RATE MATTERS - FERC Rate Matters (Details) $ in Millions	Sep. 30, 2026 USD ($)	May 31, 2026 filing	Jun. 30, 2025 order	Jan. 31, 2024 order
Public Utilities, General Disclosures [Line Items]
Number of order FERC issues \| order			2	2
Independence Energy Connection Project \| Location, Statement of Financial Position, Balance [Axis]: us-gaap:RegulatoryAssetsNoncurrent
Public Utilities, General Disclosures [Line Items]
AEP share of independence energy connection capital costs	$ 20
Independence Energy Connection Project \| Location, Statement of Financial Position, Balance [Axis]: aep:RegulatedAndNonregulatedPropertyPlantAndEquipmentNet
Public Utilities, General Disclosures [Line Items]
AEP share of independence energy connection capital costs	$ 73
Transource Energy
Public Utilities, General Disclosures [Line Items]
FERC matters, petition, number of filings requested to be consolidated \| filing		3