v3.26.1
FAIR VALUE MEASUREMENTS - Changes in Fair Value (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning Balance $ 132 $ 123 $ 259 $ 166
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) 86 53 265 154
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date (7) (3) (8) 17
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income 2 (1) 10 6
Settlements (157) (101) (473) (263)
Transfers into Level 3 1 5 2 0
Transfers out of Level 3 (2) (2) (1) 0
Changes in Fair Value Allocated to Regulated Jurisdiction 325 309 326 303
Ending Balance 380 383 380 383
APPALACHIAN POWER COMPANY        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning Balance 21 8 81 35
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) 50 10 162 49
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date 0 0 0 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income 0 0 0 0
Settlements (71) (18) (243) (84)
Transfers into Level 3 0 0 0 0
Transfers out of Level 3 0 0 0 0
Changes in Fair Value Allocated to Regulated Jurisdiction 171 108 171 108
Ending Balance 171 108 171 108
INDIANA MICHIGAN POWER COMPANY        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning Balance 2 4 9 6
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) 6 3 12 13
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date 0 0 0 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income 0 0 0 0
Settlements (8) (7) (20) (19)
Transfers into Level 3 0 0 0 0
Transfers out of Level 3 0 0 0 0
Changes in Fair Value Allocated to Regulated Jurisdiction 22 12 21 12
Ending Balance 22 12 22 12
OHIO POWER COMPANY        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning Balance (32) (51) (33) (47)
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) 0 0 1 0
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date 0 0 0 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income 0 0 0 0
Settlements 2 2 2 4
Transfers into Level 3 0 0 0 0
Transfers out of Level 3 0 0 0 0
Changes in Fair Value Allocated to Regulated Jurisdiction 2 1 2 (5)
Ending Balance (28) (48) (28) (48)
PUBLIC SERVICE COMPANY OF OKLAHOMA        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning Balance 21 15 41 20
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) 8 18 47 38
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date 0 0 0 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income 0 0 0 0
Settlements (29) (33) (88) (58)
Transfers into Level 3 0 0 0 0
Transfers out of Level 3 0 0 0 0
Changes in Fair Value Allocated to Regulated Jurisdiction 43 97 43 97
Ending Balance 43 97 43 97
SOUTHWESTERN ELECTRIC POWER COMPANY        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]        
Beginning Balance 15 13 35 17
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) 9 19 18 42
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date 0 0 0 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income 0 0 0 0
Settlements (24) (32) (52) (59)
Transfers into Level 3 0 0 0 0
Transfers out of Level 3 0 0 0 0
Changes in Fair Value Allocated to Regulated Jurisdiction 42 69 41 69
Ending Balance $ 42 $ 69 $ 42 $ 69