XML 37 R52.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Fair Value Of Financial Instruments (Narrative) (Detail) (USD $) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2012 | Sep. 30, 2011 | Sep. 30, 2012 | Sep. 30, 2011 | Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Net insured derivative liability | $ 3,300,000,000 |  | $ 3,300,000,000 |  | $ 4,800,000,000
Impact of excluding the nonperformance risk in valuation of pre-tax net insured derivative liability | 4,400,000,000 |  | 4,400,000,000 |  | 5,700,000,000
Percentage of level 3 assets at fair in total assets measured at fair value |  |  | 30.00% |  | 29.00%
Percentage of level 3 liabilities at fair value in total liabilities measured at fair value |  |  | 74.00% |  | 77.00%
Transfers into Level 3 | 168,000,000 | 144,000,000 | 270,000,000 | 350,000,000 |
Transfers out of Level 3 | 44,000,000 | 77,000,000 | 99,000,000 | 354,000,000 |
Transfers into Level 2 | 44,000,000 | 77,000,000 | 99,000,000 | 354,000,000 |
Transfers out of Level 2 | 168,000,000 | 144,000,000 | 270,000,000 | 350,000,000 |
Transfers into or out of Level 1 | $ 0 | $ 0 | $ 0 | $ 0 |
Binomial Expansion Technique [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Percentage of insured credit derivatives | 81.00% |  | 81.00% |  |
Percentage of sector specific transactions | 9.00% |  | 9.00% |  |
Direct Price Model [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Percentage of insured credit derivatives | 19.00% |  | 19.00% |  |
Corporate Spreads [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Percentage of sector specific transactions | 46.00% |  | 46.00% |  |
Spreads Benchmarked Relevant Spread Source [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Percentage of sector specific transactions | 45.00% |  | 45.00% |  |
WARF Sourced [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Percentage of sector specific transactions | 77.00% |  | 77.00% |  |

X
- Definition Approximate percentage of level 3 assets at fair value in total assets measured at fair value. + References No definition available. + Details
Name: | mbi_ApproximatePercentageOfLevel3AssetsAtFairValueInTotalAssetsMeasuredAtFairValue
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Approximate percentage of level 3 liabilities at fair value in total liabilities measured at fair value. + References No definition available. + Details
Name: | mbi_ApproximatePercentageOfLevel3LiabilitiesAtFairValueInTotalLiabilitiesMeasuredAtFairValue
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Impact Of Non Performance Risk On Insured Derivative Liability + References No definition available. + Details
Name: | mbi_ImpactOfNonPerformanceRiskOnInsuredDerivativeLiability
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percentage Of Insured Credit Derivatives Value + References No definition available. + Details
Name: | mbi_PercentageOfInsuredCreditDerivativesValue
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage Of Transactions + References No definition available. + Details
Name: | mbi_PercentageOfTransactions
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Transfers of assets measured at fair value on a recurring basis into and out of level one during the period. + References No definition available. + Details
Name: | mbi_TransfersIntoAndOutOfLevelOne
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Transfers of assets measured at fair value on a recurring basis into level three during the period. + References No definition available. + Details
Name: | mbi_TransfersIntoLevelThree
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Transfers of assets measured at fair value on a recurring basis into level two during the period. + References No definition available. + Details
Name: | mbi_TransfersIntoLevelTwo
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Transfers of assets measured at fair value on a recurring basis out of level three during the period. + References No definition available. + Details
Name: | mbi_TransfersOutOfLevelThree
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Transfers of assets measured at fair value on a recurring basis out of level two during the period. + References No definition available. + Details
Name: | mbi_TransfersOutOfLevelTwo
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 107 -Paragraph 10 -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. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 4, 17 -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
Name: | us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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