CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 210,223	$ 226,168
Adjustments to reconcile net income to cash flows from operating activities
Unrealized loss (gain) on derivative instruments	20,057	(17,532)
Depreciation and amortization	80,362	74,773
Amortization of acquired wholesale energy contracts	260	1,283
Allowance for equity used during construction	(3,572)	(2,801)
Allowance for doubtful accounts	(24)	(395)
Non cash lease expense	2,130	1,848
Deferred income taxes	49,301	36,072
Equivalent value of ITCs recognized on equipment financing	(10,605)	(899)
Manufactured gas plant remediation costs	(12,577)	(4,362)
Cost of removal - asset retirement obligations	(763)	(644)
Contributions to postemployment benefit plans	(2,191)	(634)
Taxes related to stock-based compensation	1,186	554
Changes in:
Components of working capital	(3,021)	(42,519)
Other noncurrent assets and liabilities	7,836	72,209
Cash flows from operating activities	338,602	343,121
Expenditures for:
Cost of removal	(17,436)	(16,757)
Distribution from equity investees in excess of equity in earnings	2,284	1,374
Cash flows used in investing activities	(235,018)	(261,737)
CASH FLOWS USED IN FINANCING ACTIVITIES
Proceeds from long-term debt	50,000	175,000
Payments of long-term debt	(82,790)	(10,534)
Payments of term loan	0	(150,000)
Payments of short-term debt, net	(55,950)	(86,300)
Proceeds from sale leaseback transactions - solar	24,394	61,808
Proceeds from sale leaseback transactions - natural gas meters	8,814	8,441
Payments of common stock dividends	(82,156)	(75,200)
Proceeds from waiver discount issuance of common stock	35,838	17,919
Proceeds from issuance of common stock - DRP	7,522	7,610
Tax withholding payments related to net settled stock compensation	(5,027)	(4,024)
Cash flows used in financing activities	(99,355)	(55,280)
Change in cash, cash equivalents and restricted cash	4,229	26,104
Cash, cash equivalents and restricted cash at beginning of period	1,517	1,452
Cash, cash equivalents and restricted cash at end of period	5,746	27,556
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(144,321)	(8,877)
Inventories	115,166	185,444
Recovery of natural gas costs	(3,853)	(28,825)
Natural gas purchases payable	13,178	(159,016)
Natural gas purchases payable - related parties	0	5
Deferred revenue, current	48,294	1,587
Accounts payable and other	(15,888)	(24,095)
Prepaid expenses	(6,350)	(6,493)
Prepaid and accrued taxes	30,705	51,591
Restricted broker margin accounts	(15,015)	(43,414)
Customers' credit balances and deposits	(20,032)	(7,725)
Other current assets and liabilities	(4,905)	(2,701)
Total	(3,021)	(42,519)
Cash paid for:
Interest (net of amounts capitalized)	60,256	57,622
Income taxes	6,699	1,967
Accrued capital expenditures	17,513	24,318
Utility plant
Expenditures for:
Payments to acquire PP&E	(160,937)	(157,914)
Solar equipment
Expenditures for:
Payments to acquire PP&E	(37,083)	(57,699)
Storage and Transportation and other
Expenditures for:
Payments to acquire PP&E	$ (21,846)	$ (30,741)