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Insurance in Force (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020
Guarantor Obligations [Line Items] |  |
Transactions guaranteed by MBIA on behalf of affiliated companies | $ 1,300 |
Aggregate amount of insurance in force ceded to reinsurers | 2,200 | $ 3,000
Aggregate amount of insured par outstanding ceded to reinsurers | 1,017 | $ 1,500
U S Public Finance Insurance [Member] |  |
Guarantor Obligations [Line Items] |  |
Aggregate amount of insured par outstanding ceded to reinsurers | 800 |
Structured Finance And International Insurance [Member] |  |
Guarantor Obligations [Line Items] |  |
Aggregate amount of insured par outstanding ceded to reinsurers | $ 169 |
Financial Guaranty Insurance Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Financial guaranty maturity year | 2058 |
Investment agreements, MTNs and other affiliated contracts [Member] |  |
Guarantor Obligations [Line Items] |  |
Financial guaranty maturity year | 2037 |

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- Definition Aggregate amount insurance in force outstanding ceded to reinsurers. + References No definition available. + Details
Name: | mbi_AggregateAmountInsuranceInForceOutstandingCededToReinsurers
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Aggregate amount of insured par outstanding ceded to reinsurers. + References No definition available. + Details
Name: | mbi_AggregateAmountOfInsuredParOutstandingCededToReinsurers
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Represents the latest maturity year on financial guaranty obligations. + References No definition available. + Details
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Namespace Prefix: | mbi_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

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- Definition Transactions guaranteed on behalf of various affiliates. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |