v3.26.3
INVESTMENTS - Schedule of Gross Unrealized Losses and Fair Values for Investments in Unrealized Loss Position (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Fair value, less than 12 months $ 1,281.3 $ 81.8
Gross unrealized losses, less than 12 months (1.2) (0.2)
Fair value, 12 months or greater 25.2 69.8
Gross unrealized losses, 12 months or greater (0.7) (1.2)
Fair value, total 1,306.5 151.6
Gross unrealized losses, total (1.9) (1.4)
U.S. government and agency securities    
Debt Securities, Available-for-sale [Line Items]    
Fair value, less than 12 months 616.9 0.0
Gross unrealized losses, less than 12 months (0.1) 0.0
Fair value, 12 months or greater 7.4 11.2
Gross unrealized losses, 12 months or greater (0.4) (0.4)
Fair value, total 624.3 11.2
Gross unrealized losses, total (0.5) (0.4)
Asset-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Fair value, less than 12 months 7.6 5.1
Gross unrealized losses, less than 12 months (0.1) (0.1)
Fair value, 12 months or greater 17.8 24.3
Gross unrealized losses, 12 months or greater (0.3) (0.5)
Fair value, total 25.4 29.4
Gross unrealized losses, total (0.4) (0.6)
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Fair value, less than 12 months 656.8 76.7
Gross unrealized losses, less than 12 months (1.0) (0.1)
Fair value, 12 months or greater 0.0 34.3
Gross unrealized losses, 12 months or greater 0.0 (0.3)
Fair value, total 656.8 111.0
Gross unrealized losses, total $ (1.0) $ (0.4)