Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 38,499	$ 31,293
Reserve for Gas Replacement	13,047	32,364
Liability for Royalty and Working Interests	15,754	86,206
Other Accruals and Current Liabilities	260,897	257,327
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	51,078	64,720
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	86,509	0
Other Accruals [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	51,583	57,634
Non-Qualified [Member] | Current [Member]
Summary Of Significant Accounting Policies [Line Items]
Non-Qualified Benefit Plan Liability	$ 17,474	$ 17,474