XML 54 R47.htm IDEA: XBRL DOCUMENT
v3.25.1

Fair Value of Financial Instruments (Company's Assets And Liabilities Measured At Fair Value On Recurring Basis) (Parenthetical) (Details) - USD ($) $ in Millions | Mar. 31, 2025 | Dec. 31, 2024 | Mar. 31, 2024
--- | --- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Exchange-traded bond fund | $ 10 | $ 10 |
Corporate Obligations [Member] | Loans Carried at Fair Value [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans receivable at fair value | $ 14 | $ 15 | $ 6

X
- Definition Exchange-traded bond fund. + References No definition available. + Details
Name: | mbi_ExchangeTradedBondFund
Namespace Prefix: | mbi_
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://www.xbrl.org/2009/role/commonPracticeRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 40 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481628/310-20-40-7 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481990/310-10-45-2 + Details
Name: | us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 + Details
Name: | us-gaap_LoansReceivableFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_CorporateObligationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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