Summary Of Significant Accounting Policies (Average Depreciation Depletion And Amortization Rates) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciation depletion and amortization rate per Mcfe	[1]	$ 0.56	$ 0.71	$ 0.73
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.60%	2.40%	2.20%
Gathering [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.60%	3.20%	3.60%
Utility [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.70%	2.70%	2.70%
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.40%	3.60%	1.80%
Oil And Gas Producing Properties [Member]
Segment Reporting Information [Line Items]
Depreciation depletion and amortization rate per Mcfe		$ 0.54	$ 0.69	$ 0.71

[1] Amounts include depletion of oil and gas producing properties as well as depreciation of fixed assets. As disclosed in Note N — Supplementary Information for Oil and Gas Producing Activities, depletion of oil and gas producing properties amounted to $0.54, $0.69 and $0.71 per Mcfe of production in 2021, 2020 and 2019, respectively.