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COMMITMENTS, GUARANTEES AND CONTINGENCIES - Environmental Matters (Details)
$ in Millions
 6 Months Ended
May 08, 2024
USD ($)
Jun. 30, 2025
USD ($)
Nov. 06, 2024
state
Sep. 29, 2023
state
Jun. 05, 2023
state
Environmental Matters [Line Items]          
Number of states contributed to downwind states’ challenges in attaining or maintaining ozone NAAQS         23
Number of states restrictions on fossil-fuel fired power plants         22
Number of states restricted on certain industrial sources         20
States were EPA issued an updated final interim rule addressing the stays       5  
Number of remaining covered states     10    
Incurred remediation costs | $   $ 2.0      
Coal Combustion Residuals | Minnesota Power          
Environmental Matters [Line Items]          
Expected period for costs of compliance 10 years 12 years      
Average of the estimated cost range amount | $ $ 67.8        
Coal Combustion Residuals | Minnesota Power | Minimum          
Environmental Matters [Line Items]          
Estimated costs of compliance | $ 50.0 $ 65.0      
Coal Combustion Residuals | Minnesota Power | Maximum          
Environmental Matters [Line Items]          
Estimated costs of compliance | $ $ 85.0 $ 120.0