v3.26.3
Segment Information - Schedule of Gross Written Premium by State (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 450.7 $ 333.3 $ 1,174.6 $ 872.0
Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 100.00% 100.00% 100.00% 100.00%
California        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 88.9 $ 70.2 $ 240.5 $ 191.9
California | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 19.70% 21.10% 20.50% 22.00%
Texas        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 63.5 $ 42.0 $ 156.3 $ 113.3
Texas | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 14.10% 12.60% 13.30% 13.00%
New York        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 40.1 $ 34.1 $ 107.4 $ 87.0
New York | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 8.90% 10.20% 9.10% 10.00%
Washington        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 21.6 $ 17.0 $ 58.9 $ 44.5
Washington | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 4.80% 5.10% 5.00% 5.10%
Illinois        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 20.1 $ 16.0 $ 50.8 $ 41.7
Illinois | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 4.50% 4.80% 4.30% 4.80%
Colorado        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 19.2 $ 11.8 $ 48.2 $ 29.3
Colorado | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 4.30% 3.50% 4.10% 3.40%
New Jersey        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 18.0 $ 14.9 $ 47.9 $ 39.4
New Jersey | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 4.00% 4.50% 4.10% 4.50%
Florida        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 15.0 $ 9.8 $ 39.2 $ 24.3
Florida | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 3.30% 2.90% 3.30% 2.80%
Pennsylvania        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 13.0 $ 9.5 $ 33.3 $ 24.8
Pennsylvania | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 2.90% 2.90% 2.80% 2.80%
Arizona        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 12.4 $ 8.2 $ 32.8 $ 21.7
Arizona | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 2.80% 2.50% 2.80% 2.50%
All other        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 118.5 $ 86.5 $ 307.4 $ 221.8
All other | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 26.20% 26.00% 26.30% 25.40%
US        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 430.3 $ 320.0 $ 1,122.7 $ 839.7
US | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 95.50% 96.10% 95.60% 96.30%
Europe and UK        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
Amount $ 20.4 $ 13.3 $ 51.9 $ 32.3
Europe and UK | Gross written premium | Geographic Concentration Risk        
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Line Items]        
% of GWP 4.50% 3.90% 4.40% 3.70%