XML 78 R36.htm IDEA: XBRL DOCUMENT
v3.20.1

Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | $ 5,099 | $ 5,526
Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 12 | 15
Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 32 | 34
Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 651 | 781
Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 32 | 33
Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 493 | 447
Global Structured Finance [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 3,376 | 3,600
Global Structured Finance [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 12 | 15
Global Structured Finance [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 24 | 26
Global Structured Finance [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 651 | 781
Global Structured Finance [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 24 | 24
Global Structured Finance [Member] | Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 493 | 447
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 2,122 | 2,253
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 12 | 15
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 17 | 19
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 119 | 107
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 16 | 16
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] | Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 474 | 436
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 21 | 26
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 0 | 0
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] | Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 0 | 0
Global Structured Finance [Member] | Consumer Asset Backed [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 363 | 384
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 1 | 1
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 1 | 1
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 1 | 1
Global Structured Finance [Member] | Consumer Asset Backed [Member] | Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 17 | 11
Global Structured Finance [Member] | Corporate Asset Backed [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 870 | 937
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 6 | 6
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 531 | 673
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 7 | 7
Global Structured Finance [Member] | Corporate Asset Backed [Member] | Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 2 | 0
Global Public Finance [Member] |  |
Variable Interest Entity [Line Items] |  |
Maximum Exposure to Loss | 1,723 | 1,926
Global Public Finance [Member] | Investments [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Public Finance [Member] | Premiums Receivable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 8 | 8
Global Public Finance [Member] | Insurance Loss Recoverable [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Assets | 0 | 0
Global Public Finance [Member] | Unearned Premium Revenue [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | 8 | 9
Global Public Finance [Member] | Loss And Loss Adjustment Expense Reserves Member [Member] |  |
Variable Interest Entity [Line Items] |  |
Carrying Value of VIE Liabilities | $ 0 | $ 0

X
- Definition The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5747-111685 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph b -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685 + Details
Name: | us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- 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
Name: | us-gaap_VariableInterestEntityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph a -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685 + Details
Name: | us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph a -URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685 + Details
Name: | us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_InvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_PremiumsReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=mbi_InsuranceLossRecoverableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=mbi_UnearnedPremiumRevenueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=mbi_LossAndLossAdjustmentExpenseReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=mbi_GlobalStructuredFinanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=mbi_ConsumerAssetBackedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=mbi_CorporateAssetBackedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=mbi_GlobalPublicFinanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |