RATE MATTERS - Regulatory Assets Pending Final Approval (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Nov. 30, 2025
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	$ 5,070	$ 4,804
AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	441	402
AEP TRANSMISSION COMPANY, LLC
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	78	73
APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	1,504	1,439
Regulatory asset, requested to be financed through securitization	2,607
INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	553	585
PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	676	637
SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	929	903
West Virginia | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	2,600
Total Regulatory Assets Pending Final Regulatory Approval
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	1,500	1,307
Total Regulatory Assets Pending Final Regulatory Approval | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	216	181
Total Regulatory Assets Pending Final Regulatory Approval | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	517	440
Total Regulatory Assets Pending Final Regulatory Approval | INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	121	118
Total Regulatory Assets Pending Final Regulatory Approval | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	101	84
Total Regulatory Assets Pending Final Regulatory Approval | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	488	445
Total Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | AEP TRANSMISSION COMPANY, LLC
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	9	9
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	235	220
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	235	220
UTM Deferred Costs | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	80	56
UTM Deferred Costs | Regulatory Assets Currently Earning a Return | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	80	56
Pirkey Plant Accelerated Depreciation | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	46	93
Pirkey Plant Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	46	93
Storm-Related Costs | VIRGINIA
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization, approved			$ 141
Storm-Related Costs | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	158
Storm-Related Costs | APPALACHIAN POWER COMPANY | VIRGINIA
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization, approved			$ 141
Storm-Related Costs | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	48	43
Storm-Related Costs | Regulatory Assets Currently Earning a Return | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	41	41
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	273	191
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	34	31
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	62	39
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	32	29
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	32	25
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	88	43
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	40
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Regulatory asset, requested to be financed through securitization	40
West Virginia MRBC Surcharge | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	34	0
West Virginia MRBC Surcharge | Regulatory Assets Currently Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	28	0
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	31	17
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	20	17
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	11	1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	21	6
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	2	2
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	4	4
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	7	2
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	134	112
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	9	9
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	29	18
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	6	7
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	15	14
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	21	20
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	263	257
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	173	169
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	79	78
2024-2025 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	192	172
2024-2025 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	192	172
NOLC Costs | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	87	89
NOLC Costs | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	21	23
NOLC Costs | Regulatory Assets Currently Not Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	65	66
Pension Settlement | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	24	24
Pension Settlement | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	16	16
Deferred Pension and OPEB Costs | Regulatory Assets Currently Not Earning a Return
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	32	27
Deferred Pension and OPEB Costs | Regulatory Assets Currently Not Earning a Return | AEP TEXAS INC.
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	32	27
Income Taxes, Net | Regulatory Assets Currently Not Earning a Return | AEP TRANSMISSION COMPANY, LLC
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	9	9
2026-2027 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	15	0
Virginia Corporate Alternative Minimum Tax | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	0	13
West Virginia Corporate Alternative Minimum Tax | Regulatory Assets Currently Not Earning a Return | APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	0	11
Generation PBA and Delayed Retirement Deferral | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	17	13
Oklahoma Senate Bill 998 Deferral | Regulatory Assets Currently Not Earning a Return | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	16	9
Retired Plant Costs - FERC | Regulatory Assets Currently Earning a Return | SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Noncurrent Regulatory Assets	$ 15	$ 0