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Loss And Loss Adjustment Expense Reserves (RMBS Recoveries) (Narrative) (Detail) (USD $) In Millions, unless otherwise specified | 9 Months Ended | 12 Months Ended
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Sep. 30, 2014 | Dec. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items] |  |
Remaining weighted average contract period (in years) | 9 years 0 months 0 days | 9 years 8 months 12 days
Second-Lien RMBS Ineligible Mortgage Loans [Member] |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |
Contract claims on ineligible mortgage loans inception to date, incurred loss on transactions | $ 432 |

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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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