Retirement Plan And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,330	$ 2,120	$ 6,989	$ 6,362
Interest Cost		7,483	9,594	22,448	28,783
Expected Return on Plan Assets		(15,016)	(15,591)	(45,048)	(46,775)
Amortization of Prior Service Cost (Credit)		182	206	547	619
Amortization of Losses		9,846	8,024	29,538	24,072
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	604	(113)	7,651	5,490
Net Periodic Benefit Cost		5,429	4,240	22,125	18,551
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		402	380	1,206	1,140
Interest Cost		3,228	4,286	9,685	12,858
Expected Return on Plan Assets		(7,308)	(7,539)	(21,924)	(22,618)
Amortization of Prior Service Cost (Credit)		(107)	(107)	(322)	(321)
Amortization of Losses		134	1,490	401	4,471
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	6,036	3,757	21,131	14,294
Net Periodic Benefit Cost		$ 2,385	$ 2,267	$ 10,177	$ 9,824

[1] The Company’s policy is to record retirement plan and other post-retirement benefit costs in the Utility segment on a volumetric basis to reflect the fact that the Utility segment experiences higher throughput of natural gas in the winter months and lower throughput of natural gas in the summer months.