CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES
Net income	$ 81,045,000	$ 75,752,000
Adjustments to reconcile net income to cash flows from operating activities
Unrealized gain on derivative instruments	(37,491,000)	(41,766,000)
Depreciation and amortization	27,362,000	24,637,000
Amortization of acquired wholesale energy contracts	716,000	134,000
Allowance for equity used during construction	(4,931,000)	(2,732,000)
Allowance for doubtful accounts	3,970,000	430,000
Non cash lease expense	1,324,000	861,000
Deferred income taxes	17,667,000	19,976,000
Manufactured gas plant remediation costs	(1,274,000)	(2,974,000)
Equity in earnings, net of distributions received from equity investees	(1,189,000)	(1,332,000)
Cost of removal - asset retirement obligations	(256,000)	(61,000)
Contributions to postemployment benefit plans	(1,670,000)	(2,256,000)
Tax benefit from stock-based compensation	76,000	798,000
Changes in:
Components of working capital	(74,434,000)	(117,241,000)
Other noncurrent assets	11,806,000	1,312,000
Other noncurrent liabilities	9,002,000	1,398,000
Cash flows from (used in) operating activities	31,723,000	(43,064,000)
Expenditures for:
Cost of removal	(14,765,000)	(7,936,000)
Acquisition of assets, net of cash acquired of $5.1 million	0	(368,126,000)
Distribution from equity investees in excess of equity in earnings	1,413,000	643,000
Investments in equity investees	(286,000)	(509,000)
Cash flows used in investing activities	(108,753,000)	(494,175,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from term loan	0	350,000,000
Payments of term loan	0	(212,900,000)
Payments of long-term debt	(5,203,000)	(3,853,000)
Proceeds from (payments of) short-term debt, net	9,000,000	228,159,000
Proceeds from sale leaseback transaction - solar	12,124,000	0
Proceeds from sale leaseback transaction	0	4,000,000
Payments of common stock dividends	(31,902,000)	(26,974,000)
Proceeds from issuance of common stock - public equity offering	0	212,900,000
Proceeds from issuance of common stock - DRP	3,911,000	3,572,000
Tax withholding payments related to net settled stock compensation	(5,534,000)	(3,543,000)
Cash flows (used in) from financing activities	(17,604,000)	551,361,000
Change in cash, cash equivalents and restricted cash	(94,634,000)	14,122,000
Cash, cash equivalents and restricted cash at beginning of period	119,423,000	4,063,000
Cash, cash equivalents and restricted cash at end of period	24,789,000	18,185,000
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(108,143,000)	(164,622,000)
Inventories	5,792,000	(17,055,000)
Recovery of natural gas costs	(10,542,000)	7,951,000
Natural gas purchases payable	24,146,000	44,086,000
Natural gas purchases payable - related parties	74,000	0
Prepaid expenses	(5,045,000)	(12,482,000)
Prepaid and accrued taxes	10,568,000	15,390,000
Accounts payable and other	(39,232,000)	(27,080,000)
Restricted broker margin accounts	38,986,000	34,976,000
Customers' credit balances and deposits	7,014,000	2,457,000
Other current assets	1,948,000	(862,000)
Total	74,434,000	117,241,000
Cash paid for:
Interest (net of amounts capitalized)	11,298,000	14,938,000
Income taxes	230,000	0
Accrued capital expenditures	4,205,000	14,864,000
Utility Plant
Expenditures for:
Payments to acquire PP&E	(64,481,000)	(69,861,000)
Solar Equipment
Expenditures for:
Payments to acquire PP&E	(22,335,000)	(45,699,000)
Storage and Transportation and other
Expenditures for:
Payments to acquire PP&E	$ (8,299,000)	$ (2,687,000)