RATE MATTERS - Net Book Value (Details) - Generating Units Probable of Abandonment - SWEPCo $ in Millions	9 Months Ended
	Sep. 30, 2025 USD ($)
Northeastern Plant, Unit 3
Public Utilities, General Disclosures [Line Items]
Net Book Value	$ 73.9
Accelerated Depreciation Regulatory Asset	212.8
Cost of Removal Regulatory Liability	21.2
Annual Depreciation	16.1
Welsh Plant, Units 1 and 3
Public Utilities, General Disclosures [Line Items]
Net Book Value	278.8
Accelerated Depreciation Regulatory Asset	206.2
Cost of Removal Regulatory Liability	57.6
Annual Depreciation	$ 46.5