BUSINESS SEGMENTS - Schedule of AEPTCo's Reportable Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Segment Reporting Information [Line Items]
Total Revenues	$ 6,020	$ 5,463
Other Operation and Maintenance	1,161	1,071
Depreciation and Amortization	907	833
Taxes Other Than Income Taxes	443	422
Allowance for Equity Funds Used During Construction	70	57
Interest Expense	552	495
Income Tax Expense	44	125
Other Segment Items	(15)	(41)
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	874	800
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	874	800
Gross Property Additions	3,795	2,100
Total Assets	117,776		$ 114,460
Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	6,020	5,463
Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	6,599	5,954
Other Operation and Maintenance	1,659	1,528
Depreciation and Amortization	912	838
Taxes Other Than Income Taxes	435	415
Allowance for Equity Funds Used During Construction	70	57
Interest Expense	420	371
Income Tax Expense	81	182
Other Segment Items	(27)	(45)
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	983	826
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	983	826
Gross Property Additions	3,642	2,059
Total Assets	116,882		112,772
Operating Segments | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	6,017	5,447
Corporate and Other
Segment Reporting Information [Line Items]
Total Revenues	31	44
Other Operation and Maintenance	38	16
Depreciation and Amortization	(5)	(5)
Taxes Other Than Income Taxes	0	1
Allowance for Equity Funds Used During Construction	0	0
Interest Expense	166	147
Income Tax Expense	(37)	(57)
Other Segment Items	(22)	(19)
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	(109)	(26)
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	(109)	(26)
Gross Property Additions	147	30
Total Assets	6,451		6,733
Corporate and Other | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	3	16
Reconciling Adjustments
Segment Reporting Information [Line Items]
Total Revenues	(610)	(535)
Other Operation and Maintenance	(536)	(473)
Depreciation and Amortization	0	0
Taxes Other Than Income Taxes	8	6
Allowance for Equity Funds Used During Construction	0	0
Interest Expense	(34)	(23)
Income Tax Expense	0	0
Other Segment Items	34	23
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	0	0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	0	0
Gross Property Additions	6	11
Total Assets	(5,557)		(5,045)
Reconciling Adjustments | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	0	0
AEP TRANSMISSION COMPANY, LLC
Segment Reporting Information [Line Items]
Total Revenues	578	527
Other Operation and Maintenance	51	34
Depreciation and Amortization	128	114
Taxes Other Than Income Taxes	88	74
Interest Income	2	0
Allowance for Equity Funds Used During Construction	22	22
Interest Expense	65	55
Income Tax Expense	60	61
Other Segment Items	27
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	183	211
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	183	211
Gross Property Additions	403	422
Total Assets	18,531		17,999
AEP TRANSMISSION COMPANY, LLC | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	110	104
AEP TRANSMISSION COMPANY, LLC | Affiliated Entity
Segment Reporting Information [Line Items]
Total Revenues	468	423
AEP TRANSMISSION COMPANY, LLC | Corporate and Other
Segment Reporting Information [Line Items]
Total Revenues	0	0
Other Operation and Maintenance	0	0
Depreciation and Amortization	0	0
Taxes Other Than Income Taxes	0	0
Interest Income	73	89
Allowance for Equity Funds Used During Construction	0	0
Interest Expense	72	60
Income Tax Expense	0	0
Other Segment Items	27
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	(26)	29
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	(26)	29
Gross Property Additions	0	0
Total Assets	6,997		6,766
AEP TRANSMISSION COMPANY, LLC | Corporate and Other | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	0	0
AEP TRANSMISSION COMPANY, LLC | Corporate and Other | Affiliated Entity
Segment Reporting Information [Line Items]
Total Revenues	0	0
AEP TRANSMISSION COMPANY, LLC | Reconciling Adjustments
Segment Reporting Information [Line Items]
Total Revenues	0	0
Other Operation and Maintenance	0	0
Depreciation and Amortization	0	0
Taxes Other Than Income Taxes	0	0
Interest Income	(72)	(89)
Allowance for Equity Funds Used During Construction	0	0
Interest Expense	(72)	(89)
Income Tax Expense	0	0
Other Segment Items	0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	0	0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	0	0
Gross Property Additions	0	0
Total Assets	(6,922)		(6,750)
AEP TRANSMISSION COMPANY, LLC | Reconciling Adjustments | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	0	0
AEP TRANSMISSION COMPANY, LLC | Reconciling Adjustments | Affiliated Entity
Segment Reporting Information [Line Items]
Total Revenues	0	0
State Transcos | AEP TRANSMISSION COMPANY, LLC | Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	578	527
Other Operation and Maintenance	51	34
Depreciation and Amortization	128	114
Taxes Other Than Income Taxes	88	74
Interest Income	1	0
Allowance for Equity Funds Used During Construction	22	22
Interest Expense	65	84
Income Tax Expense	60	61
Other Segment Items	0
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Basic	209	182
EARNINGS ATTRIBUTABLE TO AEP COMMON SHAREHOLDERS, Diluted	209	182
Gross Property Additions	403	422
Total Assets	18,456		$ 17,983
State Transcos | AEP TRANSMISSION COMPANY, LLC | Operating Segments | Nonrelated Party
Segment Reporting Information [Line Items]
Total Revenues	110	104
State Transcos | AEP TRANSMISSION COMPANY, LLC | Operating Segments | Affiliated Entity
Segment Reporting Information [Line Items]
Total Revenues	$ 468	$ 423