Long-Duration Insurance Contracts - Amounts Recognized in the Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	$ 59.3	$ 57.7	$ 118.7	$ 116.9
Interest expense	18.6	18.8	37.4	37.7
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	7.4	6.9	14.4	13.8
Interest expense	3.2	3.0	6.3	6.0
Term Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	11.1	11.0	22.8	22.2
Interest expense	1.5	1.3	2.9	2.6
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	7.3	7.7	14.7	15.4
Interest expense	10.5	10.8	21.1	21.6
Limited-Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	1.6	1.6	3.4	3.4
Interest expense	0.7	0.7	1.5	1.4
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	31.2	30.0	62.1	60.4
Interest expense	1.7	1.9	3.5	3.9
SPIA (life contingent)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	0.7	0.5	1.3	1.7
Interest expense	$ 1.0	$ 1.1	$ 2.1	$ 2.2