v3.25.2
Loss and loss adjustment expense reserves - Narrative (Details)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Apr. 30, 2024
USD ($)
Jun. 30, 2023
USD ($)
Sep. 30, 2022
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                
Prior year loss reserve development $ (8.7) $ (1.1) $ (42.9) $ (40.0)        
Loss reserves           $ 400.0 $ 905.6 $ 1,300.0
Funds held liability $ 256.6   $ 256.6          
Aggregate limit, percentage of booked reserves 1.30   1.30     1.50    
Reinsurance balances payable $ 1,539.9   $ 1,539.9   $ 1,781.6      
Pallas Reinsurance Company Ltd.                
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                
Reinsurance balances payable 469.9   469.9          
Reinsurance recoverable $ 484.1   $ 484.1