Segment Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues		$ 690,431	$ 714,519	$ 606,584
Depreciation and amortization		(100,352)	(85,549)	(76,983)
Operating Income (Loss)		146,385	137,743	117,294
Interest (expense) income, net		(30,429)	(26,647)	(24,112)
Income tax (provision) benefit		(27,803)	(26,224)	(4,115)
Equity earnings of investments		10,631	9,136	9,270
Net Income		117,699	110,952	105,761
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		2,675,458	2,517,600	2,371,906
Segment, Expenditure, Addition to Long-Lived Assets		222,071	175,030	153,169
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		489,729	465,167	420,286
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		200,012	248,672	185,620
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		690	680	678
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		690,431	714,519	606,584
Depreciation and amortization		(100,352)	(85,549)	(76,983)
Operating Income (Loss)		146,385	137,743	117,294
Interest (expense) income, net		(30,429)	(26,647)	(24,112)
Income tax (provision) benefit		(27,803)	(26,224)	(4,115)
Equity earnings of investments		10,631	9,136	9,270
Net Income		117,699	110,952	105,761
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		490,651	465,123	420,842
Depreciation and amortization		(77,440)	(62,897)	(56,672)
Operating Income (Loss)		90,991	77,672	58,993
Interest (expense) income, net		(20,609)	(17,578)	(15,261)
Income tax (provision) benefit		(10,182)	(7,299)	10,672
Equity earnings of investments		0	0	0
Net Income		75,946	65,187	63,910
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		1,777,903	1,626,373	1,525,163
Segment, Expenditure, Addition to Long-Lived Assets		180,743	141,273	115,234
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		215,513	282,745	208,348
Depreciation and amortization		(15,531)	(15,261)	(12,852)
Operating Income (Loss)		21,663	26,261	25,133
Interest (expense) income, net		(6,038)	(4,787)	(4,315)
Income tax (provision) benefit		(7,175)	(8,492)	(4,922)
Equity earnings of investments		0	0	0
Net Income		14,068	18,215	15,511
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		533,876	530,733	485,345
Segment, Expenditure, Addition to Long-Lived Assets		36,402	27,656	34,071
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		42,276	42,235	41,544
Depreciation and amortization		(7,381)	(7,391)	(7,459)
Operating Income (Loss)		34,729	34,683	33,936
Interest (expense) income, net		(4,004)	(4,322)	(4,577)
Income tax (provision) benefit		(8,370)	(8,272)	(7,998)
Equity earnings of investments		0	0	0
Net Income		22,356	22,090	21,361
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		245,232	247,841	252,584
Segment, Expenditure, Addition to Long-Lived Assets		4,926	6,101	3,864
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	0
Interest (expense) income, net		2	0	0
Income tax (provision) benefit		(2,897)	(2,490)	(2,486)
Equity earnings of investments		10,631	9,136	9,339
Net Income		7,736	6,647	6,852
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets	[1]	86,516	80,642	75,990
Segment, Expenditure, Addition to Long-Lived Assets		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)		(998)	(873)	(768)
Interest (expense) income, net		220	40	41
Income tax (provision) benefit		821	329	619
Equity earnings of investments		0	0	(69)
Net Income		(2,407)	(1,187)	(1,873)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		469,392	467,112	467,954
Segment, Expenditure, Addition to Long-Lived Assets		0	0	0
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(58,009)	(75,584)	(64,150)
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		(437,461)	(435,101)	(435,130)
Segment, Expenditure, Addition to Long-Lived Assets		0	0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		922	(44)	556
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		15,501	34,073	22,728
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		41,586	41,555	40,866
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		690,431	714,519	606,584
Depreciation and amortization		(100,352)	(85,549)	(76,983)
Operating Income (Loss)		147,383	138,616	118,062
Interest (expense) income, net		(30,651)	(26,687)	(24,153)
Income tax (provision) benefit		(25,727)	(24,063)	(2,248)
Net Income		90,502	83,916	78,391
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		2,554,968	2,404,639	2,262,775
Segment, Expenditure, Addition to Long-Lived Assets		222,071	175,030	153,169
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		489,729	465,167	420,286
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		200,012	248,672	185,620
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		690	680	678
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues		690,431	714,519	606,584
Depreciation and amortization		(100,352)	(85,549)	(76,983)
Operating Income (Loss)		147,383	138,616	118,062
Interest (expense) income, net		(30,651)	(26,687)	(24,153)
Income tax (provision) benefit		(25,727)	(24,063)	(2,248)
Net Income		90,502	83,916	78,391
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues		490,651	465,123	420,842
Depreciation and amortization		(77,440)	(62,897)	(56,672)
Operating Income (Loss)		90,991	77,672	58,993
Interest (expense) income, net		(20,609)	(17,578)	(15,261)
Income tax (provision) benefit		(10,182)	(7,299)	10,672
Net Income		75,946	65,187	63,910
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		1,777,903	1,626,373	1,525,163
Segment, Expenditure, Addition to Long-Lived Assets		180,743	141,273	115,234
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		215,513	282,745	208,348
Depreciation and amortization		(15,531)	(15,261)	(12,852)
Operating Income (Loss)		21,663	26,261	25,133
Interest (expense) income, net		(6,038)	(4,787)	(4,315)
Income tax (provision) benefit		(7,175)	(8,492)	(4,922)
Net Income		14,068	18,215	15,511
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		533,876	530,733	485,345
Segment, Expenditure, Addition to Long-Lived Assets		36,402	27,656	34,071
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		42,276	42,235	41,544
Depreciation and amortization		(7,381)	(7,391)	(7,459)
Operating Income (Loss)		34,729	34,683	33,936
Interest (expense) income, net		(4,004)	(4,322)	(4,577)
Income tax (provision) benefit		(8,370)	(8,272)	(7,998)
Net Income		22,356	22,090	21,361
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		245,181	247,791	252,534
Segment, Expenditure, Addition to Long-Lived Assets		4,926	6,101	3,864
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues		(58,009)	(75,584)	(64,150)
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		(21,868)	(21,576)	(22,391)
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Assets		(1,992)	(258)	(267)
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		922	(44)	556
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues		15,501	34,073	22,728
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues		$ 41,586	$ 41,555	$ 40,866

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