Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2018 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ (1,527)
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	1,527
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	(1,289)
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	1,289
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	(238)
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	$ 238