Deferred Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Acquisition Costs
Balance, January 1	$ 1.8	$ 0.6
Add:
Premium taxes and other acquisition costs	5.8	3.2
Direct commissions	0.8	0.1
Less:
Amortization of net deferred acquisition costs	(4.9)	(2.1)	$ (0.7)
Balance, December 31	3.5	1.8	0.6
Other Insurance Expense
Amortization of net deferred acquisition costs	4.9	2.1	0.7
Period costs	9.5	7.5
Total other insurance expense	$ 14.4	$ 9.6	$ 4.2