Long-Duration Insurance Contracts - Deferred Policy Acquisition Costs, Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period			$ 347.2
Amortization expense	$ (29.9)	$ (27.0)	(59.5)	$ (54.0)
Balance, end of period	351.4		351.4
Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	24.1	22.6	23.8	22.3
Capitalizations	0.8	0.7	1.4	1.4
Amortization expense	(0.3)	(0.3)	(0.6)	(0.6)
Experience adjustment	0.0	0.0	0.0	(0.1)
Balance, end of period	24.6	23.0	24.6	23.0
Term Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	34.5	32.9	34.2	32.6
Capitalizations	1.0	1.4	2.2	2.6
Amortization expense	(0.7)	(0.8)	(1.6)	(1.7)
Experience adjustment	0.0	0.0	0.0	0.0
Balance, end of period	34.8	33.5	34.8	33.5
Experience life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	5.4	5.7	5.5	5.7
Capitalizations	0.1	0.0	0.1	0.1
Amortization expense	(0.1)	(0.1)	(0.2)	(0.2)
Experience adjustment	0.0	0.0	0.0	0.0
Balance, end of period	5.4	5.6	5.4	5.6
Limited-Pay Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	8.0	7.5	8.0	7.4
Capitalizations	0.2	0.3	0.3	0.5
Amortization expense	(0.1)	(0.1)	(0.2)	(0.2)
Experience adjustment	0.0	0.0	0.0	0.0
Balance, end of period	8.1	7.7	8.1	7.7
Indexed Universal Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	19.8	17.1	19.2	16.8
Capitalizations	0.8	0.9	1.6	1.6
Amortization expense	(0.3)	(0.2)	(0.5)	(0.5)
Experience adjustment	0.0	0.0	0.0	(0.1)
Balance, end of period	20.3	17.8	20.3	17.8
Supplemental health
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	11.2	8.7	10.6	8.2
Capitalizations	1.1	0.8	2.1	1.6
Amortization expense	(0.2)	(0.2)	(0.5)	(0.4)
Experience adjustment	0.0	0.0	(0.1)	(0.1)
Balance, end of period	12.1	9.3	12.1	9.3
Total Annuities
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	210.4	212.9	211.4	214.0
Capitalizations	3.2	4.1	6.8	8.0
Amortization expense	(3.9)	(4.2)	(7.9)	(7.9)
Experience adjustment	(0.3)	(0.4)	(0.9)	(1.7)
Balance, end of period	$ 209.4	$ 212.4	$ 209.4	$ 212.4