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Derivative Instruments (Credit Derivatives Sold) (Detail) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2015 | Dec. 31, 2014
Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Weighted average remaining expected maturity | 2 years 1 month 6 days | 1 year 7 months 6 days
Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Weighted average remaining expected maturity | 16 years 8 months 12 days | 16 years 8 months 12 days
Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | $ 7,146 | $ 13,525
Total fair value of credit derivatives | (124) | (246)
Insurance Operations [Member] | Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 3,318 | 9,481
Total fair value of credit derivatives | (121) | (244)
Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 3,828 | 4,044
Total fair value of credit derivatives | (3) | (2)
Insurance Operations [Member] | Other Credit Derivatives [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Total fair value of credit derivatives | 0 | 0
Credit Rating Aaa [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 2,018 | 6,914
Total fair value of credit derivatives | 0 | (2)
Credit Rating Aaa [Member] | Insurance Operations [Member] | Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 2,018 | 6,914
Credit Rating Aaa [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Credit Rating Aaa [Member] | Insurance Operations [Member] | Other Credit Derivatives [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Credit Rating Aa [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 111 | 363
Total fair value of credit derivatives | 0 | 0
Credit Rating Aa [Member] | Insurance Operations [Member] | Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 246
Credit Rating Aa [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 111 | 117
Credit Rating Aa [Member] | Insurance Operations [Member] | Other Credit Derivatives [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Credit Rating A [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 3,043 | 3,903
Total fair value of credit derivatives | (3) | (2)
Credit Rating A [Member] | Insurance Operations [Member] | Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 304 | 968
Credit Rating A [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 2,739 | 2,935
Credit Rating A [Member] | Insurance Operations [Member] | Other Credit Derivatives [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Credit Rating Bbb [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 957 | 1,163
Total fair value of credit derivatives | (2) | (2)
Credit Rating Bbb [Member] | Insurance Operations [Member] | Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 193
Credit Rating Bbb [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 957 | 970
Credit Rating Bbb [Member] | Insurance Operations [Member] | Other Credit Derivatives [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Credit Rating Below Investment Grade [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 1,017 | 1,182
Total fair value of credit derivatives | (119) | (240)
Credit Rating Below Investment Grade [Member] | Insurance Operations [Member] | Credit Default Swap [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 996 | 1,160
Credit Rating Below Investment Grade [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 21 | 22
Credit Rating Below Investment Grade [Member] | Insurance Operations [Member] | Other Credit Derivatives [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | $ 0 | $ 0

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Weighted Average Remaining Maturity Credit Derivatives In Years + References No definition available. + Details
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- Definition Fair value of credit risk derivative liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4K -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5708775-113959 + 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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