v3.26.1
Summary of Significant Accounting Principles (Details-1) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Supplemental Cash Flow Information [Abstract]        
US Federal [1] $ (7,232) $ 3,681    
Accrued capital expenditures 26,099 9,120    
Short-Term Debt [Abstract]        
Short-Term Debt 34,750   $ 94,527  
Cash, Cash Equivalents, And Restricted Cash [Abstract]        
Cash and cash equivalents 16,621   5,666  
Restricted cash 1,014   952  
Receivable - margin account 2,048   2,118  
Cash, cash equivalents, and restricted cash 19,683 13,136 8,736 $ 24,496
Indemnification Agreement [Member] | Renewable Tax Credits Transferred [Member]        
Effects of The Inflation Reduction Act [Abstract]        
Guarantor Obligations, Liquidation Proceeds, Monetary Amount 9,500      
Wisconsin        
Supplemental Cash Flow Information [Abstract]        
US State and Local 3,800 5,000    
US State and Local - Other        
Supplemental Cash Flow Information [Abstract]        
US State and Local 91 66    
MGE [Member]        
Supplemental Cash Flow Information [Abstract]        
US Federal [1],[2] (7,872) 3,351    
Accrued capital expenditures [2] 26,099 9,120    
Short-Term Debt [Abstract]        
Short-Term Debt 34,750   94,527  
Cash, Cash Equivalents, And Restricted Cash [Abstract]        
Cash and cash equivalents 10,737   2,248  
Restricted cash 1,014   952  
Receivable - margin account 2,048   2,118  
Cash, cash equivalents, and restricted cash 13,799 6,092 $ 5,318 $ 20,059
MGE [Member] | Wisconsin        
Supplemental Cash Flow Information [Abstract]        
US State and Local [2] 3,620 4,980    
MGE [Member] | US State and Local - Other        
Supplemental Cash Flow Information [Abstract]        
US State and Local [2] $ 0 $ 0    
[1] For the six months ended June 30, 2026, federal tax receipts include $9.5 million of proceeds from the transfer of federal tax credits under Internal Revenue Code Section 6418.
[2] MGE Energy files a consolidated federal income tax return with its subsidiaries. While taxes are filed on a consolidated basis, MGE calculates its respective share of tax liability and makes intercompany tax payments to or from its parent company.