v3.26.3
RATE MATTERS - Regulated Generating Units (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2026
Jan. 31, 2026
Sep. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Public Utilities, General Disclosures [Line Items]              
Asset impairments and other related charges     $ 0   $ 0 $ 31 $ 0
SWEPCo              
Public Utilities, General Disclosures [Line Items]              
Asset impairments and other related charges     0 $ 31 $ 0 31 $ 0
Approved stipulation and settlement, validity period 7 years            
Pirkey Plant | SWEPCo              
Public Utilities, General Disclosures [Line Items]              
Regulatory asset, net investment $ 167   167     167  
Pirkey Plant | SWEPCo | Texas              
Public Utilities, General Disclosures [Line Items]              
Net book value $ 47   47     47  
Pirkey Plant | SWEPCo | 2021 Arkansas Rate Case              
Public Utilities, General Disclosures [Line Items]              
Public utilities, approved recovery, amount   10 years          
Public utilities, return on recovery, percent   3.00%          
Pirkey Plant | SWEPCo | 2025 Texas Base Rate Case              
Public Utilities, General Disclosures [Line Items]              
Public utilities, approved recovery, amount 19 years            
Northeastern Plant, Unit 3 | PSO              
Public Utilities, General Disclosures [Line Items]              
Plant retired, amount       $ 325      
Unrecovered amount $ 152   $ 152     $ 152