Retirement Plan And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 2,928	$ 3,012	$ 5,855	$ 6,024
Interest Cost		10,579	10,304	21,158	20,608
Expected Return on Plan Assets		(14,842)	(14,904)	(29,685)	(29,808)
Amortization of Prior Service Cost (Credit)		308	46	617	92
Amortization of Losses		8,062	9,032	16,124	18,065
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	5,609	7,055	7,516	8,346
Net Periodic Benefit Cost		12,644	14,545	21,585	23,327
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		583	673	1,166	1,346
Interest Cost		5,096	4,821	10,193	9,642
Expected Return on Plan Assets		(7,883)	(8,522)	(15,768)	(17,044)
Amortization of Prior Service Cost (Credit)		(228)	(478)	(456)	(956)
Amortization of Losses		1,382	1,037	2,765	2,074
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	[1]	6,599	7,396	10,720	12,316
Net Periodic Benefit Cost		$ 5,549	$ 4,927	$ 8,620	$ 7,378

[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.