Unpaid Loss and Loss Adjustment Expense ("LAE") (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid loss and LAE at beginning of period			$ 28.2	$ 13.1
Less: Reinsurance recoverable at beginning of period			18.5	11.3
Net unpaid loss and LAE at beginning of period			9.7	1.8
Add: Incurred loss and LAE, net of reinsurance, related to:
Current year			33.5	15.4
Prior years			5.2	2.4
Total incurred	$ 20.5	$ 9.9	38.7	17.8
Deduct: Paid loss and LAE, net of reinsurance, related to:
Current year			24.4	11.6
Prior years			13.2	4.2
Total paid			37.6	15.8
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	10.8	3.8	10.8	3.8
Reinsurance recoverable at end of period	24.5	16.9	24.5	16.9
Unpaid loss and LAE, gross of reinsurance recoverable, at end of period	$ 35.3	$ 20.7	35.3	20.7
Reserve deficiencies			$ 2.6	$ 1.2