Rate Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019
Fuel Rules [Abstract]
Return of electric fuel credit, total	[1]						$ (3.2)	$ (1.5)
Deferred fuel rules monitored costs			$ 8.8	[2]	$ 3.3	[1],[3]
Electric Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage			8.81%	[4]	0.00%	[5]
Authorized return on equity, percentage			9.80%		9.80%
Approved equity capital structure, percentage			55.60%		55.80%
Fuel Rules [Abstract]
Fuel rules, bandwidth			1.00%
Effects Of The Tax Cuts And Jobs Act [Abstract]
Return of unprotected excess deferred taxes					$ 18.2
Electric Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	[6]	9.01%
Authorized return on equity, percentage		9.80%
Approved equity capital structure, percentage		55.60%
Fuel Rules [Abstract]
Fuel rules, bandwidth		2.00%
Gas Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage			2.15%	[4]	4.00%	[5]
Authorized return on equity, percentage			9.80%		9.80%
Approved equity capital structure, percentage			55.60%		55.80%
Gas Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	[4]	0.96%
Authorized return on equity, percentage		9.80%
Approved equity capital structure, percentage		55.60%

[1] There was no change to the recovery (refund) in the fuel rules proceedings from the amount MGE deferred.

[2] These costs will be subject to the PSCW's annual review of 2022 fuel costs, expected to be completed in 2023.

[3] In August 2022, the PSCW issued a final decision in the 2021 fuel rules proceedings for MGE to include the recovery of these costs as part of the 2023 electric limited reopener, and the recovery of such costs was included in the reopener.

[4] The electric and gas rate increases were driven by an increase in rate base including our investments in Badger Hollow I and a new customer information system. Also driving the requested electric increase were higher fuel and purchased power costs as well as the completion in 2021 of the one-time return of the electric excess deferred tax credit related to the 2017 Tax Act not restricted by IRS normalization rules. Included in the electric residential rate is a reduction in the customer charge.

[5] The electric rate settlement included an increase in rate base but the associated rate increase was primarily offset by lower fuel and purchased power costs and a one-time $18.2 million return to customers of the portion of excess deferred taxes related to the 2017 Tax Act not restricted by IRS normalization rules. The gas rate increase covered infrastructure costs and technology improvements. The settlement agreement also included escrow accounting treatment for pension and other postretirement benefit costs, bad debt expense, and customer credit card fees. Escrow accounting treatment allows MGE to defer any difference between estimated costs in rates and actual costs incurred until a future rate filing. Any difference would be recorded as a regulatory asset or regulatory liability.

[6] The electric rate increase is driven by generation assets including our investments in Badger Hollow II (solar), Paris (solar and battery), Red Barn (wind), and West Riverside (natural gas). In addition, the reopener request includes an increase in fuel costs and the recovery of deferred 2021 fuel costs. The reopener also revises the depreciation schedule for Columbia Unit 2 and shared equipment to 2029 to align with the depreciation schedule for Columbia Unit 1.