Long-Duration Insurance Contracts - Deferred Policy Acquisition Costs, Reconciliation to Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	$ 358.2		$ 358.2
Whole Life
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	25.5	$ 25.1	24.9	$ 24.6	$ 24.1	$ 23.8
Term Life
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	35.9	35.9	35.5	34.8	34.5	34.2
Experience life
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	5.0	5.1	5.2	5.4	5.4	5.5
Limited-Pay Whole Life
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	8.4	8.3	8.3	8.1	8.0	8.0
Indexed Universal Life
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	24.9	23.9	22.8	20.3	19.8	19.2
Supplemental health
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	15.6	14.6	13.7	12.1	11.2	10.6
Total Annuities
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	205.3	$ 206.4	207.7	$ 209.4	$ 210.4	$ 211.4
Reconciling items
Deferred Policy Acquisition Cost [Line Items]
Deferred policy acquisition costs	$ 37.6		$ 40.1