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Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Additional Information (Details) |  | 3 Months Ended | 9 Months Ended |  |
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Jul. 01, 2023 rISK | Sep. 30, 2023 USD ($) policy Entity Security entity consolidatedInvestmentVehicle | Sep. 30, 2022 USD ($) | Sep. 30, 2023 USD ($) policy Entity Security entity consolidatedInvestmentVehicle | Sep. 30, 2022 USD ($) | Aug. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) consolidatedInvestmentVehicle Security policy Entity entity
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Estimated Fair Value |  | $ 6,267,000,000 |  | $ 6,267,000,000 |  |  | $ 7,119,000,000
Amortized Cost |  | 6,971,000,000 |  | 6,971,000,000 |  |  | 7,707,000,000
Fixed-maturity securities, trading |  | 350,000,000 |  | 350,000,000 |  |  | 303,000,000
Gross Unrealized Gains |  | 30,000,000 |  | 30,000,000 |  |  | 65,000,000
Gross unrealized losses |  | $ 648,000,000 |  | $ 648,000,000 |  |  | $ 588,000,000
Number of securities | Security |  | 1,308 |  | 1,308 |  |  | 466
Fair Value |  | $ 3,150,000,000 |  | $ 3,150,000,000 |  |  | $ 1,017,000,000
Number of securities | Security |  | 795 |  | 795 |  |  | 1,340
Fair Value |  | $ 2,093,000,000 |  | $ 2,093,000,000 |  |  | $ 3,751,000,000
Fair value gains (losses) on credit derivatives |  | 9,000,000 | $ (48,000,000) | 115,000,000 | $ (42,000,000) |  |
Other consolidated VIE assets |  | 87,000,000 |  | 87,000,000 |  |  | 86,000,000
Other consolidated VIE liabilities |  | $ 7,000,000 |  | $ 7,000,000 |  |  | $ 12,000,000
Number of policies monitored | policy |  | 15,000 |  | 15,000 |  |  |
Number of policies monitored, not within the scope of ASC 810 | policy |  | 14,000 |  | 14,000 |  |  |
Number of policies that contain provisions for consolidation | policy |  | 66 |  | 66 |  |  | 85
Net fair value gains and losses on FG VIEs are expected to reverse to zero at maturity of the VIE debt |  | $ 251,000,000 |  | $ 251,000,000 |  |  |
Net |  | 241,833,000,000 |  | 241,833,000,000 |  | $ 108,000,000 | $ 233,258,000,000
Carrying value of investments not consolidated |  | 239,000,000 |  | 239,000,000 |  |  |
Other assets |  | 12,000,000 |  | 12,000,000 |  |  |
Sound Point Agreement |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Deconsolidated assets |  | 4,700,000,000 |  | 4,700,000,000 |  |  |
Deconsolidated liabilities |  | 4,400,000,000 |  | 4,400,000,000 |  |  |
Loss on deconsolidation |  | 16,000,000 |  | 16,000,000 |  |  |
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Maximum loss exposure |  | 0 |  | 0 |  |  |
Gain (loss) in the instrument specific credit risk of the VIEs' assets |  | $ 3,000,000 | $ 15,000,000 | $ 1,000,000 | 11,000,000 |  |
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Total number of entities consolidated | entity |  | 24 |  | 24 |  |  | 45
Estimated Fair Value |  | $ 146,000,000 |  | $ 146,000,000 |  | $ 73,000,000 | $ 204,000,000
Amortized Cost |  | 136,000,000 |  | 136,000,000 |  |  | 204,000,000
Gross Unrealized Gains |  | 10,000,000 |  | 10,000,000 |  |  | 4,000,000
Gross unrealized losses |  | $ 0 |  | $ 0 |  |  | $ 4,000,000
Number of securities | Security |  | 0 |  | 0 |  |  |
Number of securities | Security |  |  |  |  |  |  | 14
Fair Value |  |  |  |  |  |  | $ 110,000,000
Securities in excess of carrying value | Security |  |  |  |  |  |  | 8
Unrealized losses for securities |  |  |  |  |  |  | $ 3,000,000
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Structured Finance and Other |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Total number of entities consolidated | Entity |  | 25 |  | 25 |  |  | 25
Puerto Rico Trusts | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Custody receipts, notice period |  | 30 days |  | 30 days |  |  |
Consolidated Investment Vehicles |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Number of remaining CIVs | rISK | 3 |  |  |  |  |  |
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Total number of entities consolidated | consolidatedInvestmentVehicle |  | 3 |  | 3 |  |  | 22
Collateral posting requirement |  | $ 36,000,000 |  | $ 36,000,000 |  |  | $ 46,000,000
Fair value gains (losses) on credit derivatives |  |  |  |  | $ 7,000,000 |  |
Consolidated Investment Vehicles | Voting Interest Entity |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Total number of entities consolidated | consolidatedInvestmentVehicle |  |  |  |  |  |  | 2
Consolidated Investment Vehicles | Maximum | Future Equity Investments |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Committed capital |  |  |  | 143,000,000 |  |  |
Consolidated Investment Vehicles | Average | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |
Collateral posting requirement |  | $ 41,000,000 |  | $ 41,000,000 |  |  | $ 47,000,000

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