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Outstanding Exposure - Additional Information (Details) $ in Millions |  |  | 6 Months Ended |
--- | --- | --- | --- | ---
Jul. 10, 2024 | Jun. 26, 2023 USD ($) | Jun. 30, 2024 USD ($) Category | Dec. 31, 2023 USD ($)
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Number of surveillance categories | Category |  |  | 3 |
Loss Mitigation Securities |  |  | $ 1,200 | $ 1,200
Net par outstanding |  |  | 254,396 | 249,153
Estimated Fair Value |  |  | 6,006 | 6,307
Fixed-maturity securities, trading |  |  | 221 | 318
Puerto Rico Electric Power Authority | Guarantee Obligations |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Damages sought, estimate |  | $ 2,400 |  |
Damages sought |  | $ 8,500 |  |
Puerto Rico Electric Power Authority | Guarantee Obligations | Subsequent Event |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Stay implemented | 60 days |  |  |
Puerto Rico |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Net par outstanding |  |  | 961 | 1,105
Puerto Rico | Puerto Rico Defaulted Exposures Subject to a Plan Support Agreement | Puerto Rico Electric Power Authority |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Net par outstanding |  |  | 624 | 624
Public finance |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Net par outstanding |  |  | 244,176 | 239,296
Structured finance |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Net par outstanding |  |  | 10,220 | 9,857
Aircraft residual value insurance (RVI) |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Residual value insurance policies exposure downgraded |  |  | 308 | 355
Net Exposure |  |  | 177 | 200
Diversified real estate |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Residual value insurance policies exposure downgraded |  |  | 1,498 | 1,569
Net Exposure |  |  | 1,498 | 1,569
Commitment to Provide Guarantees | Public finance |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Outstanding commitments to provide guaranties |  |  | 1,100 |
Potential future commitment |  |  |  | 353
Commitment to Provide Guarantees | Structured finance |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Outstanding commitments to provide guaranties |  |  | $ 1,600 |
Potential future commitment |  |  |  | 50
BIG |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Maximum period of liquidity claims (in years) |  |  | 1 year |
Net par outstanding |  |  | $ 5,502 | 5,437
BIG | Public finance |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Net par outstanding |  |  | 4,575 | 4,402
BIG | Structured finance |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Net par outstanding |  |  | 927 | 1,035
BIG | Aircraft residual value insurance (RVI) |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Residual value insurance policies exposure downgraded |  |  | 144 | 144
Net Exposure |  |  | $ 84 | $ 84
Minimum |  |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |  |
Probability of paying more claims than being reimbursed (as a percent) |  |  | 50.00% |

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