XML 115 R60.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Loss And Loss Adjustment Expense Reserves (RMBS Reserves) (Narrative) (Detail) (USD $) | 12 Months Ended | 6 Months Ended | 0 Months Ended | 18 Months Ended
--- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Nov. 30, 2014 | May 31, 2015 | Dec. 31, 2015 | May 31, 2016
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Schedule Of Insured Financial Obligations With Credit Deterioration Insured Contractual Payments Outstanding Principal | $ 11,263,000,000 us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal | [1] | $ 14,264,000,000 us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal | [1] |  |  |  |  |
Policyholder (Benefits) And Claims Incurred Net | 133,000,000 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet |  | 117,000,000 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet |  | 50,000,000 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet |  |  |  |
Loss And Lae Reserves [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | 506,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember |  | 641,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember |  | 853,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember |  |  |  |
Expected recoveries of future payments | 147,000,000 mbi_GrossReserveRecoveriesOnUnpaidLosses / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember |  | 206,000,000 mbi_GrossReserveRecoveriesOnUnpaidLosses / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember |  |  |  |  |  |
Classified [Member] | Loss And Lae Reserves [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | 506,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember / mbi_ClassifiedStatusAxis = mbi_ClassifiedMember |  | 641,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember / mbi_ClassifiedStatusAxis = mbi_ClassifiedMember |  |  |  |  |  |
First Lien R M B S Reserves [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
90+ day roll rate to loss set stress scenario |  |  |  |  |  | 90.00%mbi_PercentageOfRollRateToLossSet / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  |  |
First Lien R M B S Reserves [Member] | Loss And Lae Reserves [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | 263,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  | 241,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  |  |  |  |  |
First Lien R M B S Reserves [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | 2,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  | 2,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  |  |  |  |  |
First Lien R M B S Reserves [Member] | ALT-A [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Percentage of roll to loss after declining over a 24-month period |  |  |  |  |  | 25.00%mbi_PercentageOfLossAfterDecliningOverTwentyFourMonthPeriod / mbi_DelinquencyPeriodAxis = mbi_AltMember / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  |  |
First Lien R M B S Reserves [Member] | Foreclosure [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Assumed roll rate for loans |  |  |  |  |  | 90.00%mbi_AssumedRollRateForLoans / mbi_LoanStatusAxis = mbi_ForeclosureMember / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  |  |
First Lien R M B S Reserves [Member] | Real Estate Owned [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Assumed roll rate for loans |  |  |  |  |  | 90.00%mbi_AssumedRollRateForLoans / mbi_LoanStatusAxis = mbi_RealEstateOwnedMember / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  |  |
First Lien R M B S Reserves [Member] | Bankruptcy [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Assumed roll rate for loans |  |  |  |  |  | 75.00%mbi_AssumedRollRateForLoans / mbi_LoanStatusAxis = mbi_BankruptcyMember / us-gaap_StatementBusinessSegmentsAxis = mbi_FirstLienRMBSReservesMember |  |  |
Rmbs And Heloc And Ces [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Assumed roll rate for ninety plus day delinquent loans excluding foreclosure and real estate owned |  |  |  |  |  | 95.00%mbi_AssumedRollRateForNinetyPlusDayDelinquentLoansExcludingForeclosureAndRealEstateOwned / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |
Period of elevated delinquency and loss for base case, beginning, months |  |  |  |  |  |  | 6 mbi_PeriodOfElevatedDelinquencyAndLossForBaseCaseBeginningMonths / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |
Percentage of loans in 30-59 days delinquent bucket |  |  |  |  |  | 10.00%mbi_PercentageOfLoansInThirtyToFiftyNineDayDelinquentBucket / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |
Percentage of loans charged-off |  |  |  |  |  | 30.00%mbi_PercentageOfLoansChargedOff / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |
Percentage of Current Roll to Loss for the transaction |  |  |  |  |  | 3.00%mbi_PercentageOfCurrentRollToLossForTransaction / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |
Addition to case basis reserves if losses remain at peak levels | 45,000,000 mbi_IncreaseDecreaseToCaseBasisReserves / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |  |  |  |  |  |
Rmbs And Heloc And Ces [Member] | Scenario Forecast [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Decrease in percentage of Current Roll to Loss for transaction |  |  |  |  |  |  | 25.00%mbi_DecreaseInPercentageOfCurrentRollToLossForTransaction / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |  |
Current Roll to Loss |  |  |  |  |  |  |  | 0.00%mbi_PercentageOfFurtherReductionOfCurrentRollToLossForTransaction / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |
Rmbs And Heloc And Ces [Member] | Scenario Forecast [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Period Of Current Roll To Loss For Stress Case Additional Months |  |  |  |  |  |  | 6 mbi_Periodofcurrentrolltolossforstresscaseadditionalmonths / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |  |
Rmbs And Heloc And Ces [Member] | Scenario Forecast [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Period Of Current Roll To Loss For Stress Case Additional Months |  |  |  |  |  |  |  |  | 18 mbi_Periodofcurrentrolltolossforstresscaseadditionalmonths / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember
Rmbs And Heloc And Ces [Member] | Scenario Forecast [Member] | Rate Reduction [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Decrease in percentage of Current Roll to Loss for transaction |  |  |  |  |  |  | 0.75%mbi_DecreaseInPercentageOfCurrentRollToLossForTransaction / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember / us-gaap_ValuationAllowancesAndReservesTypeAxis = mbi_RateReductionMember |  |
Rmbs And Heloc And Ces [Member] | Excess Spread [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Insurance loss recoverable | 496,000,000 mbi_InsuranceLossRecoverable / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  | 647,000,000 mbi_InsuranceLossRecoverable / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |  |  |  |
Total excess spread recoveries | 523,000,000 us-gaap_EstimatedInsuranceRecoveries / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  | 681,000,000 us-gaap_EstimatedInsuranceRecoveries / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |  |  |  |
Expected recoveries of future payments | 27,000,000 mbi_GrossReserveRecoveriesOnUnpaidLosses / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  | 34,000,000 mbi_GrossReserveRecoveriesOnUnpaidLosses / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember |  |  |  |  |  |
Rmbs And Heloc And Ces [Member] | Excess Spread [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Insurance loss recoverable | 132,000,000 mbi_InsuranceLossRecoverable / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  | 183,000,000 mbi_InsuranceLossRecoverable / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  |  |  |  |  |
Total excess spread recoveries | 137,000,000 us-gaap_EstimatedInsuranceRecoveries / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  | 190,000,000 us-gaap_EstimatedInsuranceRecoveries / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  |  |  |  |  |
Expected recoveries of future payments | 5,000,000 mbi_GrossReserveRecoveriesOnUnpaidLosses / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  | 7,000,000 mbi_GrossReserveRecoveriesOnUnpaidLosses / mbi_LoanStatusAxis = mbi_ExcessSpreadMember / us-gaap_StatementBusinessSegmentsAxis = mbi_RmbsAndHelocAndCesMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  |  |  |  |  |
U S Public Finance Insurance [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | 45,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 87,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |  |  |  |  |
Insurance loss recoverable | 4,000,000 mbi_InsuranceLossRecoverable / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 13,000,000 mbi_InsuranceLossRecoverable / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |  |  |  |  |
Policyholder (Benefits) And Claims Incurred Net | (10,000,000)us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |  |  |  |  |  |  |
U S Public Finance Insurance [Member] | General obligations |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Schedule Of Insured Financial Obligations With Credit Deterioration Insured Contractual Payments Outstanding Principal | 98,900,000,000 us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal / us-gaap_InvestmentTypeAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 124,900,000,000 us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal / us-gaap_InvestmentTypeAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |  |  |  |  |
U S Public Finance Insurance [Member] | General obligations | Classified [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Schedule Of Insured Financial Obligations With Credit Deterioration Insured Contractual Payments Outstanding Principal | 152,000,000 us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal / mbi_ClassifiedStatusAxis = mbi_ClassifiedMember / us-gaap_InvestmentTypeAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  | 161,000,000 us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal / mbi_ClassifiedStatusAxis = mbi_ClassifiedMember / us-gaap_InvestmentTypeAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementBusinessSegmentsAxis = mbi_USPublicFinanceInsuranceMember |  |  |  |  |  |
Second Lien R M B S Securitizations [Member] | Loss And Lae Reserves [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | 70,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember / us-gaap_StatementBusinessSegmentsAxis = mbi_SecondLienRMBSSecuritizationsMember |  | 126,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / mbi_ClaimLiabilityAxis = mbi_LossAndLaeReservesMember / us-gaap_StatementBusinessSegmentsAxis = mbi_SecondLienRMBSSecuritizationsMember |  |  |  |  |  |
Second Lien R M B S Securitizations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |
Loss and loss adjustment expense reserves | $ 21,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / us-gaap_StatementBusinessSegmentsAxis = mbi_SecondLienRMBSSecuritizationsMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  | $ 43,000,000 us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense / us-gaap_StatementBusinessSegmentsAxis = mbi_SecondLienRMBSSecuritizationsMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_VariableInterestEntityPrimaryBeneficiaryMember |  |  |  |  |  |
[1] | Represents contractual principal and interest payments due by the issuer of the obligations insured by MBIA.

X
- Definition Assumed Roll Rate For Loans + References No definition available. + Details
Name: | mbi_AssumedRollRateForLoans
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Assumed roll rate for ninety plus day delinquent loans exluding foreclosure and real estate owned + References No definition available. + Details
Name: | mbi_AssumedRollRateForNinetyPlusDayDelinquentLoansExcludingForeclosureAndRealEstateOwned
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Decrease In Percentage Of Current Roll To Loss For Transaction + References No definition available. + Details
Name: | mbi_DecreaseInPercentageOfCurrentRollToLossForTransaction
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Gross reserve, recoveries on unpaid losses + References No definition available. + Details
Name: | mbi_GrossReserveRecoveriesOnUnpaidLosses
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Increase Decrease To Case Basis Reserves + References No definition available. + Details
Name: | mbi_IncreaseDecreaseToCaseBasisReserves
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of paid insurance policy claims and LAE expense expected to be recovered. + References No definition available. + Details
Name: | mbi_InsuranceLossRecoverable
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | mbi_LossAndLossAdjustmentExpenseReservesLineItems
Namespace Prefix: | mbi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Current Roll To Loss For Transaction + References No definition available. + Details
Name: | mbi_PercentageOfCurrentRollToLossForTransaction
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Further Reduction Of Current Roll To Loss For Transaction + References No definition available. + Details
Name: | mbi_PercentageOfFurtherReductionOfCurrentRollToLossForTransaction
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Loans Charged Off + References No definition available. + Details
Name: | mbi_PercentageOfLoansChargedOff
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Loans In 30-59 Day Delinquent Bucket + References No definition available. + Details
Name: | mbi_PercentageOfLoansInThirtyToFiftyNineDayDelinquentBucket
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Loss After Declining Over Twenty Four Month Period + References No definition available. + Details
Name: | mbi_PercentageOfLossAfterDecliningOverTwentyFourMonthPeriod
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Roll Rate To Loss Set + References No definition available. + Details
Name: | mbi_PercentageOfRollRateToLossSet
Namespace Prefix: | mbi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Of Current Roll To Loss For Stress Case Additional Months + References No definition available. + Details
Name: | mbi_Periodofcurrentrolltolossforstresscaseadditionalmonths
Namespace Prefix: | mbi_
Data Type: | xbrli:positiveIntegerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Of Elevated Delinquency And Loss For Base Case, Beginning, Months + References No definition available. + Details
Name: | mbi_PeriodOfElevatedDelinquencyAndLossForBaseCaseBeginningMonths
Namespace Prefix: | mbi_
Data Type: | xbrli:positiveIntegerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of amounts expected to be recovered under the terms of insurance contracts. + 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 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 17 -Article 5 + Details
Name: | us-gaap_EstimatedInsuranceRecoveries
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a),(b),(c) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- 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
Name: | us-gaap_PolicyholderBenefitsAndClaimsIncurredNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This element represents the amount of insured contractual payments outstanding attributable to the principal of the underlying insured obligations for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=6933462&loc=SL5751133-161288 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(iii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 + Details
Name: | us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationInsuredContractualPaymentsOutstandingPrincipal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | mbi_ClaimLiabilityAxis=mbi_LossAndLaeReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mbi_ClassifiedStatusAxis=mbi_ClassifiedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mbi_FirstLienRMBSReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mbi_RmbsAndHelocAndCesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mbi_SecondLienRMBSSecuritizationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mbi_USPublicFinanceInsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |