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Fair Value Of Financial Instruments (Quantitative Information Regarding Significant Unobservable Inputs For Assets And Liabilities Measured At Fair Value On Recurring Basis) (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012
Credit Derivatives [Member] | Commercial Mortgage-Backed [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Valuation Techniques | BET Model
Fair Value | $ 1,590
Credit Derivatives [Member] | Multi-Sector CDO [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Valuation Techniques | Direct Price Model
Fair Value | 525
Credit Derivatives [Member] | Other [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Valuation Techniques | BET Model
Fair Value | 806
Loans Receivable [Member] | Variable Interest Entity [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Valuation Techniques | Quoted market prices adjusted for financial guarantees provided to VIE obligations
Fair Value | 1,881
Loans Receivable [Member] | Variable Interest Entity [Member] | Impact Of Financial Guarantee Asset [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 0.00%
Loans Receivable [Member] | Variable Interest Entity [Member] | Impact Of Financial Guarantee Asset [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 14.00%
Loans Receivable [Member] | Variable Interest Entity [Member] | Impact Of Financial Guarantee Asset [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 3.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Valuation Techniques | Discounted cash flow
Fair Value | 1,086
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] | Recovery Rates [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 10.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] | Recovery Rates [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 75.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] | Recovery Rates [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 47.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] | Breach Rates [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 66.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] | Breach Rates [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 94.00%
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] | Breach Rates [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 78.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Valuation Techniques | Quoted market prices of VIE assets adjusted for financial guarantees provided
Fair Value, liabilities | $ 1,932
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] | Impact Of Financial Guarantee Liability [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 0.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] | Impact Of Financial Guarantee Liability [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 23.00%
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] | Impact Of Financial Guarantee Liability [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 6.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Recovery Rates [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 21.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Recovery Rates [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 90.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Recovery Rates [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 51.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Nonperformance Risk [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 19.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Nonperformance Risk [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 59.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Nonperformance Risk [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 58.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Weighted Average Life [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range (in years) | 0.1
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Weighted Average Life [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range (in years) | 5.6
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | Weighted Average Life [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range (in years) | 4.4
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | CMBS Spreads [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 1.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | CMBS Spreads [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 23.00%
Credit Derivative Liabilities [Member] | Commercial Mortgage-Backed [Member] | CMBS Spreads [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 13.00%
Credit Derivative Liabilities [Member] | Multi-Sector CDO [Member] | Nonperformance Risk [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 59.00%
Credit Derivative Liabilities [Member] | Multi-Sector CDO [Member] | Nonperformance Risk [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 59.00%
Credit Derivative Liabilities [Member] | Multi-Sector CDO [Member] | Nonperformance Risk [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 59.00%
Credit Derivative Liabilities [Member] | Other [Member] | Recovery Rates [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 42.00%
Credit Derivative Liabilities [Member] | Other [Member] | Recovery Rates [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 75.00%
Credit Derivative Liabilities [Member] | Other [Member] | Recovery Rates [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 47.00%
Credit Derivative Liabilities [Member] | Other [Member] | Nonperformance Risk [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 42.00%
Credit Derivative Liabilities [Member] | Other [Member] | Nonperformance Risk [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 59.00%
Credit Derivative Liabilities [Member] | Other [Member] | Nonperformance Risk [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range Percentage | 58.00%
Credit Derivative Liabilities [Member] | Other [Member] | Weighted Average Life [Member] | Minimum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range (in years) | 0.1
Credit Derivative Liabilities [Member] | Other [Member] | Weighted Average Life [Member] | Maximum [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range (in years) | 19.6
Credit Derivative Liabilities [Member] | Other [Member] | Weighted Average Life [Member] | Weighted Average [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Range (in years) | 3.0

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- Definition This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c -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. + Details
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- Definition This element represents a liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
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