Unpaid Loss and Loss Adjustment Expense - Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid loss and LAE at beginning of period			$ 262.3	$ 256.2
Less: Reinsurance recoverable at beginning of period			120.2	124.6
Net unpaid loss and LAE at beginning of period			142.1	131.6
Add: Incurred loss and LAE, net of reinsurance, related to:
Current year			145.0	140.8
Prior years			(8.6)	(1.3)
Total incurred	$ 70.5	$ 75.9	136.4	139.5
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year			82.1	75.0
Prior years			51.9	59.7
Total paid			134.0	134.7
Unpaid loss and LAE, net of reinsurance recoverable, at end of period	144.5	136.4	144.5	136.4
Reinsurance recoverable at end of period	137.7	119.2	137.7	119.2
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 282.2	$ 255.6	$ 282.2	$ 255.6