Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Operating revenues		$ 159,452	$ 145,713	$ 378,422	$ 337,049
Depreciation and amortization		(28,354)	(26,932)	(56,032)	(53,532)
Income tax (provision) benefit		(2,975)	(1,472)	(9,271)	(4,280)
Equity in earnings of investment				6,241	5,526
Net Income (Loss)		26,498	23,794	68,090	57,608
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				111,753	111,622
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		129,313	120,383	254,767	236,508
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		29,925	25,116	123,406	100,285
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		214	214	249	256
Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0	0
All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		159,452	145,713	378,422	337,049
Fuel and purchased power		(21,854)	(20,087)	(43,801)	(42,233)
Purchased gas costs		(11,313)	(6,293)	(65,277)	(48,170)
Depreciation and amortization		(28,354)	(26,932)	(56,032)	(53,532)
Interest expense		(9,142)	(8,989)	(18,304)	(18,001)
Other segment items	[1]	(62,376)	(60,926)	(123,888)	(118,751)
Income tax (provision) benefit		(2,975)	(1,472)	(9,271)	(4,280)
Equity in earnings of investment		3,060	2,780	6,241	5,526
Net Income (Loss)		26,498	23,794	68,090	57,608
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		129,285	120,328	254,691	236,399
Fuel and purchased power		(22,524)	(20,840)	(45,630)	(43,910)
Purchased gas costs		0	0	0	0
Depreciation and amortization		(22,094)	(20,888)	(43,629)	(41,538)
Interest expense		(6,485)	(6,323)	(12,978)	(12,651)
Other segment items	[1]	(58,130)	(57,257)	(114,109)	(110,802)
Income tax (provision) benefit		(472)	641	1,430	3,926
Equity in earnings of investment		0	0	0	0
Net Income (Loss)		19,580	15,661	39,775	31,424
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				83,034	86,755
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		32,483	27,288	132,436	107,668
Fuel and purchased power		0	0	0	0
Purchased gas costs		(13,211)	(7,720)	(72,501)	(53,893)
Depreciation and amortization		(4,347)	(4,163)	(8,579)	(8,245)
Interest expense		(1,768)	(1,709)	(3,531)	(3,419)
Other segment items	[1]	(15,015)	(14,456)	(31,111)	(29,161)
Income tax (provision) benefit		561	810	(4,426)	(2,286)
Equity in earnings of investment		0	0	0	0
Net Income (Loss)		(1,297)	50	12,288	10,664
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				22,975	20,879
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,335	11,160	22,474	22,029
Fuel and purchased power		0	0	0	0
Purchased gas costs		0	0	0	0
Depreciation and amortization		(1,913)	(1,881)	(3,824)	(3,749)
Interest expense		(889)	(957)	(1,795)	(1,931)
Other segment items	[1]	(23)	(17)	(67)	(41)
Income tax (provision) benefit		(2,318)	(2,262)	(4,573)	(4,442)
Equity in earnings of investment		0	0	0	0
Net Income (Loss)		6,192	6,043	12,215	11,866
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				5,744	3,988
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0	0
Fuel and purchased power		0	0	0	0
Purchased gas costs		0	0	0	0
Depreciation and amortization		0	0	0	0
Interest expense		0	0	0	0
Other segment items	[1]	0	0	0	(2)
Income tax (provision) benefit		(835)	(758)	(1,702)	(1,506)
Equity in earnings of investment		3,060	2,780	6,241	5,526
Net Income (Loss)		2,225	2,022	4,539	4,018
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				0	0
Operating Segments [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		173,103	158,776	409,601	366,096
Fuel and purchased power		(22,524)	(20,840)	(45,630)	(43,910)
Purchased gas costs		(13,211)	(7,720)	(72,501)	(53,893)
Depreciation and amortization		(28,354)	(26,932)	(56,032)	(53,532)
Interest expense		(9,142)	(8,989)	(18,304)	(18,001)
Other segment items	[1]	(73,168)	(71,730)	(145,287)	(140,006)
Income tax (provision) benefit		(3,064)	(1,569)	(9,271)	(4,308)
Equity in earnings of investment		3,060	2,780	6,241	5,526
Net Income (Loss)		26,700	23,776	68,817	57,972
Operating Segments [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0	0
Fuel and purchased power		0	0	0	0
Purchased gas costs		0	0	0	0
Depreciation and amortization		0	0	0	0
Interest expense		0	0	0	0
Other segment items	[1]	(291)	(79)	(727)	(392)
Income tax (provision) benefit		89	97	0	28
Equity in earnings of investment		0	0	0	0
Net Income (Loss)		(202)	18	(727)	(364)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				0	0
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(13,651)	(13,063)	(31,179)	(29,047)
Fuel and purchased power		670	753	1,829	1,677
Purchased gas costs		1,898	1,427	7,224	5,723
Depreciation and amortization		0	0	0	0
Interest expense		0	0	0	0
Other segment items	[1]	11,083	10,883	22,126	21,647
Income tax (provision) benefit		0	0	0	0
Equity in earnings of investment		0	0	0	0
Net Income (Loss)		0	0	0	0
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		(28)	(55)	(76)	(109)
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		2,558	2,172	9,030	7,383
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,121	10,946	22,225	21,773
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0	0
Consolidation Elimination Entries [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		13,651	13,063	31,179	29,047
Consolidation Elimination Entries [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0	0
MGE [Member]
Segment Reporting Information [Line Items]
Operating revenues		159,452	145,713	378,422	337,049
Depreciation and amortization		(28,354)	(26,932)	(56,032)	(53,532)
Income tax (provision) benefit		(2,229)	(811)	(7,569)	(2,802)
Net Income (Loss) Attributable to Noncontrolling Interest		5,714	5,766	11,313	11,363
Net Income (Loss)		18,761	15,988	52,965	42,591
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				111,753	111,622
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		129,313	120,383	254,767	236,508
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		29,925	25,116	123,406	100,285
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		214	214	249	256
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		159,452	145,713	378,422	337,049
Fuel and purchased power		(21,854)	(20,087)	(43,801)	(42,233)
Purchased gas costs		(11,313)	(6,293)	(65,277)	(48,170)
Depreciation and amortization		(28,354)	(26,932)	(56,032)	(53,532)
Interest expense		(9,142)	(8,989)	(18,304)	(18,001)
Other segment items	[2]	(62,085)	(60,847)	(123,161)	(118,357)
Income tax (provision) benefit		(2,229)	(811)	(7,569)	(2,802)
Net Income (Loss) Attributable to Noncontrolling Interest		(5,714)	(5,766)	(11,313)	(11,363)
Net Income (Loss)		18,761	15,988	52,965	42,591
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		129,285	120,328	254,691	236,399
Fuel and purchased power		(22,524)	(20,840)	(45,630)	(43,910)
Purchased gas costs		0	0	0	0
Depreciation and amortization		(22,094)	(20,888)	(43,629)	(41,538)
Interest expense		(6,485)	(6,323)	(12,978)	(12,651)
Other segment items	[2]	(58,130)	(57,257)	(114,109)	(110,802)
Income tax (provision) benefit		(472)	641	1,430	3,926
Net Income (Loss) Attributable to Noncontrolling Interest		0	0	0	0
Net Income (Loss)		19,580	15,661	39,775	31,424
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				83,034	86,755
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		32,483	27,288	132,436	107,668
Fuel and purchased power		0	0	0	0
Purchased gas costs		(13,211)	(7,720)	(72,501)	(53,893)
Depreciation and amortization		(4,347)	(4,163)	(8,579)	(8,245)
Interest expense		(1,768)	(1,709)	(3,531)	(3,419)
Other segment items	[2]	(15,015)	(14,456)	(31,111)	(29,161)
Income tax (provision) benefit		561	810	(4,426)	(2,286)
Net Income (Loss) Attributable to Noncontrolling Interest		0	0	0	0
Net Income (Loss)		(1,297)	50	12,288	10,664
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				22,975	20,879
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,335	11,160	22,474	22,029
Fuel and purchased power		0	0	0	0
Purchased gas costs		0	0	0	0
Depreciation and amortization		(1,913)	(1,881)	(3,824)	(3,749)
Interest expense		(889)	(957)	(1,795)	(1,931)
Other segment items	[2]	(23)	(17)	(67)	(41)
Income tax (provision) benefit		(2,318)	(2,262)	(4,573)	(4,442)
Net Income (Loss) Attributable to Noncontrolling Interest		0	0	0	0
Net Income (Loss)		6,192	6,043	12,215	11,866
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				5,744	3,988
MGE [Member] | Operating Segments [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		173,103	158,776	409,601	366,096
Fuel and purchased power		(22,524)	(20,840)	(45,630)	(43,910)
Purchased gas costs		(13,211)	(7,720)	(72,501)	(53,893)
Depreciation and amortization		(28,354)	(26,932)	(56,032)	(53,532)
Interest expense		(9,142)	(8,989)	(18,304)	(18,001)
Other segment items	[2]	(73,168)	(71,730)	(145,287)	(140,004)
Income tax (provision) benefit		(2,229)	(811)	(7,569)	(2,802)
Net Income (Loss) Attributable to Noncontrolling Interest		0	0	0	0
Net Income (Loss)		24,475	21,754	64,278	53,954
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(13,651)	(13,063)	(31,179)	(29,047)
Fuel and purchased power		670	753	1,829	1,677
Purchased gas costs		1,898	1,427	7,224	5,723
Depreciation and amortization		0	0	0	0
Interest expense		0	0	0	0
Other segment items	[2]	11,083	10,883	22,126	21,647
Income tax (provision) benefit		0	0	0	0
Net Income (Loss) Attributable to Noncontrolling Interest		(5,714)	(5,766)	(11,313)	(11,363)
Net Income (Loss)		(5,714)	(5,766)	(11,313)	(11,363)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets				0	0
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		(28)	(55)	(76)	(109)
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		2,558	2,172	9,030	7,383
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,121	10,946	22,225	21,773
MGE [Member] | Consolidation Elimination Entries [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		$ 13,651	$ 13,063	$ 31,179	$ 29,047

[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.