Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 50,713	$ 50,332
Reserve for Gas Replacement	(29,991)	(36,632)
Liability for Royalty and Working Interests	20,052	18,057
Other Accruals and Current Liabilities	173,603	139,600
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	59,933	33,713
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	1,100	0
Other Accruals [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	28,611	24,304
Non-Qualified [Member] | Current [Member]
Summary Of Significant Accounting Policies [Line Items]
Non-Qualified Benefit Plan Liability	$ 13,194	$ 13,194