RATE MATTERS - February 2021 Severe Winter Weather Impacts in SPP (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Mar. 31, 2021
Public Utilities, General Disclosures [Line Items]
Total Noncurrent Regulatory Assets	$ 5,129.2	$ 5,092.4
SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Total Noncurrent Regulatory Assets	921.3	1,131.8
February 2021 Severe Storm Fuel Costs | SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Total Noncurrent Regulatory Assets	180.5	253.3
February 2021 Severe Storm Fuel Costs | Arkansas | SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Total Noncurrent Regulatory Assets	$ 37.2	54.2
Remaining Recovery Period	6 years
February 2021 Severe Storm Fuel Costs | Louisiana | SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Total Noncurrent Regulatory Assets	$ 70.6	97.2
Remaining Recovery Period			5 years
February 2021 Severe Storm Fuel Costs | Texas | SOUTHWESTERN ELECTRIC POWER COMPANY
Public Utilities, General Disclosures [Line Items]
Total Noncurrent Regulatory Assets	$ 72.7	$ 101.9
Remaining Recovery Period	5 years
Approved Carrying Charge	1.65%