Long-Duration Insurance Contracts - Market Risk Benefits Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Market Risk Benefit [Roll Forward]
Balance, beginning of period	$ (9.0)	$ (6.8)
Balance, beginning of period, before effects of changes in the instrument-specific credit risk	(9.1)	(7.4)
Changes in market risk benefits	2.6	1.4
Balance, end of period	(6.5)	(6.0)
Effect of changes in the instrument-specific credit risk	0.3	0.8
Balance, end of period	(6.2)	(5.2)
Net amount at risk	$ 17.5	$ 19.4
Weighted-average attained age of contract holders	62 years	63 years

Amount, before tax, of accumulated other comprehensive income (loss) (AOCI) from (increase) decrease in instrument-specific credit risk on contract or contract feature in long-duration contract issued by insurance entity protecting contract holder from other-than-nominal capital market risk and exposing insurance entity to other-than-nominal capital market risk.

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- Definition

Amount, before effect of reinsurance and after accumulated increase (decrease) in instrument-specific credit risk, of contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (h)(1)
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- Definition

Amount, before effect of reinsurance and cumulative increase (decrease) in instrument-specific credit risk, of contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk.

+ References

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- Definition

Amount of guaranteed benefit in excess of current account balance of contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount of increase (decrease) in contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Weighted average attained age of policyholders or contract holders in the specified guarantee type and subset of guarantee class, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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