Summary Of Significant Accounting Policies (Reclassification Out Of Accumulated Other Comprehensive Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating Revenues	$ 550,072	$ 452,854
Purchased Gas	167,605	121,919
Income Before Income Taxes	137,677	111,493
Income Tax Expense	55,425	43,549
Net Income Available for Common Stock	82,252	67,944
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Loss [Member] | Gains And Losses On Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Before Income Taxes	10,183
Income Tax Expense	(4,299)
Net Income Available for Common Stock	5,884
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive 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	9,787
Purchased Gas	$ 396