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Schedule II - Condensed Statements Of Cash Flows (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Cash flows from operating activities:      
Investment income received $ 419us-gaap_ProceedsFromInterestAndDividendsReceived $ 426us-gaap_ProceedsFromInterestAndDividendsReceived $ 594us-gaap_ProceedsFromInterestAndDividendsReceived
Operating expenses paid (238)us-gaap_PaymentsForOperatingActivities (277)us-gaap_PaymentsForOperatingActivities (400)us-gaap_PaymentsForOperatingActivities
Interest paid, net of interest converted to principal (179)us-gaap_InterestPaidNet (224)us-gaap_InterestPaidNet (400)us-gaap_InterestPaidNet
Income taxes (paid) received (17)us-gaap_IncomeTaxesPaidNet (1)us-gaap_IncomeTaxesPaidNet (6)us-gaap_IncomeTaxesPaidNet
Net cash provided (used) by operating activities (333)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations 1,829us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations (1,027)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
Cash flows from investing activities:      
Purchases of available-for-sale investments (1,494)us-gaap_PaymentsToAcquireAvailableForSaleSecurities (2,397)us-gaap_PaymentsToAcquireAvailableForSaleSecurities (3,086)us-gaap_PaymentsToAcquireAvailableForSaleSecurities
Sales of available-for-sale investments 757us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities 1,726us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities 4,658us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
Paydowns and maturities of available-for-sale investments 484us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities 452us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities 609us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities
Purchases of investments at fair value (631)mbi_PaymentsToAcquireFairValueOptionAndTradingSecurities (371)mbi_PaymentsToAcquireFairValueOptionAndTradingSecurities (346)mbi_PaymentsToAcquireFairValueOptionAndTradingSecurities
Sales, paydowns and maturities of investments at fair value 789mbi_ProceedsFromSalesMaturitiesAndPaydownsOfFairValueAndTradingSecurities 595mbi_ProceedsFromSalesMaturitiesAndPaydownsOfFairValueAndTradingSecurities 960mbi_ProceedsFromSalesMaturitiesAndPaydownsOfFairValueAndTradingSecurities
Sales, paydowns and maturities (purchases) of short-term investments, net 515us-gaap_PaymentsForProceedsFromShortTermInvestments (358)us-gaap_PaymentsForProceedsFromShortTermInvestments 739us-gaap_PaymentsForProceedsFromShortTermInvestments
Proceeds From Sales Maturities Prepayments and Calls Of Other Investments 1mbi_ProceedsFromSalesMaturitiesPrepaymentsAndCallsOfOtherInvestments 0mbi_ProceedsFromSalesMaturitiesPrepaymentsAndCallsOfOtherInvestments 0mbi_ProceedsFromSalesMaturitiesPrepaymentsAndCallsOfOtherInvestments
(Payments) proceeds for derivative settlements (26)us-gaap_PaymentsForProceedsFromDerivativeInstrumentInvestingActivities (54)us-gaap_PaymentsForProceedsFromDerivativeInstrumentInvestingActivities (288)us-gaap_PaymentsForProceedsFromDerivativeInstrumentInvestingActivities
Collateral (to) from swap counterparty 144us-gaap_IncreaseDecreaseCashCollateralFromCounterparties 122us-gaap_IncreaseDecreaseCashCollateralFromCounterparties (285)us-gaap_IncreaseDecreaseCashCollateralFromCounterparties
Net cash provided (used) by investing activities 812us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations (6)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations 4,195us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations
Cash flows from financing activities:      
Proceeds from investment agreements 30us-gaap_ProceedsFromIssuanceOfOtherLongTermDebt 31us-gaap_ProceedsFromIssuanceOfOtherLongTermDebt 36us-gaap_ProceedsFromIssuanceOfOtherLongTermDebt
Principal paydowns of investment agreements (192)us-gaap_RepaymentsOfOtherLongTermDebt (285)us-gaap_RepaymentsOfOtherLongTermDebt (688)us-gaap_RepaymentsOfOtherLongTermDebt
Payments for securities sold under agreements to repurchase 0us-gaap_ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase 0us-gaap_ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase (287)us-gaap_ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase
Payments for retirement of debt 0us-gaap_RepaymentsOfLongTermDebt (3)us-gaap_RepaymentsOfLongTermDebt (540)us-gaap_RepaymentsOfLongTermDebt
Purchases of treasury stock (32)us-gaap_PaymentsForRepurchaseOfCommonStock 0us-gaap_PaymentsForRepurchaseOfCommonStock 0us-gaap_PaymentsForRepurchaseOfCommonStock
Restricted stock awards settlements 0us-gaap_ProceedsFromStockPlans 0us-gaap_ProceedsFromStockPlans 1us-gaap_ProceedsFromStockPlans
Net cash provided (used) by financing activities (892)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations (1,566)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations (2,811)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations
Effect of exchange rate changes on cash and cash equivalents (8)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalentsContinuingOperations 11us-gaap_EffectOfExchangeRateOnCashAndCashEquivalentsContinuingOperations 0us-gaap_EffectOfExchangeRateOnCashAndCashEquivalentsContinuingOperations
Net increase (decrease) in cash and cash equivalents (421)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease 268us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease 357us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Cash and cash equivalents - beginning of year 1,258us-gaap_CashAndCashEquivalentsAtCarryingValue 990us-gaap_CashAndCashEquivalentsAtCarryingValue 633us-gaap_CashAndCashEquivalentsAtCarryingValue
Cash and cash equivalents - end of year 782us-gaap_CashAndCashEquivalentsAtCarryingValue 1,258us-gaap_CashAndCashEquivalentsAtCarryingValue 990us-gaap_CashAndCashEquivalentsAtCarryingValue
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]      
Net income (loss) 569us-gaap_NetIncomeLoss 250us-gaap_NetIncomeLoss 1,234us-gaap_NetIncomeLoss
Change in: [Abstract]      
Net investment losses related to other-than-temporary impairments 15mbi_NetOtherThanTemporaryImpairments 0mbi_NetOtherThanTemporaryImpairments 105mbi_NetOtherThanTemporaryImpairments
Net (gains) losses on financial instruments at fair value and foreign exchange (128)mbi_IncreaseDecreaseInNetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange (244)mbi_IncreaseDecreaseInNetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange (73)mbi_IncreaseDecreaseInNetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange
Other net realized (gains) losses (25)mbi_IncreaseDecreaseInOtherNetRealizedGainsLosses 28mbi_IncreaseDecreaseInOtherNetRealizedGainsLosses (7)mbi_IncreaseDecreaseInOtherNetRealizedGainsLosses
Deferred income tax provision (benefit) 50us-gaap_DeferredIncomeTaxExpenseBenefit 157us-gaap_DeferredIncomeTaxExpenseBenefit 365us-gaap_DeferredIncomeTaxExpenseBenefit
(Gains) losses on extinguishment of debt 0mbi_AdjustmentGainsLossesOnExtinguishmentOfDebt (61)mbi_AdjustmentGainsLossesOnExtinguishmentOfDebt (49)mbi_AdjustmentGainsLossesOnExtinguishmentOfDebt
Other operating 114us-gaap_OtherNoncashIncomeExpense 103us-gaap_OtherNoncashIncomeExpense 138us-gaap_OtherNoncashIncomeExpense
Total adjustments to net income (loss) (902)us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities 1,579us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities (2,261)us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities
Net cash provided (used) by operating activities (333)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations 1,829us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations (1,027)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
Parent Company [Member]      
Cash flows from operating activities:      
Fees and reimbursements received 1us-gaap_ProceedsFromFeesReceived
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_ProceedsFromFeesReceived
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
5us-gaap_ProceedsFromFeesReceived
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Investment income received 256us-gaap_ProceedsFromInterestAndDividendsReceived
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
250us-gaap_ProceedsFromInterestAndDividendsReceived
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
118us-gaap_ProceedsFromInterestAndDividendsReceived
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Operating expenses paid (35)us-gaap_PaymentsForOperatingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(35)us-gaap_PaymentsForOperatingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(43)us-gaap_PaymentsForOperatingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Interest paid, net of interest converted to principal (93)us-gaap_InterestPaidNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(93)us-gaap_InterestPaidNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(101)us-gaap_InterestPaidNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Income taxes (paid) received 59us-gaap_IncomeTaxesPaidNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
111us-gaap_IncomeTaxesPaidNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
224us-gaap_IncomeTaxesPaidNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net cash provided (used) by operating activities 188us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
233us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
203us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Cash flows from investing activities:      
Purchases of available-for-sale investments (125)us-gaap_PaymentsToAcquireAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(287)us-gaap_PaymentsToAcquireAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(560)us-gaap_PaymentsToAcquireAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Sales of available-for-sale investments 268us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
147us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1,148us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Paydowns and maturities of available-for-sale investments 98us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
252us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1,036us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Purchases of investments at fair value (266)mbi_PaymentsToAcquireFairValueOptionAndTradingSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(144)mbi_PaymentsToAcquireFairValueOptionAndTradingSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(42)mbi_PaymentsToAcquireFairValueOptionAndTradingSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Sales, paydowns and maturities of investments at fair value 280mbi_ProceedsFromSalesMaturitiesAndPaydownsOfFairValueAndTradingSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
126mbi_ProceedsFromSalesMaturitiesAndPaydownsOfFairValueAndTradingSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
139mbi_ProceedsFromSalesMaturitiesAndPaydownsOfFairValueAndTradingSecurities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Sales, paydowns and maturities (purchases) of short-term investments, net (242)us-gaap_PaymentsForProceedsFromShortTermInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
94us-gaap_PaymentsForProceedsFromShortTermInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
114us-gaap_PaymentsForProceedsFromShortTermInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(Payments) proceeds for derivative settlements (26)us-gaap_PaymentsForProceedsFromDerivativeInstrumentInvestingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(32)us-gaap_PaymentsForProceedsFromDerivativeInstrumentInvestingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(207)us-gaap_PaymentsForProceedsFromDerivativeInstrumentInvestingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Collateral (to) from swap counterparty 144us-gaap_IncreaseDecreaseCashCollateralFromCounterparties
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
122us-gaap_IncreaseDecreaseCashCollateralFromCounterparties
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(285)us-gaap_IncreaseDecreaseCashCollateralFromCounterparties
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Contributions to subsidiaries, net (20)mbi_ContributionsToSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2mbi_ContributionsToSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(12)mbi_ContributionsToSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Advances to subsidiaries, net (12)us-gaap_PaymentsForProceedsFromOtherInvestingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_PaymentsForProceedsFromOtherInvestingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1us-gaap_PaymentsForProceedsFromOtherInvestingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net cash provided (used) by investing activities 99us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
280us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1,332us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Cash flows from financing activities:      
Proceeds from investment agreements 23us-gaap_ProceedsFromIssuanceOfOtherLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
25us-gaap_ProceedsFromIssuanceOfOtherLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
31us-gaap_ProceedsFromIssuanceOfOtherLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Principal paydowns of investment agreements (181)us-gaap_RepaymentsOfOtherLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(274)us-gaap_RepaymentsOfOtherLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(679)us-gaap_RepaymentsOfOtherLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Payments for securities sold under agreements to repurchase 0us-gaap_ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(32)us-gaap_ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(639)us-gaap_ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Payments for retirement of debt 0us-gaap_RepaymentsOfLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(3)us-gaap_RepaymentsOfLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(180)us-gaap_RepaymentsOfLongTermDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Payments for affiliate loans (153)us-gaap_RepaymentsOfRelatedPartyDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(194)us-gaap_RepaymentsOfRelatedPartyDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(109)us-gaap_RepaymentsOfRelatedPartyDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Purchases of treasury stock (32)us-gaap_PaymentsForRepurchaseOfCommonStock
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_PaymentsForRepurchaseOfCommonStock
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_PaymentsForRepurchaseOfCommonStock
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Restricted stock awards settlements 16us-gaap_ProceedsFromStockPlans
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
13us-gaap_ProceedsFromStockPlans
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1us-gaap_ProceedsFromStockPlans
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net cash provided (used) by financing activities (327)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(465)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(1,575)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net increase (decrease) in cash and cash equivalents (40)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
48us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(40)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Cash and cash equivalents - beginning of year 140us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
92us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
132us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Cash and cash equivalents - end of year 100us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
140us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
92us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]      
Net income (loss) 569us-gaap_NetIncomeLoss
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
250us-gaap_NetIncomeLoss
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1,234us-gaap_NetIncomeLoss
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Change in: [Abstract]      
Intercompany accounts receivable (24)us-gaap_IncreaseDecreaseInAccountsReceivableRelatedParties
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(14)us-gaap_IncreaseDecreaseInAccountsReceivableRelatedParties
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(9)us-gaap_IncreaseDecreaseInAccountsReceivableRelatedParties
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Current income taxes 70us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
116us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
57us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Equity in earnings of subsidiaries (463)mbi_EquityInNetIncomeLossOfSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(118)mbi_EquityInNetIncomeLossOfSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(762)mbi_EquityInNetIncomeLossOfSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Dividends from subsidiaries 225us-gaap_CashDividendsPaidToParentCompanyByConsolidatedSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
219us-gaap_CashDividendsPaidToParentCompanyByConsolidatedSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
60us-gaap_CashDividendsPaidToParentCompanyByConsolidatedSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net investment losses related to other-than-temporary impairments 0mbi_NetOtherThanTemporaryImpairments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0mbi_NetOtherThanTemporaryImpairments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
59mbi_NetOtherThanTemporaryImpairments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net (gains) losses on financial instruments at fair value and foreign exchange (24)mbi_IncreaseDecreaseInNetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(11)mbi_IncreaseDecreaseInNetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
119mbi_IncreaseDecreaseInNetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Other net realized (gains) losses (1)mbi_IncreaseDecreaseInOtherNetRealizedGainsLosses
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0mbi_IncreaseDecreaseInOtherNetRealizedGainsLosses
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(6)mbi_IncreaseDecreaseInOtherNetRealizedGainsLosses
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Deferred income tax provision (benefit) (176)us-gaap_DeferredIncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(207)us-gaap_DeferredIncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(613)us-gaap_DeferredIncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(Gains) losses on extinguishment of debt (1)mbi_AdjustmentGainsLossesOnExtinguishmentOfDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(43)mbi_AdjustmentGainsLossesOnExtinguishmentOfDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2mbi_AdjustmentGainsLossesOnExtinguishmentOfDebt
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Other operating 13us-gaap_OtherNoncashIncomeExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
41us-gaap_OtherNoncashIncomeExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
62us-gaap_OtherNoncashIncomeExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Total adjustments to net income (loss) (381)us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(17)us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(1,031)us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net cash provided (used) by operating activities $ 188us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 233us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 203us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember