FAIR VALUE MEASUREMENTS - Fair Value of Assets and Liabilities on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Assets:
Restricted Cash	$ 71	$ 43
Total Other Temporary Investments and Restricted Cash	291	258
Total Risk Management Assets	617	499
Total Spent Nuclear Fuel and Decommissioning Trusts	4,916	4,395
Total Assets	5,824	5,152
Liabilities:
Total Risk Management Liabilities	310	324
Commodity
Assets:
Total Risk Management Assets	513	374
Liabilities:
Total Risk Management Liabilities	274	252
Commodity Contract, Cash Flow Hedging
Assets:
Total Risk Management Assets	104	125
Liabilities:
Total Risk Management Liabilities	6	0
Fair Value Hedge Instruments
Liabilities:
Total Risk Management Liabilities	30	72
AEP TEXAS INC.
Assets:
Restricted Cash	14	24
Total Risk Management Assets	0	0
Liabilities:
Total Risk Management Liabilities	0	0
APPALACHIAN POWER COMPANY
Assets:
Restricted Cash	18	16
Total Risk Management Assets	82	37
Total Assets	100	53
Liabilities:
Total Risk Management Liabilities	3	2
APPALACHIAN POWER COMPANY | Commodity
Assets:
Total Risk Management Assets	82	37
Liabilities:
Total Risk Management Liabilities	3	2
INDIANA MICHIGAN POWER COMPANY
Assets:
Total Risk Management Assets	10	18
Total Spent Nuclear Fuel and Decommissioning Trusts	4,916	4,395
Total Assets	4,926	4,413
Liabilities:
Total Risk Management Liabilities	0	0
INDIANA MICHIGAN POWER COMPANY | Commodity
Assets:
Total Risk Management Assets	10	18
Liabilities:
Total Risk Management Liabilities	0	0
OHIO POWER COMPANY
Assets:
Total Risk Management Assets	0	0
Liabilities:
Total Risk Management Liabilities	33	47
OHIO POWER COMPANY | Commodity
Liabilities:
Total Risk Management Liabilities	33	47
PUBLIC SERVICE COMPANY OF OKLAHOMA
Assets:
Total Risk Management Assets	42	22
Liabilities:
Total Risk Management Liabilities	28	6
PUBLIC SERVICE COMPANY OF OKLAHOMA | Commodity
Assets:
Total Risk Management Assets	42	22
Liabilities:
Total Risk Management Liabilities	28	6
SOUTHWESTERN ELECTRIC POWER COMPANY
Assets:
Restricted Cash	15	3
Total Risk Management Assets	35	18
Total Assets	50	21
Liabilities:
Total Risk Management Liabilities	11	2
SOUTHWESTERN ELECTRIC POWER COMPANY | Commodity
Assets:
Total Risk Management Assets	35	18
Liabilities:
Total Risk Management Liabilities	11	2
Other
Assets:
Total Other Temporary Investments and Restricted Cash	36	13
Risk management asset, offset	727	(531)
Total Spent Nuclear Fuel and Decommissioning Trusts	15	14
Assets including netting	(676)	(504)
Liabilities:
Risk management liabilities, offset	(647)	(447)
Other | Commodity
Assets:
Risk management asset, offset	(713)	(518)
Liabilities:
Risk management liabilities, offset	(633)	(434)
Other | Commodity Contract, Cash Flow Hedging
Assets:
Risk management asset, offset	(14)	(13)
Liabilities:
Risk management liabilities, offset	(14)	(13)
Other | Fair Value Hedge Instruments
Liabilities:
Risk management liabilities, offset	0	0
Other | AEP TEXAS INC.
Assets:
Restricted Cash	0	0
Other | APPALACHIAN POWER COMPANY
Assets:
Restricted Cash	0	0
Risk management asset, offset	(2)	(5)
Other | APPALACHIAN POWER COMPANY | Commodity
Assets:
Risk management asset, offset	(2)	(5)
Liabilities:
Risk management liabilities, offset	(3)	(5)
Other | INDIANA MICHIGAN POWER COMPANY
Assets:
Total Spent Nuclear Fuel and Decommissioning Trusts	15	14
Assets including netting	4	6
Other | INDIANA MICHIGAN POWER COMPANY | Commodity
Assets:
Risk management asset, offset	(11)	(8)
Liabilities:
Risk management liabilities, offset	(11)	(10)
Other | OHIO POWER COMPANY | Commodity
Liabilities:
Risk management liabilities, offset	0	0
Other | PUBLIC SERVICE COMPANY OF OKLAHOMA | Commodity
Assets:
Risk management asset, offset	(2)	(2)
Liabilities:
Risk management liabilities, offset	(2)	(2)
Other | SOUTHWESTERN ELECTRIC POWER COMPANY
Assets:
Restricted Cash	0	0
Risk management asset, offset	(2)	(1)
Other | SOUTHWESTERN ELECTRIC POWER COMPANY | Commodity
Assets:
Risk management asset, offset	(2)	(1)
Liabilities:
Risk management liabilities, offset	(2)	(1)
Mutual Funds
Assets:
Fixed Income Securities:	165	162
Equity securities, fair value disclosure	42	40
Mutual Funds | Other
Assets:
Fixed Income Securities:	0	0
Equity securities, fair value disclosure	0	0
Subtotal Fixed Income Securities
Assets:
Fixed Income Securities:	1,727	1,533
Subtotal Fixed Income Securities | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	1,727	1,533
Subtotal Fixed Income Securities | Other
Assets:
Fixed Income Securities:	0	0
Subtotal Fixed Income Securities | Other | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
United States Government
Assets:
Fixed Income Securities:	1,351	1,323
United States Government | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	1,351	1,323
United States Government | Other
Assets:
Fixed Income Securities:	0	0
United States Government | Other | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Corporate Debt
Assets:
Fixed Income Securities:	376	210
Corporate Debt | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	376	210
Corporate Debt | Other
Assets:
Fixed Income Securities:	0	0
Corporate Debt | Other | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Equity Securities - Domestic
Assets:
Equity securities, fair value disclosure	3,160	2,838
Equity Securities - Domestic | INDIANA MICHIGAN POWER COMPANY
Assets:
Equity securities, fair value disclosure	3,160	2,838
Equity Securities - Domestic | Other
Assets:
Equity securities, fair value disclosure	0	0
Equity Securities - Domestic | Other | INDIANA MICHIGAN POWER COMPANY
Assets:
Equity securities, fair value disclosure	0	0
Restricted Cash | Other
Assets:
Restricted Cash	23	0
Other Cash Deposits
Assets:
Cash and cash equivalents, fair value disclosure	13	13
Other Cash Deposits | Other
Assets:
Cash and cash equivalents, fair value disclosure	13	13
Cash and Cash Equivalents
Assets:
Cash and cash equivalents, fair value disclosure	29	24
Cash and Cash Equivalents | INDIANA MICHIGAN POWER COMPANY
Assets:
Cash and cash equivalents, fair value disclosure	29	24
Cash and Cash Equivalents | Other
Assets:
Cash and cash equivalents, fair value disclosure	15	14
Cash and Cash Equivalents | Other | INDIANA MICHIGAN POWER COMPANY
Assets:
Cash and cash equivalents, fair value disclosure	15	14
Level 1 | 2026
Liabilities:
Maturities of net fair value of risk management contracts	(2)
Level 1 | 2025
Liabilities:
Maturities of net fair value of risk management contracts		(1)
Level 1 | Estimate of Fair Value Measurement
Assets:
Restricted Cash	48	43
Total Other Temporary Investments and Restricted Cash	255	245
Risk Management Assets	2	3
Total Spent Nuclear Fuel and Decommissioning Trusts	3,174	2,848
Total Assets	3,431	3,096
Liabilities:
Risk Management Liabilities	4	4
Level 1 | Estimate of Fair Value Measurement | Commodity
Assets:
Risk Management Assets	2	3
Liabilities:
Risk Management Liabilities	4	4
Level 1 | Estimate of Fair Value Measurement | Commodity Contract, Cash Flow Hedging
Assets:
Risk Management Assets	0	0
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Estimate of Fair Value Measurement | Fair Value Hedge Instruments
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Estimate of Fair Value Measurement | AEP TEXAS INC.
Assets:
Restricted Cash	14	24
Level 1 | Estimate of Fair Value Measurement | APPALACHIAN POWER COMPANY
Assets:
Restricted Cash	18	16
Total Assets	18	16
Level 1 | Estimate of Fair Value Measurement | APPALACHIAN POWER COMPANY | Commodity
Assets:
Risk Management Assets	0	0
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Total Spent Nuclear Fuel and Decommissioning Trusts	3,174	2,848
Total Assets	3,174	2,848
Level 1 | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY | Commodity
Assets:
Risk Management Assets	0	0
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Estimate of Fair Value Measurement | OHIO POWER COMPANY | Commodity
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Estimate of Fair Value Measurement | PUBLIC SERVICE COMPANY OF OKLAHOMA | Commodity
Assets:
Risk Management Assets	0	0
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Estimate of Fair Value Measurement | SOUTHWESTERN ELECTRIC POWER COMPANY
Assets:
Restricted Cash	15	3
Total Assets	15	3
Level 1 | Estimate of Fair Value Measurement | SOUTHWESTERN ELECTRIC POWER COMPANY | Commodity
Assets:
Risk Management Assets	0	0
Liabilities:
Risk Management Liabilities	0	0
Level 1 | Mutual Funds | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	165	162
Equity securities, fair value disclosure	42	40
Level 1 | Subtotal Fixed Income Securities | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Level 1 | Subtotal Fixed Income Securities | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Level 1 | United States Government | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Level 1 | United States Government | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Level 1 | Corporate Debt | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Level 1 | Corporate Debt | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Level 1 | Equity Securities - Domestic | Estimate of Fair Value Measurement
Assets:
Equity securities, fair value disclosure	3,160	2,838
Level 1 | Equity Securities - Domestic | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Equity securities, fair value disclosure	3,160	2,838
Level 1 | Other Cash Deposits | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents, fair value disclosure	0	0
Level 1 | Cash and Cash Equivalents | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents, fair value disclosure	14	10
Level 1 | Cash and Cash Equivalents | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Cash and cash equivalents, fair value disclosure	14	10
Level 2 | 2026
Liabilities:
Maturities of net fair value of risk management contracts	12
Level 2 | 2027 - 2029
Liabilities:
Maturities of net fair value of risk management contracts	65
Level 2 | 2030 - 2031
Liabilities:
Maturities of net fair value of risk management contracts	1
Level 2 | 2025
Liabilities:
Maturities of net fair value of risk management contracts		(16)
Level 2 | 2026 - 2028
Liabilities:
Maturities of net fair value of risk management contracts		(43)
Level 2 | 2029 - 2030
Liabilities:
Maturities of net fair value of risk management contracts		4
Level 2 | Estimate of Fair Value Measurement
Assets:
Restricted Cash	0	0
Total Other Temporary Investments and Restricted Cash	0	0
Risk Management Assets	931	713
Total Spent Nuclear Fuel and Decommissioning Trusts	1,727	1,533
Total Assets	2,658	2,246
Liabilities:
Risk Management Liabilities	801	619
Level 2 | Estimate of Fair Value Measurement | Commodity
Assets:
Risk Management Assets	831	597
Liabilities:
Risk Management Liabilities	752	534
Level 2 | Estimate of Fair Value Measurement | Commodity Contract, Cash Flow Hedging
Assets:
Risk Management Assets	100	116
Liabilities:
Risk Management Liabilities	19	13
Level 2 | Estimate of Fair Value Measurement | Fair Value Hedge Instruments
Liabilities:
Risk Management Liabilities	30	72
Level 2 | Estimate of Fair Value Measurement | AEP TEXAS INC.
Assets:
Restricted Cash	0	0
Level 2 | Estimate of Fair Value Measurement | APPALACHIAN POWER COMPANY
Assets:
Restricted Cash	0	0
Total Assets	3	7
Level 2 | Estimate of Fair Value Measurement | APPALACHIAN POWER COMPANY | Commodity
Assets:
Risk Management Assets	3	7
Liabilities:
Risk Management Liabilities	6	7
Level 2 | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Total Spent Nuclear Fuel and Decommissioning Trusts	1,727	1,533
Total Assets	1,739	1,552
Level 2 | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY | Commodity
Assets:
Risk Management Assets	12	19
Liabilities:
Risk Management Liabilities	11	9
Level 2 | Estimate of Fair Value Measurement | OHIO POWER COMPANY | Commodity
Liabilities:
Risk Management Liabilities	0	0
Level 2 | Estimate of Fair Value Measurement | PUBLIC SERVICE COMPANY OF OKLAHOMA | Commodity
Assets:
Risk Management Assets	1	3
Liabilities:
Risk Management Liabilities	28	7
Level 2 | Estimate of Fair Value Measurement | SOUTHWESTERN ELECTRIC POWER COMPANY
Assets:
Restricted Cash	0	0
Total Assets	0	1
Level 2 | Estimate of Fair Value Measurement | SOUTHWESTERN ELECTRIC POWER COMPANY | Commodity
Assets:
Risk Management Assets	0	1
Liabilities:
Risk Management Liabilities	11	2
Level 2 | Mutual Funds | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Equity securities, fair value disclosure	0	0
Level 2 | Subtotal Fixed Income Securities | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	1,727	1,533
Level 2 | Subtotal Fixed Income Securities | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	1,727	1,533
Level 2 | United States Government | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	1,351	1,323
Level 2 | United States Government | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	1,351	1,323
Level 2 | Corporate Debt | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	376	210
Level 2 | Corporate Debt | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	376	210
Level 2 | Equity Securities - Domestic | Estimate of Fair Value Measurement
Assets:
Equity securities, fair value disclosure	0	0
Level 2 | Equity Securities - Domestic | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Equity securities, fair value disclosure	0	0
Level 2 | Other Cash Deposits | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents, fair value disclosure	0	0
Level 2 | Cash and Cash Equivalents | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents, fair value disclosure	0	0
Level 2 | Cash and Cash Equivalents | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Cash and cash equivalents, fair value disclosure	0	0
Level 3 | 2026
Liabilities:
Maturities of net fair value of risk management contracts	210
Level 3 | 2027 - 2029
Liabilities:
Maturities of net fair value of risk management contracts	51
Level 3 | 2030 - 2031
Liabilities:
Maturities of net fair value of risk management contracts	(6)
Level 3 | 2032 - 2034
Liabilities:
Maturities of net fair value of risk management contracts	(13)
Level 3 | 2025
Liabilities:
Maturities of net fair value of risk management contracts		106
Level 3 | 2026 - 2028
Liabilities:
Maturities of net fair value of risk management contracts		45
Level 3 | 2029 - 2030
Liabilities:
Maturities of net fair value of risk management contracts		9
Level 3 | 2031 - 2034
Liabilities:
Maturities of net fair value of risk management contracts		(16)
Level 3 | Estimate of Fair Value Measurement
Assets:
Restricted Cash	0	0
Total Other Temporary Investments and Restricted Cash	0	0
Risk Management Assets	411	314
Total Spent Nuclear Fuel and Decommissioning Trusts	0	0
Total Assets	411	314
Liabilities:
Risk Management Liabilities	152	148
Level 3 | Estimate of Fair Value Measurement | Commodity
Assets:
Risk Management Assets	393	292
Liabilities:
Risk Management Liabilities	151	148
Level 3 | Estimate of Fair Value Measurement | Commodity Contract, Cash Flow Hedging
Assets:
Risk Management Assets	18	22
Liabilities:
Risk Management Liabilities	1	0
Level 3 | Estimate of Fair Value Measurement | Fair Value Hedge Instruments
Liabilities:
Risk Management Liabilities	0	0
Level 3 | Estimate of Fair Value Measurement | AEP TEXAS INC.
Assets:
Restricted Cash	0	0
Level 3 | Estimate of Fair Value Measurement | APPALACHIAN POWER COMPANY
Assets:
Restricted Cash	0	0
Total Assets	81	35
Level 3 | Estimate of Fair Value Measurement | APPALACHIAN POWER COMPANY | Commodity
Assets:
Risk Management Assets	81	35
Liabilities:
Risk Management Liabilities	0	0
Level 3 | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Total Spent Nuclear Fuel and Decommissioning Trusts	0	0
Total Assets	9	7
Level 3 | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY | Commodity
Assets:
Risk Management Assets	9	7
Liabilities:
Risk Management Liabilities	0	1
Level 3 | Estimate of Fair Value Measurement | OHIO POWER COMPANY | Commodity
Liabilities:
Risk Management Liabilities	33	47
Level 3 | Estimate of Fair Value Measurement | PUBLIC SERVICE COMPANY OF OKLAHOMA | Commodity
Assets:
Risk Management Assets	43	21
Liabilities:
Risk Management Liabilities	2	1
Level 3 | Estimate of Fair Value Measurement | SOUTHWESTERN ELECTRIC POWER COMPANY
Assets:
Restricted Cash	0	0
Total Assets	37	18
Level 3 | Estimate of Fair Value Measurement | SOUTHWESTERN ELECTRIC POWER COMPANY | Commodity
Assets:
Risk Management Assets	37	18
Liabilities:
Risk Management Liabilities	2	1
Level 3 | Mutual Funds | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Equity securities, fair value disclosure	0	0
Level 3 | Subtotal Fixed Income Securities | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Level 3 | Subtotal Fixed Income Securities | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Level 3 | United States Government | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Level 3 | United States Government | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Level 3 | Corporate Debt | Estimate of Fair Value Measurement
Assets:
Fixed Income Securities:	0	0
Level 3 | Corporate Debt | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Fixed Income Securities:	0	0
Level 3 | Equity Securities - Domestic | Estimate of Fair Value Measurement
Assets:
Equity securities, fair value disclosure	0	0
Level 3 | Equity Securities - Domestic | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Equity securities, fair value disclosure	0	0
Level 3 | Other Cash Deposits | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents, fair value disclosure	0	0
Level 3 | Cash and Cash Equivalents | Estimate of Fair Value Measurement
Assets:
Cash and cash equivalents, fair value disclosure	0	0
Level 3 | Cash and Cash Equivalents | Estimate of Fair Value Measurement | INDIANA MICHIGAN POWER COMPANY
Assets:
Cash and cash equivalents, fair value disclosure	$ 0	$ 0