Summary Of Significant Accounting Policies (Average Depreciation Depletion And Amortization Rates) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciation depletion and amortization rate per Mcfe	[1]	$ 0.71	$ 0.73	$ 0.70
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.40%	2.20%	2.20%
Gathering [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.20%	3.60%	3.40%
Utility [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.70%	2.70%	2.80%
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.60%	1.80%	2.40%
Oil And Gas Producing Properties [Member]
Segment Reporting Information [Line Items]
Depreciation depletion and amortization rate per Mcfe		$ 0.69	$ 0.71	$ 0.67

[1] Amounts include depletion of oil and gas producing properties as well as depreciation of fixed assets. As disclosed in Note O — Supplementary Information for Oil and Gas Producing Activities, depletion of oil and gas producing properties amounted to $0.69, $0.71 and $0.67 per Mcfe of production in 2020, 2019 and 2018, respectively.