Long-Duration Insurance Contracts - Deferred Policy Acquisition Costs, Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	$ 358.2
Amortization expense	(32.3)	$ (29.6)
Balance, end of period	357.3
Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	24.9	23.8
Capitalizations	0.6	0.6
Amortization expense	(0.3)	(0.3)
Experience adjustment	(0.1)	0.0
Balance, end of period	25.1	24.1
Term Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	35.5	34.2
Capitalizations	1.1	1.2
Amortization expense	(0.7)	(0.9)
Experience adjustment	0.0	0.0
Balance, end of period	35.9	34.5
Experience life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	5.2	5.5
Capitalizations	0.0	0.0
Amortization expense	(0.1)	(0.1)
Experience adjustment	0.0	0.0
Balance, end of period	5.1	5.4
Limited-Pay Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	8.3	8.0
Capitalizations	0.1	0.1
Amortization expense	(0.1)	(0.1)
Experience adjustment	0.0	0.0
Balance, end of period	8.3	8.0
Indexed Universal Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	22.8	19.2
Capitalizations	1.4	0.8
Amortization expense	(0.3)	(0.2)
Experience adjustment	0.0	0.0
Balance, end of period	23.9	19.8
Supplemental health
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	13.7	10.6
Capitalizations	1.3	1.0
Amortization expense	(0.3)	(0.3)
Experience adjustment	(0.1)	(0.1)
Balance, end of period	14.6	11.2
Total Annuities
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	207.7	211.4
Capitalizations	3.2	3.6
Amortization expense	(4.2)	(4.0)
Experience adjustment	(0.3)	(0.6)
Balance, end of period	$ 206.4	$ 210.4