v3.26.1
Investments - Schedule of Fixed-maturity Securities Classified by Contractual Maturity Securities Date (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Amortized cost    
Due in one year or less $ 114.2  
Due after one year through five years 407.5  
Due after five years through ten years 63.9  
Due after ten years 1.3  
Total fixed maturity and short-term investments 664.2 $ 707.1
Fair value    
Due in one year or less 114.2  
Due after one year through five years 406.3  
Due after five years through ten years 63.3  
Due after ten years 1.3  
Total fixed maturity and short-term investments 662.2 712.0
Residential mortgage-backed    
Amortized cost    
Without single maturity date, amortized cost 54.3  
Total fixed maturity and short-term investments 54.3 55.5
Fair value    
Without single maturity date, fair value 54.1  
Total fixed maturity and short-term investments 54.1 55.6
Commercial mortgage-backed    
Amortized cost    
Without single maturity date, amortized cost 7.6  
Total fixed maturity and short-term investments 7.6 14.8
Fair value    
Without single maturity date, fair value 7.7  
Total fixed maturity and short-term investments 7.7 15.0
Other asset-backed securities    
Amortized cost    
Without single maturity date, amortized cost 15.4  
Total fixed maturity and short-term investments 15.4 21.8
Fair value    
Without single maturity date, fair value 15.3  
Total fixed maturity and short-term investments $ 15.3 $ 21.9