RATE MATTERS - Impact to the Statements of Income Recorded by the Registrants (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025
Regulatory Asset [Line Items]
Total Revenues	$ 6,020		$ 5,463
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	(2,118)		(1,853)
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	922		889
Income Tax Expense (Benefit)	44		125
Net Income	903		802
Net Income Attributable to Noncontrolling Interest	29		2
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	874		800
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	874		800
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		241
Income Tax Expense (Benefit)		(313)
Net Income		554
Net Income Attributable to Noncontrolling Interest		55
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		499
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		499
AEP TRANSMISSION COMPANY, LLC
Regulatory Asset [Line Items]
Total Revenues	578		527
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	270		272
Income Tax Expense (Benefit)	60		61
Net Income	210		211
Net Income Attributable to Noncontrolling Interest	27		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	183		211
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	183		211
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		214
Income Tax Expense (Benefit)		(203)
Net Income		417
Net Income Attributable to Noncontrolling Interest		55
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		362
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		362
APPALACHIAN POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues	1,167		1,173
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	(364)		(407)
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	206		205
Income Tax Expense (Benefit)	11		40
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		8
Income Tax Expense (Benefit)		(21)
Net Income		29
Net Income Attributable to Noncontrolling Interest		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		29
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		29
INDIANA MICHIGAN POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues	933		723
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	174		65
Income Tax Expense (Benefit)	26		7
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		17
Income Tax Expense (Benefit)		(28)
Net Income		45
Net Income Attributable to Noncontrolling Interest		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		45
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		45
OHIO POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues	1,085		1,004
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	129		76
Income Tax Expense (Benefit)	12		14
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		0
Income Tax Expense (Benefit)		0
Net Income		0
Net Income Attributable to Noncontrolling Interest		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		0
PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Revenues	439		394
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	(164)		(129)
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	(25)		26
Income Tax Expense (Benefit)	(40)		(2)
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		(13)
Income Tax Expense (Benefit)		(16)
Net Income		3
Net Income Attributable to Noncontrolling Interest		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		3
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		3
SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Total Revenues	571		531
Purchased Electricity, Fuel and Other Consumables Used for Electric Generation	(171)		(191)
INCOME (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)	8		43
Income Tax Expense (Benefit)	(49)		(6)
Net Income	57		49
Net Income Attributable to Noncontrolling Interest	1		1
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	56		48
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	$ 56		$ 48
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 (LOSS) BEFORE INCOME TAX EXPENSE (BENEFIT)		17
Income Tax Expense (Benefit)		(39)
Net Income		56
Net Income Attributable to Noncontrolling Interest		0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic		56
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted		$ 56