Supplementary Information On Oil, NGL And Natural Gas Reserves (Narrative) (Details)	12 Months Ended
	Sep. 30, 2017 Mcfe Item $ / bbl $ / Mcf	Sep. 30, 2016 Mcfe $ / bbl $ / Mcf	Sep. 30, 2015 $ / bbl $ / Mcf
Supplementary Oil And Gas Disclosures [Line Items]
Positive pricing revisions	17,900,000
Positive revisions, developed	17,300,000
Positive revisions, undeveloped	600,000
Negative performance revisions result of selling marginal wells	300,000
Proved developed reserve extensions, discoveries and other additions	9,900,000
Proved undeveloped reserves, additions	29,100,000
Proved undeveloped Reserves	56,880,555	42,634,659
Proved undeveloped reserves transferred to proved developed	15,670,848
Percentage transferred to proved developed	37.00%
Revisions of proved undeveloped reserves	819,338
Revisions percentage of proved undeveloped reserves	2.00%
Oklahoma [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Divestiture of marginal properties	1,000,000
Anadarko Woodford Shale in Canadian County, Oklahoma [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Number of wells participated | Item	6
Oil [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Price used to calculate reserves and future cash flows from reserves | $ / bbl	46.31	36.77	55.27
Natural Gas Liquids [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Price used to calculate reserves and future cash flows from reserves | $ / bbl	17.55	12.22	19.10
Natural Gas [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Price used to calculate reserves and future cash flows from reserves | $ / Mcf	2.81	1.97	2.84