Long-Duration Insurance Contracts - Deferred Policy Acquisition Costs, Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period			$ 358.2
Amortization expense	$ (32.0)	$ (29.9)	(64.3)	$ (59.5)
Balance, end of period	358.2		358.2
Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	25.1	24.1	24.9	23.8
Capitalizations	0.7	0.8	1.3	1.4
Amortization expense	(0.3)	(0.3)	(0.6)	(0.6)
Experience adjustment	0.0	0.0	(0.1)	0.0
Balance, end of period	25.5	24.6	25.5	24.6
Term Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	35.9	34.5	35.5	34.2
Capitalizations	0.9	1.0	2.0	2.2
Amortization expense	(0.8)	(0.7)	(1.5)	(1.6)
Experience adjustment	(0.1)	0.0	(0.1)	0.0
Balance, end of period	35.9	34.8	35.9	34.8
Experience life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	5.1	5.4	5.2	5.5
Capitalizations	0.0	0.1	0.0	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	5.0	5.4	5.0	5.4
Limited-Pay Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	8.3	8.0	8.3	8.0
Capitalizations	0.2	0.2	0.3	0.3
Amortization expense	(0.1)	(0.1)	(0.2)	(0.2)
Experience adjustment	0.0	0.0	0.0	0.0
Balance, end of period	8.4	8.1	8.4	8.1
Indexed Universal Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	23.9	19.8	22.8	19.2
Capitalizations	1.3	0.8	2.7	1.6
Amortization expense	(0.3)	(0.3)	(0.6)	(0.5)
Experience adjustment	0.0	0.0	0.0	0.0
Balance, end of period	24.9	20.3	24.9	20.3
Supplemental health
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	14.6	11.2	13.7	10.6
Capitalizations	1.4	1.1	2.7	2.1
Amortization expense	(0.4)	(0.2)	(0.7)	(0.5)
Experience adjustment	0.0	0.0	(0.1)	(0.1)
Balance, end of period	15.6	12.1	15.6	12.1
Total Annuities
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	206.4	210.4	207.7	211.4
Capitalizations	3.4	3.2	6.6	6.8
Amortization expense	(4.1)	(3.9)	(8.3)	(7.9)
Experience adjustment	(0.4)	(0.3)	(0.7)	(0.9)
Balance, end of period	$ 205.3	$ 209.4	$ 205.3	$ 209.4