VARIABLE INTEREST ENTITIES AND EQUITY METHOD INVESTMENTS - Narrative (Details) $ in Millions	1 Months Ended		12 Months Ended
	Jan. 31, 2026 USD ($)	Aug. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) generatingPlant line MW	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Nov. 30, 2025
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			$ 3,429	$ 2,638
Securitized Assets			933	554
Long-term Debt Due Within One Year – Nonaffiliated			3,194	3,335
Long-term Debt – Nonaffiliated			44,128	39,308
Construction Work in Progress			$ 7,635	6,347
Number of generation plants | generatingPlant			2
Equity method investment			$ 1,252	1,056	$ 1,074
Equity Earnings of Unconsolidated Subsidiaries			$ 101	94	59
Berkshire Hathaway
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage			50.00%
AEPTHCo
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage			50.00%
ETT
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Equity method investment			$ 969	897
Equity Earnings of Unconsolidated Subsidiaries			80	86	74
Gigawatt.AI
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage		10.00%
Equity method investment		$ 100	100
Payments to acquire equity method investments		100
Contingent consideration, additional investment in equity method investment		$ 100
Potential additional ownership percentage		10.00%
Gigawatt.AI | Subsequent Event
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Payments to acquire equity method investments	$ 25
Incremental ownership percentage	2.50%
Gigawatt.AI | Gigawatt AI Warrant
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of ownership in investment called by warrants		5.00%
Amount of investment called by warrant		$ 50
SOUTHWESTERN ELECTRIC POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitized Assets			315	331
Long-term Debt Due Within One Year – Nonaffiliated			917	23
Construction Work in Progress			712	627
Equity Earnings of Unconsolidated Subsidiaries			1	2	2
SOUTHWESTERN ELECTRIC POWER COMPANY | Affiliated Entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			89	57
Long-term Debt – Nonaffiliated			1,000	0
INDIANA MICHIGAN POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Long-term Debt Due Within One Year – Nonaffiliated			117	269
Long-term Debt – Nonaffiliated			3,444	3,225
Construction Work in Progress			403	335
INDIANA MICHIGAN POWER COMPANY | Billings from AEP Generating Company
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE			268	209	181
INDIANA MICHIGAN POWER COMPANY | Carrying Amount in AEP Generating Company's Accounts Payable
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
As Reported on the Balance Sheet			19	14
INDIANA MICHIGAN POWER COMPANY | Affiliated Entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			125	99
AEP TEXAS INC.
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitized Assets			94	117
Long-term Debt Due Within One Year – Nonaffiliated			75	325
Long-term Debt – Nonaffiliated			6,941	6,117
Construction Work in Progress			1,766	1,118
AEP TEXAS INC. | Affiliated Entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			60	35
APPALACHIAN POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitized Assets			78	106
Long-term Debt Due Within One Year – Nonaffiliated			1,131	799
Long-term Debt – Nonaffiliated			5,128	4,862
Construction Work in Progress			802	743
APPALACHIAN POWER COMPANY | Affiliated Entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			$ 173	206
Transource Energy
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Equity and voting ownership percentage			86.50%
AEGCo | Rockport Generating Plant
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percent of Ownership			50.00%
OHIO POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Long-term Debt – Nonaffiliated			$ 3,718	3,716
Construction Work in Progress			811	691
Equity Earnings of Unconsolidated Subsidiaries			2	(1)	0
OHIO POWER COMPANY | Affiliated Entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			$ 197	205
Cleco Power, LLC
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of VIE sales of lignite produced			50.00%
Variable Interest Entity, Primary Beneficiary
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			$ 462
Minimum percentage of equity AEP provides			5.00%
Percentage of short term borrowing needs in excess of third party financings			35.00%
Number of lines of insurance for protected cells | line			7
Insurance premium expense to protected cell			$ 39	37	34
Debt-to-total capitalization maximum			67.50%
Variable Interest Entity, Primary Beneficiary | Term loan
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Long-term Debt Due Within One Year – Nonaffiliated			$ 16
Long-term Debt – Nonaffiliated			453
Variable Interest Entity, Primary Beneficiary | SOUTHWESTERN ELECTRIC POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Guarantees of mine reclamation amount			155
Estimated final cost mine reclamation			68
Amount recorded in ARO for final mine closure and reclamation costs			66
Amount collected through rider for final mine closure and reclamation costs			102
Amount recorded in other noncurrent assets for final mine closure and reclamation costs			77
Securitized Assets			315	331
Variable Interest Entity, Primary Beneficiary | SOUTHWESTERN ELECTRIC POWER COMPANY | Current Liabilities
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			17	23
Variable Interest Entity, Primary Beneficiary | SOUTHWESTERN ELECTRIC POWER COMPANY | Noncurrent Liabilities
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			304	309
Variable Interest Entity, Primary Beneficiary | SOUTHWESTERN ELECTRIC POWER COMPANY | Affiliated Entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Accounts payable - affiliated companies for collected reclamation costs that have been billed to SWEPCo			113
Variable Interest Entity, Primary Beneficiary | INDIANA MICHIGAN POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Capital lease payments made			$ 119	111	97
Capital lease term			54 months
Variable Interest Entity, Primary Beneficiary | AEP TEXAS INC. | AEP Texas Restoration Funding
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitized Assets			$ 94	117
Variable Interest Entity, Primary Beneficiary | AEP TEXAS INC. | Current Liabilities | AEP Texas Restoration Funding
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			25	24
Variable Interest Entity, Primary Beneficiary | AEP TEXAS INC. | Noncurrent Liabilities | AEP Texas Restoration Funding
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			78	102
Variable Interest Entity, Primary Beneficiary | APPALACHIAN POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitized Assets			78	106
Variable Interest Entity, Primary Beneficiary | APPALACHIAN POWER COMPANY | Current Liabilities
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			30	28
Variable Interest Entity, Primary Beneficiary | APPALACHIAN POWER COMPANY | Noncurrent Liabilities
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Securitization Bonds			$ 62	91
Variable Interest Entity, Primary Beneficiary | Great Plains Energy Inc.
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Equity and voting ownership percentage			13.50%
Variable Interest Entity, Not Primary Beneficiary
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
AEP's ownership In OVEC			43.47%
Approximate OVEC generating capacity (MWs) | MW			2,400
Outstanding indebtedness			$ 873	997
Variable Interest Entity, Not Primary Beneficiary | Parent
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
AEP's ownership In OVEC			39.17%
Variable Interest Entity, Not Primary Beneficiary | SOUTHWESTERN ELECTRIC POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE			$ 207	194	185
Percentage of VIE sales of lignite produced			50.00%
Percentage of VIE debt guaranteed			50.00%
Percentage of VIE management fee received			100.00%
Dividends			$ 1	1	1
Variable Interest Entity, Not Primary Beneficiary | INDIANA MICHIGAN POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE			$ 189	188	178
Power participation ratio			7.85%
Outstanding indebtedness			$ 68	78
Variable Interest Entity, Not Primary Beneficiary | AEP TEXAS INC.
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE			278	243	229
Variable Interest Entity, Not Primary Beneficiary | APPALACHIAN POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE			$ 352	335	325
Power participation ratio			15.69%
Outstanding indebtedness			$ 137	156
Variable Interest Entity, Not Primary Beneficiary | OHIO POWER COMPANY
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Billings from VIE			$ 282	283	$ 270
Power acquired, solid oxide fuel cells | MW			100
Construction Work in Progress			$ 480	457
Borrowings			$ 485	456
AEP's ownership In OVEC			4.30%			4.30%
Power participation ratio			19.93%			19.93%
Outstanding indebtedness			$ 174	$ 199