Consolidated Statements Of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2023
Operating Activities
Net Income Available for Common Stock		$ 518,504		$ 77,513		$ 476,866
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Impairment of Assets		141,802	[1]	519,129	[1]	0
Depreciation, Depletion and Amortization	[1]	456,594		457,026		409,573
Deferred Income Taxes		121,274		(2,610)		151,403
Premium Paid on Early Redemption of Debt		2,385		0		0
Stock-Based Compensation		19,754		22,080		20,630
Other		24,936		24,411		19,647
Change in:
Receivables and Unbilled Revenue		(54,521)		34,369		213,579
Gas Stored Underground and Materials and Supplies		(1,378)		1,738		(8,406)
Unrecovered Purchased Gas Costs		(5,769)		0		99,342
Other Current Assets		11,387		8,144		(41,077)
Accounts Payable		12,785		5,616		(37,095)
Amounts Payable to Customers		(41,752)		(16,299)		58,600
Customer Advances		(2,185)		(1,630)		(5,105)
Customer Security Deposits		(6,412)		7,501		4,481
Other Accruals and Current Liabilities		489		2,637		(67,664)
Other Assets		(29,106)		(48,183)		(26,564)
Other Liabilities		(68,760)		(25,481)		(31,135)
Net Cash Provided by Operating Activities		1,100,027		1,065,961		1,237,075
Investing Activities
Capital Expenditures		(912,821)		(931,236)		(1,009,868)
Sale of Fixed Income Mutual Fund Shares in Grantor Trust		7,000		0		10,000
Acquisition of Upstream Assets		0		0		(124,758)
Other		14,121		(2,669)		12,279
Net Cash Used in Investing Activities		(891,700)		(933,905)		(1,112,347)
Financing Activities
Proceeds from Issuance of Short-Term Note Payable to Bank		0		0		250,000
Repayment of Short-Term Note Payable to Bank		0		0		(250,000)
Net Change in Other Short-Term Notes Payable to Banks and Commercial Paper		59,500		(196,800)		227,500
Net Proceeds from Issuance of Long-Term Debt		988,729		299,359		297,306
Shares Repurchased Under Repurchase Plan		(54,430)		(64,086)		0
Reduction of Long-Term Debt		(1,004,086)		0		(549,000)
Net Repurchases of Common Stock Under Stock and Benefit Plans		(4,658)		(3,956)		(6,709)
Dividends Paid on Common Stock		(188,438)		(183,798)		(176,096)
Net Cash Used in Financing Activities		(203,383)		(149,281)		(206,999)
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash		4,944		(17,225)		(82,271)
Cash, Cash Equivalents and Restricted Cash At Beginning of Year		38,222		55,447		137,718
Cash, Cash Equivalents and Restricted Cash At End of Year		43,166		38,222		55,447
Cash Paid For:
Interest		159,362		125,130		124,441
Income Taxes		48,876		4,132		38,098
Non-Cash Investing Activities:
Non-Cash Capital Expenditures		$ 125,268		$ 119,988		$ 109,208

[1] The Company considers this line to be a significant expense.