v3.26.1
Contingent Liabilities (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Contingent Liabilities [Line Items]            
Allowance for credit losses on reinsurance recoverables $ 1.7 $ 1.7 $ 1.6 $ 1.5 $ 1.5 $ 1.2
Excess & Surplus Lines | Commercial Auto LPT | Aleka | Loss Fund Trust            
Contingent Liabilities [Line Items]            
Cash equivalent collateral trust arrangement 2.2          
Excess & Surplus Lines | Commercial Auto LPT | Rasier | Indemnity Trust And Loss Fund Trust            
Contingent Liabilities [Line Items]            
Cash equivalent collateral trust arrangement 19.5          
Excess & Surplus Lines | Commercial Auto LPT | Rasier | Loss Fund Trust            
Contingent Liabilities [Line Items]            
Cash equivalent collateral trust arrangement 5.3          
Excess & Surplus Lines | Commercial Auto LPT | Rasier and Aleka | Loss Fund Trust            
Contingent Liabilities [Line Items]            
Cash equivalent collateral trust arrangement 8.6          
Commercial Auto LPT | Excess & Surplus Lines | Commercial Auto LPT | Aleka            
Contingent Liabilities [Line Items]            
Reinsurance recoverables 7.7          
Commercial Auto LPT | Excess & Surplus Lines | Commercial Auto LPT | Aleka | LPT Trust And Loss Fund Trust            
Contingent Liabilities [Line Items]            
Cash equivalent collateral trust arrangement $ 8.2          
Commercial Auto LPT | Excess & Surplus Lines | Commercial Auto LPT | Rasier and Aleka            
Contingent Liabilities [Line Items]            
Required collateral, percentage 102.00%