Long-Duration Insurance Contracts - Undiscounted and Discounted Expected Gross Premiums and Expected Future Benefits and Expenses (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	$ 547.9	$ 547.3
Expected future benefits and expenses, undiscounted	1,345.7	1,340.4
Expected future gross premiums, discounted	346.4	364.1
Expected future benefits and expenses, discounted	615.8	631.9
Term Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	694.9	692.2
Expected future benefits and expenses, undiscounted	742.6	735.9
Expected future gross premiums, discounted	451.8	456.7
Expected future benefits and expenses, discounted	432.5	429.8
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	444.6	453.1
Expected future benefits and expenses, undiscounted	1,512.5	1,531.5
Expected future gross premiums, discounted	252.0	256.3
Expected future benefits and expenses, discounted	757.1	763.3
Limited-Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	75.1	75.9
Expected future benefits and expenses, undiscounted	339.4	337.8
Expected future gross premiums, discounted	55.2	56.0
Expected future benefits and expenses, discounted	118.5	118.1
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	1,621.9	1,613.0
Expected future benefits and expenses, undiscounted	681.4	674.0
Expected future gross premiums, discounted	1,163.2	1,160.1
Expected future benefits and expenses, discounted	463.9	462.7
SPIA (life contingent)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	0.0	0.0
Expected future benefits and expenses, undiscounted	142.6	144.6
Expected future gross premiums, discounted	0.0	0.0
Expected future benefits and expenses, discounted	$ 101.7	$ 103.0