Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 15.4	$ 15.4	$ 25.7	$ 30.3
Warrant shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.0	1.6	(5.2)	2.5
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5.8	7.1	12.3	14.8
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	9.6	6.7	18.6	13.0
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	1.1	1.0
Other insurance expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.6	0.6	1.3	1.2
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.8	2.6	(3.5)	4.6
Technology development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	6.9	6.4	13.7	12.8
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6.5	$ 5.3	$ 13.1	$ 10.7