v3.26.3
Investments - Aging of Gross Unrealized Losses (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Fair Value    
Less than 12 Months $ 697.4 $ 53.5
12 Months or More 2.5 4.9
Fair Value 699.9 58.4
Gross Unrealized Losses    
Less than 12 Months (12.8) 0.0
12 Months or More 0.0 0.0
Gross Unrealized Losses (12.8) 0.0
Gross Unrealized Losses for 12 Months or More (less than) 0.0 0.0
Corporate debt securities    
Fair Value    
Less than 12 Months 453.3 45.9
12 Months or More 0.0 4.9
Fair Value 453.3 50.8
Gross Unrealized Losses    
Less than 12 Months (9.2) 0.0
12 Months or More 0.0 0.0
Gross Unrealized Losses (9.2) 0.0
Gross Unrealized Losses for 12 Months or More (less than) 0.0 0.0
U.S. Government obligations    
Fair Value    
Less than 12 Months 153.8 0.4
12 Months or More 0.0 0.0
Fair Value 153.8 0.4
Gross Unrealized Losses    
Less than 12 Months (2.9) 0.0
12 Months or More 0.0 0.0
Gross Unrealized Losses (2.9) 0.0
Gross Unrealized Losses for 12 Months or More (less than) 0.0 0.0
Asset-backed securities and collateralized loan obligations    
Fair Value    
Less than 12 Months 66.3 0.0
12 Months or More 0.0 0.0
Fair Value 66.3 0.0
Gross Unrealized Losses    
Less than 12 Months (0.5) 0.0
12 Months or More 0.0 0.0
Gross Unrealized Losses (0.5) 0.0
Gross Unrealized Losses for 12 Months or More (less than) 0.0 0.0
Non-U.S. government obligations    
Fair Value    
Less than 12 Months 24.0 7.2
12 Months or More 2.5 0.0
Fair Value 26.5 7.2
Gross Unrealized Losses    
Less than 12 Months (0.2) 0.0
12 Months or More (0.1) 0.0
Gross Unrealized Losses (0.2) 0.0
Gross Unrealized Losses for 12 Months or More (less than) $ 0.1 $ 0.0