Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 38,920	$ 34,059
Reserve for Gas Replacement	(24,139)	(35,689)
Other	37,761	38,673
Other Accruals and Current Liabilities	121,596	111,889
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	28,488	37,382
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	1,739	0
Federal [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Payable	8,688	1,775
2017 Tax Reform Act Refund [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	$ 6,000	$ 0