Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
less: Loss and loss adjustment expenses, net		$ 89.6			$ 77.9			$ 252.5	$ 214.3
Other insurance expense		24.1			19.8			71.6	55.9
Sales and marketing		57.4			51.4			160.2	118.6
Technology development		24.7			21.9			69.1	64.0
Depreciation and amortization								12.6	15.3
Income tax expense		1.2			1.9			3.5	6.1
Net loss		(37.5)	$ (43.9)	$ (62.4)	(67.7)	$ (57.2)	$ (47.3)	(143.8)	(172.2)
Gain on early lease termination	$ 2.3	2.3						2.3	0.0
Gain from litigation settlement								1.0
New York
Segment Reporting Information [Line Items]
Operating lease, impairment loss									0.3
Domestic Tax Jurisdiction | CARES Act, ERC Program
Segment Reporting Information [Line Items]
Tax credits received under ERC program			$ 11.7					11.7
Reportable Segment
Segment Reporting Information [Line Items]
Total revenue		194.5			136.6			509.8	377.7
less: Loss and loss adjustment expenses, net		89.6			77.9			252.5	214.3
Other insurance expense		24.1			19.8			71.6	55.9
Sales and marketing		11.3			11.5			26.3	33.1
Advertising expenses		46.1			39.9			133.9	85.5
Technology development		24.7			21.9			69.1	64.0
General and administrative		30.3			24.5			87.2	72.0
Interest expense		4.6			1.8			11.9	3.4
Depreciation and amortization		3.4			5.1			12.6	15.3
Other expenses		(3.3)			0.0			(15.0)	0.3
Income tax expense		1.2			1.9			3.5	6.1
Net loss		$ (37.5)			$ (67.7)			$ (143.8)	$ (172.2)