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Contracts Accounted for as Insurance - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2022 | Mar. 31, 2021 | Dec. 31, 2021
Guarantor Obligations [Line Items] |  |  |
Weighted average risk-free rates for U.S. dollar denominated financial guaranty insurance obligations | 2.26% |  | 1.02%
Net Economic Loss Development (Benefit) | $ (44) | $ 13 |
Public finance |  |  |
Guarantor Obligations [Line Items] |  |  |
Net Economic Loss Development (Benefit) | $ (50) | $ 3 |
Minimum |  |  |
Guarantor Obligations [Line Items] |  |  |
Weighted average risk-free rates for U.S. dollar denominated financial guaranty insurance obligations | 0.00% |  | 0.00%
Maximum |  |  |
Guarantor Obligations [Line Items] |  |  |
Weighted average risk-free rates for U.S. dollar denominated financial guaranty insurance obligations | 2.61% |  | 1.98%
Foreign Currency Concentration Risk | Premiums Receivable | Premiums Receivable |  |  |
Guarantor Obligations [Line Items] |  |  |
Percentage of installment premiums denominated in currencies other than the U.S. dollar | 77.00% |  | 78.00%

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