Consolidated Statements Of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
OPERATING ACTIVITIES
Net Income Available for Common Stock	$ 177,463	$ 153,664
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation, Depletion and Amortization	183,089	152,361
Deferred Income Taxes	71,939	102,557
Excess Tax Benefits Associated with Stock-Based Compensation Awards	(3,149)	0
Stock-Based Compensation	8,045	6,596
Other	(118)	8,013
Change in:
Hedging Collateral Deposits	1,094	(386)
Receivables and Unbilled Revenue	(198,277)	(109,403)
Gas Stored Underground and Materials and Supplies	52,661	32,391
Unrecovered Purchased Gas Costs	10,583	0
Other Current Assets	(443)	4,389
Accounts Payable	69,379	20,456
Amounts Payable to Customers	11,837	(1,725)
Customer Advances	(21,878)	(23,910)
Customer Security Deposits	(602)	(804)
Other Accruals and Current Liabilities	102,222	39,273
Other Assets	23,445	(6,200)
Other Liabilities	15,946	(10,417)
Net Cash Provided by Operating Activities	503,236	366,855
INVESTING ACTIVITIES
Capital Expenditures	(367,393)	(339,737)
Other	4,927	(3,445)
Net Cash Used in Investing Activities	(362,466)	(343,182)
Financing Activities
Changes in Notes Payable to Banks and Commercial Paper	0	(171,000)
Excess Tax Benefits Associated with Stock-Based Compensation Awards	3,149	0
Net Proceeds from Issuance of Long-Term Debt	0	495,415
Reduction of Long-Term Debt	0	(250,000)
Dividends Paid on Common Stock	(62,776)	(60,879)
Net Proceeds from Issuance of Common Stock	4,863	710
Net Cash Provided by (Used in) Financing Activities	(54,764)	14,246
Net Increase in Cash and Temporary Cash Investments	86,006	37,919
Cash and Temporary Cash Investments at October 1	64,858	74,494
Cash and Temporary Cash Investments at March 31	150,864	112,413
Supplemental Disclosure of Cash Flow Information, Non-Cash Investing Activities:
Non-Cash Capital Expenditures	$ 109,355	$ 77,093