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Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - New Recovery Bonds (Details) - USD ($) $ in Millions	Sep. 30, 2023	Aug. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 6,971		$ 7,707
Gross Unrealized Gains	30		65
Gross unrealized loss	(648)		(588)
Estimated Fair Value	6,267		7,119
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | Puerto Rico Trusts
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	136		204
Gross Unrealized Gains	10		4
Gross unrealized loss	0		(4)
Estimated Fair Value	$ 146	$ 73	$ 204

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