Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities:
Net Income	$ 117,699	$ 110,952	$ 105,761
Items not affecting cash:
Depreciation and amortization	100,352	85,549	76,983
Deferred income taxes	22,999	23,435	4,837
Provision for doubtful receivables	1,764	1,764	1,550
Employee benefit plan (credit) cost	(5,796)	(8,142)	(2,203)
Equity earnings in investments	(10,631)	(9,136)	(9,270)
Other items	(388)	(1,535)	120
Changes in working capital items:
Accounts receivable and unbilled revenues	11,174	(16,726)	(24,651)
Inventories	(850)	(22,226)	(6,342)
Prepaid taxes	(3,178)	1,082	(5,035)
Other current assets	5,028	(3,729)	(192)
Accounts payable	(5,208)	5,102	2,729
Other current liabilities	(2,264)	(5,562)	(6,734)
Dividends from investments	8,508	7,090	7,832
Cash contributions to pension and other postretirement plans	(7,747)	(7,308)	(6,935)
Other noncurrent items, net	6,099	(6,875)	(923)
Cash Provided by Operating Activities	237,561	153,735	137,527
Investing Activities:
Capital expenditures	(222,071)	(175,030)	(153,169)
Capital contributions to investments	(6,995)	(5,185)	(4,027)
Other	(954)	70	221
Cash Used for Investing Activities	(230,020)	(180,145)	(156,975)
Financing Activities:
Cash dividends paid on common stock	(60,393)	(57,500)	(54,788)
Repayment of long-term debt	(54,314)	(4,889)	(4,771)
Issuance of long-term debt	139,300	25,000	100,000
(Repayments of) proceeds from short-term debt	(32,500)	65,000	(47,000)
Other	(2,576)	(2,068)	(2,197)
Cash (Used for) Provided by Financing Activities	(10,483)	25,543	(8,756)
Change in cash, cash equivalents, and restricted cash:	(2,942)	(867)	(28,204)
Cash, cash equivalents, and restricted cash at beginning of period	17,968	18,835	47,039
Cash, cash equivalents, and restricted cash at end of period	15,026	17,968	18,835
Supplemential Disclosures of Cash Flow Information:
Interest paid	29,526	25,957	23,502
Income taxes paid, net	9,800	3,166	4,000
Significant noncash investing activities:
Accrued capital expenditures	17,247	5,970	14,414
MGE [Member]
Operating Activities:
Net Income	112,370	105,492	100,782
Items not affecting cash:
Depreciation and amortization	100,352	85,549	76,983
Deferred income taxes	21,536	22,767	3,654
Provision for doubtful receivables	1,764	1,764	1,550
Employee benefit plan (credit) cost	(5,796)	(8,142)	(2,203)
Other items	(241)	672	2,002
Changes in working capital items:
Accounts receivable and unbilled revenues	11,130	(16,697)	(24,680)
Inventories	(850)	(22,226)	(6,342)
Prepaid taxes	(3,871)	912	(4,531)
Other current assets	5,032	(3,774)	(148)
Accounts payable	(5,209)	5,104	2,775
Accrued interest and taxes	1,413	(2,737)	244
Other current liabilities	(3,272)	(2,541)	(11,107)
Cash contributions to pension and other postretirement plans	(7,747)	(7,308)	(6,935)
Other noncurrent items, net	5,211	(7,768)	(1,804)
Cash Provided by Operating Activities	231,822	151,067	130,240
Investing Activities:
Capital expenditures	(222,071)	(175,030)	(153,169)
Other	(1,956)	(1,065)	(1,709)
Cash Used for Investing Activities	(224,027)	(176,095)	(154,878)
Financing Activities:
Cash dividends paid to parent by MGE	(41,000)	(33,500)	(5,000)
Distributions to parent from noncontrolling interest	(20,500)	(22,000)	(15,000)
Repayment of long-term debt	(54,314)	(4,889)	(4,771)
Issuance of long-term debt	139,300	25,000	100,000
(Repayments of) proceeds from short-term debt	(32,500)	65,000	(47,000)
Other	(2,576)	(1,881)	(2,197)
Cash (Used for) Provided by Financing Activities	(11,590)	27,730	26,032
Change in cash, cash equivalents, and restricted cash:	(3,795)	2,702	1,394
Cash, cash equivalents, and restricted cash at beginning of period	10,500	7,798	6,404
Cash, cash equivalents, and restricted cash at end of period	6,705	10,500	7,798
Supplemential Disclosures of Cash Flow Information:
Interest paid	29,526	25,957	23,502
Significant noncash investing activities:
Accrued capital expenditures	$ 17,247	$ 5,970	$ 14,414