INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	$ 2,786	$ 2,652
Deferred Tax Liabilities	(13,737)	(12,624)
Net Deferred Tax Liabilities	(10,951)	(9,972)
Property Related Temporary Differences	(9,456)	(8,940)
Amounts Due to Customers for Future Income Taxes	641	780
Securitized Assets	(211)	(133)
Regulatory Assets	(902)	(966)
Accrued Nuclear Decommissioning	(1,180)	(1,052)
Net Operating Loss Carryforward	155	110
Valuation Allowance	(49)	(35)
Tax Credit Carryforward	148	198
Operating Lease Liability	166	145
Investment in Partnership	(306)	(302)
All Other, Net	43	223
AEP TEXAS INC.
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	131	139
Deferred Tax Liabilities	(1,561)	(1,462)
Net Deferred Tax Liabilities	(1,430)	(1,323)
Property Related Temporary Differences	(1,442)	(1,364)
Amounts Due to Customers for Future Income Taxes	105	109
Securitized Assets	(28)	(27)
Regulatory Assets	(73)	(63)
Accrued Nuclear Decommissioning	0	0
Net Operating Loss Carryforward	0	0
Valuation Allowance	0	0
Tax Credit Carryforward	10	4
Operating Lease Liability	12	12
Investment in Partnership	0	0
All Other, Net	(14)	6
AEP TRANSMISSION COMPANY, LLC
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	170	173
Deferred Tax Liabilities	(1,651)	(1,452)
Net Deferred Tax Liabilities	(1,481)	(1,279)
Property Related Temporary Differences	(1,526)	(1,417)
Amounts Due to Customers for Future Income Taxes	44	121
Securitized Assets	0	0
Regulatory Assets	(4)	0
Accrued Nuclear Decommissioning	0	0
Net Operating Loss Carryforward	0	2
Valuation Allowance	0	0
Tax Credit Carryforward	0	0
Operating Lease Liability	1	0
Investment in Partnership	0	0
All Other, Net	4	15
APPALACHIAN POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	411	379
Deferred Tax Liabilities	(2,541)	(2,413)
Net Deferred Tax Liabilities	(2,130)	(2,034)
Property Related Temporary Differences	(1,881)	(1,785)
Amounts Due to Customers for Future Income Taxes	109	119
Securitized Assets	(19)	(26)
Regulatory Assets	(308)	(302)
Accrued Nuclear Decommissioning	0	0
Net Operating Loss Carryforward	0	0
Valuation Allowance	0	0
Tax Credit Carryforward	33	0
Operating Lease Liability	23	16
Investment in Partnership	0	0
All Other, Net	(87)	(56)
INDIANA MICHIGAN POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	1,160	1,072
Deferred Tax Liabilities	(2,379)	(2,248)
Net Deferred Tax Liabilities	(1,219)	(1,176)
Property Related Temporary Differences	(49)	(190)
Amounts Due to Customers for Future Income Taxes	57	73
Securitized Assets	0	0
Regulatory Assets	(46)	(49)
Accrued Nuclear Decommissioning	(1,180)	(1,052)
Net Operating Loss Carryforward	0	0
Valuation Allowance	0	0
Tax Credit Carryforward	0	40
Operating Lease Liability	14	14
Investment in Partnership	0	0
All Other, Net	(15)	(12)
OHIO POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	171	187
Deferred Tax Liabilities	(1,439)	(1,388)
Net Deferred Tax Liabilities	(1,268)	(1,201)
Property Related Temporary Differences	(1,333)	(1,291)
Amounts Due to Customers for Future Income Taxes	92	96
Securitized Assets	0	0
Regulatory Assets	(48)	(45)
Accrued Nuclear Decommissioning	0	0
Net Operating Loss Carryforward	0	3
Valuation Allowance	0	0
Tax Credit Carryforward	43	39
Operating Lease Liability	11	13
Investment in Partnership	(1)	(1)
All Other, Net	(32)	(15)
PUBLIC SERVICE COMPANY OF OKLAHOMA
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	287	267
Deferred Tax Liabilities	(1,400)	(1,198)
Net Deferred Tax Liabilities	(1,113)	(931)
Property Related Temporary Differences	(1,195)	(1,010)
Amounts Due to Customers for Future Income Taxes	74	81
Securitized Assets	0	0
Regulatory Assets	(60)	(53)
Accrued Nuclear Decommissioning	0	0
Net Operating Loss Carryforward	44	28
Valuation Allowance	0	0
Tax Credit Carryforward	33	27
Operating Lease Liability	32	27
Investment in Partnership	0	0
All Other, Net	(41)	(31)
SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	328	293
Deferred Tax Liabilities	(1,786)	(1,564)
Net Deferred Tax Liabilities	(1,458)	(1,271)
Property Related Temporary Differences	(1,477)	(1,353)
Amounts Due to Customers for Future Income Taxes	74	90
Securitized Assets	(50)	(81)
Regulatory Assets	(119)	(87)
Accrued Nuclear Decommissioning	0	0
Net Operating Loss Carryforward	45	36
Valuation Allowance	(3)	0
Tax Credit Carryforward	0	32
Operating Lease Liability	50	36
Investment in Partnership	(1)	(2)
All Other, Net	$ 23	$ 58