XML 79 R66.htm IDEA: XBRL DOCUMENT
v3.22.4

Fair Value Of Financial Instruments (Realized And Unrealized Gains And Losses Included In Earnings Pertaining To Level 3 Assets And Liabilities) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | $ 45 | $ 40 | $ (80)
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Realized Investment Gains (Losses) |  |
Variable Interest Entity Primary Beneficiary [Member] |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | $ (14) | (8) | 108
Fair Value Inputs Level 3 [Member] | Total Gains (Losses) Included in Earnings [Member] |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | 40 | 17 | (24)
Total revenues | 30 | 2 | 77
Fair Value Inputs Level 3 [Member] | Change in Unrealized Gains (Losses) for the Period Included in Earnings for Assets and Liabilities still held [Member] |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | 23 | 17 | (30)
Total revenues | 32 | 17 | 73
Fair Value Inputs Level 3 [Member] | Variable Interest Entity Primary Beneficiary [Member] | Total Gains (Losses) Included in Earnings [Member] |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | (10) | (15) | 101
Fair Value Inputs Level 3 [Member] | Variable Interest Entity Primary Beneficiary [Member] | Change in Unrealized Gains (Losses) for the Period Included in Earnings for Assets and Liabilities still held [Member] |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | $ 9 | $ 0 | $ 103

X
- Definition Change in the fair value of and realized gains and losses on sale of financial instruments and foreign exchange included in earnings. + References No definition available. + Details
Name: | mbi_NetGainsLossesOnFinancialInstrumentsAtFairValueAndForeignExchange
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in income from asset and liability measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarnings
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Indicates line item in statement in which net income is reported that includes gain (loss) from asset (liability), measured at fair value using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetLiabilityGainLossStatementOfIncomeExtensibleList
Namespace Prefix: | us-gaap_
Data Type: | enum2:enumerationSetItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mbi_FairValueByConsolidatedStatementsOfOperationsAxis=mbi_TotalGainsLossesIncludedInEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mbi_FairValueByConsolidatedStatementsOfOperationsAxis=mbi_ChangeInUnrealizedGainsLossesForPeriodIncludedInEarningsForAssetsAndLiabilitiesStillHeldMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |