v3.26.3
Investments - Schedule of Continuous Loss Position (Details)
$ in Millions
Sep. 30, 2026
USD ($)
security
Dec. 31, 2025
USD ($)
security
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 2,331.1 $ 136.2
Gross unrealized losses (48.6) (0.5)
Gross unrealized losses $ (0.1) $ (0.1)
Number of securities | security 1,389 215
U.S. Treasuries    
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 552.4 $ 50.1
Gross unrealized losses (7.1) (0.1)
Gross unrealized losses $ 0.0 $ (0.1)
Number of securities | security 169 49
Non-U.S. government    
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 35.5 $ 5.3
Gross unrealized losses (0.5) 0.0
Gross unrealized losses $ 0.0 $ 0.0
Number of securities | security 26 3
Corporate bonds    
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 1,290.7 $ 53.3
Gross unrealized losses (34.2) (0.3)
Gross unrealized losses $ (0.1) $ 0.0
Number of securities | security 957 132
Residential mortgage-backed    
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 262.7 $ 2.2
Gross unrealized losses (4.5) 0.0
Gross unrealized losses $ 0.0 $ 0.0
Number of securities | security 113 1
Commercial mortgage-backed    
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 8.3  
Gross unrealized losses (0.2)  
Gross unrealized losses $ 0.0  
Number of securities | security 14  
Other asset-backed securities    
Debt Securities, Available-for-Sale [Line Items]    
Fair value $ 181.5 $ 25.3
Gross unrealized losses (2.1) (0.1)
Gross unrealized losses $ 0.0 $ 0.0
Number of securities | security 110 30