CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 150,647,000	$ 151,419,000
Adjustments to reconcile net income to cash flows from operating activities
Unrealized gain on derivative instruments	(21,827,000)	(25,353,000)
Realized and unrealized gains on investments in equity securities	0	(1,567,000)
Gain on sale of businesses	0	(645,000)
Depreciation and amortization	89,758,000	67,292,000
Amortization of acquired wholesale energy contracts	4,356,000	7,813,000
Allowance for equity used during construction	(12,328,000)	(6,135,000)
Allowance for doubtful accounts	1,657,000	1,686,000
Non cash lease expense	2,864,000	0
Deferred income taxes	(3,066,000)	(29,092,000)
Manufactured gas plant remediation costs	(6,629,000)	(9,582,000)
Equity in earnings, net of distributions received from equity investees	(4,985,000)	(2,700,000)
Cost of removal - asset retirement obligations	(183,000)	(194,000)
Contributions to postemployment benefit plans	(5,969,000)	(5,994,000)
Tax benefit from stock-based compensation	644,000	1,289,000
Changes in:
Components of working capital	(17,397,000)	(14,829,000)
Other noncurrent assets	10,177,000	16,906,000
Other noncurrent liabilities	(4,936,000)	15,476,000
Cash flows from operating activities	182,783,000	165,790,000
Expenditures for:
Cost of removal	(24,343,000)	(32,212,000)
Acquisition of assets, net of cash acquired of $5.1 million	(523,647,000)	0
Distribution from equity investees in excess of equity in earnings	1,411,000	1,473,000
Investments in equity investees	(1,491,000)	(2,696,000)
Proceeds from sale of businesses, net of closing costs	0	205,745,000
Proceeds from sale of investments in equity securities, net	0	34,484,000
Cash flows used in investing activities	(890,966,000)	(105,012,000)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES
Proceeds from term loan	350,000,000	0
Payments of term loan	(212,900,000)	0
Proceeds from long-term debt	50,000,000	35,800,000
Payments of long-term debt	(11,947,000)	(15,001,000)
Proceeds from (payments of) short-term debt, net	390,562,000	(52,650,000)
Proceeds from sale-leaseback transaction - solar	42,927,000	0
Proceeds from sale-leaseback transaction	4,000,000
Proceeds from sale-leaseback transaction		9,895,000
Payments of common stock dividends	(86,709,000)	(77,730,000)
Proceeds from issuance of common stock - public equity offering	212,900,000	0
Proceeds from waiver discount issuance of common stock	0	57,391,000
Proceeds from issuance of common stock - DRP	14,498,000	13,199,000
Tax withholding payments related to net settled stock compensation	(3,966,000)	(6,704,000)
Cash flows from (used in) financing activities	749,365,000	(35,800,000)
Change in cash, cash equivalents and restricted cash	41,182,000	24,978,000
Cash, cash equivalents and restricted cash at beginning of period	4,063,000	1,710,000
Cash, cash equivalents and restricted cash at end of period	45,245,000	26,688,000
CHANGES IN COMPONENTS OF WORKING CAPITAL
Receivables	(3,019,000)	28,385,000
Inventories	42,566,000	51,833,000
Recovery of gas costs	(5,722,000)	(14,870,000)
Gas purchases payable	(55,593,000)	(66,060,000)
Prepaid expenses	1,487,000	(2,385,000)
Prepaid and accrued taxes	(991,000)	10,110,000
Accounts payable and other	(13,084,000)	(31,883,000)
Restricted broker margin accounts	11,900,000	13,092,000
Customers' credit balances and deposits	(7,060,000)	(7,832,000)
Other current assets	12,119,000	4,781,000
Total	(17,397,000)	(14,829,000)
Cash paid for:
Interest (net of amounts capitalized)	47,642,000	42,107,000
Income taxes	1,127,000	8,550,000
Accrued capital expenditures	20,814,000	32,143,000
Utility Plant
Expenditures for:
Payments to acquire PP&E	(213,667,000)	(207,357,000)
Solar Equipment
Expenditures for:
Payments to acquire PP&E	(110,968,000)	(91,333,000)
Midstream and Other Property
Expenditures for:
Payments to acquire PP&E	$ (18,261,000)	$ (13,116,000)