Variable Interest Entities (Details) - USD ($) $ in Thousands		Dec. 31, 2025	Dec. 31, 2024
Variable Interest Entity [Line Items]
In-service utility plant, net		$ 2,279,899	$ 2,149,138
Construction work in progress		292,969	138,208
Accrued interest and accrued (prepaid) taxes		10,269	11,558
Deferred income taxes		337,798	316,397
Unamortized discount and debt issuance costs		4,277	4,419
MGE Power Elm Road [Member]
Variable Interest Entity [Line Items]
In-service utility plant, net		157,652	159,576
Construction work in progress		485	514
Other Receivables		$ 0	$ 0
Other Receivable, after Allowance for Credit Loss, Related Party [Extensible Enumeration]		Affiliated Entity [Member]	Affiliated Entity [Member]
Accrued interest and accrued (prepaid) taxes		$ (129)	$ (184)
Deferred income taxes		31,153	30,902
Long-term debt	[1]	38,447	41,082
Noncontrolling interest		104,479	104,304
Unamortized discount and debt issuance costs		200	200
MGE Power West Campus [Member]
Variable Interest Entity [Line Items]
In-service utility plant, net		78,970	76,378
Construction work in progress		4,174	3,052
Other Receivables		$ 861	$ 911
Other Receivable, after Allowance for Credit Loss, Related Party [Extensible Enumeration]		Affiliated Entity [Member]	Affiliated Entity [Member]
Accrued interest and accrued (prepaid) taxes		$ (46)	$ (78)
Deferred income taxes		15,601	15,435
Long-term debt	[1]	25,941	28,550
Noncontrolling interest		52,309	46,082
Unamortized discount and debt issuance costs		$ 100	$ 100

[1] MGE Power Elm Road's long-term debt includes debt issuance costs of $0.2 million as of December 31, 2025 and 2024. 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, 2025 and 2024. 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.