Summary Of Significant Accounting Policies (Schedule Of Depreciable Plant By Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Depreciable plant	$ 11,906,360	$ 10,788,616
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Depreciable plant	6,384,086	5,747,731
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Depreciable plant	2,418,265	2,191,166
Gathering [Member]
Segment Reporting Information [Line Items]
Depreciable plant	849,204	577,021
Utility [Member]
Segment Reporting Information [Line Items]
Depreciable plant	2,234,433	2,159,841
All Other And Corporate [Member]
Segment Reporting Information [Line Items]
Depreciable plant	$ 20,372	$ 112,857