Summary Of Significant Accounting Policies (Schedule Of Depreciable Plant By Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Depreciable plant	$ 9,167,865	$ 8,575,493
Utility [Member]
Segment Reporting Information [Line Items]
Depreciable plant	1,998,605	1,888,489
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Depreciable plant	1,956,708	1,710,947
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciable plant	4,645,226	4,556,096
Energy Marketing [Member]
Segment Reporting Information [Line Items]
Depreciable plant	3,528	3,494
Gathering [Member]
Segment Reporting Information [Line Items]
Depreciable plant	454,343	307,274
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Depreciable plant	$ 109,455	$ 109,193