XML 72 R58.htm IDEA: XBRL DOCUMENT v3.24.1.u1
Business Segments - (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Business Segments [Line Items]      
Total Operating Revenue $ 403.3 $ 564.9  
Net Income Attributable to ALLETE 50.7 58.2  
Assets 6,604.6   $ 6,656.4
Corporate and Other      
Business Segments [Line Items]      
Total Operating Revenue 403.3 564.9  
Regulated Operations      
Business Segments [Line Items]      
Net Income Attributable to ALLETE 44.2 40.6  
Assets 4,345.1   4,335.0
Regulated Operations | Operating Segments      
Business Segments [Line Items]      
Total Operating Revenue 338.3 312.6  
Regulated Operations | Residential | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 51.5 49.4  
Regulated Operations | Commercial | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 49.7 47.7  
Regulated Operations | Municipal | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 9.0 8.9  
Regulated Operations | Industrial | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 159.5 144.9  
Regulated Operations | Other Power Suppliers | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 40.0 35.9  
Regulated Operations | Other | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 28.6 25.8  
ALLETE Clean Energy      
Business Segments [Line Items]      
Net Income Attributable to ALLETE 3.8 8.5  
Assets 1,580.0   1,594.1
ALLETE Clean Energy | Operating Segments      
Business Segments [Line Items]      
Total Operating Revenue 19.1 201.5  
ALLETE Clean Energy | Long-term PSA | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 17.8 18.4  
ALLETE Clean Energy | Sale of Wind Energy Facilities | Operating Segments      
Business Segments [Line Items]      
Operating Revenue 0.0 181.8  
ALLETE Clean Energy | Other | Operating Segments      
Business Segments [Line Items]      
Operating revenue, other than customer revenue 1.3 1.3  
Corporate and Other      
Business Segments [Line Items]      
Net Income Attributable to ALLETE 2.7 9.1  
Assets 679.5   $ 727.3
Corporate and Other | Corporate and Other      
Business Segments [Line Items]      
Total Operating Revenue 45.9 50.8  
Corporate and Other | Long-term Contract | Corporate and Other      
Business Segments [Line Items]      
Operating Revenue 25.4 25.5  
Corporate and Other | Sale of Renewable Development Projects | Corporate and Other      
Business Segments [Line Items]      
Operating Revenue 13.9 19.8  
Corporate and Other | Other | Corporate and Other      
Business Segments [Line Items]      
Operating Revenue $ 6.6 $ 5.5