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Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income | $ 2 | $ 0 | $ 11 | $ (84)
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income | 4 | 6 | 36 | (10)
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | Credit Default Swap [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income | (5) | (7) | (49) | (41)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swap [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income | 7 | (3) | 33 | (8)
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income | (4) | 0 | (4) | (19)
Foreign Exchange And Other Derivative Financial Instruments Attributable To V I E [Member] | Interest Rate Swaps V I E [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income |  | 0 | 0 | 0
Foreign Exchange And Other Derivative Financial Instruments Attributable To V I E [Member] | Currency Swaps Vie [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Net gain/(loss) recognized in income | $ 0 | $ 4 | $ (5) | $ (6)

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + 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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