FINANCING ACTIVITIES - Schedule of Short-term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Short-Term Debt [Line Items]
Short-term – Securitized Debt of Receivables	$ 900.0	$ 888.0
Interest Rate	4.73%	5.65%
Commercial Paper	$ 1,618.3	$ 1,937.9
Total Short-term Debt	2,523.8	2,830.2
SOUTHWESTERN ELECTRIC POWER COMPANY
Short-Term Debt [Line Items]
Notes Payable	5.5	4.3
Total Short-term Debt	$ 5.5	$ 4.3
Commercial Paper
Short-Term Debt [Line Items]
Weighted-Average Interest Rate	4.70%	5.69%
Notes Payable | SOUTHWESTERN ELECTRIC POWER COMPANY
Short-Term Debt [Line Items]
Weighted-Average Interest Rate	6.69%	7.71%