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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,992	$ 2,928	$ 8,977	$ 8,783
Interest Cost		9,596	10,579	28,788	31,736
Expected Return on Plan Assets		(14,929)	(14,842)	(44,788)	(44,527)
Amortization of Prior Service Cost (Credit)		264	308	793	925
Amortization of Losses		10,672	8,062	32,015	24,186
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	(3,193)	14	3,577	7,531
Net Periodic Benefit Cost		5,402	7,049	29,362	28,634
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		612	583	1,837	1,748
Interest Cost		4,752	5,096	14,256	15,289
Expected Return on Plan Assets		(7,865)	(7,883)	(23,594)	(23,651)
Amortization of Prior Service Cost (Credit)		(107)	(228)	(322)	(684)
Amortization of Losses		4,604	1,382	13,811	4,147
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	1,302	3,936	6,404	14,657
Net Periodic Benefit Cost		$ 3,298	$ 2,886	$ 12,392	$ 11,506

[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.