of Year	17,374	19,073
Gas [Member]
Reserve Quantities [Line Items]
Beginning of the period	42,536,167	43,939,005
Revisions of previous estimates	2,579,426	(13,028,885)
Extensions and discoveries	40,437,710	16,916,629
Production	(6,273,384)	(3,783,427)
Purchases of minerals in place	(2,346,798)
Sales of minerals in place-leaseholds		(1,507,155)
End of period	76,933,121	42,536,167
Proved Developed Reserves, End of Year	62,489,000	42,536,167
NGL [Member]
Reserve Quantities [Line Items]
Beginning of the period	890,367	1,649,873
Revisions of previous estimates	124,580	(722,757)
Extensions and discoveries	453,816	63,537
Production	(127,530)	(100,284)
Purchases of minerals in place	(72,026)
Sales of minerals in place-leaseholds		(2)
End of period	1,269,207	890,367
Proved Developed Reserves, End of Year	1,269,207	890,367