Summary of Significant Accounting Policies (Details-1) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Trade Receivables, Allowance for Doubtful Accounts, and Concentration Risk
Late payment charge on upaid receivables	1.00%
Accounts receivable, allowance for credit loss, writeoff	$ 3.8	$ 2.2
Accounts receivable, allowance for credit loss, period increase	3.9	3.4
Accounts receivable, allowance for credit loss	8.4	8.3
Inventories
Renewable energy credit allowance included in inventory	0.2	1.0
Purchased Gas Adjustment Clause
Purchased gas adjustment, over (under) collected	4.9	1.4
Allowance for Funds Used During Construction
AFUDC - borrowed funds	1.1	1.7	$ 2.1
AFUDC - equity funds	3.0	5.0	5.9
Capitalized Software Costs
Capitalized software	76.2	85.8
Capitalized software - accumulated amortization	53.4	42.6
Capitalized software - amortization	10.8	5.7	5.1
Capitalized Software Hosting Agreement Costs
Capitalized software hosting agreement	12.9	15.6
Capitalized software hosting agreement - accumulated amortization	8.5	5.4
Capitalized software hosting agreement - amortization expense	$ 3.1	2.2	1.8
Excise taxes
License fee tax rate, electric, retail sales	3.19%
License fee tax rate, electric, resale by purchaser	1.59%
License fee tax rate, natural gas	0.97%
License fee tax expense	$ 14.7	$ 13.5	$ 14.1
Minimum [Member]
Capitalized Software Hosting Agreement Costs
Capitalized software hosting agreement, useful life	3 years
Minimum [Member] \| Capitalized Software [Member]
Property, Plant, and Equiptment
Property, plant, and equipment, useful life	4 years
Maximum [Member]
Capitalized Software Hosting Agreement Costs
Capitalized software hosting agreement, useful life	10 years
Maximum [Member] \| Capitalized Software [Member]
Property, Plant, and Equiptment
Property, plant, and equipment, useful life	15 years
PSCW [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate	50.00%	50.00%	50.00%
Rate at which AFUDC was capitalized	7.11%	6.89%	7.03%
Authorized AFUDC rate - Signficiant projects (100%)	100.00%	100.00%	100.00%
Electric [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates	3.20%	3.20%	3.50%
Gas [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates	2.10%	2.20%	2.20%
Non Regulated Energy [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates	2.30%	2.40%	2.30%
MGE Power Elm Road [Member]
Principles of Consolidation
Ownership percentage by parent	100.00%
MGE Power West Campus [Member]
Principles of Consolidation
Ownership percentage by parent	100.00%

Late payment charge recorded on all receivables that remain unpaid after due date.

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The carrying amount of accumulated ammortization of capitalized computer software costs in a hosting arrangement as of the balance sheet date.

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For each income statement presented, the amount charged to expense for amortization of capitalized computer software costs in a hosting arrangement.

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The carrying amount of capitalized computer software costs in a hosting arrangement as of the balance sheet date.

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Useful life of capitalized software assets in hosting agreements

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Electric license fee tax rate for resale by purchaser.

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Natural gas license fee tax rate.

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Rate at which AFUDC was capitalized.

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Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction on 100 percent of Construction Work in Progress. This PSCW authorized rate is on significant projects. Projects that fit this description are: Saratoga Wind, Badger Hollow I, Two Creeks, its customer information billing project, and on certain environmental costs for Columbia.

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Renewable energy credit allowance balances included in inventory and recorded based on specific identification.

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Natural gas rates are subject to a fuel adjustment clause designed to recover or refund the difference between the actual cost of purchased gas and the amount included in rates. Differences between the amounts billed to customers and the actual costs recoverable are deferred and recovered or refunded in future periods by means of prospective monthly adjustments to rates.

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Amount of allowance for credit loss on accounts receivable.

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Amount of increase (decrease) in allowance for credit loss on accounts receivable.

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Amount of direct write-downs of accounts receivable charged against the allowance.

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For each balance sheet presented, the amount of accumulated amortization for capitalized computer software costs.

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Amount of expense for amortization of capitalized computer software costs.

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The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

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The amount of excise and sales taxes included in sales and revenues, which are then deducted as a cost of sales. Includes excise taxes, which are applied to specific types of transactions or items (such as gasoline or alcohol); and sales, use and value added taxes, which are applied to a broad class of revenue-producing transactions involving a wide range of goods and services.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments.

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The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.

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Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction.

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Composite depreciation rate for public utility plants in service.

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