Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 45,338	$ 50,332
Reserve for Gas Replacement	(8,860)	(36,632)
Liability for Royalty and Working Interests	13,987	18,057
Other Accruals and Current Liabilities	150,239	139,600
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	31,886	33,713
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	23,978	0
Other Accruals [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	21,856	24,304
Non-Qualified [Member] | Current [Member]
Summary Of Significant Accounting Policies [Line Items]
Non-Qualified Benefit Plan Liability	$ 13,194	$ 13,194