Supplementary Information On Natural Gas, Oil And NGL Reserves (Narrative) (Details)	12 Months Ended
	Sep. 30, 2021 $ / bbl $ / Mcf	Sep. 30, 2021 Bcfe $ / bbl $ / Mcf	Sep. 30, 2021 Mcfe $ / bbl $ / Mcf	Sep. 30, 2020 Bcfe $ / bbl $ / Mcf	Sep. 30, 2019 Bcfe $ / bbl $ / Mcf
Supplementary Oil And Gas Disclosures [Line Items]
Positive pricing revisions		28.1
Positive revisions, developed		28.7
Positive revisions, undeveloped		0.6
Negative revisions		2.1
Reserve extensions, discoveries and other additions		0.7
Proved developed reserve		0.4
Proved undeveloped reserve		0.3
Production of oil and natural gas properties		9.1		8.6	10.4
Net PUD reserves increased		2.2
Proved undeveloped reserves transferred to proved developed		2.1	2,060,368
Percentage transferred to proved developed	67.00%
Remaining revisions of proved undeveloped reserves		4.3
Revisions percentage of proved undeveloped reserves	140.00%
Negative revisions, undeveloped		0.6
Proved undeveloped reserves, additions		0.2
Oklahoma [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Proved developed sale		0.9
Additional proved undeveloped acquisition		4.6
Oil [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Price used to calculate reserves and future cash flows from reserves | $ / bbl	56.51	56.51	56.51	40.18	54.40
NGL [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Price used to calculate reserves and future cash flows from reserves | $ / bbl	20.58	20.58	20.58	9.95	19.30
Natural Gas [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Price used to calculate reserves and future cash flows from reserves | $ / Mcf	2.79	2.79	2.79	1.62	2.48
Oil, NGL And Natural Gas [Member] | East Texas, Western Louisiana, Mississippi Woodford and Oklahoma [Member]
Supplementary Oil And Gas Disclosures [Line Items]
Acquisition		8.6
Proved developed acquisition		4.0
Proved undeveloped acquisition		4.6