Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ (1,616)
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	1,616
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	(1,753)
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	1,753
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	137
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	$ (137)