Reserves - Policyholder Account Balances, Future Policy Benefits and Claims (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Future policy benefits and expenses	$ 487.2	$ 507.9
Long-term care
Liability for Claims and Claims Adjustment Expense [Line Items]
Future policy benefits and expenses	414.2	428.2	$ 621.4
Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Future policy benefits and expenses	$ 73.0	$ 79.7