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Loss And Loss Adjustment Expense Reserves (Loss And LAE Activity)(Narrative) (Detail) (USD $) | 9 Months Ended |  | 9 Months Ended | 57 Months Ended | 9 Months Ended |  |  | 9 Months Ended |
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Sep. 30, 2012 | Dec. 31, 2011 | Sep. 30, 2012 ABS CDO Portfolio [Member] | Sep. 30, 2012 ABS CDO Portfolio [Member] | Sep. 30, 2012 RMBS And HELOC And CES [Member] | Sep. 30, 2012 RMBS And HELOC And CES [Member] Classified [Member] Reviewed [Member] | Sep. 30, 2012 RMBS And HELOC And CES [Member] Insured Issues Designated As "Classified List" [Member] | Sep. 30, 2012 Financial Guarantee [Member] | Sep. 30, 2012 Financial Guarantee [Member] Variable Interest Entity [Member] | Sep. 30, 2012 Loss And LAE Reserves [Member] | Dec. 31, 2011 Loss And LAE Reserves [Member] | Sep. 30, 2012 Second-Lien RMBS Reserves [Member] | Sep. 30, 2012 Recorded Recoveries [Member] RMBS And HELOC And CES [Member] Classified [Member] Reviewed [Member]
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
ABS CDO exposure decrease since December 31,2007 |  |  |  | 88.00% |  |  |  |  |  |  |  |  |
Aggregate ABS CDO Loss And LAE Reserves |  |  |  |  |  |  |  | $ 171,000,000 | $ 242,000,000 |  |  |  |
Policy holder Benefits And Claims Incurred Net | 330,000,000 |  | 6,000,000 |  |  |  |  |  |  |  |  |  |
Elimination of loss and LAE expense as result of consolidating VIE |  |  | 18,000,000 |  |  |  |  |  |  |  |  |  |
Excess interest cash flows from securitizations | 185,000,000 |  |  |  | 80,000,000 |  |  |  |  |  |  |  |
Reserves for expected future claim payments |  |  |  |  |  |  |  |  |  | 1,300,000,000 | 1,400,000,000 |  |
Expected recoveries of future payments | 395,000,000 | 562,000,000 |  |  |  |  |  |  |  | 395,000,000 | 562,000,000 |  |
Paid losses and LAE, net of reinsurance and collections | 489,000,000 |  |  |  |  |  |  |  |  |  |  | 330,000,000 |
Increase in insurance loss recoverable related to paid losses |  |  |  |  |  |  |  |  |  |  |  | $ 270,000,000 |
Number of insured issues reviewed |  |  |  |  |  | 29 | 34 |  |  |  |  |  |
Number of insured issues reviewed with recorded recoveries |  |  |  |  |  |  |  |  |  |  |  |  | 26
Number of transactions received consideration and excluded from loan files reviewed with potential recoveries | 2 |  |  |  |  |  |  |  |  |  |  |  |
Weighted average risk-free rate used to discount claim liability | 1.26% |  |  |  |  |  |  |  |  |  |  |  |

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- Definition ABS CDO exposure decrease. + References No definition available. + Details
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- Definition Aggregate ABS CDO loss and LAE reserves. + References No definition available. + Details
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- Definition Elimination Of Loss And LAE Expense As Result Of Consolidating VIEs + References No definition available. + Details
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- Definition Excess Interest Cash Flows From Securitizations + References No definition available. + Details
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- Definition Gross reserve, recoveries on unpaid losses + References No definition available. + Details
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- Definition Increase decrease in carrying amount as of the balance sheet date of amounts expected to be recovered under the terms of insurance contracts related to recoveries related to commitments to recoveries on paid claims. + References No definition available. + Details
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- Details
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- Definition Losses And Loss Adjustment Expenses Net Of Reinsurance + References No definition available. + Details
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- Definition Number Of Insured Issues Reviewed + References No definition available. + Details
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- Definition Number Of Insured Issues Reviewed With Recorded Recoveries + References No definition available. + Details
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- Definition Number Of Transactions Received Consideration And Excluded From Loan Files Reviewed With Potential Recoveries + References No definition available. + Details
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- Definition Reserves For Expected Future Claim Payments + References No definition available. + Details
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- Definition This element represents the weighted average risk free rate used to discount the claim liability related to financial guarantee insurance contracts. + 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)(1) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 163 -Paragraph 30 -Subparagraph f(1) -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 Provision for benefits, claims and claims settlement expenses incurred during the period net of the effects of contracts assumed and ceded. + 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 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 + Details
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