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Commitments and Contingencies (Narrative) (Detail) (USD $) In Millions, unless otherwise specified | 9 Months Ended | 0 Months Ended
--- | --- | ---
Sep. 30, 2013 numberoflawsuits | May 02, 2013 Flagstar Bank [Member]
Commitment And Contingencies [Line Items] |  |
Proceeds from legal settlements |  | $ 110
Other material lawsuits pending | 0 |

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- Details
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Balance Type: | na
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- Definition Other material lawsuits pending + References No definition available. + Details
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Namespace Prefix: | mbi_
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- Definition Cash received for the settlement of litigation during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 + Details
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