v3.26.1
RATE MATTERS - Net Book Value (Details) - Generating Units Probable of Abandonment - SOUTHWESTERN ELECTRIC POWER COMPANY
$ in Millions
6 Months Ended
Jun. 30, 2026
USD ($)
Northeastern Plant, Unit 3  
Public Utilities, General Disclosures [Line Items]  
Net Book Value $ 53
Accelerated Depreciation Regulatory Asset 251
Cost of Removal Regulatory Liability 21
Annual Depreciation 11
Welsh Plant, Units 1 and 3  
Public Utilities, General Disclosures [Line Items]  
Net Book Value 230
Accelerated Depreciation Regulatory Asset 249
Cost of Removal Regulatory Liability 55
Annual Depreciation $ 44