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Fair Value Measurement - Additional Information (Details) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2024 USD ($) Trust security | Dec. 31, 2023 security
Puerto Rico Trusts | Financial Guaranty Variable Interest Entities |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of fixed maturity debt securities classified as Level 3 | security | 1 | 1
Total |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Percentage of CDS contracts fair valued using minimum premium | 16.40% | 11.50%
AGC |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of custodial trusts | Trust | 8 |
Share value, amount | $ | $ 400 |
Maximum amount | $ | $ 50 |
Recurring | Level 3 |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of fixed maturity securities valued using model processes | security | 175 |
Recurring | Level 3 | CDR | Total | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Conditional prepayment rate | 3.08% | 3.26%
Recurring | Level 3 | CDR | Total | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Conditional prepayment rate | 4.27% | 4.81%

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