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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,480	$ 2,992	$ 7,441	$ 8,977
Interest Cost		8,252	9,596	24,754	28,788
Expected Return on Plan Assets		(15,429)	(14,929)	(46,286)	(44,788)
Amortization of Prior Service Cost (Credit)		235	264	703	793
Amortization of Losses		9,301	10,672	27,904	32,015
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	712	(3,193)	8,926	3,577
Net Periodic Benefit Cost		5,551	5,402	23,442	29,362
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		458	612	1,373	1,837
Interest Cost		3,700	4,752	11,101	14,256
Expected Return on Plan Assets		(7,871)	(7,865)	(23,612)	(23,594)
Amortization of Prior Service Cost (Credit)		(107)	(107)	(322)	(322)
Amortization of Losses		2,639	4,604	7,918	13,811
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	3,386	1,302	13,243	6,404
Net Periodic Benefit Cost		$ 2,205	$ 3,298	$ 9,701	$ 12,392

[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.