Supplementary Information on Oil and Gas Producing Activities (Unaudited) - Summary of the Proved Reserves (Detail)	12 Months Ended
	Dec. 31, 2013 bbl	Dec. 31, 2012 bbl
Reserve Quantities [Line Items]
Revisions of previous estimates	8.2
Oil [Member]
Reserve Quantities [Line Items]
Beginning of the period	133,735	163,906
Revisions of previous estimates	(1,808)	(20,749)
Extensions and discoveries	6,267	6,740
Improved recovery Production	(1,414)	(16,162)
Purchases of minerals in place
Sales of minerals in place-leaseholds	(117,707)
End of period	19,073	133,735
Proved Developed Reserves, End of Year	19,073	129,468
Gas [Member]
Reserve Quantities [Line Items]
Beginning of the period	43,939,005	16,695,133
Revisions of previous estimates	(13,028,885)	838,105
Extensions and discoveries	16,916,629	29,356,710
Improved recovery Production	(3,783,427)	(2,950,943)
Purchases of minerals in place
Sales of minerals in place-leaseholds	(1,507,155)
End of period	42,536,167	43,939,005
Proved Developed Reserves, End of Year	42,536,167	28,072,921
NGL [Member]
Reserve Quantities [Line Items]
Beginning of the period	1,649,873	559,389
Revisions of previous estimates	(722,757)	224,307
Extensions and discoveries	63,537	976,248
Improved recovery Production	(100,284)	(110,071)
Purchases of minerals in place
Sales of minerals in place-leaseholds	(2)
End of period	890,367	1,649,873
Proved Developed Reserves, End of Year	890,367	1,037,577