v3.26.1
Investments - Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Cost or Amortized Cost    
Due in one year or less, cost or amortized cost $ 153.9  
Due after one year through five years, cost or amortized cost 1,363.4  
Due after five years through ten years, cost or amortized cost 3,722.2  
Due after ten years, cost or amortized cost 1,435.7  
Total, cost or amortized cost 6,675.2  
Fixed maturity securities available for sale, amortized cost 9,133.1 $ 8,635.3
Fair Value    
Due in one year or less, fair value 153.7  
Due after one year through five years, fair value 1,370.8  
Due after five years through ten years, fair value 3,738.4  
Due after ten years, fair value 1,321.6  
Total, fair value 6,584.5  
Fixed maturity securities, fair value 8,989.5 8,577.7
Commercial mortgage-backed    
Cost or Amortized Cost    
Cost or amortized cost 482.9  
Fair Value    
Fair value 467.0  
Residential mortgage-backed    
Cost or Amortized Cost    
Cost or amortized cost 1,113.9  
Fair Value    
Fair value 1,081.2  
Asset-backed    
Cost or Amortized Cost    
Cost or amortized cost 861.1  
Fixed maturity securities available for sale, amortized cost 861.1 850.2
Fair Value    
Fair value 856.8  
Fixed maturity securities, fair value $ 856.8 $ 845.7