v3.26.1
RATE MATTERS - Regulated Generating Units (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 6 Months Ended
Jan. 31, 2026
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Public Utilities, General Disclosures [Line Items]            
Asset Impairments and Other Related Charges   $ 0   $ 0 $ 31 $ 0
SOUTHWESTERN ELECTRIC POWER COMPANY            
Public Utilities, General Disclosures [Line Items]            
Asset Impairments and Other Related Charges   0 $ 31 $ 0 31 $ 0
Pirkey Plant | SOUTHWESTERN ELECTRIC POWER COMPANY            
Public Utilities, General Disclosures [Line Items]            
Regulatory asset, net investment   171     171  
Pirkey Plant | SOUTHWESTERN ELECTRIC POWER COMPANY | Texas            
Public Utilities, General Disclosures [Line Items]            
Net Book Value   46     46  
Pirkey Plant | SOUTHWESTERN ELECTRIC POWER COMPANY | 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%          
Northeastern Plant, Unit 3 | PUBLIC SERVICE COMPANY OF OKLAHOMA            
Public Utilities, General Disclosures [Line Items]            
Plant retired, amount     $ 325      
Unrecovered amount   $ 151     $ 151