Description of Business and Summary of Significant Accounting Policies - Allowance, Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Allowance for uncollectible receivables	$ 0.5	$ 0.4
Deferred policy acquisition costs	8.7	4.0
Amortized deferred acquisition costs	$ 14.5	$ 2.5