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Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Derivative [Line Items] |  |  |
Net gain/(loss) recognized in income | $ (68) | $ (15) | $ 69
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Net gain/(loss) recognized in income | 0 | 21 | 157
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | Credit Default Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Net gain/(loss) recognized in income | (51) | (40) | (28)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Net gain/(loss) recognized in income | 3 | (11) | (108)
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member] |  |  |
Derivative [Line Items] |  |  |
Net gain/(loss) recognized in income | (19) | (2) | 7
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 | 8 | 31
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 | $ (1) | $ 9 | $ 10

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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=64837297&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=64837297&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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