Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 29,118	$ 60,860
Reserve for Gas Replacement	6,302	33,669
Liability for Royalty and Working Interests	41,143	31,483
Other Accruals and Current Liabilities	218,139	194,169
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	41,216	42,541
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	43,752	0
Other Accruals [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	47,351	43,723
Federal [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Payable	151	154
Non-Qualified [Member] | Current [Member]
Summary Of Significant Accounting Policies [Line Items]
Non-Qualified Benefit Plan Liability	$ 15,408	$ 15,408