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Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2011
Significant Accounting Policies [Abstract] |
Pre-tax mark-to-market loss | $ 207

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- Definition Pre tax mark to market loss + References No definition available. + Details
Name: | mbi_PreTaxMarkToMarketLoss
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration