Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 41,409	$ 34,059
Reserve for Gas Replacement	(6,842)	(35,689)
Other	33,672	38,673
Other Accruals and Current Liabilities	147,549	111,889
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	26,800	37,382
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	34,332	0
Federal [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Payable	0	1,775
2017 Tax Reform Act Regulatory Refund [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	$ 11,336	$ 0