Asset Retirement Obligations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation, beginning balance		$ 54,430	$ 50,260
Liabilities incurred	[1]	25,756	2,402
Accretion expense		2,671	2,035
Liabilities settled	[2]	(7,548)	(107)
Revisions in estimated cash flows	[3]	(6,177)	(160)
Asset retirement obligation, ending balance		$ 69,132	$ 54,430

[1] In June 2024, MGE recorded an asset retirement obligation for its estimated share of the legal liability associated with the effect of the CCR Legacy Rule for remediation and groundwater compliance monitoring at Columbia. See Footnote 16 for further information on the CCR Legacy Rule.

[2] In 2024, MGE settled $6.8 million of liabilities related to the Columbia Ash Pond.

[3] In December 2024, revisions were made related to the Columbia CCR asset retirement obligation estimates based on additional analysis completed on the impacted areas.