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Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Additional Information (Details) | 3 Months Ended | 6 Months Ended |  |
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Jun. 30, 2023 USD ($) Entity Security policy consolidatedInvestmentVehicle entity | Jun. 30, 2022 USD ($) | Jun. 30, 2023 USD ($) Entity Security policy consolidatedInvestmentVehicle entity fund | Jun. 30, 2022 USD ($) fund | Jul. 28, 2023 USD ($) | Dec. 31, 2022 USD ($) Security consolidatedInvestmentVehicle entity policy Entity
Variable Interest Entity [Line Items] |  |  |  |  |  |
Estimated Fair Value | $ 6,488,000,000 |  | $ 6,488,000,000 |  |  | $ 7,119,000,000
Amortized Cost | 7,044,000,000 |  | 7,044,000,000 |  |  | 7,707,000,000
Fixed-maturity securities, trading | 340,000,000 |  | 340,000,000 |  |  | 303,000,000
Gross Unrealized Gains | 51,000,000 |  | 51,000,000 |  |  | 65,000,000
Gross unrealized losses | $ 528,000,000 |  | $ 528,000,000 |  |  | $ 588,000,000
Number of securities | Security | 1,079 |  | 1,079 |  |  | 466
Fair Value | $ 2,673,000,000 |  | $ 2,673,000,000 |  |  | $ 1,017,000,000
Number of securities | Security | 778 |  | 778 |  |  | 1,340
Fair Value | $ 1,998,000,000 |  | $ 1,998,000,000 |  |  | $ 3,751,000,000
Fair value gains (losses) on credit derivatives | 91,000,000 | $ 9,000,000 | 106,000,000 | $ 6,000,000 |  |
Other consolidated VIE assets | 89,000,000 |  | 89,000,000 |  |  | 86,000,000
Other consolidated VIE liabilities | $ 9,000,000 |  | $ 9,000,000 |  |  | $ 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 | 85 |  | 85 |  |  | 85
Net fair value gains and losses on FG VIEs are expected to reverse to zero at maturity of the VIE debt | $ 1,000,000 |  | $ 1,000,000 |  |  | $ 1,000,000
Net | 244,013,000,000 |  | 244,013,000,000 |  |  | $ 233,258,000,000
Subsequent Event |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Net |  |  |  |  | $ 108,000,000 |
Joint Healthcare Fund | Variable Interest Entity, Primary Beneficiary | Line of Credit |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Maximum borrowing capacity | 110,000,000 |  | 110,000,000 |  |  |
Long-term line of credit | 54,000,000 |  | 54,000,000 |  |  |
Consolidated Healthcare Fund | Variable Interest Entity, Primary Beneficiary | Line of Credit |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Maximum borrowing capacity | 71,000,000 |  | $ 71,000,000 |  |  |
Prime Rate | Joint Healthcare Fund | Variable Interest Entity, Primary Beneficiary | Line of Credit |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Base interest rate floor |  |  | 3.00% |  |  |
EURIBOR | Joint Healthcare Fund | Line of Credit |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Base interest rate floor |  |  | 0.00% |  |  |
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 | $ (1,000,000) | 1,000,000 | $ (2,000,000) | (4,000,000) |  |
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Total number of entities consolidated | entity | 45 |  | 45 |  |  | 45
Estimated Fair Value | $ 218,000,000 |  | $ 218,000,000 |  |  | $ 204,000,000
Amortized Cost | 205,000,000 |  | 205,000,000 |  |  | 204,000,000
Fixed-maturity securities, trading | 5,000,000 |  | 5,000,000 |  |  | 5,000,000
Gross Unrealized Gains | 15,000,000 |  | 15,000,000 |  |  | 4,000,000
Gross unrealized losses | $ 2,000,000 |  | $ 2,000,000 |  |  | $ 4,000,000
Number of securities | Security | 11 |  | 11 |  |  |
Fair Value | $ 21,000,000 |  | $ 21,000,000 |  |  |
Number of securities | Security |  |  |  |  |  | 14
Fair Value |  |  |  |  |  | $ 110,000,000
Securities in excess of carrying value | Security | 3 |  | 3 |  |  | 8
Unrealized losses for securities | $ 1,000,000 |  | $ 1,000,000 |  |  | $ 3,000,000
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts | Forecast |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Estimated Fair Value |  |  |  |  | $ 94,000,000 |
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, Primary Beneficiary |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Total number of entities consolidated | consolidatedInvestmentVehicle | 18 |  | 18 |  |  | 22
Collateral posting requirement | $ 39,000,000 |  | $ 39,000,000 |  |  | $ 46,000,000
Fair value gains (losses) on credit derivatives |  | $ 4,000,000 |  | $ 8,000,000 |  |
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary | Line of Credit |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Maximum borrowing capacity | 820,000,000 |  | 820,000,000 |  |  |
Remaining borrowing capacity | $ 217,000,000 |  | 217,000,000 |  |  |
Borrowing (payment) under credit facilities |  |  | $ 134,000,000 |  |  |
Consolidated Investment Vehicles | Voting Interest Entity |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Total number of entities consolidated | consolidatedInvestmentVehicle | 1 |  | 1 |  |  | 2
Consolidated Investment Vehicles | EURIBOR | Variable Interest Entity, Primary Beneficiary | Line of Credit |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Basis spread on variable rate |  |  | 3.00% |  |  |
Consolidated Investment Vehicles | Maximum | Future Equity Investments |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Committed capital |  |  | $ 452,000,000 |  |  |
Consolidated Investment Vehicles | Average | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Collateral posting requirement | $ 42,000,000 |  | $ 42,000,000 |  |  | $ 47,000,000
Consolidated Investment Vehicles | CLO Warehouse | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Number of financial assets securitized | fund |  |  | 0 | 2 |  |
Consolidated Investment Vehicles | Fund investments: | Variable Interest Entity, Primary Beneficiary | Investments |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
Net assets |  |  |  |  |  | $ 127,000,000

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