CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 335,627	$ 289,775	$ 264,724
Adjustments to reconcile net income to cash flows from operating activities
Unrealized (gain) loss on derivative instruments	(12,126)	19,574	(38,081)
Gain on sale of assets	(58,200)	0	0
Depreciation and amortization	188,774	166,567	152,941
Amortization of acquired wholesale energy contracts	0	125	2,271
Allowance for equity used during construction	(9,973)	(6,874)	(7,137)
Allowance for doubtful accounts	10,030	1,229	1,570
Non-cash lease expense	4,451	4,674	3,708
Deferred income taxes	76,971	85,735	30,462
Equivalent value of ITCs recognized on equipment financing	(16,983)	(15,328)	(6,986)
Manufactured gas plant remediation costs	(12,854)	(23,451)	(9,571)
Cost of removal - asset retirement obligations	(2,044)	(1,727)	(1,526)
Contributions to postemployment benefit plans	(1,025)	(2,659)	(4,706)
Taxes related to stock-based compensation	(1,934)	(1,219)	(588)
Changes in:
Components of working capital	(31,899)	(61,058)	61,525
Other noncurrent assets and liabilities	(2,466)	(27,956)	30,387
Cash flows from operating activities	466,349	427,407	478,993
Expenditures for:
Cost of removal	(46,030)	(48,385)	(40,555)
Distribution from equity investees in excess of equity in earnings	612	2,246	2,294
Proceeds from sale of assets	137,195	0	0
Cash flows used in investing activities	(568,271)	(569,073)	(538,625)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	300,000	250,000	225,000
Payments of long-term debt	(206,922)	(125,066)	(71,934)
Payments of term loan	0	0	(150,000)
(Payments of) proceeds from short-term debt, net	(96,200)	39,700	(21,850)
Proceeds from sale leaseback transactions - solar	251,171	64,694	167,790
Proceeds from sale leaseback transactions - natural gas meters	11,714	8,814	8,441
Payments of common stock dividends	(180,066)	(165,063)	(150,973)
Proceeds from waiver discount issuance of common stock	19,910	59,730	42,807
Proceeds from issuance of common stock - DRP	14,918	14,676	14,993
Tax withholding payments related to net settled stock compensation	(12,566)	(5,724)	(4,577)
Cash flows from financing activities	101,959	141,761	59,697
Change in cash, cash equivalents and restricted cash	37	95	65
Cash, cash equivalents and restricted cash at beginning of period	1,612	1,517	1,452
Cash, cash equivalents and restricted cash at end of period	1,649	1,612	1,517
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(15,100)	(12,744)	112,628
Inventories	(21,647)	(11,086)	67,445
Recovery of natural gas costs	6,931	734	(14,427)
Natural gas purchases payable	5,078	6,238	(183,772)
Natural gas purchases payable - related parties	(234)	16	8
Deferred revenue	1,033	(39,832)	934
Accounts payable and other	6,188	15,640	7,537
Prepaid expenses	906	(2,013)	(1,169)
Prepaid and accrued taxes	1,052	(23,517)	16,415
Restricted broker margin accounts	(1,295)	19,535	46,364
Customers’ credit balances and deposits	(7,298)	(6,315)	11,664
Other current assets and liabilities	(7,513)	(7,714)	(2,102)
Total	(31,899)	(61,058)	61,525
Cash paid for:
Interest (net of amounts capitalized)	130,333	120,239	108,194
Income taxes	9,883	21,313	4,282
Accrued capital expenditures	60,965	22,535	25,867
Notes receivable recognized as non-cash investing activity	42,500	0	0
Utility plant
Expenditures for:
Payments to acquire PP&E	(391,906)	(372,019)	(350,304)
Solar equipment
Expenditures for:
Payments to acquire PP&E	(238,185)	(104,287)	(107,303)
Storage and transportation and other
Expenditures for:
Payments to acquire PP&E	$ (29,957)	$ (46,628)	$ (42,757)