ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and Cash Equivalents	$ 197	$ 203
Restricted Cash	71	43
Total Cash, Cash Equivalents and Restricted Cash	268	246	$ 379	$ 557
AEP Texas
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and Cash Equivalents	0	0
Restricted Cash	14	24
Total Cash, Cash Equivalents and Restricted Cash	14	24	34	32
APCo
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and Cash Equivalents	5	4
Restricted Cash	18	16
Total Cash, Cash Equivalents and Restricted Cash	23	20	20	22
SWEPCo
Restricted Cash and Cash Equivalent Item [Line Items]
Cash and Cash Equivalents	2	2
Restricted Cash	15	3
Total Cash, Cash Equivalents and Restricted Cash	$ 17	$ 5	$ 3	$ 89