Retirement Plan And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,330	$ 2,120
Interest Cost		7,483	9,594
Expected Return on Plan Assets		(15,016)	(15,591)
Amortization of Prior Service Cost (Credit)		182	206
Amortization of Losses		9,846	8,024
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	1,527	819
Net Periodic Benefit Cost		6,352	5,172
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		402	380
Interest Cost		3,228	4,286
Expected Return on Plan Assets		(7,308)	(7,539)
Amortization of Prior Service Cost (Credit)		(107)	(107)
Amortization of Losses		134	1,490
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	6,249	3,971
Net Periodic Benefit Cost		$ 2,598	$ 2,481

[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.