Retirement Plan And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2015		Mar. 31, 2014
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 3,012		$ 2,997		$ 6,024		$ 5,993
Interest Cost	10,304		10,893		20,608		21,787
Expected Return on Plan Assets	(14,904)		(14,993)		(29,808)		(29,986)
Amortization of Prior Service Cost (Credit)	46		52		92		105
Amortization of Losses	9,032		9,002		18,065		18,003
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	7,055	[1]	8,557	[1]	8,346	[1]	10,135	[1]
Net Periodic Benefit Cost	14,545		16,508		23,327		26,037
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	673		735		1,346		1,469
Interest Cost	4,821		5,327		9,642		10,654
Expected Return on Plan Assets	(8,522)		(9,356)		(17,044)		(18,712)
Amortization of Prior Service Cost (Credit)	(478)		(534)		(956)		(1,069)
Amortization of Losses	1,037		661		2,074		1,323
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	7,396	[1]	7,928	[1]	12,316	[1]	13,988	[1]
Net Periodic Benefit Cost	$ 4,927		$ 4,761		$ 7,378		$ 7,653

[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.