Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Operating Activities
Net Income Available for Common Stock	$ 60,699	$ 58,543
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation, Depletion and Amortization	62,547	53,313
Deferred Income Taxes	39,398	36,600
Other	2,375	3,543
Change in:
Hedging Collateral Deposits	(5,417)	(20,312)
Receivables and Unbilled Utility Revenue	(51,054)	(53,984)
Gas Stored Underground and Materials and Supplies	(2,226)	(5,828)
Unrecovered Purchased Gas Costs	(3,002)	0
Prepayments and Other Current Assets	(5,182)	8,768
Accounts Payable	(21,500)	29,246
Amounts Payable to Customers	(3,522)	(14,195)
Customer Advances	6,171	(5)
Customer Security Deposits	364	188
Other Accruals and Current Liabilities	(4,008)	1,387
Other Assets	(28,139)	(10,463)
Other Liabilities	31,724	670
Net Cash Provided by Operating Activities	79,228	87,471
Investing Activities
Capital Expenditures	(232,670)	(193,802)
Other	(966)	(298)
Net Cash Used in Investing Activities	(233,636)	(194,100)
Financing Activities
Changes in Notes Payable to Banks and Commercial Paper	(20,000)	20,500
Net Proceeds from Issuance of Long-Term Debt	496,085	0
Reduction of Long-Term Debt	(150,000)	(200,000)
Dividends Paid on Common Stock	(29,398)	(28,316)
Net Proceeds from Issuance (Repurchase) of Common Stock	1,555	(3,104)
Net Cash Provided by (Used in) Financing Activities	298,242	(210,920)
Net Increase (Decrease) in Cash and Temporary Cash Investments	143,834	(317,549)
Cash and Temporary Cash Investments at October 1	80,428	397,171
Cash and Temporary Cash Investments at December 31	$ 224,262	$ 79,622