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Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Narrative (Details) $ in Millions |  | 12 Months Ended |  |  |
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Jul. 01, 2023 consolidatedInvestmentVehicle | Dec. 31, 2023 USD ($) consolidatedInvestmentVehicle | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) Entity | Dec. 31, 2023 USD ($) | Dec. 31, 2023 consolidatedInvestmentVehicle | Dec. 31, 2023 Security | Dec. 31, 2023 entity | Dec. 31, 2023 consolidatedCLO | Dec. 31, 2023 Entity | Dec. 31, 2023 policy | Aug. 31, 2023 USD ($) | Dec. 31, 2022 consolidatedInvestmentVehicle | Dec. 31, 2022 Security | Dec. 31, 2022 entity | Dec. 31, 2022 consolidatedCLO | Dec. 31, 2022 Entity | Dec. 31, 2022 policy
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized Cost |  |  | $ 7,707 |  | $ 6,746 |  |  |  |  |  |  |  |  |  |  |  |  |
Net Par Outstanding |  |  | 233,258 |  | 249,153 |  |  |  |  |  |  | $ 108 |  |  |  |  |  |
Fixed-maturity securities, available-for-sale, at fair value, net of allowance for credit loss |  |  | 7,119 |  | 6,307 |  |  |  |  |  |  |  |  |  |  |  |  |
Less than 12 months (in securities) | Security |  |  |  |  |  |  | 274 |  |  |  |  |  |  | 1,340 |  |  |  |
Gross unrealized losses |  |  | 588 |  | 417 |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value |  |  | 3,751 |  | 766 |  |  |  |  |  |  |  |  |  |  |  |  |
Deconsolidation of investment vehicles |  | $ (132) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
VIE, other consolidated, carrying amount, assets |  |  | 86 |  | 92 |  |  |  |  |  |  |  |  |  |  |  |  |
VIE, other consolidated, carrying amount, liabilities |  |  | 12 |  | 7 |  |  |  |  |  |  |  |  |  |  |  |  |
VIE, number of policies monitored | policy |  |  |  |  |  |  |  |  |  |  | 15,000 |  |  |  |  |  |  |
VIE, number of policies monitored, not within the scope of ASC 810 | policy |  |  |  |  |  |  |  |  |  |  | 14,000 |  |  |  |  |  |  |
VIE, number of policies that contain provisions for consolidation | policy |  |  |  |  |  |  |  |  |  |  | 68 |  |  |  |  |  |  | 85
Maximum loss exposure |  |  |  |  | 326 |  |  |  |  |  |  |  |  |  |  |  |  |
Carrying value of investments not consolidated |  |  |  |  | 314 |  |  |  |  |  |  |  |  |  |  |  |  |
Other assets not consolidated |  |  |  |  | 12 |  |  |  |  |  |  |  |  |  |  |  |  |
Nonredeemable Noncontrolling Interests |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deconsolidation of investment vehicles |  | (132) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sound Point Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  |  |  |  | 4,700 |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities |  |  |  |  | 4,400 |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on disposal of discontinued operation, net of tax |  | 16 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in the instrument specific credit risk of the VIEs' assets |  | $ 3 | 10 | $ 14 |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  | 45 |  |  |
Amortized Cost |  |  | 204 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed-maturity securities, available-for-sale, at fair value, net of allowance for credit loss |  |  | 204 |  |  |  |  |  |  |  |  | $ 73 |  |  |  |  |  |
Less than 12 months (in securities) | Security |  |  |  |  |  |  |  |  |  |  |  |  |  | 14 |  |  |  |
Gross unrealized losses |  |  | 4 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value |  |  | 110 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities in excess of carrying value | Security |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 |  |  |  |
Value securities in excess of carrying value |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Puerto Rico Trusts | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Custody receipts, notice period |  | 30 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated Investment Vehicles |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of remaining entities | consolidatedInvestmentVehicle | 3 | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total number of entities consolidated |  |  |  | 20 |  | 3 |  |  |  | 3 |  |  | 22 |  |  |  | 22 |
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary | CLO contracts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total number of entities consolidated | consolidatedCLO |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  | 10 |  |
Deconsolidation, net assets |  |  | 417 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated Investment Vehicles | Foreign Exchange Forward | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount |  |  | 46 |  | 36 |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated Investment Vehicles | Foreign Exchange Forward | Variable Interest Entity, Primary Beneficiary | Arithmetic Average |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount |  |  | $ 47 |  | $ 41 |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated Investment Vehicles | Assured IM | Variable Interest Entity, Primary Beneficiary |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain consolidation |  |  |  | $ 31 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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