BENEFIT PLANS - Schedule of Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 96	$ 101	$ 94
Interest Cost	211	207	219
Expected Return on Plan Assets	(281)	(320)	(339)
Amortization of Net Actuarial Loss	16	5	2
Settlements		93
Net Periodic Benefit Cost (Credit)	42	86	(24)
Capitalized Portion	(45)	(47)	(44)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(3)	39	(68)
Pension Plans | AEP TEXAS INC.
Defined Benefit Plan Disclosure [Line Items]
Service Cost	9	9	8
Interest Cost	17	17	18
Expected Return on Plan Assets	(23)	(25)	(28)
Amortization of Net Actuarial Loss	1	0	0
Settlements		10
Net Periodic Benefit Cost (Credit)	4	11	(2)
Capitalized Portion	(5)	(5)	(4)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(1)	6	(6)
Pension Plans | APPALACHIAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	9	9	9
Interest Cost	25	25	26
Expected Return on Plan Assets	(38)	(43)	(44)
Amortization of Net Actuarial Loss	2	0	0
Settlements		12
Net Periodic Benefit Cost (Credit)	(2)	3	(9)
Capitalized Portion	(4)	(4)	(4)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(6)	(1)	(13)
Pension Plans | INDIANA MICHIGAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	13	13	12
Interest Cost	25	24	25
Expected Return on Plan Assets	(39)	(42)	(44)
Amortization of Net Actuarial Loss	2	1	0
Settlements		9
Net Periodic Benefit Cost (Credit)	1	5	(7)
Capitalized Portion	(4)	(4)	(4)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(3)	1	(11)
Pension Plans | OHIO POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	9	9	8
Interest Cost	19	19	20
Expected Return on Plan Assets	(28)	(33)	(34)
Amortization of Net Actuarial Loss	1	0	0
Settlements		7
Net Periodic Benefit Cost (Credit)	1	2	(6)
Capitalized Portion	(5)	(5)	(5)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(4)	(3)	(11)
Pension Plans | PUBLIC SERVICE COMPANY OF OKLAHOMA
Defined Benefit Plan Disclosure [Line Items]
Service Cost	6	6	5
Interest Cost	10	10	11
Expected Return on Plan Assets	(15)	(17)	(18)
Amortization of Net Actuarial Loss	1	0	0
Settlements		5
Net Periodic Benefit Cost (Credit)	2	4	(2)
Capitalized Portion	(3)	(3)	(3)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(1)	1	(5)
Pension Plans | SOUTHWESTERN ELECTRIC POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	8	8	8
Interest Cost	13	12	14
Expected Return on Plan Assets	(15)	(17)	(20)
Amortization of Net Actuarial Loss	1	0	0
Settlements		9
Net Periodic Benefit Cost (Credit)	7	12	2
Capitalized Portion	(3)	(3)	(3)
Net Periodic Benefit Cost (Credit) Recognized in Expense	4	9	(1)
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service Cost	4	4	5
Interest Cost	34	42	46
Expected Return on Plan Assets	(113)	(111)	(110)
Amortization of Prior Service Credit	(3)	(13)	(63)
Amortization of Net Actuarial Loss		3	15
Special/Contractual Termination Benefits		4
Net Periodic Benefit Cost (Credit)	(78)	(71)	(107)
Capitalized Portion	(2)	(2)	(2)
Net Periodic Benefit Cost (Credit) Recognized in Expense	(80)	(73)	(109)
OPEB | AEP TEXAS INC.
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	0	0
Interest Cost	3	3	4
Expected Return on Plan Assets	(9)	(8)	(9)
Amortization of Prior Service Credit	0	(1)	(5)
Amortization of Net Actuarial Loss		0	1
Special/Contractual Termination Benefits		0
Net Periodic Benefit Cost (Credit)	(6)	(6)	(9)
Capitalized Portion	0	0	0
Net Periodic Benefit Cost (Credit) Recognized in Expense	(6)	(6)	(9)
OPEB | APPALACHIAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1	0	1
Interest Cost	5	7	7
Expected Return on Plan Assets	(17)	(16)	(16)
Amortization of Prior Service Credit	0	(2)	(9)
Amortization of Net Actuarial Loss		0	2
Special/Contractual Termination Benefits		1
Net Periodic Benefit Cost (Credit)	(11)	(10)	(15)
Capitalized Portion	0	0	0
Net Periodic Benefit Cost (Credit) Recognized in Expense	(11)	(10)	(15)
OPEB | INDIANA MICHIGAN POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	1	1
Interest Cost	4	5	5
Expected Return on Plan Assets	(13)	(14)	(13)
Amortization of Prior Service Credit	1	(2)	(9)
Amortization of Net Actuarial Loss		1	2
Special/Contractual Termination Benefits		0
Net Periodic Benefit Cost (Credit)	(8)	(9)	(14)
Capitalized Portion	0	0	0
Net Periodic Benefit Cost (Credit) Recognized in Expense	(8)	(9)	(14)
OPEB | OHIO POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	0	0
Interest Cost	3	4	4
Expected Return on Plan Assets	(11)	(11)	(12)
Amortization of Prior Service Credit	(1)	(1)	(6)
Amortization of Net Actuarial Loss		0	2
Special/Contractual Termination Benefits		0
Net Periodic Benefit Cost (Credit)	(9)	(8)	(12)
Capitalized Portion	0	0	0
Net Periodic Benefit Cost (Credit) Recognized in Expense	(9)	(8)	(12)
OPEB | PUBLIC SERVICE COMPANY OF OKLAHOMA
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	0	0
Interest Cost	2	2	2
Expected Return on Plan Assets	(6)	(5)	(6)
Amortization of Prior Service Credit	0	(1)	(4)
Amortization of Net Actuarial Loss		0	1
Special/Contractual Termination Benefits		0
Net Periodic Benefit Cost (Credit)	(4)	(4)	(7)
Capitalized Portion	0	0	0
Net Periodic Benefit Cost (Credit) Recognized in Expense	(4)	(4)	(7)
OPEB | SOUTHWESTERN ELECTRIC POWER COMPANY
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	0	0
Interest Cost	2	3	3
Expected Return on Plan Assets	(8)	(7)	(7)
Amortization of Prior Service Credit	0	(1)	(5)
Amortization of Net Actuarial Loss		0	1
Special/Contractual Termination Benefits		0
Net Periodic Benefit Cost (Credit)	(6)	(5)	(8)
Capitalized Portion	0	0	0
Net Periodic Benefit Cost (Credit) Recognized in Expense	$ (6)	$ (5)	$ (8)