Summary Of Significant Accounting Policies (Schedule Of Depreciable Plant By Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Depreciable plant	$ 10,076,671	$ 9,570,679
Utility [Member]
Segment Reporting Information [Line Items]
Depreciable plant	2,104,437	2,045,074
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Depreciable plant	2,110,714	2,002,736
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciable plant	5,222,037	4,925,409
Energy Marketing [Member]
Segment Reporting Information [Line Items]
Depreciable plant	3,604	3,564
Gathering [Member]
Segment Reporting Information [Line Items]
Depreciable plant	527,188	484,768
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Depreciable plant	$ 108,691	$ 109,128