Long-Duration Insurance Contracts - Deferred Policy Acquisition Costs, Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period			$ 358.2
Amortization expense	$ (31.9)	$ (31.5)	(96.2)	$ (91.0)
Balance, end of period	360.1		360.1
Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	25.5	24.6	24.9	23.8
Capitalizations	0.5	0.6	1.8	1.9
Amortization expense	(0.3)	(0.3)	(0.9)	(0.9)
Experience adjustment	0.0	(0.1)	(0.2)	(0.1)
Balance, end of period	25.7	24.8	25.7	24.8
Term Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	36.0	34.8	35.5	34.2
Capitalizations	0.9	1.4	2.9	3.6
Amortization expense	(0.8)	(0.8)	(2.2)	(2.4)
Experience adjustment	(0.1)	(0.1)	(0.1)	(0.1)
Balance, end of period	36.0	35.3	36.0	35.3
Experience life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	5.0	5.4	5.2	5.5
Capitalizations	0.0	0.0	0.0	0.1
Amortization expense	(0.1)	(0.1)	(0.3)	(0.3)
Experience adjustment	0.0	(0.1)	(0.1)	(0.1)
Balance, end of period	4.9	5.3	4.9	5.3
Limited-Pay Whole Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	8.4	8.1	8.3	8.0
Capitalizations	0.1	0.2	0.4	0.5
Amortization expense	(0.1)	(0.1)	(0.2)	(0.3)
Experience adjustment	0.0	(0.1)	(0.1)	(0.1)
Balance, end of period	8.4	8.2	8.4	8.2
Indexed Universal Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	24.9	20.3	22.8	19.2
Capitalizations	1.5	1.3	4.2	2.9
Amortization expense	(0.3)	(0.2)	(0.9)	(0.7)
Experience adjustment	0.0	(0.1)	(0.1)	(0.1)
Balance, end of period	26.1	21.4	26.1	21.4
Supplemental health
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	15.6	12.1	13.7	10.6
Capitalizations	1.3	1.2	4.1	3.3
Amortization expense	(0.4)	(0.4)	(1.1)	(0.9)
Experience adjustment	(0.1)	(0.1)	(0.2)	(0.2)
Balance, end of period	16.5	12.8	16.5	12.8
Total Annuities
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	205.3	209.4	207.7	211.4
Capitalizations	3.7	3.7	10.3	10.5
Amortization expense	(4.1)	(3.9)	(12.4)	(11.8)
Experience adjustment	(0.4)	(0.4)	(1.1)	(1.3)
Balance, end of period	$ 204.4	$ 208.8	$ 204.4	$ 208.8