Long-Duration Insurance Contracts - Amounts Recognized in the Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	$ 59.1	$ 58.8	$ 118.2	$ 118.3
Interest expense	18.9	19.0	37.9	38.0
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	6.7	6.2	13.3	12.3
Interest expense	2.9	2.9	5.8	5.6
Term Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	11.4	10.4	22.2	20.3
Interest expense	1.2	1.1	2.4	2.2
Experience Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	7.9	8.3	16.1	16.8
Interest expense	10.9	11.0	21.9	22.1
Limited Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	1.7	2.5	3.3	4.3
Interest expense	0.7	0.6	1.3	1.2
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	30.0	30.6	59.7	61.3
Interest expense	2.1	2.3	4.3	4.7
SPIA (life contingent)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Gross premiums or assessments	1.4	0.8	3.6	3.3
Interest expense	$ 1.1	$ 1.1	$ 2.2	$ 2.2