Segment Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating revenues		$ 714,519	$ 606,584	$ 538,633
Depreciation and amortization		(85,549)	(76,983)	(74,188)
Operating Income (Loss)		137,743	117,294	109,997
Interest (expense) income, net		(26,647)	(24,112)	(23,521)
Income tax (provision) benefit		(26,224)	(4,115)	(19,423)
Equity earnings of investments		9,136	9,270	10,221
Net Income		110,952	105,761	92,418
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		2,517,600	2,371,906	2,253,651
Capital expenditure		175,030	153,169	203,139
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		465,167	420,286	393,692
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		248,672	185,620	144,261
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		680	678	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		714,519	606,584	538,633
Depreciation and amortization		(85,549)	(76,983)	(74,188)
Operating Income (Loss)		137,743	117,294	109,997
Interest (expense) income, net		(26,647)	(24,112)	(23,521)
Income tax (provision) benefit		(26,224)	(4,115)	(19,423)
Equity earnings of investments		9,136	9,270	10,221
Net Income		110,952	105,761	92,418
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		465,123	420,842	394,457
Depreciation and amortization		(62,897)	(56,672)	(54,658)
Operating Income (Loss)		77,672	58,993	57,847
Interest (expense) income, net		(17,578)	(15,261)	(14,446)
Income tax (provision) benefit		(7,299)	10,672	(4,230)
Equity earnings of investments		0	0	0
Net Income		65,187	63,910	50,522
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		1,626,373	1,525,163	1,421,302
Capital expenditure		141,273	115,234	162,210
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		282,745	208,348	156,418
Depreciation and amortization		(15,261)	(12,852)	(12,049)
Operating Income (Loss)		26,261	25,133	19,674
Interest (expense) income, net		(4,787)	(4,315)	(4,370)
Income tax (provision) benefit		(8,492)	(4,922)	(4,805)
Equity earnings of investments		0	0	0
Net Income		18,215	15,511	14,167
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		530,733	485,345	444,702
Capital expenditure		27,656	34,071	36,906
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		42,235	41,544	41,082
Depreciation and amortization		(7,391)	(7,459)	(7,481)
Operating Income (Loss)		34,683	33,936	33,460
Interest (expense) income, net		(4,322)	(4,577)	(4,826)
Income tax (provision) benefit		(8,272)	(7,998)	(7,800)
Equity earnings of investments		0	0	0
Net Income		22,090	21,361	20,834
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		247,841	252,584	254,298
Capital expenditure		6,101	3,864	4,023
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
Depreciation and amortization		0	0	0
Operating Income (Loss)		0	0	(1)
Interest (expense) income, net		0	0	0
Income tax (provision) benefit		(2,490)	(2,486)	(2,786)
Equity earnings of investments		9,136	9,339	10,221
Net Income		6,647	6,852	7,434
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets	[1]	80,642	75,990	74,480
Capital expenditure		0	0	0
Operating Segments [Member] | All Others [Members]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
Depreciation and amortization		0	0	0
Operating Income (Loss)		(873)	(768)	(983)
Interest (expense) income, net		40	41	121
Income tax (provision) benefit		329	619	198
Equity earnings of investments		0	(69)	0
Net Income		(1,187)	(1,873)	(539)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		467,112	467,954	495,483
Capital expenditure		0	0	0
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(75,584)	(64,150)	(53,324)
Depreciation and amortization		0	0	0
Operating Income (Loss)		0	0	0
Interest (expense) income, net		0	0	0
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]
Assets		(435,101)	(435,130)	(436,614)
Capital expenditure		0	0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		(44)	556	765
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		34,073	22,728	12,157
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		41,555	40,866	40,402
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0
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		714,519	606,584	538,633
Depreciation and amortization		(85,549)	(76,983)	(74,188)
Operating Income (Loss)		138,616	118,062	110,981
Interest (expense) income, net		(26,687)	(24,153)	(23,642)
Income tax (provision) benefit		(24,063)	(2,248)	(16,835)
Net Income		83,916	78,391	63,130
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		2,404,639	2,262,775	2,119,971
Capital expenditure		175,030	153,169	203,139
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		465,167	420,286	393,692
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		248,672	185,620	144,261
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		680	678	680
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		714,519	606,584	538,633
Depreciation and amortization		(85,549)	(76,983)	(74,188)
Operating Income (Loss)		138,616	118,062	110,981
Interest (expense) income, net		(26,687)	(24,153)	(23,642)
Income tax (provision) benefit		(24,063)	(2,248)	(16,835)
Net Income		83,916	78,391	63,130
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		465,123	420,842	394,457
Depreciation and amortization		(62,897)	(56,672)	(54,658)
Operating Income (Loss)		77,672	58,993	57,847
Interest (expense) income, net		(17,578)	(15,261)	(14,446)
Income tax (provision) benefit		(7,299)	10,672	(4,230)
Net Income		65,187	63,910	50,522
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		1,626,373	1,525,163	1,421,302
Capital expenditure		141,273	115,234	162,210
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		282,745	208,348	156,418
Depreciation and amortization		(15,261)	(12,852)	(12,049)
Operating Income (Loss)		26,261	25,133	19,674
Interest (expense) income, net		(4,787)	(4,315)	(4,370)
Income tax (provision) benefit		(8,492)	(4,922)	(4,805)
Net Income		18,215	15,511	14,167
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		530,733	485,345	444,702
Capital expenditure		27,656	34,071	36,906
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		42,235	41,544	41,082
Depreciation and amortization		(7,391)	(7,459)	(7,481)
Operating Income (Loss)		34,683	33,936	33,460
Interest (expense) income, net		(4,322)	(4,577)	(4,826)
Income tax (provision) benefit		(8,272)	(7,998)	(7,800)
Net Income		22,090	21,361	20,834
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		247,791	252,534	254,248
Capital expenditure		6,101	3,864	4,023
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(75,584)	(64,150)	(53,324)
Depreciation and amortization		0	0	0
Operating Income (Loss)		0	0	0
Interest (expense) income, net		0	0	0
Income tax (provision) benefit		0	0	0
Net Income		(21,576)	(22,391)	(22,393)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		(258)	(267)	(281)
Capital expenditure		0	0	0
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		(44)	556	765
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		34,073	22,728	12,157
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		$ 41,555	$ 40,866	$ 40,402

[1] The Transmission Investment segment represents MGE Energy's investment in equity method investees.