Consolidated Statements of Income and Earnings Reinvested in the Business - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2023
INCOME
Operating Revenues		$ 2,277,541		$ 1,944,810		$ 2,173,771
Operating Expenses:
Purchased Gas	[1]	213,441		150,062		437,595
Property, Franchise and Other Taxes		94,380		88,851		92,700
Depreciation, Depletion and Amortization	[1]	456,594		457,026		409,573
Impairment of Assets		141,802	[1]	519,129	[1]	0
Total Operating Expenses		1,464,082		1,735,086		1,418,624
Operating Income		813,459		209,724		755,147
Other Income (Expense):
Other Income (Deductions)		36,428		16,226		18,138
Interest Expense on Long-Term Debt		(140,870)		(122,799)		(111,948)
Other Interest Expense		(14,964)		(15,896)		(19,938)
Income Before Income Taxes		694,053		87,255		641,399
Income Tax Expense	[1]	175,549		9,742		164,533
Net Income Available for Common Stock		518,504		77,513		476,866
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Year		1,727,326		1,885,856		1,587,085
Beginning Retained Earnings Unappropriated and Current Period Net Income		2,245,830		1,963,369		2,063,951
Dividends on Common Stock		(189,919)		(185,220)		(178,095)
Balance at End of Year		$ 2,012,529		$ 1,727,326		$ 1,885,856
Basic:
Net Income Available for Common Stock (in dollars per share)		$ 5.73		$ 0.84		$ 5.20
Diluted:
Net Income Available for Common Stock (in dollars per share)		$ 5.68		$ 0.84		$ 5.17
Weighted Average Common Shares Outstanding:
Used in Basic Calculation (in shares)		90,500,916		91,791,167		91,748,890
Used in Diluted Calculation (in shares)		91,227,473		92,344,511		92,285,918
Earnings Reinvested in the Business
Other Income (Expense):
Net Income Available for Common Stock		$ 518,504		$ 77,513		$ 476,866
EARNINGS REINVESTED IN THE BUSINESS
Share Repurchases Under Repurchase Plan		(43,382)		(50,823)		0
Dividends on Common Stock		(189,919)		(185,220)		(178,095)
Utility
INCOME
Operating Revenues		817,274		696,807		941,779
Operating Expenses:
Operation and Maintenance		230,639		218,393		205,239
Integrated Upstream and Gathering and Other Revenues
INCOME
Operating Revenues		1,184,136		976,615		972,346
Operating Expenses:
Operation and Maintenance		206,616		187,024		168,390
Pipeline and Storage
INCOME
Operating Revenues		276,131		271,388		259,646
Operating Expenses:
Operation and Maintenance		$ 120,610		$ 114,601		$ 105,127

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