INCOME TAXES - Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Federal:
Current	$ (209)	$ (3)	$ (117)
Deferred	298	(58)	116
Total Federal	89	(61)	(1)
State and Local:
Current	28	(5)	69
Deferred	12	27	(13)
Total State and Local	40	22	56
Income Tax Expense (Benefit)	129	(39)	55
AEP TEXAS INC.
Federal:
Current	27	22	20
Deferred	70	77	63
Total Federal	97	99	83
State and Local:
Current	4	3	3
Deferred	0	0	0
Total State and Local	4	3	3
Income Tax Expense (Benefit)	101	102	86
AEP TRANSMISSION COMPANY, LLC
Federal:
Current	148	75	94
Deferred	(173)	89	52
Total Federal	(25)	164	146
State and Local:
Current	18	6	9
Deferred	22	20	(8)
Total State and Local	40	26	1
Income Tax Expense (Benefit)	15	190	147
APPALACHIAN POWER COMPANY
Federal:
Current	42	80	62
Deferred	43	(18)	(60)
Total Federal	85	62	2
State and Local:
Current	2	13	6
Deferred	(1)	0	6
Total State and Local	1	13	12
Income Tax Expense (Benefit)	86	75	14
INDIANA MICHIGAN POWER COMPANY
Federal:
Current	(3)	17	94
Deferred	(14)	(119)	(57)
Total Federal	(17)	(102)	37
State and Local:
Current	19	7	21
Deferred	(1)	0	1
Total State and Local	18	7	22
Income Tax Expense (Benefit)	1	(95)	59
OHIO POWER COMPANY
Federal:
Current	27	42	46
Deferred	42	(3)	3
Total Federal	69	39	49
State and Local:
Current	(2)	3	0
Deferred	5	10	5
Total State and Local	3	13	5
Income Tax Expense (Benefit)	72	52	54
PUBLIC SERVICE COMPANY OF OKLAHOMA
Federal:
Current	(221)	(119)	(61)
Deferred	149	20	3
Total Federal	(72)	(99)	(58)
State and Local:
Current	0	0	0
Deferred	2	(1)	4
Total State and Local	2	(1)	4
Income Tax Expense (Benefit)	(70)	(100)	(54)
SOUTHWESTERN ELECTRIC POWER COMPANY
Federal:
Current	(180)	(112)	(88)
Deferred	89	(86)	60
Total Federal	(91)	(198)	(28)
State and Local:
Current	3	2	1
Deferred	(7)	12	(6)
Total State and Local	(4)	14	(5)
Income Tax Expense (Benefit)	$ (95)	$ (184)	$ (33)