Long-Duration Insurance Contracts - Amounts Recognized in the Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	$ 60.4	$ 60.1	$ 179.1	$ 177.0
Interest expense	18.6	18.8	56.0	56.5
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	7.1	7.1	21.5	20.9
Interest expense	3.1	3.1	9.4	9.1
Term Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	12.4	11.1	35.2	33.3
Interest expense	1.5	1.4	4.4	4.0
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	7.2	8.5	21.9	23.9
Interest expense	10.5	10.7	31.6	32.3
Limited-Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	1.9	1.8	5.3	5.2
Interest expense	0.8	0.7	2.3	2.1
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	31.3	30.3	93.4	90.7
Interest expense	1.7	1.9	5.2	5.8
SPIA (life contingent)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	0.5	1.3	1.8	3.0
Interest expense	$ 1.0	$ 1.0	$ 3.1	$ 3.2