Deferred Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred Acquisition Costs:
Balance, January 1	$ 3.5	$ 1.8
Add:
Premium taxes and other acquisition costs	9.8	5.8
Direct commissions	2.4	0.8
Less:
Amortization of net deferred acquisition costs	(9.5)	(4.9)	$ (2.1)
Balance, December 31	6.2	3.5	1.8
Other Insurance Expense:
Amortization of net deferred acquisition costs	9.5	4.9	2.1
Period costs	14.6	9.5
Total other insurance expense	$ 24.1	$ 14.4	$ 9.6