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Contracts Accounted for as Insurance - Loss and LAE Reserve and Salvage and Subrogation Recoverable Net of Reinsurance (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	$ (127)	$ 75
Public finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE)
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	(9)	120
Other structured finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE)
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	33	42
Structured finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE)
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	(118)	(45)
U.S. | Public finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE)
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	(14)	119
U.S. | RMBS | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE)
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	(151)	(87)
Non U.S. | Public finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE)
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Net reserve (salvage)	$ 5	$ 1

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- Definition

[Line Items] for Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Table]

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Represents the reserve for losses and loss adjustment expenses, net of reinsurance recoverable on unpaid losses and net of salvage and subrogation recoverable.

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