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, 2013		Mar. 31, 2012		Mar. 31, 2013		Mar. 31, 2012
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 3,961		$ 3,551		$ 7,923		$ 7,101
Interest Cost	9,124		10,381		18,249		20,763
Expected Return on Plan Assets	(14,336)		(14,925)		(28,673)		(29,850)
Amortization of Prior Service Cost	60		67		119		134
Amortization of Transition Amount	0		0		0		0
Amortization of Losses	13,194		9,904		26,388		19,807
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	1,724	[1]	2,200	[1]	(1,958)	[1]	399	[1]
Net Periodic Benefit Cost	13,727		11,178		22,048		18,354
Other Post-Retirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1,176		1,004		2,352		2,008
Interest Cost	4,803		5,329		9,606		10,657
Expected Return on Plan Assets	(8,218)		(7,243)		(16,436)		(14,486)
Amortization of Prior Service Cost	(534)		(534)		(1,069)		(1,069)
Amortization of Transition Amount	2		3		4		5
Amortization of Losses	5,223		6,014		10,446		12,029
Net Amortization and Deferral For Regulatory Purposes (Including Volumetric Adjustments)	6,459	[1]	5,141	[1]	9,162	[1]	7,274	[1]
Net Periodic Benefit Cost	$ 8,911		$ 9,714		$ 14,065		$ 16,418

[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.