v3.26.1
BENEFIT PLANS - Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension Plans        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost $ 26 $ 24 $ 51 $ 48
Interest Cost 52 53 103 106
Expected Return on Plan Assets (63) (71) (128) (141)
Amortization of Net Actuarial Gain (Loss) 11 4 21 8
Settlements 4   (7)  
Net Periodic Benefit Cost (Credit) 30 10 40 21
Pension Plans | AEP Texas        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 3 2 5 4
Interest Cost 4 4 8 9
Expected Return on Plan Assets (5) (5) (10) (11)
Amortization of Net Actuarial Gain (Loss) 1 1 2 1
Settlements (4)   (8)  
Net Periodic Benefit Cost (Credit) (1) 2 (3) 3
Pension Plans | APCo        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 3 2 5 4
Interest Cost 6 7 12 13
Expected Return on Plan Assets (8) (10) (16) (19)
Amortization of Net Actuarial Gain (Loss) 1 0 2 1
Settlements 0   0  
Net Periodic Benefit Cost (Credit) 2 (1) 3 (1)
Pension Plans | I&M        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 2 2 5 5
Interest Cost 6 7 12 13
Expected Return on Plan Assets (8) (10) (16) (19)
Amortization of Net Actuarial Gain (Loss) 1 1 2 1
Settlements 0   0  
Net Periodic Benefit Cost (Credit) 1 0 3 0
Pension Plans | OPCo        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 3 3 5 5
Interest Cost 4 4 9 9
Expected Return on Plan Assets (7) (8) (13) (15)
Amortization of Net Actuarial Gain (Loss) 1 1 2 1
Settlements 0   (6)  
Net Periodic Benefit Cost (Credit) 1 0 (3) 0
Pension Plans | PSO        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 1 2 3 3
Interest Cost 2 2 5 5
Expected Return on Plan Assets (3) (3) (7) (7)
Amortization of Net Actuarial Gain (Loss) 1 0 1 0
Settlements 4   4  
Net Periodic Benefit Cost (Credit) 5 1 6 1
Pension Plans | SWEPCo        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 3 2 5 4
Interest Cost 3 3 6 6
Expected Return on Plan Assets (3) (3) (7) (7)
Amortization of Net Actuarial Gain (Loss) 0 0 1 0
Settlements 0   0  
Net Periodic Benefit Cost (Credit) 3 2 5 3
OPEB        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 1 1 2 2
Interest Cost 7 9 15 17
Expected Return on Plan Assets (30) (28) (59) (56)
Amortization of Prior Service Credit 0 (1) (1) (1)
Amortization of Net Actuarial Gain (Loss) 0   (1) (1)
Net Periodic Benefit Cost (Credit) (22) (19) (44) (39)
OPEB | AEP Texas        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0 1 0 1
Interest Cost 0 0 1 1
Expected Return on Plan Assets (2) (2) (5) (5)
Amortization of Prior Service Credit 0 0 0 0
Amortization of Net Actuarial Gain (Loss) 0   0 0
Net Periodic Benefit Cost (Credit) (2) (1) (4) (3)
OPEB | APCo        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0 0 0 0
Interest Cost 1 2 2 3
Expected Return on Plan Assets (4) (5) (8) (9)
Amortization of Prior Service Credit 0 0 0 0
Amortization of Net Actuarial Gain (Loss) 0   0 0
Net Periodic Benefit Cost (Credit) (3) (3) (6) (6)
OPEB | I&M        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0 0 0 0
Interest Cost 1 1 2 2
Expected Return on Plan Assets (3) (4) (7) (7)
Amortization of Prior Service Credit 0 0 0 0
Amortization of Net Actuarial Gain (Loss) 0   0 0
Net Periodic Benefit Cost (Credit) (2) (3) (5) (5)
OPEB | OPCo        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0 0 0 0
Interest Cost 1 1 1 2
Expected Return on Plan Assets (2) (3) (5) (6)
Amortization of Prior Service Credit 0 0 0 0
Amortization of Net Actuarial Gain (Loss) 0   0 0
Net Periodic Benefit Cost (Credit) (1) (2) (4) (4)
OPEB | PSO        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0 0 0 0
Interest Cost 1 1 1 1
Expected Return on Plan Assets (2) (2) (3) (3)
Amortization of Prior Service Credit 0 0 0 0
Amortization of Net Actuarial Gain (Loss) 0   0 0
Net Periodic Benefit Cost (Credit) (1) (1) (2) (2)
OPEB | SWEPCo        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0 0 0 0
Interest Cost 0 0 1 1
Expected Return on Plan Assets (2) (2) (4) (4)
Amortization of Prior Service Credit 0 0 0 0
Amortization of Net Actuarial Gain (Loss) 0   0 0
Net Periodic Benefit Cost (Credit) $ (2) $ (2) $ (3) $ (3)