Long-Duration Insurance Contracts - Reconciliation of Policyholder Account Balances to the Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Policyholder Account Balance [Line Items]
Policyholders' account balances	$ 5,064.1	$ 5,100.3
Indexed Universal Life
Policyholder Account Balance [Line Items]
Policyholders' account balances	95.5	72.9	$ 57.8
Experience Life
Policyholder Account Balance [Line Items]
Policyholders' account balances	54.8	58.0	61.2
Fixed account annuities
Policyholder Account Balance [Line Items]
Policyholders' account balances	4,486.8	4,508.4	4,556.0
Fixed indexed account annuities
Policyholder Account Balance [Line Items]
Policyholders' account balances	373.3	409.5	449.0
SPIA (non-life contingent)
Policyholder Account Balance [Line Items]
Policyholders' account balances	26.1	28.6	$ 32.6
Reconciling items
Policyholder Account Balance [Line Items]
Policyholders' account balances	$ 27.6	$ 22.9