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Contracts Accounted for as Insurance - Loss and LAE Reported on the Statements of Operations (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | $ 100 | $ (75) | $ 159 | $ (29)
Public finance | Financial Guarantee Insurance And Other Product Line |  |  |  |
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | 134 | 1 | 186 | 67
Public finance | Financial Guarantee Insurance And Other Product Line | United States |  |  |  |
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | 134 | 1 | 186 | 67
Public finance | Financial Guarantee Insurance And Other Product Line | Non United States |  |  |  |
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | 0 | 0 | 0 | 0
RMBS | Financial Guarantee Insurance And Other Product Line | United States |  |  |  |
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | (35) | (78) | (31) | (97)
Other structured finance | Financial Guarantee Insurance And Other Product Line |  |  |  |
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | 1 | 2 | 4 | 1
Structured finance | Financial Guarantee Insurance And Other Product Line |  |  |  |
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |  |  |
Loss and loss adjustment expenses (benefit) | $ (34) | $ (76) | $ (27) | $ (96)

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- Definition [Line Items] for Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Table] + References No definition available. + Details
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- Definition Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(5)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1 + Details
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