v3.26.1
Segment information - Schedule of Revenues by Geography (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]        
Ceding commission income $ 75.1 $ 101.6 $ 155.6 $ 172.3
Direct commission income 92.5 34.2 143.3 62.3
Net earned premiums 129.1 70.6 258.9 133.6
Net investment income 7.2 12.8 19.3 25.0
Net realized gains (losses) on investments 26.0 0.4 26.1 2.7
Net unrealized gains (losses) on investments 27.0 (0.5) 27.0 1.2
Total revenues 356.9 219.1 630.2 397.1
North America        
Segment Reporting [Line Items]        
Ceding commission income 67.3 77.7 128.7 126.7
Direct commission income 74.5 18.3 108.4 32.3
Net earned premiums 56.8 26.8 125.4 41.9
Net investment income 6.6 7.8 13.3 15.2
Net realized gains (losses) on investments 26.3 0.2 26.4 0.4
Net unrealized gains (losses) on investments 27.0 (0.5) 27.0 1.2
Total revenues 258.5 130.3 429.2 217.7
UK and EU        
Segment Reporting [Line Items]        
Ceding commission income 7.8 23.9 26.9 45.6
Direct commission income 18.0 15.9 34.9 30.0
Net earned premiums 72.3 43.8 133.5 91.7
Net investment income 0.6 5.0 6.0 9.8
Net realized gains (losses) on investments (0.3) 0.2 (0.3) 2.3
Net unrealized gains (losses) on investments 0.0 0.0 0.0 0.0
Total revenues $ 98.4 $ 88.8 $ 201.0 $ 179.4