Financial Instruments (Schedule Of Derivatives And Hedged Items In Fair Value Hedging Relationships) (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2016 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	$ 12,303
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	(12,303)
Operating Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	12,683
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	(12,683)
Purchased Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) on Derivative Recognized in the Consolidated Statement of Income	(380)
Amount of Gain or (Loss) on Hedged Item Recognized in the Consolidated Statement of Income	$ 380