XML 61 R51.htm IDEA: XBRL DOCUMENT
v3.23.3

Fair Value of Financial Instruments (Aggregate Fair Value And Remaining Contractual Principal Balance Outstanding On Fair Value Option) (Detail) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Residential Mortgage Loans [Member] | Loans Receivable [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Loans receivable and other instruments, contractual outstanding principal | $ 18 | $ 39
Loans receivable and other instruments, 90 days or more past due, contractual outstanding principal | 57 | 149
Loans receivable and other instruments, fair value | 18 | 39
Loans receivable and other instruments, 90 days or more past due, fair value | 14 | 39
Loans receivable and other instruments, difference | 0 | 0
Loans receivable and other instruments, 90 days or more past due, difference | 43 | 110
Total Loans Receivable and Other Instruments [Member] | Loans Receivable [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Loans receivable and other instruments, contractual outstanding principal | 75 | 188
Loans receivable and other instruments, fair value | 32 | 78
Loans receivable and other instruments, difference | 43 | 110
Variable Interest Entity Notes [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Long-term debt instruments, contractual outstanding principal | 329 | 780
Long-term debt instruments, fair value | 78 | 172
Long-term debt instruments, difference | 251 | 608
Medium Term Notes [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Long-term debt instruments, contractual outstanding principal | 53 | 53
Long-term debt instruments, fair value | 37 | 41
Long-term debt instruments, difference | $ 16 | $ 12

X
- Definition Fair Value Option Aggregate Fair Value Loans Receivable + References No definition available. + Details
Name: | mbi_FairValueOptionAggregateFairValueLoansReceivable
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair Value Option Aggregate Fair Value Long Term Debt Instruments + References No definition available. + Details
Name: | mbi_FairValueOptionAggregateFairValueLongTermDebtInstruments
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value Option Contractual Outstanding Principal Loans Receivable + References No definition available. + Details
Name: | mbi_FairValueOptionContractualOutstandingPrincipalLoansReceivable
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair Value Option Contractual Outstanding Principal Loans Receivable 90 Days or More Past Due + References No definition available. + Details
Name: | mbi_FairValueOptionContractualOutstandingPrincipalLoansReceivable90DaysOrMorePastDue
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair Value Option Contractual Outstanding Principal Long-Term Debt Instruments + References No definition available. + Details
Name: | mbi_FairValueOptionContractualOutstandingPrincipalLongTermDebtInstruments
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (d)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482907/825-10-50-28 + Details
Name: | us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of long-term debt instruments that have contractual principal amounts and for which the fair value option has been elected. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (d)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482907/825-10-50-28 + Details
Name: | us-gaap_FairValueOptionAggregateDifferencesLongTermDebtInstruments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482907/825-10-50-28 + Details
Name: | us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition For loans held as assets for which the fair value option has been elected, this item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of those loans that are 90 days or more past due. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (e)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482907/825-10-50-28 + Details
Name: | us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDueAggregateDifference
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479808/944-20-55-15 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480078/944-80-55-17 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 80 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480109/944-80-50-1 + Details
Name: | us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mbi_ResidentialMortgageLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_LoansReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mbi_TotalLoansReceivableAndOtherInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mbi_VariableInterestEntityNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_MediumTermNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |