Segment Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues		$ 676,944	$ 690,431	$ 714,519
Depreciation and amortization		(108,581)	(100,352)	(85,549)
Operating Income (Loss)		146,262	146,385	137,743
Interest (expense) income, net		(32,930)	(30,429)	(26,647)
Income tax (provision) benefit		(10,596)	(27,803)	(26,224)
Equity earnings of investments		12,275	10,631	9,136
Net Income		120,569	117,699	110,952
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		236,925	222,071	175,030
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		497,673	489,729	465,167
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		178,587	200,012	248,672
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		684	690	680
Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
All Others [Members]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		676,944	690,431	714,519
Fuel and purchased power		(86,846)	(98,851)	(108,150)
Purchased gas costs		(82,693)	(106,647)	(152,570)
Depreciation and amortization		(108,581)	(100,352)	(85,549)
Interest expense		(36,352)	(33,091)	(28,073)
Other segment items	[1]	243,582	(216,619)	(212,137)
Income tax (provision) benefit		(10,596)	(27,803)	(26,224)
Equity earnings of investments		12,275	10,631	9,136
Net Income		120,569	117,699	110,952
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		497,479	490,651	465,123
Fuel and purchased power		(90,726)	(102,520)	(111,915)
Purchased gas costs		0	0	0
Depreciation and amortization		(84,264)	(77,440)	(62,896)
Interest expense		(25,616)	(22,883)	(18,884)
Other segment items	[1]	225,985	(201,680)	(198,942)
Income tax (provision) benefit		3,620	(10,182)	(7,299)
Equity earnings of investments		0	0	0
Net Income		74,508	75,946	65,187
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		192,469	180,743	141,273
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		193,570	215,513	282,745
Fuel and purchased power		0	0	0
Purchased gas costs		(93,834)	(118,509)	(182,904)
Depreciation and amortization		(16,779)	(15,531)	(15,262)
Interest expense		(6,943)	(6,146)	(4,867)
Other segment items	[1]	60,290	(54,084)	(53,005)
Income tax (provision) benefit		(1,995)	(7,175)	(8,492)
Equity earnings of investments		0	0	0
Net Income		13,729	14,068	18,215
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		38,101	36,402	27,656
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		44,515	42,276	42,236
Fuel and purchased power		0	0	0
Purchased gas costs		0	0	0
Depreciation and amortization		(7,538)	(7,381)	(7,391)
Interest expense		(3,793)	(4,062)	(4,322)
Other segment items	[1]	113	(107)	(161)
Income tax (provision) benefit		(9,009)	(8,370)	(8,272)
Equity earnings of investments		0	0	0
Net Income		24,062	22,356	22,090
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		6,355	4,926	6,101
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
Fuel and purchased power		0	0	0
Purchased gas costs		0	0	0
Depreciation and amortization		0	0	0
Interest expense		0	0	0
Other segment items	[1]	0	2	0
Income tax (provision) benefit		(3,345)	(2,897)	(2,489)
Equity earnings of investments		12,275	10,631	9,136
Net Income		8,930	7,736	6,647
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		0	0	0
Operating Segments [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		735,564	748,440	790,104
Fuel and purchased power		(90,726)	(102,520)	(111,915)
Purchased gas costs		(93,834)	(118,509)	(182,904)
Depreciation and amortization		(108,581)	(100,352)	(85,549)
Interest expense		(36,352)	(33,091)	(28,073)
Other segment items	[1]	286,388	(255,869)	(252,108)
Income tax (provision) benefit		(10,729)	(28,624)	(26,552)
Equity earnings of investments		12,275	10,631	9,136
Net Income		121,229	120,106	112,139
Operating Segments [Member] | All Others [Members]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
Fuel and purchased power		0	0	0
Purchased gas costs		0	0	0
Depreciation and amortization		0	0	0
Interest expense		0	0	0
Other segment items	[1]	793	(3,228)	(1,515)
Income tax (provision) benefit		133	821	328
Equity earnings of investments		0	0	0
Net Income		(660)	(2,407)	(1,187)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		0	0	0
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(58,620)	(58,009)	(75,585)
Fuel and purchased power		3,880	3,669	3,765
Purchased gas costs		11,141	11,862	30,334
Depreciation and amortization		0	0	0
Interest expense		0	0	0
Other segment items	[1]	43,599	42,478	41,486
Income tax (provision) benefit		0	0	0
Equity earnings of investments		0	0	0
Net Income		0	0	0
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		0	0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		(194)	922	(44)
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		14,983	15,501	34,073
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		43,831	41,586	41,556
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
Consolidation Elimination Entries [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		58,620	58,009	75,585
Consolidation Elimination Entries [Member] | All Others [Members]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
MGE [Member]
Segment Reporting Information [Line Items]
Operating revenues		676,944	690,431	714,519
Depreciation and amortization		(108,581)	(100,352)	(85,549)
Operating Income (Loss)		147,167	147,383	138,616
Interest (expense) income, net		(33,369)	(30,651)	(26,687)
Income tax (provision) benefit		(7,384)	(25,727)	(24,063)
Net income attributable to noncontrolling interest, net of tax		22,855	21,868	21,576
Net Income		89,444	90,502	83,916
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		236,925	222,071	175,030
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		497,673	489,729	465,167
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		178,587	200,012	248,672
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		684	690	680
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		676,944	690,431	714,519
Fuel and purchased power		(86,846)	(98,851)	(108,150)
Purchased gas costs		(82,693)	(106,647)	(152,570)
Depreciation and amortization		(108,581)	(100,352)	(85,549)
Interest expense		(36,352)	(33,091)	(28,073)
Other segment items	[2]	(242,789)	(213,393)	(210,622)
Income tax (provision) benefit		(7,384)	(25,727)	(24,063)
Net income attributable to noncontrolling interest, net of tax		(22,855)	(21,868)	(21,576)
Net Income		89,444	90,502	83,916
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		497,479	490,651	465,123
Fuel and purchased power		(90,726)	(102,520)	(111,915)
Purchased gas costs		0	0	0
Depreciation and amortization		(84,264)	(77,440)	(62,896)
Interest expense		(25,616)	(22,883)	(18,884)
Other segment items	[2]	(225,985)	(201,680)	(198,942)
Income tax (provision) benefit		3,620	(10,182)	(7,299)
Net income attributable to noncontrolling interest, net of tax		0	0	0
Net Income		74,508	75,946	65,187
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		192,469	180,743	141,273
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		193,570	215,513	282,745
Fuel and purchased power		0	0	0
Purchased gas costs		(93,834)	(118,509)	(182,904)
Depreciation and amortization		(16,779)	(15,531)	(15,262)
Interest expense		(6,943)	(6,146)	(4,867)
Other segment items	[2]	(60,290)	(54,084)	(53,005)
Income tax (provision) benefit		(1,995)	(7,175)	(8,492)
Net income attributable to noncontrolling interest, net of tax		0	0	0
Net Income		13,729	14,068	18,215
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		38,101	36,402	27,656
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		44,515	42,276	42,236
Fuel and purchased power		0	0	0
Purchased gas costs		0	0	0
Depreciation and amortization		(7,538)	(7,381)	(7,391)
Interest expense		(3,793)	(4,062)	(4,322)
Other segment items	[2]	(113)	(107)	(161)
Income tax (provision) benefit		(9,009)	(8,370)	(8,272)
Net income attributable to noncontrolling interest, net of tax		0	0	0
Net Income		24,062	22,356	22,090
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		6,355	4,926	6,101
MGE [Member] | Operating Segments [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		735,564	748,440	790,104
Fuel and purchased power		(90,726)	(102,520)	(111,915)
Purchased gas costs		(93,834)	(118,509)	(182,904)
Depreciation and amortization		(108,581)	(100,352)	(85,549)
Interest expense		(36,352)	(33,091)	(28,073)
Other segment items	[2]	(286,388)	(255,871)	(252,108)
Income tax (provision) benefit		(7,384)	(25,727)	(24,063)
Net income attributable to noncontrolling interest, net of tax		0	0	0
Net Income		112,299	112,370	105,492
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(58,620)	(58,009)	(75,585)
Fuel and purchased power		3,880	3,669	3,765
Purchased gas costs		11,141	11,862	30,334
Depreciation and amortization		0	0	0
Interest expense		0	0	0
Other segment items	[2]	43,599	42,478	41,486
Income tax (provision) benefit		0	0	0
Net income attributable to noncontrolling interest, net of tax		(22,855)	(21,868)	(21,576)
Net Income		(22,855)	(21,868)	(21,576)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		0	0	0
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		(194)	922	(44)
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		14,983	15,501	34,073
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		43,831	41,586	41,556
MGE [Member] | Consolidation Elimination Entries [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		$ 58,620	$ 58,009	$ 75,585

[1] Other segment items include AFUDC Income, Other Income, Net, Other Operations and Maintenance, Other General Taxes, and Interest Revenue.

[2] Other segment items include AFUDC Income, Other Income, Net, Other Operations and Maintenance, Other General Taxes, and Interest Revenue.