XML 72 R62.htm IDEA: XBRL DOCUMENT
v3.23.1

Derivative Instruments (Credit Derivatives Sold) (Detail) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2023 | Dec. 31, 2022
Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Weighted average remaining expected maturity | 13 years 8 months 12 days | 13 years 8 months 12 days
Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Total fair value of credit derivatives | $ 0 | $ 0
Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 1,328 | 1,350
Total fair value of credit derivatives | 0 | 0
Credit Rating Aaa [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Total fair value of credit derivatives | 0 | 0
Credit Rating Aaa [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 0 | 0
Credit Rating Aa [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Total fair value of credit derivatives | 0 | 0
Credit Rating Aa [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 48 | 50
Credit Rating A [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Total fair value of credit derivatives | 0 | 0
Credit Rating A [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 1,010 | 1,013
Credit Rating Bbb [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Total fair value of credit derivatives | 0 | 0
Credit Rating Bbb [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | 210 | 227
Credit Rating Below Investment Grade [Member] | Insurance Operations [Member] |  |
Derivative [Line Items] |  |
Total fair value of credit derivatives | 0 | 0
Credit Rating Below Investment Grade [Member] | Insurance Operations [Member] | Insured Swaps [Member] |  |
Derivative [Line Items] |  |
Derivative notional amount | $ 60 | $ 60

X
- Definition Weighted Average Remaining Maturity Credit Derivatives In Years + References No definition available. + Details
Name: | mbi_WeightedAverageRemainingMaturityCreditDerivativesInYears
Namespace Prefix: | mbi_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of credit risk derivative liability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4K -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5708775-113959 + Details
Name: | us-gaap_CreditRiskDerivativeLiabilitiesAtFairValue
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_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959 + Details
Name: | us-gaap_DerivativeNotionalAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_CreditDerivativesByContractTypeAxis=mbi_InsuredSwapsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=mbi_CreditRatingAaaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=mbi_CreditRatingAaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=mbi_CreditRatingAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=mbi_CreditRatingBbbMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=mbi_CreditRatingBelowInvestmentGradeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |