FAIR VALUE MEASUREMENTS - Debt Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	$ 42,642.8	$ 40,143.2
Fair Value	38,964.7	37,325.7
AEP TEXAS INC.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	6,441.6	5,889.8
Fair Value	5,831.4	5,400.7
AEP TRANSMISSION COMPANY, LLC
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	5,768.1	5,414.4
Fair Value	4,853.1	4,796.9
APPALACHIAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	5,660.3	5,588.3
Fair Value	5,346.0	5,390.1
INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	3,494.3	3,499.4
Fair Value	3,153.8	3,291.6
OHIO POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	3,715.7	3,366.8
Fair Value	3,203.4	2,992.1
PUBLIC SERVICE COMPANY OF OKLAHOMA
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	2,855.6	2,384.6
Fair Value	2,562.1	2,154.3
SOUTHWESTERN ELECTRIC POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book Value	3,980.8	3,646.9
Fair Value	$ 3,431.5	$ 3,209.7