v3.26.1
FAIR VALUE MEASUREMENTS - Securities Activity (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Purchases of Investments     $ 1,264 $ 1,337
INDIANA MICHIGAN POWER COMPANY        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Purchases of Investments     1,249 1,330
Spent Nuclear Fuel and Decommissioning Trusts        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Proceeds from Investment Sales $ 661 $ 717 1,209 1,294
Purchases of Investments 676 729 1,249 1,330
Gross Realized Gains on Investment Sales 3 2 8 4
Gross Realized Losses on Investment Sales 3 2 7 3
Spent Nuclear Fuel and Decommissioning Trusts | INDIANA MICHIGAN POWER COMPANY        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Proceeds from Investment Sales 661 717 1,209 1,294
Purchases of Investments 676 729 1,249 1,330
Gross Realized Gains on Investment Sales 3 2 8 4
Gross Realized Losses on Investment Sales $ 3 $ 2 $ 7 $ 3