CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 320,555	$ 198,649
Adjustments to reconcile net income to cash flows from operating activities
Unrealized (gain) loss on derivative instruments	(10,072)	23,860
Gain on sale of assets	(56,092)	0
Depreciation and amortization	140,296	121,269
Amortization of acquired wholesale energy contracts	0	187
Allowance for equity used during construction	(6,756)	(5,368)
Allowance for doubtful accounts	8,598	1,849
Non cash lease expense	3,282	3,611
Deferred income taxes	48,510	49,598
Equivalent value of ITCs recognized on equipment financing	(14,322)	(12,600)
Manufactured gas plant remediation costs	(7,289)	(19,464)
Cost of removal - asset retirement obligations	(1,295)	(1,145)
Contributions to postemployment benefit plans	(759)	(2,438)
Taxes related to stock-based compensation	1,808	1,186
Changes in:
Components of working capital	(50,182)	21,519
Other noncurrent assets and liabilities	8,892	(17,819)
Cash flows from operating activities	385,174	362,894
Expenditures for:
Cost of removal	(32,911)	(29,552)
Distribution from equity investees in excess of equity in earnings	625	3,202
Proceeds from sale of assets	136,947	0
Cash flows used in investing activities	(305,931)	(392,584)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES
Proceeds from long-term debt	100,000	175,000
Payments of long-term debt	(190,322)	(89,555)
Proceeds from short-term debt, net	14,850	2,700
Proceeds from sale leaseback transactions - solar	100,271	24,394
Proceeds from sale leaseback transactions - natural gas meters	11,714	8,814
Payments of common stock dividends	(134,897)	(123,446)
Proceeds from waiver discount issuance of common stock	19,910	47,286
Proceeds from issuance of common stock - DRP	11,243	11,141
Tax withholding payments related to net settled stock compensation	(11,635)	(5,027)
Cash flows (used in) from financing activities	(78,866)	51,307
Change in cash, cash equivalents and restricted cash	377	21,617
Cash, cash equivalents and restricted cash at beginning of period	1,612	1,517
Cash, cash equivalents and restricted cash at end of period	1,989	23,134
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(74,552)	(34,335)
Inventories	26,442	62,644
Recovery of natural gas costs	5,589	(3,206)
Natural gas purchases payable	5,790	2,094
Natural gas purchases payable - related parties	(229)	16
Deferred revenue, current	1,944	38,162
Accounts payable and other	(29,592)	(1,683)
Prepaid expenses	(3,310)	(3,902)
Prepaid and accrued taxes	24,109	(13,310)
Restricted broker margin accounts	12,425	(220)
Customers' credit balances and deposits	(14,711)	(16,029)
Other current assets and liabilities	(4,087)	(8,712)
Total	(50,182)	21,519
Cash paid for:
Interest (net of amounts capitalized)	98,938	90,006
Income taxes	8,654	13,042
Accrued capital expenditures	28,391	21,122
Utility plant
Expenditures for:
Payments to acquire PP&E	(274,028)	(259,125)
Solar equipment
Expenditures for:
Payments to acquire PP&E	(117,978)	(74,096)
Storage and Transportation and other
Expenditures for:
Payments to acquire PP&E	$ (18,586)	$ (33,013)