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Contracts Accounted for as Insurance - Loss and LAE Reported on the Statements of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE (benefit)	$ (26)	$ 162	$ 16
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]
Loss and LAE (benefit)	16	192	125
Public finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE) | U.S.
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE (benefit)	12	192	125
Public finance | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE) | Non U.S.
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE (benefit)	4	0	0
RMBS | Financial Guarantee Insurance And Other Product Line | Consolidated Entity Excluding Variable Interest Entities (VIE) | U.S.
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE (benefit)	(43)	(34)	(112)
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]
Loss and LAE (benefit)	1	4	3
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]
Loss and LAE (benefit)	$ (42)	$ (30)	$ (109)

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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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No definition available.

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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/1943274/2147477250/944-220-S99-1

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