Summary Of Significant Accounting Policies (Schedule Of Depreciable Plant By Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Depreciable plant	$ 9,570,679	$ 9,167,865
Utility [Member]
Segment Reporting Information [Line Items]
Depreciable plant	2,045,074	1,998,605
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Depreciable plant	2,002,736	1,956,708
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciable plant	4,925,409	4,645,226
Energy Marketing [Member]
Segment Reporting Information [Line Items]
Depreciable plant	3,564	3,528
Gathering [Member]
Segment Reporting Information [Line Items]
Depreciable plant	484,768	454,343
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Depreciable plant	$ 109,128	$ 109,455