Summary Of Significant Accounting Policies (Reclassification Out Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating Revenues	$ 523,909	$ 550,072
Purchased Gas	(127,091)	(167,605)
Income Before Income Taxes	139,900	137,677
Income Tax Expense	(55,160)	(55,425)
Net Income Available for Common Stock	84,740	82,252
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Before Income Taxes	24,265	10,183
Income Tax Expense	(10,089)	(4,299)
Net Income Available for Common Stock	14,176	5,884
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Income (Loss) [Member] | Commodity Contracts [Member] | Gains And Losses On Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating Revenues	20,036	9,787
Purchased Gas	$ 4,229	$ 396