Consolidated Statements Of Income And Earnings Reinvested In The Business (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
INCOME
Operating Revenues	$ 452,854	$ 432,423
Operating Expenses
Purchased Gas	121,919	132,193
Operation and Maintenance	107,732	100,059
Property, Franchise and Other Taxes	19,664	19,230
Depreciation, depletion and Amortization	72,331	62,547
Total Operating Expenses	321,646	314,029
Operating Income	131,208	118,394
Other Income (Expense):
Interest Income	1,386	1,105
Other Income	1,415	1,336
Interest Expense on Long-Term Debt	(21,448)	(18,641)
Other Interest Expense	(1,068)	(770)
Income Before Income Taxes	111,493	101,424
Income Tax Expense	43,549	40,725
Net Income Available for Common Stock	67,944	60,699
EARNINGS REINVESTED IN THE BUSINESS
Balance at October 1	1,306,284	1,206,022
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	1,374,228	1,266,721
Dividends on Common Stock	(30,463)	(29,479)
Balance at December 31	$ 1,343,765	$ 1,237,242
Earnings Per Common Share, Basic:
Net Income Available for Common Stock	$ 0.81	$ 0.73
Diluted:
Net Income Available for Common Stock	$ 0.81	$ 0.73
Weighted Average Common Shares Outstanding:
Used in Basic Calculation	83,390,278	82,870,931
Used in Diluted Calculation	84,006,050	83,699,981