EFFECTS OF REGULATION - Regulatory Asset, Early Retirement (Details) - Generating Units Probable of Abandonment $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($)
Northeastern Plant, Unit 3 | PUBLIC SERVICE COMPANY OF OKLAHOMA
Public Utilities, General Disclosures [Line Items]
Net Book Value	$ 73
Accelerated Depreciation Regulatory Asset	221
Cost of Removal Regulatory Liability	21
Annual Depreciation	15
Welsh Plant, Units 1 and 3 | SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Net Book Value	269
Accelerated Depreciation Regulatory Asset	220
Cost of Removal Regulatory Liability	56
Annual Depreciation	$ 47