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Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Number of Consolidated FG VIEs (Details) - Variable Interest Entity, Primary Beneficiary | 12 Months Ended
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Dec. 31, 2024 Entity entity | Dec. 31, 2023 Entity entity | Dec. 31, 2022 Entity entity
Financial Guaranty Variable Interest Entities | Structured finance |  |  |
Schedule of Consolidated FG VIEs Rollforward [Roll Forward] |  |  |
Beginning of year | 24 | 25 | 25
Consolidated | 0 | 0 | 2
Deconsolidated | (1) | (1) | (2)
December 31 | 23 | 24 | 25
Consolidated investment vehicles |  |  |
Schedule of Consolidated FG VIEs Rollforward [Roll Forward] |  |  |
Consolidated | entity | 0 | 0 | 4
Deconsolidated | entity | (1) | (19) | (2)

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