Long-Duration Insurance Contracts - Deferred Policy Acquisition Costs, Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period			$ 347.2
Amortization expense	$ (31.5)	$ (28.1)	(91.0)	$ (82.1)
Balance, end of period	358.3		358.3
Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	24.6	23.0	23.8	22.3
Capitalizations	0.6	0.8	1.9	2.2
Amortization expense	(0.3)	(0.4)	(0.9)	(1.0)
Experience adjustment	(0.1)	0.0	(0.1)	(0.1)
Balance, end of period	24.8	23.4	24.8	23.4
Term Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	34.8	33.5	34.2	32.6
Capitalizations	1.4	1.2	3.6	3.8
Amortization expense	(0.8)	(0.9)	(2.4)	(2.6)
Experience adjustment	(0.1)	0.0	(0.1)	0.0
Balance, end of period	35.3	33.8	35.3	33.8
Experience life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	5.4	5.6	5.5	5.7
Capitalizations	0.0	0.1	0.1	0.2
Amortization expense	(0.1)	(0.1)	(0.3)	(0.3)
Experience adjustment	(0.1)	0.0	(0.1)	0.0
Balance, end of period	5.3	5.6	5.3	5.6
Limited-Pay Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	8.1	7.7	8.0	7.4
Capitalizations	0.2	0.3	0.5	0.8
Amortization expense	(0.1)	(0.1)	(0.3)	(0.3)
Experience adjustment	(0.1)	(0.1)	(0.1)	(0.1)
Balance, end of period	8.2	7.8	8.2	7.8
Indexed Universal Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	20.3	17.8	19.2	16.8
Capitalizations	1.3	0.8	2.9	2.4
Amortization expense	(0.2)	(0.3)	(0.7)	(0.8)
Experience adjustment	(0.1)	0.0	(0.1)	(0.1)
Balance, end of period	21.4	18.3	21.4	18.3
Supplemental health
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	12.1	9.3	10.6	8.2
Capitalizations	1.2	0.8	3.3	2.4
Amortization expense	(0.4)	(0.2)	(0.9)	(0.6)
Experience adjustment	(0.1)	0.0	(0.2)	(0.1)
Balance, end of period	12.8	9.9	12.8	9.9
Total Annuities
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	209.4	212.4	211.4	214.0
Capitalizations	3.7	3.9	10.5	11.9
Amortization expense	(3.9)	(4.1)	(11.8)	(12.0)
Experience adjustment	(0.4)	(0.2)	(1.3)	(1.9)
Balance, end of period	$ 208.8	$ 212.0	$ 208.8	$ 212.0