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Loss And Loss Adjustment Expense Reserves (RMBS Recoveries) (Narrative) (Detail) (USD $) | 12 Months Ended |  |  | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Jan. 07, 2013 Bank Of America Settlement With Fannie Mae [Member] | Dec. 31, 2012 Second-Lien RMBS Reserves [Member] | Dec. 31, 2012 RMBS And HELOC And CES [Member] | Dec. 31, 2012 Second-Lien RMBS Ineligible Mortgage Loans [Member] Minimum [Member] | Dec. 31, 2012 Second-Lien RMBS Ineligible Mortgage Loans [Member] Maximum [Member]
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |
Total estimated recoveries from ineligible loans |  |  |  |  | $ 3,600,000,000 |  |  |
Insurance loss recoverable |  |  |  |  | 2,500,000,000 |  |  |
Loan repurchase commitments |  |  |  |  | 1,100,000,000 |  |  |
Federal statutory rate | 35.00% | 35.00% | 35.00% |  |  |  |  |
Estimated insurance recoveries, after income taxes | 2,300,000,000 | 2,000,000,000 |  |  |  |  |  |
Percentage of recognized estimated recoveries in relationship to consolidated total shareholder's equity | 73.00% | 119.00% |  |  |  |  |  |
Sum of probabilities assigned to all scenarios |  |  |  |  |  | 100.00% |  |
Current risk-free rate associated with underlying transaction, range, minimum |  |  |  |  |  | 0.90% |  |
Current risk-free rate associated with underlying transaction, range, maximum |  |  |  |  |  | 1.70% |  |
Remaining weighted average contract period (in years) | 8 years 8 months 12 days | 8 years 9 months 18 days |  |  |  |  | 5 years 7 months 6 days | 10 years 2 months 12 days
Contract claims on ineligible mortgage loans, incurred loss on transactions |  |  |  |  |  | 5,100,000,000 |  |
Aggregate of estimated potential recoveries on put-back claims, gross of income taxes | 3,600,000,000 |  |  |  |  |  |  |
Bank of America repurchase requests resolved |  |  | 8,000,000,000 | 10,300,000,000 |  |  |  |
Assured Guaranty favorable ruling on breach of mortgage representations | $ 90,000,000 |  |  |  |  |  |  |

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- Definition The fair value of financial instruments that represent the right of the Trust against the seller/servicer for loans that were not compliant with the representations and warranties of the loan underwriting. The Trust has the right to demand that the transferor replace ineligible loans with a compliant loan or repurchase the non-compliant loan. + References No definition available. + Details
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- Definition The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 47 -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 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=6889476&loc=d3e330036-122817 + Details
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- Definition Remaining weighted average contract period of financial guarantee insurance contracts, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(ii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=6933462&loc=SL5751133-161288 + Details
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