Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating Activities
Net Income Available for Common Stock	$ 128,091	$ 174,154
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Gain on Sale of Unconsolidated Subsidiaries	0	(50,879)
Depreciation, Depletion and Amortization	125,698	113,324
Deferred Income Taxes	81,696	106,510
Excess Tax Benefits Associated with Stock-Based Compensation Awards	(1,076)	0
Other	4,269	5,703
Change in:
Hedging Collateral Deposits	829	(50,692)
Receivables and Unbilled Utility Revenue	(50,906)	(123,393)
Gas Stored Underground and Materials and Supplies	37,156	30,144
Prepayments and Other Current Assets	(943)	57,447
Accounts Payable	(28,656)	33,234
Amounts Payable to Customers	1,808	(12,634)
Customer Advances	(19,439)	(24,938)
Customer Security Deposits	(300)	(256)
Other Accruals and Current Liabilities	65,039	93,473
Other Assets	(48,692)	15,239
Other Liabilities	44,323	(23,214)
Net Cash Provided by Operating Activities	338,897	343,222
Investing Activities
Capital Expenditures	(499,607)	(392,338)
Net Proceeds from Sale of Unconsolidated Subsidiaries	0	59,365
Other	(789)	(3,097)
Net Cash Used in Investing Activities	(500,396)	(336,070)
Financing Activities
Changes in Notes Payable to Banks and Commercial Paper	(20,000)	0
Excess Tax Benefits Associated with Stock-Based Compensation Awards	1,076	0
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	(58,877)	(56,723)
Net Proceeds from Issuance (Repurchase) of Common Stock	5,030	(2,833)
Net Cash Provided by (Used in) Financing Activities	273,314	(259,556)
Net Increase (Decrease) in Cash and Temporary Cash Investments	111,815	(252,404)
Cash and Temporary Cash Investments at October 1	80,428	397,171
Cash and Temporary Cash Investments at March 31	$ 192,243	$ 144,767