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Schedule I - Condensed Parent Company Finanical Statements (Details-Notes 1) - Line of Credit [Member] - USD ($)
Dec. 31, 2020
Dec. 31, 2019
Credit facilities [Line Items]    
Line Of Credit Facility Current Borrowing Capacity [1] $ 96,815,000 $ 150,000,000
MGE Energy unsecured committed revolving line of credit totaling $50 million [Member] | MGE Energy [Member]    
Credit facilities [Line Items]    
Line of credit, borrowings outstanding $ 0  
[1] MGE Energy short-term borrowings include MGE Energy and MGE lines of credit and MGE commercial paper.