Supplementary Information On Natural Gas, Oil And NGL Reserves (Summary of Net Quantities of Proved, Developed and Undeveloped Natural Gas Oil and NGL Reserves) (Details)	12 Months Ended
Sep. 30, 2020 Bcfe bbl Mcf	Sep. 30, 2019 Bcfe bbl Mcf	Sep. 30, 2018 Bcfe bbl Mcf
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance \| Bcfe	106.4	173.6	168.6
Revisions of previous estimates \| Bcfe	(45.9)	(60.6)	(6.7)
Acquisitions (divestitures) \| Bcfe	1.7	(3.0)	(0.2)
Extensions, discoveries and other additions \| Bcfe	4.1	6.8	24.2
Production \| Bcfe	(8.6)	(10.4)	(12.3)
Proved Natural Gas and Oil Reserves, Ending Balance \| Bcfe	57.7	106.4	173.6
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance \| Mcf	80,273,906	120,062,036	121,195,120
Revisions of previous estimates \| Mcf	(34,666,426)	(35,644,135)	(29,247)
Acquisitions (divestitures) \| Mcf	911,853	(948,496)	(1,782,949)
Extensions, discoveries and other additions \| Mcf	1,816,144	3,891,262	9,400,374
Production \| Mcf	(5,962,704)	(7,086,761)	(8,721,262)
Proved Natural Gas and Oil Reserves, Ending Balance \| Mcf	42,372,773	80,273,906	120,062,036
Oil [Member]
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance	2,380,090	5,984,422	5,509,667
Revisions of previous estimates	(1,094,923)	(3,266,351)	(1,407,995)
Acquisitions (divestitures)	57,721	(322,023)	236,690
Extensions, discoveries and other additions	260,555	313,241	1,982,624
Production	(269,786)	(329,199)	(336,564)
Proved Natural Gas and Oil Reserves, Ending Balance	1,333,657	2,380,090	5,984,422
NGL [Member]
Reserve Quantities [Line Items]
Proved Natural Gas and Oil Reserves, Beginning Balance	1,973,280	2,934,190	2,384,699
Revisions of previous estimates	(774,214)	(890,046)	303,728
Acquisitions (divestitures)	70,933	(18,881)	24,765
Extensions, discoveries and other additions	118,480	164,276	476,174
Production	(168,622)	(216,259)	(255,176)
Proved Natural Gas and Oil Reserves, Ending Balance	1,219,857	1,973,280	2,934,190

Proved developed and undeveloped reserve purchase sales of mineral in place energy.

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Proved Developed And Undeveloped Reserves Purchases Sales Of Minerals In Place

+ References

No definition available.

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- Definition

Energy measure of increase in quantity of proved reserve of oil and gas resulting from the extension of the proved acreage of previously discovered reservoir or discovery of new field with proved reserve or of new reservoir of proved reserve in old field, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447

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Energy measure of proved reserve of oil and gas, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61797-109447

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Energy measure of decrease in quantity of proved reserve of oil and gas resulting from production, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447

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Energy measure of increase (decrease) in quantity of proved reserve of oil and gas related to revision of a previous estimate resulting from new information, except for an increase in proved acreage, or change in economic factors, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447

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Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447

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The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

+ References

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- Definition

Production of proved reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447

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Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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