RATE MATTERS - Net Book Value (Details) - Generating Units Probable of Abandonment - SOUTHWESTERN ELECTRIC POWER COMPANY $ in Millions	3 Months Ended
	Mar. 31, 2026 USD ($)
Northeastern Plant, Unit 3
Public Utilities, General Disclosures [Line Items]
Net Book Value	$ 53
Accelerated Depreciation Regulatory Asset	247
Cost of Removal Regulatory Liability	21
Annual Depreciation	13
Welsh Plant, Units 1 and 3
Public Utilities, General Disclosures [Line Items]
Net Book Value	249
Accelerated Depreciation Regulatory Asset	235
Cost of Removal Regulatory Liability	56
Annual Depreciation	$ 43