CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES
Net income	$ 89,411	$ 115,921
Adjustments to reconcile net income to cash flows from operating activities
Unrealized (gain) on derivative instruments	(5,400)	(31,503)
Depreciation and amortization	40,287	36,683
Amortization of acquired wholesale energy contracts	111	530
Allowance for equity used during construction	(1,482)	(1,054)
Allowance for doubtful accounts	(1,575)	(2,459)
Non cash lease expense	1,152	727
Deferred income taxes	18,758	11,861
Equivalent value of ITCs recognized on equipment financing	(2,888)	(899)
Manufactured gas plant remediation costs	(4,575)	(2,627)
Cost of removal - asset retirement obligations	(382)	(322)
Contributions to postemployment benefit plans	(1,996)	(249)
Taxes related to stock-based compensation	1,185	554
Changes in:
Components of working capital	(97,615)	(335,025)
Other noncurrent assets and liabilities	11,424	118,915
Cash flows from (used in) operating activities	46,415	(88,947)
Expenditures for:
Cost of removal	(8,977)	(7,329)
Distribution from equity investees in excess of equity in earnings	830	361
Cash flows used in investing activities	(113,792)	(145,562)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	50,000	175,000
Payments of long-term debt	(6,188)	(4,782)
Proceeds from short-term debt, net	16,550	40,500
Proceeds from sale leaseback transactions - solar	24,394	33,150
Proceeds from sale leaseback transactions - natural gas meters	8,814	8,441
Payments of common stock dividends	(40,981)	(34,508)
Proceeds from waiver discount issuance of common stock	17,919	17,919
Proceeds from issuance of common stock - DRP	3,781	3,847
Tax withholding payments related to net settled stock compensation	(5,000)	(3,642)
Cash flows from financing activities	69,289	235,925
Change in cash, cash equivalents and restricted cash	1,912	1,416
Cash, cash equivalents and restricted cash at beginning of period	1,517	1,452
Cash, cash equivalents and restricted cash at end of period	3,429	2,868
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(146,377)	(247,080)
Inventories	1,948	17,974
Recovery of natural gas costs	479	27,904
Natural gas purchases payable	24,901	(76,930)
Natural gas purchases payable - related parties	(2)	11
Deferred revenue, current	57,115	0
Accounts payable and other	(47,797)	(35,361)
Prepaid expenses	(5,794)	(10,456)
Prepaid and accrued taxes	20,895	39,301
Restricted broker margin accounts	(837)	(56,460)
Customers' credit balances and deposits	551	7,724
Other current assets (liabilities)	(2,697)	(1,652)
Total	(97,615)	(335,025)
Cash paid for:
Interest (net of amounts capitalized)	29,779	22,986
Income taxes	629	30
Accrued capital expenditures	13,333	24,119
Utility plant
Expenditures for:
Payments to acquire PP&E	(71,166)	(74,742)
Solar equipment
Expenditures for:
Payments to acquire PP&E	(25,766)	(43,993)
Storage and Transportation and other
Expenditures for:
Payments to acquire PP&E	$ (8,713)	$ (19,859)