EFFECTS OF REGULATION - Narrative (Details) - USD ($) $ in Millions	1 Months Ended
	Jan. 31, 2026	Apr. 30, 2025	Jan. 31, 2025	Jun. 30, 2024	Sep. 30, 2023	Dec. 31, 2025	Dec. 31, 2024
Public Utilities, General Disclosures [Line Items]
Net book value						$ 91,638	$ 81,701
SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Net book value						11,315	$ 9,420
Pirkey Station | SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Net investment						206
Pirkey Station | SOUTHWESTERN ELECTRIC POWER COMPANY | 2021 Arkansas Rate Case
Public Utilities, General Disclosures [Line Items]
Net book value						41
Pirkey Station | SOUTHWESTERN ELECTRIC POWER COMPANY | 2021 Arkansas Rate Case | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public utilities, approved recovery, amount	10 years
Public utilities, return on recovery, percent	3.00%
Pirkey Station | SOUTHWESTERN ELECTRIC POWER COMPANY | TEXAS
Public Utilities, General Disclosures [Line Items]
Net book value						$ 76
Pirkey Power Plant and Related Fuel Operations | SOUTHWESTERN ELECTRIC POWER COMPANY | TEXAS
Public Utilities, General Disclosures [Line Items]
Recovery of fuel costs				$ 535
Fuel disallowance		$ 6
Pirkey Power Plant and Related Fuel Operations | SOUTHWESTERN ELECTRIC POWER COMPANY | TEXAS | Minimum
Public Utilities, General Disclosures [Line Items]
Fuel disallowance			$ 2
Pirkey Power Plant and Related Fuel Operations | SOUTHWESTERN ELECTRIC POWER COMPANY | TEXAS | Maximum
Public Utilities, General Disclosures [Line Items]
Fuel disallowance			$ 33
Pirkey Power Plant and Related Fuel Operations | SOUTHWESTERN ELECTRIC POWER COMPANY | TEXAS | Sabine
Public Utilities, General Disclosures [Line Items]
Recovery of fuel costs					$ 33