Summary Of Significant Accounting Policies (Average Depreciation Depletion And Amortization Rates) (Details) (USD $)	12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010
Oil And Gas Producing Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation depletion and amortization rate per Mcfe	$ 2.19		$ 2.12		$ 2.10
Utility [Member]
Summary Of Significant Accounting Policies [Line Items]
Average depreciation, depletion and amortization rates	2.60%		2.60%		2.60%
Pipeline And Storage [Member]
Summary Of Significant Accounting Policies [Line Items]
Average depreciation, depletion and amortization rates	2.90%		3.10%		3.00%
Exploration And Production [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation depletion and amortization rate per Mcfe	$ 2.25	[1]	$ 2.17	[1]	$ 2.14	[1]
Energy Marketing [Member]
Summary Of Significant Accounting Policies [Line Items]
Average depreciation, depletion and amortization rates	3.60%		2.50%		2.90%
All Other And Corporate [Member]
Summary Of Significant Accounting Policies [Line Items]
Average depreciation, depletion and amortization rates	1.80%		1.30%		6.80%

[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 Properties, depletion of oil and gas producing properties amounted to $2.19, $2.12 and $2.10 per Mcfe of production in 2012, 2011 and 2010, respectively.