v3.26.1
Related party transactions (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Related Party Transaction [Line Items]        
Premiums written $ 742.6 $ 911.3 $ 1,586.5 $ 1,785.3
Affiliated Entity        
Related Party Transaction [Line Items]        
Transactions with related party (benefit) expense   $ (1.4)   0.7
Related Party        
Related Party Transaction [Line Items]        
Premiums written     $ 399.0 $ 292.7