Consolidated Statements Of Income And Earnings Reinvested In The Business (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
INCOME
Operating Revenues	$ 440,008	$ 328,861	$ 1,490,688	$ 1,313,593
Operating Expenses
Purchased Gas	95,164	50,160	426,900	390,889
Operation and Maintenance	108,497	93,749	338,533	311,857
Property, Franchise and Other Taxes	21,201	20,432	63,550	70,138
Depreciation, Depletion and Amortization	88,142	74,227	240,503	199,925
Total Operating Expenses	313,004	238,568	1,069,486	972,809
Operating Income	127,004	90,293	421,202	340,784
Other Income (Expense):
Interest Income	317	390	1,844	1,686
Other Income	1,163	1,086	3,666	4,076
Interest Expense on Long-Term Debt	(22,998)	(21,529)	(67,232)	(60,594)
Other Interest Expense	(1,303)	(828)	(2,898)	(2,851)
Income Before Income Taxes	104,183	69,412	356,582	283,101
Income Tax Expense	45,688	26,228	144,423	111,826
Net Income Available for Common Stock	58,495	43,184	212,159	171,275
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Period	1,398,999	1,275,107	1,306,284	1,206,022
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	1,457,494	1,318,291	1,518,443	1,377,297
Dividends on Common Stock	(31,346)	(30,393)	(92,295)	(89,399)
Balance at June 30	$ 1,426,148	$ 1,287,898	$ 1,426,148	$ 1,287,898
Earnings Per Common Share, Basic:
Net Income Available for Common Stock	$ 0.70	$ 0.52	$ 2.54	$ 2.06
Diluted:
Net Income Available for Common Stock	$ 0.69	$ 0.52	$ 2.52	$ 2.05
Weighted Average Common Shares Outstanding:
Used in Basic Calculation	83,557,968	83,227,602	83,481,849	83,068,083
Used in Diluted Calculation	84,325,465	83,674,823	84,242,128	83,690,436
Dividends Per Common Share:
Dividends Declared	$ 0.375	$ 0.365	$ 1.105	$ 1.075