XML 70 R57.htm IDEA: XBRL DOCUMENT v3.23.3
Business Segments - (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2023
Sep. 30, 2022
Dec. 31, 2022
Business Segments [Line Items]          
Total Operating Revenue $ 378.8 $ 388.3 $ 1,477.1 $ 1,144.9  
Net Income (Loss) Attributable to ALLETE 85.9 33.7 195.6 137.6  
Gain from legal settlements     44.3    
Income tax expense from settlement proceeds     3.8    
Assets 6,644.8   6,644.8   $ 6,845.6
Corporate and Other          
Business Segments [Line Items]          
Total Operating Revenue 378.8 388.3 1,477.1 1,144.9  
Regulated Operations          
Business Segments [Line Items]          
Net Income (Loss) Attributable to ALLETE 34.0 38.3 112.4 119.4  
Assets 4,272.4   4,272.4   4,291.4
Regulated Operations | Operating Segments          
Business Segments [Line Items]          
Total Operating Revenue 314.3 322.6 919.1 960.3  
Regulated Operations | Residential | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 37.9 40.1 123.3 136.7  
Regulated Operations | Commercial | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 49.2 49.0 140.9 141.7  
Regulated Operations | Municipal | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 8.7 9.8 25.2 31.9  
Regulated Operations | Industrial | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 154.3 147.3 439.4 445.7  
Regulated Operations | Other Power Suppliers | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 31.0 46.7 103.2 124.6  
Regulated Operations | Other | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 33.2 29.7 87.1 79.7  
ALLETE Clean Energy          
Business Segments [Line Items]          
Net Income (Loss) Attributable to ALLETE 54.8 (7.3) 66.4 15.0  
Assets 1,599.7   1,599.7   1,873.3
ALLETE Clean Energy | Operating Segments          
Business Segments [Line Items]          
Total Operating Revenue 14.2 15.6 396.8 65.0  
ALLETE Clean Energy | Long-term PSA | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 12.9 14.4 44.5 58.7  
ALLETE Clean Energy | Sale of Wind Energy Facilities | Operating Segments          
Business Segments [Line Items]          
Operating Revenue 0.0 0.0 348.4 0.0  
ALLETE Clean Energy | Other | Operating Segments          
Business Segments [Line Items]          
Operating revenue, other than customer revenue 1.3 1.2 3.9 6.3  
Corporate and Other          
Business Segments [Line Items]          
Net Income (Loss) Attributable to ALLETE (2.9) 2.7 16.8 3.2  
Assets 772.7   772.7   $ 680.9
Corporate and Other | Corporate and Other          
Business Segments [Line Items]          
Total Operating Revenue 50.3 50.1 161.2 119.6  
Corporate and Other | New Energy          
Business Segments [Line Items]          
Purchase price accounting impact       5.7  
Transaction costs       2.6  
Corporate and Other | Long-term Contract | Corporate and Other          
Business Segments [Line Items]          
Operating Revenue 24.6 23.5 74.0 67.5  
Corporate and Other | Sale of Renewable Development Projects | Corporate and Other          
Business Segments [Line Items]          
Operating Revenue 20.8 22.1 73.2 36.6  
Corporate and Other | Other | Corporate and Other          
Business Segments [Line Items]          
Operating Revenue $ 4.9 $ 4.5 $ 14.0 $ 15.5