INVESTMENTS - Schedule of Cost and Fair Value of Investments in Debt Securities, by Contractual Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Amortized Cost
Due in 1 year or less	$ 46.8
Due after 1 year through 5 years	0.0
Instruments not due at a single maturity date	0.0
Amortized Cost	46.8
Fair Value
Due in 1 year or less	46.8
Due after 1 year through 5 years	0.0
Instruments not due at a single maturity date	0.0
Fair Value	46.8
Amortized Cost
Due in 1 year or less	1,110.0
Due after 1 year through 5 years	11.1
Instruments not due at a single maturity date	57.1
Amortized Cost	1,178.2	$ 1,026.4
Fair Value
Due in 1 year or less	1,109.5
Due after 1 year through 5 years	11.0
Instruments not due at a single maturity date	55.9
Fair Value	$ 1,176.4	$ 1,021.3