Description of Business and Summary of Significant Accounting Policies - Accounts Receivable and Long-term Insurance Commissions Receivable and Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Allowance for uncollectible receivables	$ 0.6	$ 0.5
Amortized deferred acquisition costs	$ 49.2	$ 14.5	$ 2.5