Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Schedule of Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 115	$ 97	$ 118
Estimated Fair Value	6,091	6,307
Other invested assets (includes $4 and $3, at fair value)	875	829
Assets	12,168	12,539
Other liabilities	430	439
Liabilities	6,486	6,774
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Other liabilities	3	4
Liabilities	3	4
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Affiliated Entity
Variable Interest Entity [Line Items]
Liabilities	3	3
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Other invested assets (includes $4 and $3, at fair value)	2	0
Assets	377	366
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Affiliated Entity
Variable Interest Entity [Line Items]
Assets	309	281
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments
Variable Interest Entity [Line Items]
Cash and cash equivalents	22	35
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Equity Securities and Warrants
Variable Interest Entity [Line Items]
Estimated Fair Value	89	83
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Structured products
Variable Interest Entity [Line Items]
Estimated Fair Value	$ 264	$ 248