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Business Developments And Risks And Uncertainties (Narrative) (Detail) $ in Millions |  | 3 Months Ended |
--- | --- | --- | ---
Jan. 01, 2024 USD ($) | Mar. 31, 2024 USD ($) Segments | Jun. 26, 2023 USD ($)
Business Acquisition [Line Items] |  |  |
Number of operating segments | Segments |  | 3 |
Puerto Rico Electric Power Authority [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Outstanding insured bonds |  | $ 792 |
Maximum [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Liabilities Subject to Compromise, Provision for Expected and Allowed Claims |  |  | $ 7,600
Minimum [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Liabilities Subject to Compromise, Provision for Expected and Allowed Claims |  |  | $ 2,400
National Public Finance Guarantee Corporation [Member] | Puerto Rico Electric Power Authority [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Claims payments | $ 16 |  |

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