Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2019 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ 1,739
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	(1,739)
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	1,645
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	(1,645)
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	94
Amount of Gain or (Loss) on the Hedged Item Recognized in the Consolidated Statement of Income	$ (94)