Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 17.1	$ 16.9	$ 42.8	$ 47.2
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	6.1	7.7	18.4	22.5
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	11.0	7.2	29.6	20.2
Warrant shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.0	2.0	(5.2)	4.5
Loss and loss adjustment expense, net
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.6	0.5	1.7	1.5
Other insurance expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.8	0.7	2.1	1.9
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1.1	3.0	(2.4)	7.6
Technology development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	7.4	6.6	21.1	19.4
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7.2	$ 6.1	$ 20.3	$ 16.8