Unpaid Loss and Loss Adjustment Expense - Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid loss and LAE at beginning of period			$ 97.9	$ 46.3
Less: Reinsurance recoverable at beginning of period			72.7	36.3
Net unpaid loss and LAE at beginning of period			25.2	10.0
Add: Incurred loss and LAE, net of reinsurance, related to:
Current year			53.7	29.9
Prior years			(1.2)	(0.4)
Total incurred	$ 28.1	$ 13.0	52.5	29.5
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year			30.0	19.0
Prior years			14.4	5.5
Total paid			44.4	24.5
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	33.4	15.0	33.4	15.0
Reinsurance recoverable at end of period	89.5	49.7	89.5	49.7
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 122.9	$ 64.7	$ 122.9	$ 64.7