CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 198,649	$ 227,700
Adjustments to reconcile net income to cash flows from operating activities
Unrealized loss (gain) on derivative instruments	23,860	(30,502)
Depreciation and amortization	121,269	113,650
Amortization of acquired wholesale energy contracts	187	1,781
Allowance for equity used during construction	(5,368)	(5,054)
Allowance for doubtful accounts	1,849	1,397
Non cash lease expense	3,611	2,607
Deferred income taxes	49,598	11,026
Equivalent value of ITCs recognized on equipment financing	(12,600)	(1,232)
Manufactured gas plant remediation costs	(19,464)	(6,284)
Cost of removal - asset retirement obligations	(1,145)	(967)
Contributions to postemployment benefit plans	(2,438)	(1,133)
Taxes related to stock-based compensation	1,186	554
Changes in:
Components of working capital	21,519	22,229
Other noncurrent assets and liabilities	(17,819)	52,126
Cash flows from operating activities	362,894	387,898
Expenditures for:
Cost of removal	(29,552)	(28,719)
Distribution from equity investees in excess of equity in earnings	3,202	2,036
Cash flows used in investing activities	(392,584)	(378,178)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES
Proceeds from long-term debt	175,000	175,000
Payments of long-term debt	(89,555)	(15,698)
Payments of term loan	0	(150,000)
Proceeds from (payments of) short-term debt, net	2,700	(128,725)
Proceeds from sale leaseback transactions - solar	24,394	163,619
Proceeds from sale leaseback transactions - natural gas meters	8,814	8,441
Payments of common stock dividends	(123,446)	(112,991)
Proceeds from waiver discount issuance of common stock	47,286	42,807
Proceeds from issuance of common stock - DRP	11,141	11,419
Tax withholding payments related to net settled stock compensation	(5,027)	(4,024)
Cash flows from (used in) financing activities	51,307	(10,152)
Change in cash, cash equivalents and restricted cash	21,617	(432)
Cash, cash equivalents and restricted cash at beginning of period	1,517	1,452
Cash, cash equivalents and restricted cash at end of period	23,134	1,020
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(34,335)	103,954
Inventories	62,644	108,107
Recovery of natural gas costs	(3,206)	(20,106)
Natural gas purchases payable	2,094	(188,617)
Natural gas purchases payable - related parties	16	5
Deferred revenue, current	38,162	2,687
Accounts payable and other	(1,683)	(20,153)
Prepaid expenses	(3,902)	(2,454)
Prepaid and accrued taxes	(13,310)	24,684
Restricted broker margin accounts	(220)	22,868
Customers' credit balances and deposits	(16,029)	(2,979)
Other current assets and liabilities	(8,712)	(5,767)
Total	21,519	22,229
Cash paid for:
Interest (net of amounts capitalized)	90,006	80,550
Income taxes	13,042	2,858
Accrued capital expenditures	21,122	21,008
Utility plant
Expenditures for:
Payments to acquire PP&E	(259,125)	(248,507)
Solar equipment
Expenditures for:
Payments to acquire PP&E	(74,096)	(68,604)
Storage and Transportation and other
Expenditures for:
Payments to acquire PP&E	$ (33,013)	$ (34,384)