RATE MATTERS - Impact to the Statements of Income Recorded by the Registrants (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Regulatory Asset [Line Items]
Total Revenues		$ 21,876	$ 19,721	$ 18,982
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation		(7,031)	(5,936)	(6,578)
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		3,724	2,843	2,209
Income Tax Expense (Benefit)		129	(39)	55
NET INCOME		3,696	2,976	2,213
Net Income Attributable to Noncontrolling Interest		116	9	5
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic		3,580	2,967	2,208
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted		3,580	2,967	2,208
FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	$ 270
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	(24)
Other Operation	53
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	241
Income Tax Expense (Benefit)	(313)
NET INCOME	554
Net Income Attributable to Noncontrolling Interest	55
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	499
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	499
AEP TRANSMISSION COMPANY, LLC
Regulatory Asset [Line Items]
Total Revenues		2,319	1,891	1,671
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		1,199	878	761
Income Tax Expense (Benefit)		15	190	147
NET INCOME		1,184	688	614
Net Income Attributable to Noncontrolling Interest		109	0	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic		1,075	688	614
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted		1,075	688	614
AEP TRANSMISSION COMPANY, LLC | FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	214
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	0
Other Operation	0
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	214
Income Tax Expense (Benefit)	(203)
NET INCOME	417
Net Income Attributable to Noncontrolling Interest	55
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	362
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	362
APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues		4,209	4,033	3,721
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation		(1,398)	(1,406)	(1,435)
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		543	497	308
Income Tax Expense (Benefit)		86	75	14
NET INCOME		457	422	294
APPALACHIAN POWER COMPANY | FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	6
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	(17)
Other Operation	15
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	8
Income Tax Expense (Benefit)	(21)
NET INCOME	29
Net Income Attributable to Noncontrolling Interest	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	29
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	29
INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues		3,031	2,572	2,536
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		415	296	395
Income Tax Expense (Benefit)		1	(95)	59
NET INCOME		414	391	336
INDIANA MICHIGAN POWER COMPANY | FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	11
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	0
Other Operation	(6)
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	17
Income Tax Expense (Benefit)	(28)
NET INCOME	45
Net Income Attributable to Noncontrolling Interest	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	45
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	45
OHIO POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues		3,948	3,828	3,811
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		398	359	382
Income Tax Expense (Benefit)		72	52	54
NET INCOME		328	306	328
OHIO POWER COMPANY | FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	0
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	0
Other Operation	0
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	0
Income Tax Expense (Benefit)	0
NET INCOME	0
Net Income Attributable to Noncontrolling Interest	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	0
PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Revenues		2,022	1,846	1,977
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation		(752)	(743)	(955)
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		182	149	155
Income Tax Expense (Benefit)		(70)	(100)	(54)
NET INCOME		252	249	209
PUBLIC SERVICE COMPANY OF OKLAHOMA | FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	6
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	0
Other Operation	19
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	(13)
Income Tax Expense (Benefit)	(16)
NET INCOME	3
Net Income Attributable to Noncontrolling Interest	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	3
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	3
SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues		2,354	2,036	2,183
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation		(727)	(733)	(807)
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS		295	140	189
Income Tax Expense (Benefit)		(95)	(184)	(33)
NET INCOME		391	326	224
Net Income Attributable to Noncontrolling Interest		3	5	4
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic		388	321	220
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted		$ 388	$ 321	$ 220
SOUTHWESTERN ELECTRIC POWER COMPANY | FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Regulatory Asset [Line Items]
Total Revenues	27
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	0
Other Operation	10
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT) AND EQUITY EARNINGS	17
Income Tax Expense (Benefit)	(39)
NET INCOME	56
Net Income Attributable to Noncontrolling Interest	0
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Basic	56
EARNINGS ATTRIBUTABLE TO AEP MEMBER, Diluted	$ 56