Reinsurance - Impact of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Premium written:
Direct	$ 555.6	$ 375.7	$ 214.4
Assumed	0.1	0.0	0.0
Ceded	(333.1)	(273.4)	(171.7)
Net premium written	222.6	102.3	42.7
Premium earned:
Direct	490.5	292.0	158.7
Assumed	0.0	0.0	0.0
Ceded	(318.1)	(215.0)	(81.4)
Net premium earned	172.4	77.0	77.3
Loss and LAE incurred:
Direct	441.0	264.1	113.4
Assumed	0.0	0.0	0.0
Ceded	(273.7)	(192.2)	(58.7)
Net loss and LAE incurred	$ 167.3	$ 71.9	$ 54.7