v3.25.0.1
REGULATORY MATTERS - APC Rate RSE (Details) - Alabama Power - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Nov. 27, 2024
Oct. 03, 2023
Public Utilities, General Disclosures [Line Items]            
Rate adjustment period   2 years        
Maximum percentage of rate RSE   4.00%        
Maximum annual percentage of ratio rate   5.00%        
Adjusting point of weighted cost of equity   5.98%        
Percent of basis points   0.07%        
Authorized ROE   53.90% 52.30%      
Customer refundable fees, refund payments, tranche one, percentage   25.00%        
Customer refundable fees, refund payments, tranche two, percentage   40.00%        
Customer refundable fees, refund payments, tranche two, percentage   75.00%        
Customer refundable fees, refund payments, tranche one, review year with rate RSE upward adjustment, percentage   50.00%        
Rate RSE refund liability   $ 12 $ 15 $ 62    
Rate RSE increase         4.87%  
Rate RSE increase amount         $ 325  
Customer refund     304      
Deferred income taxes   $ 67 $ 81     $ 24
Minimum            
Public Utilities, General Disclosures [Line Items]            
Public utilities, actual weighted common equity return, threshold, percentage   6.15%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche one   6.15% 6.15% 6.15%    
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche two   6.65%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche three   7.15%        
Public utilities, actual weighted common equity return, threshold, review year with rate RSE upward adjustment, percentage   6.15%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage, tranche one   6.15%        
Maximum            
Public Utilities, General Disclosures [Line Items]            
Public utilities, actual weighted common equity return, threshold, percentage   7.65%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche one   6.65%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche two   7.15%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche three   7.65%        
Customer refundable fees, refund payments, percentage   7.65%        
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage, tranche one   6.90%        
Customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage   6.90%        
Scenario, Forecast            
Public Utilities, General Disclosures [Line Items]            
Authorized ROE 55.00%          
Deferred income taxes $ 14