FINANCING ACTIVITIES - Schedule of Accounts Receivable and Accrued Unbilled Revenues (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
APCo
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	$ 228.0	$ 192.7
I&M
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	194.6	160.5
OPCo
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	498.4	470.7
PSO
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	104.7	111.4
SWEPCo
Short-Term Debt [Line Items]
Accounts receivable and accrued unbilled revenues	$ 145.9	$ 153.5