v3.26.1

Commitments and Contingencies (Narrative) (Detail)	Mar. 31, 2026 LegalProceedings
Commitments And Contingencies [Line Items]
Other material legal proceedings pending	0

X

- Definition

CommitmentsAndContingenciesDisclosureAbstract

+ References

No definition available.

+ Details

Name:	mbi_CommitmentsAndContingenciesLineItems
Namespace Prefix:	mbi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Other material legal proceedings pending.

+ References

No definition available.

+ Details

Name:	mbi_NumberOfOtherLegalProceedings
Namespace Prefix:	mbi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant