SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT COMPANY - AEPTCO PARENT - CONDENSED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities:
Change in Other Noncurrent Assets	$ (559)	$ (348)	$ (446)
Change in Other Noncurrent Liabilities	269	306	29
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(246)	(156)	236
Accounts Payable	252	85	(253)
Other Current Liabilities	103	182	(162)
Net Cash Flows from Operating Activities	6,944	6,804	5,012
INVESTING ACTIVITIES
Net Cash Flows Used for Investing Activities	(11,939)	(7,596)	(6,267)
FINANCING ACTIVITIES
Issuance of Long-term Debt	8,261	5,117	5,463
Retirement of Long-term Debt	(3,649)	(2,685)	(2,196)
Other Financing Activities	(8)	(50)	(80)
Net Cash Flows from Financing Activities	5,017	659	1,077
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	22	(133)	(178)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	246	379	557
Cash, Cash Equivalents and Restricted Cash at End of Period	268	246	379
Parent Company
OPERATING ACTIVITIES
Net Income	3,580	2,967	2,208
Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities:
Equity Earnings of Unconsolidated Subsidiaries	(3,908)	(3,280)	(2,468)
Change in Other Noncurrent Assets	(3)	5	(28)
Change in Other Noncurrent Liabilities	61	71	92
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	10	18	29
Accounts Payable	(1)	(17)	(16)
Other Current Liabilities	10	55	(14)
Net Cash Flows from Operating Activities	3,210	889	529
INVESTING ACTIVITIES
Change in Advances to Affiliates, Net	66	60	2,008
Repayment of Notes Receivable from Affiliated Companies	0	190	0
Issuance of Notes Receivable to Unconsolidated Subsidiaries	(1,000)	0	(210)
Net Cash Flows Used for Investing Activities	(2,951)	748	1,064
FINANCING ACTIVITIES
Issuance of Long-term Debt	2,966	1,285	1,830
Retirement of Long-term Debt	(1,300)	(1,104)	(1,050)
Change in Advances from Affiliates, Net	380	(222)	(192)
Other Financing Activities	(44)	(41)	(61)
Net Cash Flows from Financing Activities	(244)	(1,747)	(1,649)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	15	(110)	(56)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	88	198	254
Cash, Cash Equivalents and Restricted Cash at End of Period	103	88	198
AEP TRANSMISSION COMPANY, LLC
OPERATING ACTIVITIES
Net Income	1,184	688	614
Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities:
Change in Other Noncurrent Assets	(80)	(1)	8
Change in Other Noncurrent Liabilities	(127)	(17)	134
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(53)	13	(41)
Accounts Payable	75	10	23
Accrued Interest	1	5	11
Other Current Liabilities	(22)	14	0
Net Cash Flows from Operating Activities	1,185	1,238	1,138
INVESTING ACTIVITIES
Change in Advances to Affiliates, Net	(41)	37	(63)
Net Cash Flows Used for Investing Activities	(1,578)	(1,428)	(1,559)
FINANCING ACTIVITIES
Capital Contribution from AEP Member	70	62	30
Return of Capital to Parent	0	(5)	(8)
Issuance of Long-term Debt	929	446	689
Retirement of Long-term Debt	(102)	(95)	(60)
Change in Advances from Affiliates, Net	58	(90)	(55)
Dividends Paid	(3,274)	(128)	(175)
Net Cash Flows from Financing Activities	393	190	421
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	0	0	0
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	0	0	0
Cash, Cash Equivalents and Restricted Cash at End of Period	0	0	0
AEP TRANSMISSION COMPANY, LLC | Parent Company
OPERATING ACTIVITIES
Net Income	1,075	688	614
Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities:
Equity Earnings of Unconsolidated Subsidiaries	(1,035)	(688)	(613)
Change in Other Noncurrent Assets	0	0	4
Change in Other Noncurrent Liabilities	7	4	12
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(35)	10	(38)
Accounts Payable	29	13	37
Accrued Interest	1	6	11
Other Current Liabilities	(9)	34	(31)
Net Cash Flows from Operating Activities	33	67	(4)
INVESTING ACTIVITIES
Change in Advances to Affiliates, Net	(50)	(20)	0
Repayment of Notes Receivable from Affiliated Companies	2,922	95	60
Issuance of Notes Receivable to Unconsolidated Subsidiaries	(936)	(450)	(700)
Return of Capital Contributions from Unconsolidated Subsidiaries	739	133	184
Capital Contributions to Subsidiaries	(189)	(62)	(30)
Net Cash Flows Used for Investing Activities	2,486	(304)	(486)
FINANCING ACTIVITIES
Capital Contribution from AEP Member	70	62	30
Return of Capital to Parent	0	(5)	(9)
Issuance of Long-term Debt	929	446	689
Retirement of Long-term Debt	(102)	(95)	(60)
Change in Advances from Affiliates, Net	0	(43)	15
Dividends Paid	(3,379)	(128)	(175)
Other Financing Activities	(37)	0	0
Net Cash Flows from Financing Activities	(2,519)	237	490
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	0	0	0
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	0	0	0
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 0	$ 0	$ 0