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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,120	$ 2,480	$ 6,362	$ 7,441
Interest Cost		9,594	8,252	28,783	24,754
Expected Return on Plan Assets		(15,591)	(15,429)	(46,775)	(46,286)
Amortization of Prior Service Cost (Credit)		206	235	619	703
Amortization of Losses		8,024	9,301	24,072	27,904
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	(113)	712	5,490	8,926
Net Periodic Benefit Cost		4,240	5,551	18,551	23,442
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		380	458	1,140	1,373
Interest Cost		4,286	3,700	12,858	11,101
Expected Return on Plan Assets		(7,539)	(7,871)	(22,618)	(23,612)
Amortization of Prior Service Cost (Credit)		(107)	(107)	(321)	(322)
Amortization of Losses		1,490	2,639	4,471	7,918
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	3,757	3,386	14,294	13,243
Net Periodic Benefit Cost		$ 2,267	$ 2,205	$ 9,824	$ 9,701

[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.