Retirement Plan And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,120	$ 2,480
Interest Cost		9,594	8,252
Expected Return on Plan Assets		(15,591)	(15,429)
Amortization of Prior Service Cost (Credit)		206	235
Amortization of Losses		8,024	9,301
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	819	1,721
Net Periodic Benefit Cost		5,172	6,560
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		380	458
Interest Cost		4,286	3,700
Expected Return on Plan Assets		(7,539)	(7,871)
Amortization of Prior Service Cost (Credit)		(107)	(107)
Amortization of Losses		1,490	2,639
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	3,971	3,608
Net Periodic Benefit Cost		$ 2,481	$ 2,427

[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.