Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2017 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ 1,744
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	(1,744)
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	1,317
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	(1,317)
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	427
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	$ (427)