Consolidated Statements Of Income And Earnings Reinvested In The Business (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
INCOME
Operating Revenues	$ 432,423	$ 450,948
Operating Expenses
Purchased Gas	132,193	163,038
Operation and Maintenance	100,059	97,450
Property, Franchise and Other Taxes	19,230	19,736
Depreciation, Depletion and Amortization	62,547	53,313
Total Operating Expenses	314,029	333,537
Operating Income	118,394	117,411
Other Income (Expense):
Interest Income	1,105	884
Other Income	1,336	(107)
Interest Expense on Long-Term Debt	(18,641)	(20,192)
Other Interest Expense	(770)	(1,401)
Income Before Income Taxes	101,424	96,595
Income Tax Expense	40,725	38,052
Net Income Available for Common Stock	60,699	58,543
EARNINGS REINVESTED IN THE BUSINESS
Balance at October 1	1,206,022	1,063,262
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	1,266,721	1,121,805
Dividends on Common Stock (2011 - $0.355 per share; 2010 - $0.345 per share)	(29,479)	(28,407)
Balance at December 31	$ 1,237,242	$ 1,093,398
Earnings Per Common Share, Basic:
Net Income Available for Common Stock	$ 0.73	$ 0.71
Diluted:
Net Income Available for Common Stock	$ 0.73	$ 0.70
Weighted Average Common Shares Outstanding:
Used in Basic Calculation	82,870,931	82,223,428
Used in Diluted Calculation	83,699,981	83,420,351