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Investments - Accrued Investment Income - Narrative (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Dec. 31, 2023
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Accrued Investment Income [Line Items] |  |
Accrued investment income | $ 73,842 | $ 66,339
Available-for-Sale Securities |  |
Accrued Investment Income [Line Items] |  |
Accrued investment income | $ 68,900 | $ 64,600

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