FINANCING ACTIVITIES - Schedule of Accounts Receivable and Accrued Unbilled Revenues (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
APPALACHIAN POWER COMPANY
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	$ 219	$ 203
INDIANA MICHIGAN POWER COMPANY
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	182	175
OHIO POWER COMPANY
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	538	501
PUBLIC SERVICE COMPANY OF OKLAHOMA
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	113	140
SOUTHWESTERN ELECTRIC POWER COMPANY
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	$ 145	$ 169