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Loss And Loss Adjustment Expense Reserves (Schedule OF Losses And Loss Adjustment Expenses Reserves and Recoveries) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Loan repurchase commitments | $ 407 | $ 404 |  |
Insurance Loss Recoverable | 511 | 504 | $ 577 | [1]
Loss and loss adjustment expense reserves | 979 | 541 |  |
Losses and loss adjustment | 683 | 220 | 123 |
Loss And Lae Reserves [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Loss and loss adjustment expense reserves | 979 | 541 | 516 |
Insurance Loss Recoverable [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Insurance Loss Recoverable | 511 | 504 | 577 |
Second Lien Residential Mortgage Backed Securities And Reserves [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Losses and loss adjustment | 62 | 121 | 63 |
CDOs [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Losses and loss adjustment | 10 | (32) | $ 29 |
U S Public Finance Insurance [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Insurance Loss Recoverable | 333 | 174 |  |
Loss and loss adjustment expense reserves | 512 | 97 |  |
International And Structured Finance Insurance [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Loan repurchase commitments | 407 | 404 |  |
Insurance Loss Recoverable | 178 | 330 |  |
Loss and loss adjustment expense reserves | 467 | 444 |  |
International And Structured Finance Insurance [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Insurance Loss Recoverable | (1,300) | (221) |  |
Loss and loss adjustment expense reserves | (243) | (206) |  |
International And Structured Finance Insurance [Member] | Non Variable Interest Entity [Member] |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |
Loan repurchase commitments | 407 | 404 |  |
Insurance Loss Recoverable | 1,478 | 551 |  |
Loss and loss adjustment expense reserves | $ 710 | $ 650 |  |
[1] | As of December 31, 2017 and December 31, 2016, excludes Puerto Rico recoveries, and as of December 31, 2016, the Zohar II recoveries, which have been netted against reserves.

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- Definition Carrying amount as of the balance sheet date of paid insurance policy claims and LAE expense expected to be recovered. + References No definition available. + Details
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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 amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
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- Definition Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred. + 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 FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387 + Details
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