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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,928	$ 3,012	$ 8,783	$ 9,036
Interest Cost		10,579	10,304	31,736	30,913
Expected Return on Plan Assets		(14,842)	(14,904)	(44,527)	(44,712)
Amortization of Prior Service Cost (Credit)		308	46	925	137
Amortization of Losses		8,062	9,032	24,186	27,097
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	14	88	7,531	8,434
Net Periodic Benefit Cost		7,049	7,578	28,634	30,905
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		583	673	1,748	2,019
Interest Cost		5,096	4,821	15,289	14,464
Expected Return on Plan Assets		(7,883)	(8,522)	(23,651)	(25,566)
Amortization of Prior Service Cost (Credit)		(228)	(478)	(684)	(1,435)
Amortization of Losses		1,382	1,037	4,147	3,111
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	3,936	4,739	14,657	17,055
Net Periodic Benefit Cost		$ 2,886	$ 2,270	$ 11,506	$ 9,648

[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.