v3.25.2
Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue $ 3,261 $ 2,830 $ 9,613 $ 8,654
Electric revenue (3,260) (2,828) (9,612) (8,651)
Off System Sales of Electricity 2 2 4 6
Pre-commercial Ops - capitalized revenue 1 0 3 (3)
Unregulated Operating Revenue 45 49 145 144
Regulated and Unregulated Operating Revenue $ 3,306 2,879 $ 9,758 $ 8,798
Total long duration contract revenue recognition 2,967   8,782  
Percent of wholesale Credit offered     310.00%  
Percent of Generation Flexibility Credit     5.00%  
NES's % of operating revenues     800.00% 800.00%
Percent of Generation Flexibility Credit     5.00%  
MLGW's % of operating revenues     800.00% 800.00%
ALABAMA        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue $ 477 409 $ 1,428 $ 1,274
GEORGIA        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue 74 65 242 214
KENTUCKY        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue 209 179 605 557
MISSISSIPPI        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue 310 277 886 816
NORTH CAROLINA        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue 18 19 67 70
TENNESSEE        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue 2,161 1,869 6,345 5,685
VIRGINIA        
Disaggregation of Revenue [Line Items]        
Regulated Operating Revenue $ 11 $ 10 $ 39 $ 35