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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
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Mar. 31, 2022 | Mar. 31, 2021
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] |  |
Loss and loss adjustment expenses | $ 57 | $ 30
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 | 55 | 18
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 | 55 | 26
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 | 0 | (8)
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 | 3 | 12
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 | (1) | 0
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 | $ 2 | $ 12

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
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