v3.26.1
Investments - Amortized Cost and Fair Values of Investment in Fixed Maturities (Details) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost $ 733.4 $ 706.0
Gross Unrealized Gains 0.6 2.8
Gross Unrealized Losses (2.2) 0.0
Fair Value 731.8 708.8
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 491.8 499.2
Gross Unrealized Gains 0.4 2.0
Gross Unrealized Losses (1.3) 0.0
Fair Value 490.9 501.2
U.S. Government obligations    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 163.7 139.5
Gross Unrealized Gains 0.1 0.6
Gross Unrealized Losses (0.7) 0.0
Fair Value 163.1 140.1
Asset-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 50.7 45.3
Gross Unrealized Gains 0.1 0.2
Gross Unrealized Losses (0.1) 0.0
Fair Value 50.7 45.5
Non-U.S. government obligations    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 27.2 22.0
Gross Unrealized Gains 0.0 0.0
Gross Unrealized Losses (0.1) 0.0
Fair Value $ 27.1 $ 22.0