Supplementary Information on Oil, Ngl and Natural Gas Reserves (Unaudited) (Details 2)	12 Months Ended
	Sep. 30, 2012 bbl	Sep. 30, 2011 bbl	Sep. 30, 2010 bbl
Oil (Barrels) [Member]
Estimated Quantities of Proved Oil and Natural Gas Reserves
Proved Oil and Natural Gas Reserves, Beginning Balance	843,738	925,009	920,873
Revisions of previous estimates	8,627	(59,360)	47,999
Divestitures			(487)
Acquisitions
Extensions and discoveries and other additions	373,097	82,230	59,003
Production	(153,143)	(104,141)	(102,379)
Proved Oil and Natural Gas Reserves, Ending Balance	1,072,319	843,738	925,009
NGL (Barrels) [Member]
Estimated Quantities of Proved Oil and Natural Gas Reserves
Proved Oil and Natural Gas Reserves, Beginning Balance	791,648
Revisions of previous estimates	(76,794)	791,648
Divestitures
Acquisitions
Extensions and discoveries and other additions	172,602
Production	(98,714)
Proved Oil and Natural Gas Reserves, Ending Balance	788,742	791,648
Natural Gas (Mcf) [Member]
Estimated Quantities of Proved Oil and Natural Gas Reserves
Proved Oil and Natural Gas Reserves, Beginning Balance	101,837,984	98,170,455	54,027,810
Revisions of previous estimates	(27,389,752)	769,676	15,762,883
Divestitures			(7,778)
Acquisitions	19,075,529	3,189,520
Extensions and discoveries and other additions	29,062,593	8,005,990	36,689,882
Production	(9,072,298)	(8,297,657)	(8,302,342)
Proved Oil and Natural Gas Reserves, Ending Balance	113,514,056	101,837,984	98,170,455