Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Operating revenues		$ 218,970	$ 191,336
Depreciation and amortization		(27,678)	(26,600)
Income tax (provision) benefit		(6,296)	(2,808)
Equity in earnings of investment		3,181	2,746
Net Income (Loss)		41,592	33,814
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		47,653	44,771
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		125,454	116,125
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		93,481	75,169
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		35	42
Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0
All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		218,970	191,336
Fuel and purchased power		(21,947)	(22,146)
Purchased gas costs		(53,964)	(41,877)
Depreciation and amortization		(27,678)	(26,600)
Interest expense		(9,162)	(9,012)
Other segment items	[1]	(61,512)	(57,825)
Income tax (provision) benefit		(6,296)	(2,808)
Equity in earnings of investment		3,181	2,746
Net Income (Loss)		41,592	33,814
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		125,406	116,070
Fuel and purchased power		(23,106)	(23,070)
Purchased gas costs		0	0
Depreciation and amortization		(21,535)	(20,648)
Interest expense		(6,493)	(6,328)
Other segment items	[1]	(55,979)	(53,546)
Income tax (provision) benefit		1,902	3,286
Equity in earnings of investment		0	0
Net Income (Loss)		20,195	15,764
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		31,322	32,964
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		99,953	80,381
Fuel and purchased power		0	0
Purchased gas costs		(59,290)	(46,173)
Depreciation and amortization		(4,232)	(4,083)
Interest expense		(1,763)	(1,710)
Other segment items	[1]	(16,096)	(14,705)
Income tax (provision) benefit		(4,987)	(3,097)
Equity in earnings of investment		0	0
Net Income (Loss)		13,585	10,613
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		14,017	8,560
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,139	10,869
Fuel and purchased power		0	0
Purchased gas costs		0	0
Depreciation and amortization		(1,911)	(1,869)
Interest expense		(906)	(974)
Other segment items	[1]	(44)	(23)
Income tax (provision) benefit		(2,255)	(2,180)
Equity in earnings of investment		0	0
Net Income (Loss)		6,023	5,823
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		2,314	3,247
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0
Fuel and purchased power		0	0
Purchased gas costs		0	0
Depreciation and amortization		0	0
Interest expense		0	0
Other segment items	[1]	0	(1)
Income tax (provision) benefit		(867)	(749)
Equity in earnings of investment		3,181	2,746
Net Income (Loss)		2,314	1,996
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		236,498	207,320
Fuel and purchased power		(23,106)	(23,070)
Purchased gas costs		(59,290)	(46,173)
Depreciation and amortization		(27,678)	(26,600)
Interest expense		(9,162)	(9,012)
Other segment items	[1]	(72,119)	(68,275)
Income tax (provision) benefit		(6,207)	(2,740)
Equity in earnings of investment		3,181	2,746
Net Income (Loss)		42,117	34,196
Operating Segments [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0
Fuel and purchased power		0	0
Purchased gas costs		0	0
Depreciation and amortization		0	0
Interest expense		0	0
Other segment items	[1]	(436)	(314)
Income tax (provision) benefit		(89)	(68)
Equity in earnings of investment		0	0
Net Income (Loss)		(525)	(382)
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		(17,528)	(15,984)
Fuel and purchased power		1,159	924
Purchased gas costs		5,326	4,296
Depreciation and amortization		0	0
Interest expense		0	0
Other segment items	[1]	11,043	10,764
Income tax (provision) benefit		0	0
Equity in earnings of investment		0	0
Net Income (Loss)		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		(48)	(55)
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		6,472	5,212
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,104	10,827
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0
Consolidation Elimination Entries [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		17,528	15,984
Consolidation Elimination Entries [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0
MGE [Member]
Segment Reporting Information [Line Items]
Operating revenues		218,970	191,336
Depreciation and amortization		(27,678)	(26,600)
Income tax (provision) benefit		(5,340)	(1,991)
Net Income (Loss) Attributable to Noncontrolling Interest		5,599	5,597
Net Income (Loss)		34,204	26,603
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		47,653	44,771
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		125,454	116,125
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		93,481	75,169
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		35	42
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		218,970	191,336
Fuel and purchased power		(21,947)	(22,146)
Purchased gas costs		(53,964)	(41,877)
Depreciation and amortization		(27,678)	(26,600)
Interest expense		(9,162)	(9,012)
Other segment items		(61,076)	(57,510)	[2]
Income tax (provision) benefit		(5,340)	(1,991)
Net Income (Loss) Attributable to Noncontrolling Interest		(5,599)	(5,597)
Net Income (Loss)		34,204	26,603
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		125,406	116,070
Fuel and purchased power		(23,106)	(23,070)
Purchased gas costs		0	0
Depreciation and amortization		(21,535)	(20,648)
Interest expense		(6,493)	(6,328)
Other segment items		(55,979)	(53,546)	[2]
Income tax (provision) benefit		1,902	3,286
Net Income (Loss) Attributable to Noncontrolling Interest		0	0
Net Income (Loss)		20,195	15,764
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		31,322	32,964
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		99,953	80,381
Fuel and purchased power		0	0
Purchased gas costs		(59,290)	(46,173)
Depreciation and amortization		(4,232)	(4,083)
Interest expense		(1,763)	(1,710)
Other segment items		(16,096)	(14,705)	[2]
Income tax (provision) benefit		(4,987)	(3,097)
Net Income (Loss) Attributable to Noncontrolling Interest		0	0
Net Income (Loss)		13,585	10,613
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		14,017	8,560
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,139	10,869
Fuel and purchased power		0	0
Purchased gas costs		0	0
Depreciation and amortization		(1,911)	(1,869)
Interest expense		(906)	(974)
Other segment items		(44)	(23)	[2]
Income tax (provision) benefit		(2,255)	(2,180)
Net Income (Loss) Attributable to Noncontrolling Interest		0	0
Net Income (Loss)		6,023	5,823
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment, Expenditure, Addition to Long-Lived Assets		2,314	3,247
MGE [Member] | Operating Segments [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		236,498	207,320
Fuel and purchased power		(23,106)	(23,070)
Purchased gas costs		(59,290)	(46,173)
Depreciation and amortization		(27,678)	(26,600)
Interest expense		(9,162)	(9,012)
Other segment items		(72,119)	(68,274)	[2]
Income tax (provision) benefit		(5,340)	(1,991)
Net Income (Loss) Attributable to Noncontrolling Interest		0	0
Net Income (Loss)		39,803	32,200
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(17,528)	(15,984)
Fuel and purchased power		1,159	924
Purchased gas costs		5,326	4,296
Depreciation and amortization		0	0
Interest expense		0	0
Other segment items		11,043	10,764	[2]
Income tax (provision) benefit		0	0
Net Income (Loss) Attributable to Noncontrolling Interest		(5,599)	(5,597)
Net Income (Loss)		(5,599)	(5,597)
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		(48)	(55)
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		6,472	5,212
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		11,104	10,827
MGE [Member] | Consolidation Elimination Entries [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Operating revenues		$ 17,528	$ 15,984

[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.