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Short- Duration Insurance Contracts - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Property & Casualty |  |  |  |
Net Amount at Risk by Product and Guarantee [Line Items] |  |  |  |
Favorable (unfavorable) development of total reserves for claims occurring in prior years | $ 0 | $ (2,000,000.0) | $ 0 | $ (8,000,000.0)
Group Benefits |  |  |  |
Net Amount at Risk by Product and Guarantee [Line Items] |  |  |  |
Favorable (unfavorable) development of total reserves for claims occurring in prior years |  |  | $ 15,500,000 | $ (11,700,000)

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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 Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479808/944-20-55-15 + Details
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