ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents	$ 202.9	$ 330.1
Restricted Cash	43.1	48.9
Total Cash, Cash Equivalents and Restricted Cash	246.0	379.0	$ 556.5	$ 451.4
AEP Texas
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents	0.1	0.1
Restricted Cash	23.5	34.0
Total Cash, Cash Equivalents and Restricted Cash	23.6	34.1	32.8	30.5
APCo
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents	3.9	5.0
Restricted Cash	16.2	14.9
Total Cash, Cash Equivalents and Restricted Cash	20.1	19.9	21.9	20.1
SWEPCo
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents	1.2	2.4
Restricted Cash	3.4	0.0
Total Cash, Cash Equivalents and Restricted Cash	$ 4.6	$ 2.4	$ 88.4	$ 51.2