Unpaid Loss and Loss Adjustment Expense - Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid loss and LAE at beginning of period			$ 256.2	$ 97.9
Less: Reinsurance recoverable at beginning of period			124.6	72.7
Net unpaid loss and LAE at beginning of period			131.6	25.2
Add: Incurred loss and LAE, net of reinsurance, related to:
Current year			140.8	53.7
Prior years			(1.3)	(1.2)
Total incurred	$ 75.9	$ 28.1	139.5	52.5
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year			75.0	30.0
Prior years			59.7	14.4
Total paid			134.7	44.4
Unpaid loss and LAE, net of reinsurance recoverable, at end of period	136.4	33.4	136.4	33.4
Reinsurance recoverable at end of period	119.2	89.5	119.2	89.5
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 255.6	$ 122.9	$ 255.6	$ 122.9