Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Operating Activities
Net Income Available for Common Stock	$ 476,866	$ 566,021	$ 363,647
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Gain on Sale of Assets	0	(12,736)	(51,066)
Impairment of Oil and Gas Producing Properties	0	0	76,152
Depreciation, Depletion and Amortization	409,573	369,790	335,303
Deferred Income Taxes	151,403	104,415	105,993
Premium Paid on Early Redemption of Debt	0	0	15,715
Stock-Based Compensation	20,630	19,506	17,065
Reduction of Other Post-Retirement Regulatory Liability	0	(18,533)	0
Other	19,647	31,983	10,896
Change in:
Receivables and Unbilled Revenue	213,579	(168,769)	(61,413)
Gas Stored Underground and Materials, Supplies and Emission Allowances	(8,406)	3,109	(2,014)
Unrecovered Purchased Gas Costs	99,342	(66,214)	(33,128)
Other Current Assets	(41,077)	291	(11,972)
Accounts Payable	(37,095)	11,907	31,352
Amounts Payable to Customers	58,600	398	(10,767)
Customer Advances	(5,105)	8,885	1,904
Customer Security Deposits	4,481	4,991	2,093
Other Accruals and Current Liabilities	(67,664)	34,260	34,314
Other Assets	(26,564)	(58,924)	1,250
Other Liabilities	(31,135)	(17,859)	(33,771)
Net Cash Provided by Operating Activities	1,237,075	812,521	791,553
Investing Activities
Capital Expenditures	(1,009,868)	(811,826)	(751,734)
Net Proceeds from Sale of Oil and Gas Producing Properties	0	254,439	0
Net Proceeds from Sale of Timber Properties	0	0	104,582
Sale of Fixed Income Mutual Fund Shares in Grantor Trust	10,000	30,000	0
Acquisition of Upstream Assets	(124,758)	0	0
Other	12,279	8,683	13,935
Net Cash Used in Investing Activities	(1,112,347)	(518,704)	(633,217)
Financing Activities
Proceeds from Issuance of Short-Term Note Payable to Bank	250,000	0	0
Repayment of Short-Term Note Payable to Bank	(250,000)	0	0
Net Change in Other Short-Term Notes Payable to Banks and Commercial Paper	227,500	(98,500)	128,500
Net Proceeds from Issuance of Long-Term Debt	297,306	0	495,267
Reduction of Long-Term Debt	(549,000)	0	(515,715)
Net Repurchases of Common Stock	(6,709)	(9,590)	(3,702)
Dividends Paid on Common Stock	(176,096)	(168,147)	(163,089)
Net Cash Used in Financing Activities	(206,999)	(276,237)	(58,739)
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	(82,271)	17,580	99,597
Cash, Cash Equivalents and Restricted Cash At Beginning of Year	137,718	120,138	20,541
Cash, Cash Equivalents and Restricted Cash At End of Year	55,447	137,718	120,138
Cash Paid For:
Interest	124,441	124,312	135,136
Income Taxes	38,098	16,680	6,374
Non-Cash Investing Activities:
Non-Cash Capital Expenditures	109,208	120,262	102,700
Non-Cash Contingent Consideration for Asset Sale	$ 0	$ 12,571	$ 0