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				6 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2012		Mar. 31, 2011
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,004		$ 1,069		$ 2,008		$ 2,138
Interest Cost	5,329		5,471		10,657		10,942
Expected Return on Plan Assets	(7,243)		(7,291)		(14,486)		(14,582)
Amortization of Prior Service Cost	(534)		(427)		(1,069)		(854)
Amortization of Transition Amount	3		135		5		270
Amortization of Losses	6,014		5,948		12,029		11,896
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	5,141	[1]	6,042	[1]	7,274	[1]	7,963	[1]
Net Periodic Benefit Cost	9,714		10,947		16,418		17,773
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	3,551		3,693		7,101		7,386
Interest Cost	10,381		10,669		20,763		21,338
Expected Return on Plan Assets	(14,925)		(14,776)		(29,850)		(29,552)
Amortization of Prior Service Cost	67		147		134		294
Amortization of Transition Amount	0		0		0		0
Amortization of Losses	9,904		8,718		19,807		17,437
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	2,200	[1]	3,556	[1]	399	[1]	1,762	[1]
Net Periodic Benefit Cost	$ 11,178		$ 12,007		$ 18,354		$ 18,665

[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.