Long-Duration Insurance Contracts - Undiscounted and Discounted Expected Gross Premiums and Expected Future Benefits and Expenses (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	$ 526.4	$ 524.0
Expected future benefits and expenses, undiscounted	1,283.2	1,272.9
Expected future gross premiums, discounted	353.1	350.5
Expected future benefits and expenses, discounted	622.1	617.4
Term Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	720.8	712.1
Expected future benefits and expenses, undiscounted	755.5	736.2
Expected future gross premiums, discounted	467.7	464.2
Expected future benefits and expenses, discounted	442.5	433.2
Experience life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	477.5	497.8
Expected future benefits and expenses, undiscounted	1,602.8	1,639.0
Expected future gross premiums, discounted	268.6	279.3
Expected future benefits and expenses, discounted	771.8	782.8
Limited-Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	72.7	73.6
Expected future benefits and expenses, undiscounted	312.0	307.2
Expected future gross premiums, discounted	54.1	54.7
Expected future benefits and expenses, discounted	116.4	114.3
Supplemental health
Liability for Future Policy Benefit, by Product Segment [Line Items]
Expected future gross premiums, undiscounted	1,606.3	1,595.3
Expected future benefits and expenses, undiscounted	686.2	684.6
Expected future gross premiums, discounted	1,165.3	1,165.4
Expected future benefits and expenses, discounted	476.8	482.8
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	147.7	150.7
Expected future gross premiums, discounted	0.0	0.0
Expected future benefits and expenses, discounted	$ 105.2	$ 107.3

Liability for Future Policy Benefit, Expected Future Policy Benefit, Discounted, before Reinsurance

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- Definition

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+ 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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