INCOME TAXES - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Amount
NET INCOME	$ 3,696	$ 2,976	$ 2,213
Income Tax Expense (Benefit)	129	(39)	55
Pretax Income	3,825	2,937	2,268
U.S. Federal Statutory Tax Rate	803	617	476
State and Local Income Taxes, Net	31	17	44
Production Tax Credits	(244)	(214)	(175)
Investment Tax Credits	(3)	(58)	(50)
Other Credits	(4)	(9)	(1)
Non-Taxable or Non-Deductible Items	0	(3)	1
Changes in Unrecognized Tax Benefits	3	7	(5)
Reversal of Origination Flow-Through	18	22	24
Tax Reform Excess ADIT Reversal	(62)	(92)	(151)
Remeasurement of Excess ADIT	(383)	(262)	(46)
AFUDC Equity	(41)	(42)	(38)
Other	11	(22)	(24)
Income Tax Expense (Benefit)	$ 129	$ (39)	$ 55
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	0.80%	0.60%	1.90%
Production Tax Credits	(6.40%)	(7.30%)	(7.70%)
Investment Tax Credits	(0.10%)	(2.00%)	(2.20%)
Other Credits	(0.10%)	(0.30%)	0.00%
Non-Taxable or Non-Deductible Items	0.00%	(0.10%)	0.00%
Changes in Unrecognized Tax Benefits	0.10%	0.20%	(0.20%)
Reversal of Origination Flow-Through	0.50%	0.70%	1.10%
Tax Reform Excess ADIT Reversal	(1.60%)	(3.10%)	(6.70%)
Remeasurement of Excess ADIT	(10.00%)	(8.90%)	(2.00%)
AFUDC Equity	(1.10%)	(1.40%)	(1.70%)
Other	0.30%	(0.70%)	(1.10%)
Effective Income Tax Rate	3.40%	(1.30%)	2.40%
AEP TEXAS INC.
Amount
NET INCOME	$ 488	$ 420	$ 370
Income Tax Expense (Benefit)	101	102	86
Pretax Income	589	522	456
U.S. Federal Statutory Tax Rate	124	110	96
State and Local Income Taxes, Net	3	2	2
Tax Credits	(1)	(1)	(1)
Tax Reform Excess ADIT Reversal	(11)	(5)	(6)
Remeasurement of Excess ADIT	0	6	0
AFUDC Equity	(10)	(9)	(5)
Other	(4)	(1)	0
Income Tax Expense (Benefit)	$ 101	$ 102	$ 86
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	0.50%	0.40%	0.40%
Tax Credits	(0.20%)	(0.20%)	(0.20%)
Tax Reform Excess ADIT Reversal	(1.90%)	(1.00%)	(1.30%)
Remeasurement of Excess ADIT	0.00%	1.10%	0.00%
AFUDC Equity	(1.70%)	(1.70%)	(1.10%)
Other	(0.60%)	0.00%	0.00%
Effective Income Tax Rate	17.10%	19.60%	18.80%
AEP TRANSMISSION COMPANY, LLC
Amount
NET INCOME	$ 1,184	$ 688	$ 614
Income Tax Expense (Benefit)	15	190	147
Pretax Income	1,199	878	761
U.S. Federal Statutory Tax Rate	252	185	160
State and Local Income Taxes, Net	31	20	1
Remeasurement of Excess ADIT	(256)	0	0
AFUDC Equity	(16)	(16)	(15)
Other	4	1	1
Income Tax Expense (Benefit)	$ 15	$ 190	$ 147
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	2.60%	2.30%	0.10%
Remeasurement of Excess ADIT	(21.40%)	0.00%	0.00%
AFUDC Equity	(1.30%)	(1.80%)	(2.00%)
Other	0.40%	0.20%	0.20%
Effective Income Tax Rate	1.30%	21.70%	19.30%
APPALACHIAN POWER COMPANY
Amount
NET INCOME	$ 457	$ 422	$ 294
Income Tax Expense (Benefit)	86	75	14
Pretax Income	543	497	308
U.S. Federal Statutory Tax Rate	114	104	65
State and Local Income Taxes, Net	1	10	10
Tax Credits	(4)	(1)	0
Reversal of Origination Flow-Through	6	5	9
Tax Reform Excess ADIT Reversal	(15)	(30)	(17)
Remeasurement of Excess ADIT	(24)	0	(46)
Removal Costs	(5)	(11)	(5)
AFUDC Equity	(2)	(2)	(4)
Flow-Through of CAMT	18	0	0
Other	(3)	0	2
Income Tax Expense (Benefit)	$ 86	$ 75	$ 14
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	0.20%	2.00%	3.20%
Tax Credits	(0.70%)	(0.20%)	0.00%
Reversal of Origination Flow-Through	1.10%	1.00%	2.90%
Tax Reform Excess ADIT Reversal	(2.80%)	(6.00%)	(5.50%)
Remeasurement of Excess ADIT	(4.40%)	0.00%	(14.90%)
Removal Costs	(0.90%)	(2.20%)	(1.60%)
AFUDC Equity	(0.40%)	(0.40%)	(1.30%)
Flow-Through of CAMT	3.30%	0.00%	0.00%
Other	(0.60%)	(0.10%)	0.80%
Effective Income Tax Rate	15.80%	15.10%	4.60%
INDIANA MICHIGAN POWER COMPANY
Amount
NET INCOME	$ 414	$ 391	$ 336
Income Tax Expense (Benefit)	1	(95)	59
Pretax Income	415	296	395
U.S. Federal Statutory Tax Rate	87	62	83
State and Local Income Taxes, Net	14	6	18
Production Tax Credits	(53)	(69)	0
Other Credits	(3)	(2)	(2)
Reversal of Origination Flow-Through	6	5	6
Tax Reform Excess ADIT Reversal	(10)	(16)	(33)
Remeasurement of Excess ADIT	(38)	(73)	0
Removal Costs	0	(6)	(12)
Other	(2)	(2)	(1)
Income Tax Expense (Benefit)	$ 1	$ (95)	$ 59
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	3.40%	2.00%	4.60%
Production Tax Credits	(12.80%)	(23.30%)	0.00%
Other Credits	(0.70%)	(0.70%)	(0.50%)
Reversal of Origination Flow-Through	1.40%	1.70%	1.50%
Tax Reform Excess ADIT Reversal	(2.40%)	(5.40%)	(8.40%)
Remeasurement of Excess ADIT	(9.20%)	(24.70%)	0.00%
Removal Costs	0.00%	(2.00%)	(3.00%)
Other	(0.50%)	(0.70%)	(0.30%)
Effective Income Tax Rate	0.20%	(32.10%)	14.90%
OHIO POWER COMPANY
Amount
NET INCOME	$ 328	$ 306	$ 328
Income Tax Expense (Benefit)	72	52	54
Pretax Income	400	358	382
U.S. Federal Statutory Tax Rate	84	75	80
State and Local Income Taxes, Net	3	11	4
Tax Reform Excess ADIT Reversal	(12)	(31)	(29)
AFUDC Equity	(4)	(4)	(3)
Other	1	1	2
Income Tax Expense (Benefit)	$ 72	$ 52	$ 54
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	0.80%	3.10%	1.00%
Tax Reform Excess ADIT Reversal	(3.00%)	(8.70%)	(7.60%)
AFUDC Equity	(1.00%)	(1.10%)	(0.80%)
Other	0.20%	0.30%	0.60%
Effective Income Tax Rate	18.00%	14.60%	14.20%
PUBLIC SERVICE COMPANY OF OKLAHOMA
Amount
NET INCOME	$ 252	$ 249	$ 209
Income Tax Expense (Benefit)	(70)	(100)	(54)
Pretax Income	182	149	155
U.S. Federal Statutory Tax Rate	38	31	33
State and Local Income Taxes, Net	2	(1)	3
Production Tax Credits	(88)	(74)	(64)
Other Credits	(1)	(2)	(1)
Tax Reform Excess ADIT Reversal	(5)	(6)	(23)
Remeasurement of Excess ADIT	(14)	(49)	0
Other	(2)	1	(2)
Income Tax Expense (Benefit)	$ (70)	$ (100)	$ (54)
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	1.10%	(0.70%)	1.90%
Production Tax Credits	(48.40%)	(49.70%)	(41.30%)
Other Credits	(0.50%)	(1.30%)	(0.60%)
Tax Reform Excess ADIT Reversal	(2.70%)	(4.00%)	(14.80%)
Remeasurement of Excess ADIT	(7.70%)	(32.90%)	0.00%
Other	(1.30%)	1.10%	(0.70%)
Effective Income Tax Rate	(38.50%)	(66.50%)	(34.50%)
SOUTHWESTERN ELECTRIC POWER COMPANY
Amount
NET INCOME	$ 391	$ 326	$ 224
Income Tax Expense (Benefit)	(95)	(184)	(33)
Pretax Income	296	142	191
U.S. Federal Statutory Tax Rate	62	30	40
State and Local Income Taxes, Net	(3)	11	(4)
Production Tax Credits	(98)	(71)	(67)
Non-Taxable or Non-Deductible Items	0	(1)	0
Tax Reform Excess ADIT Reversal	(6)	(4)	(13)
Remeasurement of Excess ADIT	(46)	(147)	0
Disallowance Cost	0	0	12
Other	(4)	(2)	(1)
Income Tax Expense (Benefit)	$ (95)	$ (184)	$ (33)
Percent
U.S. Federal Statutory Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes, Net	(1.00%)	7.70%	(2.10%)
Production Tax Credits	(33.10%)	(50.00%)	(35.10%)
Non-Taxable or Non-Deductible Items	0.00%	(0.70%)	0.00%
Tax Reform Excess ADIT Reversal	(2.00%)	(2.80%)	(6.80%)
Remeasurement of Excess ADIT	(15.50%)	(103.50%)	0.00%
Disallowance Cost	0.00%	0.00%	6.30%
Other	(1.50%)	(1.30%)	(0.60%)
Effective Income Tax Rate	(32.10%)	(129.60%)	(17.30%)