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Business Segments (Summary Of Company's Segment Results) (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Segment Reporting Information [Line Items] |  |  |  |  |
Revenues | $ 139 us-gaap_RevenueOtherFinancialServices | [1] | $ 142 us-gaap_RevenueOtherFinancialServices | [2] |
Net change in fair value of insured derivatives | 28 us-gaap_GainLossOnDerivativeInstrumentsNetPretax |  | 469 us-gaap_GainLossOnDerivativeInstrumentsNetPretax |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | 30 mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange |  | (55)mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange |  |
Net gains (losses) on extinguishment of debt |  |  | 1 us-gaap_GainsLossesOnExtinguishmentOfDebt |  |
Other net realized gains (losses) | 20 us-gaap_OtherIncome |  | 1 us-gaap_OtherIncome |  |
Revenues of consolidated VIEs | 2 mbi_RevenuesOfConsolidatedVies |  | 19 mbi_RevenuesOfConsolidatedVies |  |
Inter-segment revenues | 0 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity | [3] | 0 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity | [4] |
Total revenues | 219 mbi_SegmentRevenue |  | 577 mbi_SegmentRevenue |  |
Losses and loss adjustment | (6)us-gaap_PolicyholderBenefitsAndClaimsIncurredNet |  | 50 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet |  |
Operating | 48 us-gaap_SellingGeneralAndAdministrativeExpense |  | 56 us-gaap_SellingGeneralAndAdministrativeExpense |  |
Interest | 50 us-gaap_InterestExpense |  | 54 us-gaap_InterestExpense |  |
Expenses of consolidated VIEs | 14 mbi_ExpensesOfConsolidatedVies |  | 13 mbi_ExpensesOfConsolidatedVies |  |
Inter-segment expenses | 0 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity | [3] | 0 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity | [4] |
Total expenses | 106 mbi_SegmentExpense |  | 173 mbi_SegmentExpense |  |
Income (loss) before income taxes | 113 mbi_SegmentPretaxIncomeLoss |  | 404 mbi_SegmentPretaxIncomeLoss |  |
Provision (benefit) for income taxes | 44 us-gaap_IncomeTaxExpenseBenefit |  | 148 us-gaap_IncomeTaxExpenseBenefit |  |
Net income (loss) | 69 us-gaap_NetIncomeLoss |  | 256 us-gaap_NetIncomeLoss |  |
Identifiable assets | 15,915 us-gaap_Assets |  | 16,087 us-gaap_Assets |  | 16,284 us-gaap_Assets
U S Public Finance Insurance [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Losses and loss adjustment | (6)us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | (14)us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Operating Segments [Member] | U S Public Finance Insurance [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenues | 105 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember | [1] | 89 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember | [2] |
Net change in fair value of insured derivatives |  |  | 1 us-gaap_GainLossOnDerivativeInstrumentsNetPretax / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | 3 mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 4 mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Other net realized gains (losses) | (4)us-gaap_OtherIncome / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |  |  |
Inter-segment revenues | 10 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember | [3] | 11 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember | [4] |
Total revenues | 114 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 105 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Losses and loss adjustment | (6)us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | (14)us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Operating | 10 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 9 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Inter-segment expenses | 24 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember | [3] | 18 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember | [4] |
Total expenses | 28 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 13 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Income (loss) before income taxes | 86 mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 92 mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Provision (benefit) for income taxes | 29 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 31 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Net income (loss) | 57 us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 61 us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Identifiable assets | 5,859 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 6,124 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |
Operating Segments [Member] | International And Structured Finance Insurance [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenues | 29 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember | [1] | 32 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember | [2] |
Net change in fair value of insured derivatives | 28 us-gaap_GainLossOnDerivativeInstrumentsNetPretax / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 468 us-gaap_GainLossOnDerivativeInstrumentsNetPretax / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | (5)mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | (3)mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Revenues of consolidated VIEs | 2 mbi_RevenuesOfConsolidatedVies / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 20 mbi_RevenuesOfConsolidatedVies / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Inter-segment revenues | 18 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember | [3] | 12 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember | [4] |
Total revenues | 72 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 529 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Losses and loss adjustment |  |  | 64 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Operating | 19 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 17 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Interest | 25 us-gaap_InterestExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 28 us-gaap_InterestExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Expenses of consolidated VIEs | 14 mbi_ExpensesOfConsolidatedVies / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 13 mbi_ExpensesOfConsolidatedVies / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Inter-segment expenses | 18 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember | [3] | 17 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember | [4] |
Total expenses | 76 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 139 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Income (loss) before income taxes | (4)mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 390 mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Provision (benefit) for income taxes | (2)us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 136 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Net income (loss) | (2)us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 254 us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Identifiable assets | 10,578 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  | 10,867 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_StructuredFinanceAndInternationalInsuranceMember |  |
Operating Segments [Member] | Corporate Operations [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenues | 5 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember | [1] | 18 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember | [2] |
Net gains (losses) on financial instruments at fair value and foreign exchange | 32 mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | (52)mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Net gains (losses) on extinguishment of debt | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | 1 us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Other net realized gains (losses) | 24 us-gaap_OtherIncome / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | 1 us-gaap_OtherIncome / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Revenues of consolidated VIEs |  |  | (5)mbi_RevenuesOfConsolidatedVies / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Inter-segment revenues | 16 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember | [3] | 7 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember | [4] |
Total revenues | 77 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | (30)mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Operating | 19 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | 19 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Interest | 25 us-gaap_InterestExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | 26 us-gaap_InterestExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Inter-segment expenses | 1 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember | [3] | 4 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember | [4] |
Total expenses | 45 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | 49 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Income (loss) before income taxes | 32 mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | (79)mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Provision (benefit) for income taxes | 17 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | (21)us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Net income (loss) | 15 us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | (58)us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Identifiable assets | 2,737 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  | 2,640 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_CorporateOperationsMember |  |
Operating Segments [Member] | Advisory Services [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenues |  |  | 3 us-gaap_RevenueOtherFinancialServices / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember | [2] |
Net gains (losses) on financial instruments at fair value and foreign exchange |  |  | (4)mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Inter-segment revenues |  |  | 6 mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember | [4] |
Total revenues |  |  | 5 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Operating |  |  | 11 us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Inter-segment expenses |  |  | 1 mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember | [4] |
Total expenses |  |  | 12 mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Income (loss) before income taxes |  |  | (7)mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Provision (benefit) for income taxes |  |  | (1)us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Net income (loss) |  |  | (6)us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Identifiable assets |  |  | 34 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_AdvisoryServicesMember |  |
Operating Segments [Member] | Conduit [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenues of consolidated VIEs |  |  | 4 mbi_RevenuesOfConsolidatedVies / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember |  |
Inter-segment revenues |  |  | (1)mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember | [4] |
Total revenues |  |  | 3 mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember |  |
Income (loss) before income taxes |  |  | 3 mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember |  |
Provision (benefit) for income taxes |  |  | 1 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember |  |
Net income (loss) |  |  | 2 us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember |  |
Identifiable assets |  |  | 76 us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_OperatingSegmentsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_ConduitsMember |  |
Intersegment Elimination [Member] |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Net gains (losses) on extinguishment of debt |  |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  |
Inter-segment revenues | (44)mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember | [3] | (35)mbi_RevenueFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember | [4] |
Total revenues | (44)mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  | (35)mbi_SegmentRevenue / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  |
Inter-segment expenses | (43)mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember | [3] | (40)mbi_ExpenseFromTransactionsWithOtherOperatingSegmentsOfSameEntity / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember | [4] |
Total expenses | (43)mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  | (40)mbi_SegmentExpense / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  |
Income (loss) before income taxes | (1)mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  | 5 mbi_SegmentPretaxIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  |
Provision (benefit) for income taxes | 0 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  | 2 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  |
Net income (loss) | (1)us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  | 3 us-gaap_NetIncomeLoss / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember |  |
Identifiable assets | $ (3,259)us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember | [5] | $ (3,654)us-gaap_Assets / us-gaap_ConsolidationItemsAxis = us-gaap_IntersegmentEliminationMember | [5] |
[1] | Represents the sum of third-party financial guarantee net premiums earned, net investment income, insurance-related fees and reimbursements and other fees.
[2] | Represents the sum of third-party financial guarantee net premiums earned, net investment income, insurance-related fees and reimbursements, investment management fees and other fees.
[3] | Represents intercompany premium income and expense and intercompany interest income and expense pertaining to intercompany receivables and payables.
[4] | Represents intercompany premium income and expense, intercompany asset management fees and expenses, and intercompany interest income and expense pertaining to intercompany receivables and payables.
[5] | Consists of intercompany reinsurance balances, repurchase agreements and deferred income taxes.

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- Definition Intersegmentexpenses in the consolidated group. + References No definition available. + Details
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- Definition Intersegment revenues in the consolidated group. + References No definition available. + Details
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- Definition Total revenues of all Variable Interest Entities consolidated by the reporting entity + References No definition available. + Details
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- Definition Amount of total expense for the reportable segments, including expense from external customers, transactions with other operating segments of the same entity, and (gross) interest expense. All considered to be "operating expense" for purposes of the taxonomy. + References No definition available. + Details
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- Definition Amount of total revenue for the reportable segments, including revenue from external customers, transactions with other operating segments of the same entity, and (gross) interest revenue. All considered to be "operating revenue" for purposes of the taxonomy. + References No definition available. + Details
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- Definition Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.18) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 18 -Article 5 + Details
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- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959 + Details
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- Definition Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12317-112629 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12355-112629 + Details
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Income Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6515339 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 + Details
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- Definition Amount of the cost of borrowed funds accounted for as interest expense. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.9) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 9 -Article 9 + Details
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Other Comprehensive Income -URI http://asc.fasb.org/extlink&oid=6519514 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Net Income -URI http://asc.fasb.org/extlink&oid=6518256 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.19) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.18) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.22) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 19 -Article 5 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 20 -Article 9 + 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 SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 Reference 3: 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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- Definition Fees and other service revenues recognized in the period that are not otherwise specified in the taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1(d)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
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- Definition The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 4 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34747878&loc=d3e3636-108311 + Details
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