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Business Segments (Summary Of Premiums Earned On Financial Guarantees And Insured Derivatives By Geographic Location Of Risk) (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | $ 53 | $ 77 | $ 146 | $ 228
United States [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | 46 | 59 | 122 | 176
United Kingdom [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | 0 | 6 | 1 | 20
Europe Excluding United Kingdom [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | 0 | 1 | 1 | 4
Internationally Diversified [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | 0 | 3 | 1 | 3
Other Americas [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | 7 | 6 | 19 | 20
Asia [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | 0 | 1 | 0 | 2
Other [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total premiums earned | $ 0 | $ 1 | $ 2 | $ 3

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- Definition Premiums Earned Net Financial Guarantee Insurance Contracts And Insured Derivatives + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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Period Type: |

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- Details
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