Long-Duration Insurance Contracts - Reconciliation of LFPB to Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021	Dec. 31, 2020
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 1,761.8	$ 1,718.0	[1]
Whole life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	298.8	279.5
Term life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	130.2	112.4
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	811.3	799.3		$ 1,098.1	$ 1,191.3
Limited-pay whole life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	57.4	49.6		73.2	69.5
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	245.6	264.4		359.1	415.5
SPIA (life contingent)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	104.2	103.3		$ 124.7	$ 136.5
Limited-pay whole life DPL
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	4.1	3.2
SPIA (life contingent) DPL
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	1.3	0.8
Reconciling items
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 108.9	$ 105.5

[1] Recast for the adoption of ASU 2018-12. See Note 1 of the Consolidated Financial Statements