Summary Of Significant Accounting Policies (Average Depreciation Depletion And Amortization Rates) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciation depletion and amortization rate per Mcfe	[1]	$ 0.73	$ 0.70	$ 0.65
Utility [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.70%	2.80%	2.80%
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		2.20%	2.20%	2.20%
Gathering [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		3.60%	3.40%	3.40%
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Average depreciation, depletion and amortization rates		1.80%	2.40%	1.50%
Oil And Gas Producing Properties [Member]
Segment Reporting Information [Line Items]
Depreciation depletion and amortization rate per Mcfe		$ 0.71	$ 0.67	$ 0.63

[1] Amounts include depletion of oil and gas producing properties as well as depreciation of fixed assets. As disclosed in Note M — Supplementary Information for Oil and Gas Producing Activities, depletion of oil and gas producing properties amounted to $0.71, $0.67 and $0.63 per Mcfe of production in 2019, 2018 and 2017, respectively.