Fair Value of Financial Instruments - Financial Instrument Not Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Level 1
Financial Assets
Other investments	$ 0.0	$ 0.0
Deposit asset on reinsurance	0.0	0.0
Financial Liabilities
Policyholders' account balances	0.0	0.0
Other policyholder funds	0.0	0.0
Reverse repurchase agreement		0.0
Long-term debt	0.0	0.0
Level 2
Financial Assets
Other investments	39.3	37.0
Deposit asset on reinsurance	0.0	0.0
Financial Liabilities
Policyholders' account balances	0.0	0.0
Other policyholder funds	1,043.2	992.9
Reverse repurchase agreement		12.4
Long-term debt	629.1	575.1
Level 3
Financial Assets
Other investments	179.4	187.3
Deposit asset on reinsurance	2,143.1	2,121.9
Financial Liabilities
Policyholders' account balances	4,791.1	4,710.1
Other policyholder funds	3.0	2.8
Reverse repurchase agreement		0.0
Long-term debt	0.0	0.0
Carrying Value
Financial Assets
Other investments	215.5	221.0
Deposit asset on reinsurance	2,369.6	2,434.3
Financial Liabilities
Policyholders' account balances	4,984.9	5,020.2
Other policyholder funds	1,046.2	995.7
Reverse repurchase agreement		12.0
Long-term debt	593.4	547.0
Fair Value
Financial Assets
Other investments	218.7	224.3
Deposit asset on reinsurance	2,143.1	2,121.9
Financial Liabilities
Policyholders' account balances	4,791.1	4,710.1
Other policyholder funds	1,046.2	995.7
Reverse repurchase agreement		12.4
Long-term debt	$ 629.1	$ 575.1