v3.26.3
Fair Value Measurements - Fair Value Hierarchy for Financial Assets and Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities $ 720.9 $ 708.8
Short term investments 72.8 14.1
Total 793.7 722.9
Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 457.1 501.2
U.S. Government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 155.1 140.1
Asset-backed securities and collateralized loan obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 79.8  
Non-U.S. government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 28.9 22.0
Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 79.8 45.5
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Short term investments 0.0 0.0
Total 0.0 0.0
Level 1 | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Level 1 | U.S. Government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Level 1 | Asset-backed securities and collateralized loan obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0  
Level 1 | Non-U.S. government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Level 1 | Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities   0.0
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 720.9 708.8
Short term investments 72.8 14.1
Total 793.7 722.9
Level 2 | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 457.1 501.2
Level 2 | U.S. Government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 155.1 140.1
Level 2 | Asset-backed securities and collateralized loan obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 79.8  
Level 2 | Non-U.S. government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 28.9 22.0
Level 2 | Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities   45.5
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Short term investments 0.0 0.0
Total 0.0 0.0
Level 3 | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Level 3 | U.S. Government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0 0.0
Level 3 | Asset-backed securities and collateralized loan obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities 0.0  
Level 3 | Non-U.S. government obligations    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities $ 0.0 0.0
Level 3 | Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed maturities   $ 0.0