v3.26.3
ACQUISITIONS, DISPOSITIONS AND IMPAIRMENTS - Narrative (Details)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Jan. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
facility
Aug. 31, 2026
May 31, 2026
Aug. 31, 2025
Jun. 30, 2025
May 31, 2025
Asset Acquisition, Contingent Consideration [Line Items]                        
Asset impairments and other related charges   $ 0   $ 0 $ 31 $ 0            
AEP TRANSMISSION COMPANY, LLC | Midwest Transmission Holdings                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Ownership percentage selling 19.90%                      
Proceeds from noncontrolling interests, gross $ 2,820                      
SOUTHWESTERN ELECTRIC POWER COMPANY                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Asset impairments and other related charges   $ 0 $ 31 $ 0 $ 31 $ 0            
Lazbuddie Wind Energy, LLC | PUBLIC SERVICE COMPANY OF OKLAHOMA                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired               100.00%        
Big Sandy Peaker Plant, LLC | INDIANA MICHIGAN POWER COMPANY                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired               100.00%        
Wolf Hills Energy, LLC | AGR                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired               100.00%        
Grover Hill Wind Project | APPALACHIAN POWER COMPANY                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired                 100.00%      
Oregon Clean Energy Center | INDIANA MICHIGAN POWER COMPANY                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired     100.00%                  
Pixley Solar Energy, LLC | PUBLIC SERVICE COMPANY OF OKLAHOMA                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired                       100.00%
Flat Ridge IV Wind, LLC | PUBLIC SERVICE COMPANY OF OKLAHOMA                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired                     100.00%  
Green Country Energy, LLC | PUBLIC SERVICE COMPANY OF OKLAHOMA                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired                     100.00%  
Flat Ridge V Wind Energy, LLC | PUBLIC SERVICE COMPANY OF OKLAHOMA                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Percentage of shares acquired                   100.00%    
Three Electric Generation Facilities | PUBLIC SERVICE COMPANY OF OKLAHOMA                        
Asset Acquisition, Contingent Consideration [Line Items]                        
Number of properties | facility             4          
Payments to acquire facilities             $ 1,700