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Fair Value Of Financial Instruments (Gains And Losses (Realized And Unrealized) Included In Earnings Relating To Level 3 Assets And Liabilities) (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Unrealized gains (losses) on insured derivatives | $ 1,870 | $ (441) | $ (607)
Significant Unobservable Inputs (Level 3) [Member] | Total Gains (Losses) Included In Earnings [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Unrealized gains (losses) on insured derivatives | 1,869 | (440) | (609)
Net Realized Gains (Losses) | (547) | (2,550) | (282)
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange | 28 | (79) | (11)
Significant Unobservable Inputs (Level 3) [Member] | Change In Unrealized Gains (Losses) For The Period Included In Earnings For Assets And Liabilities Still Held [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Unrealized gains (losses) on insured derivatives | 927 | (2,702) | (1,338)
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange | (6) | (90) | (3)
Variable Interest Entity [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange | 18 | 59 | 342
Variable Interest Entity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Total Gains (Losses) Included In Earnings [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange | (376) | 230 | (340)
Variable Interest Entity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Change In Unrealized Gains (Losses) For The Period Included In Earnings For Assets And Liabilities Still Held [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange | $ (271) | $ 347 | $ (395)

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- Definition Change in the fair value of and realized gains and losses on financial instruments and foreign exchange included in earnings. + References No definition available. + Details
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- Definition The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.3(a)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 325 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6485959&loc=d3e22529-158502 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 3 -Subparagraph a -Article 7 + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 + Details
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