Unpaid Loss and Loss Adjustment Expense - Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 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	57.9	24.8
Prior years	5.7	(0.4)
Total incurred	63.6	24.4
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year	26.9	10.6
Prior years	39.5	10.8
Total paid	66.4	21.4
Unpaid loss and LAE, net of reinsurance recoverable, at end of period	128.8	28.2
Reinsurance recoverable at end of period	116.4	79.4
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 245.2	$ 107.6