Long-Duration Insurance Contracts - Undiscounted and Discounted Expected Gross Premiums and Expected Future Benefits and Expenses (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	$ 541.4	$ 547.3
Expected future benefits and expenses, undiscounted	1,340.4	1,340.4
Expected future gross premiums, discounted	341.9	364.1
Expected future benefits and expenses, discounted	613.7	631.9
Term Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	787.7	692.2
Expected future benefits and expenses, undiscounted	830.0	735.9
Expected future gross premiums, discounted	484.2	456.7
Expected future benefits and expenses, discounted	458.5	429.8
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	414.6	453.1
Expected future benefits and expenses, undiscounted	1,415.2	1,531.5
Expected future gross premiums, discounted	237.7	256.3
Expected future benefits and expenses, discounted	737.1	763.3
Limited-Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	73.8	75.9
Expected future benefits and expenses, undiscounted	334.7	337.8
Expected future gross premiums, discounted	54.4	56.0
Expected future benefits and expenses, discounted	119.4	118.1
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	1,614.1	1,613.0
Expected future benefits and expenses, undiscounted	699.3	674.0
Expected future gross premiums, discounted	1,148.0	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	138.0	144.6
Expected future gross premiums, discounted	0.0	0.0
Expected future benefits and expenses, discounted	$ 98.5	$ 103.0

Liability For Future Policy Benefit, Expected Future Policy Benefit, Discounted, Before Reinsurance

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount, before effect of reinsurance, of discounted balance for expected future gross premium component of liability for future policy benefit.

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- Definition

Amount, before effect of reinsurance, of undiscounted balance for expected future gross premium component of liability for future policy benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-6

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29E

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- Definition

Amount, before effect of reinsurance, of undiscounted balance for expected future policy benefit and expense component of liability for future policy benefit.

+ References

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