Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2019 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ (3,267)
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	3,267
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	(3,507)
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	3,507
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	240
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	$ (240)