Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 34,552	$ 14,725
Reserve for Gas Replacement	(17,793)	(34,332)
Other	34,180	32,909
Other Accruals and Current Liabilities	107,101	74,430
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	28,129	26,796
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	7,667	0
Federal [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Payable	$ 2,573	$ 0