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Business Developments And Risks And Uncertainties (Narrative) (Detail) $ in Millions |  | 1 Months Ended | 9 Months Ended
--- | --- | --- | ---
Oct. 15, 2019 USD ($) | Sep. 30, 2019 USD ($) | Sep. 30, 2019 USD ($) segments
Business Acquisition [Line Items] |  |  |
Number of business segments | segments |  |  | 3
Zohar [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Aggregate claim amount |  | $ 919 | $ 919
National [Member] | Subsequent Event [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Dividends from subsidiaries | $ 110 |  |
Puerto Rico [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Claims payments |  |  | 393
Outstanding bonds |  | $ 2,400 | $ 2,400
Puerto Rico [Member] | Restructuring Support Agreement [Member] | Minimum [Member] |  |  |
Business Acquisition [Line Items] |  |  |
PREPA percentage of voting bondholders |  | 67.00% |

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