Variable Interest Entities (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
In-service utility plant, net		$ 2,018,121	$ 1,865,352
Construction work in progress		110,091	105,748
Accrued interest and accrued (prepaid) taxes		9,372	7,868
Deferred income taxes		279,029	252,190
Unamortized discount and debt issuance costs		4,579	4,000
MGE Power Elm Road [Member]
Variable Interest Entity [Line Items]
In-service utility plant, net		162,210	161,167
Construction work in progress		834	3,410
Other Receivables		$ 0	$ 0
Other Receivable, after Allowance for Credit Loss, Related Party, Type [Extensible Enumeration]		Affiliated Entity [Member]	Affiliated Entity [Member]
Accrued interest and accrued (prepaid) taxes		$ 376	$ 51
Deferred income taxes		30,502	30,770
Long-term debt	[1]	43,714	46,343
Noncontrolling interest		103,751	103,333
Unamortized discount and debt issuance costs		300	300
MGE Power West Campus [Member]
Variable Interest Entity [Line Items]
In-service utility plant, net		75,392	77,280
Construction work in progress		1,533	809
Other Receivables		$ 2,550	$ 1,668
Other Receivable, after Allowance for Credit Loss, Related Party, Type [Extensible Enumeration]		Affiliated Entity [Member]	Affiliated Entity [Member]
Accrued interest and accrued (prepaid) taxes		$ (22)	$ (8)
Deferred income taxes		15,249	14,986
Long-term debt	[1]	31,019	33,354
Noncontrolling interest		45,780	44,830
Unamortized discount and debt issuance costs		$ 100	$ 100

[1] MGE Power Elm Road's long-term debt includes debt issuance costs of $0.3 million as of December 31, 2023 and 2022. The debt is secured by a collateral assignment of lease payments that MGE makes to MGE Power Elm Road for use of the Elm Road Units pursuant to the related long-term leases. MGE Power West Campus's long-term debt includes debt issuance costs of $0.1 million as of December 31, 2023 and 2022. The debt is secured by a collateral assignment of lease payments that MGE makes to MGE Power West Campus for use of the cogeneration facility pursuant to the long-term lease. See Footnote 14 for further information on the long-term debt securities.