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Insurance Premiums (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Insurance Premiums [Line Items] |  |  |
Weighted average risk-free rate |  | 3.00% | 2.90%
Weighted average expected collection term of the premiums receivable, years |  | 8 years 9 months | 8 years 11 months 12 days
Reinsurance premiums payable | [1] | $ 12 |
Premiums [Member] |  |  |
Insurance Premiums [Line Items] |  |  |
Reinsurance premiums payable |  | $ 4 | $ 4
[1] | Total reinsurance recoverable/(payable) is primarily related to recoverables on paid and unpaid losses net of paid and unpaid salvage due to reinsurers

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- Definition Insurance Premiums Line Items + References No definition available. + Details
Name: | mbi_InsurancePremiumsLineItems
Namespace Prefix: | mbi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a)(5) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479584/944-310-50-3 + Details
Name: | us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageCollectionPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition This element represents the weighted average risk free rate used to discount the premiums expected to be collected for financial guarantee insurance contracts where the premium is to be received over the contract period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479584/944-310-50-3 + Details
Name: | us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageRiskFreeDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements. + References No definition available. + Details
Name: | us-gaap_ReinsurancePayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
Name: | us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis=mbi_PremiumsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |