INVESTMENTS - Schedule of Gross Unrealized Losses and Fair Values for Investments in Unrealized Loss Position (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Fair value, less than 12 months	$ 8.0	$ 8.4
Gross unrealized losses, less than 12 months	(0.1)	(0.1)
Fair value, 12 months or greater	146.4	214.2
Gross unrealized losses, 12 months or greater	(3.8)	(5.2)
Fair value, total	154.4	222.6
Gross unrealized losses, total	(3.9)	(5.3)
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Fair value, less than 12 months	0.0	0.0
Gross unrealized losses, less than 12 months	0.0	0.0
Fair value, 12 months or greater	17.7	19.9
Gross unrealized losses, 12 months or greater	(0.8)	(1.1)
Fair value, total	17.7	19.9
Gross unrealized losses, total	(0.8)	(1.1)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair value, less than 12 months	8.0	8.4
Gross unrealized losses, less than 12 months	(0.1)	(0.1)
Fair value, 12 months or greater	44.6	53.3
Gross unrealized losses, 12 months or greater	(1.1)	(1.3)
Fair value, total	52.6	61.7
Gross unrealized losses, total	(1.2)	(1.4)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Fair value, less than 12 months	0.0	0.0
Gross unrealized losses, less than 12 months	0.0	0.0
Fair value, 12 months or greater	84.1	141.0
Gross unrealized losses, 12 months or greater	(1.9)	(2.8)
Fair value, total	84.1	141.0
Gross unrealized losses, total	$ (1.9)	$ (2.8)