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				9 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,004		$ 1,069		$ 3,012		$ 3,207
Interest Cost	5,329		5,471		15,986		16,413
Expected Return on Plan Assets	(7,243)		(7,291)		(21,728)		(21,873)
Amortization of Prior Service Cost	(534)		(427)		(1,604)		(1,282)
Amortization of Transition Amount	3		135		8		405
Amortization of Losses	6,014		5,948		18,043		17,845
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	718	[1]	1,602	[1]	7,993	[1]	9,564	[1]
Net Periodic Benefit Cost	5,291		6,507		21,710		24,279
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	3,551		3,693		10,652		11,079
Interest Cost	10,381		10,669		31,144		32,007
Expected Return on Plan Assets	(14,925)		(14,776)		(44,776)		(44,328)
Amortization of Prior Service Cost	67		147		202		441
Amortization of Transition Amount	0		0		0		0
Amortization of Losses	9,904		8,718		29,711		26,155
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	(2,252)	[1]	(2,346)	[1]	(1,896)	[1]	(584)	[1]
Net Periodic Benefit Cost	$ 6,726		$ 6,105		$ 25,037		$ 24,770

[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.