INVESTMENTS - Schedule of Gross Unrealized Losses and Fair Values for Investments in Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Fair value, less than 12 months	$ 8.7	$ 8.4
Gross unrealized losses, less than 12 months	(0.1)	(0.1)
Fair value, 12 months or greater	116.9	214.2
Gross unrealized losses, 12 months or greater	(2.7)	(5.2)
Fair value, total	125.6	222.6
Gross unrealized losses, total	(2.8)	(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	15.6	19.9
Gross unrealized losses, 12 months or greater	(0.7)	(1.1)
Fair value, total	15.6	19.9
Gross unrealized losses, total	(0.7)	(1.1)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair value, less than 12 months	8.7	8.4
Gross unrealized losses, less than 12 months	(0.1)	(0.1)
Fair value, 12 months or greater	36.3	53.3
Gross unrealized losses, 12 months or greater	(0.8)	(1.3)
Fair value, total	45.0	61.7
Gross unrealized losses, total	(0.9)	(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	65.0	141.0
Gross unrealized losses, 12 months or greater	(1.2)	(2.8)
Fair value, total	65.0	141.0
Gross unrealized losses, total	$ (1.2)	$ (2.8)