Retirement Plan And Other Post-Retirement Benefits (Schedule Of Benefit Obligation And Plan Assets And Funded Assets) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,004		$ 1,069
Interest Cost	5,329		5,471
Expected Return on Plan Assets	(7,243)		(7,291)
Amortization of Prior Service Cost	(534)		(427)
Amortization of Transition Amount	3		135
Amortization of Losses	6,014		5,948
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	2,132	[1]	1,921	[1]
Net Periodic Benefit Cost	6,705		6,826
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	3,551		3,693
Interest Cost	10,381		10,669
Expected Return on Plan Assets	(14,925)		(14,776)
Amortization of Prior Service Cost	67		147
Amortization of Transition Amount	0		0
Amortization of Losses	9,904		8,718
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	(1,802)	[1]	(1,793)	[1]
Net Periodic Benefit Cost	$ 7,176		$ 6,658

[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.