Unpaid Loss and Loss Adjustment Expense - Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid loss and LAE at beginning of period	$ 298.1	$ 262.3
Less: Reinsurance recoverable at beginning of period	149.5	120.2
Net unpaid loss and LAE at beginning of period	148.6	142.1
Add: Incurred loss and LAE, net of reinsurance, related to:
Current year	95.8	72.4
Prior years	(10.4)	(6.5)
Total incurred	85.4	65.9
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year	43.4	33.7
Prior years	34.7	35.1
Total paid	78.1	68.8
Unpaid loss and LAE, net of reinsurance recoverable, at end of period	155.9	139.2
Reinsurance recoverable at end of period	151.4	124.8
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 307.3	$ 264.0