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Fair Value Measurement - Additional Information (Details) $ in Millions | 6 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jun. 30, 2024 USD ($) Trust security | Dec. 31, 2023 security | Aug. 01, 2024 USD ($)
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 |
Subsequent Event |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Share value, amount | $ |  |  | $ 400
Total |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Percentage of CDS contracts fair valued using minimum premium | 15.80% | 11.50% |
AG And AGM |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Number of custodial trusts | Trust | 4 |  |
Share value, amount | $ | $ 200 |  |
Maximum amount | $ | $ 50 |  |
AGC |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Number of custodial trusts | Trust | 4 |  |
Assured Guaranty Municipal Corp. |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Number of custodial trusts | Trust | 4 |  |
Recurring | Level 3 |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Number of fixed maturity securities valued using model processes | security | 177 |  |
Recurring | Level 3 | CDR | Total | Minimum |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Conditional prepayment rate | 3.58% | 3.26% |
Recurring | Level 3 | CDR | Total | Maximum |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Conditional prepayment rate | 4.89% | 4.81% |

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