Unpaid Loss and Loss Adjustment Expense - Activity in the Liability for Unpaid Loss and LAE (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 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			175.5	145.0
Prior years			(12.6)	(8.6)
Total incurred	$ 77.5	$ 70.5	162.9	136.4
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year			101.0	82.1
Prior years			54.5	51.9
Total paid			155.5	134.0
Unpaid loss and LAE, net of reinsurance recoverable, at end of period	156.0	144.5	156.0	144.5
Reinsurance recoverable at end of period	153.8	137.7	153.8	137.7
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 309.8	$ 282.2	$ 309.8	$ 282.2