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Commitments and Contingencies (Narrative) (Detail) $ in Millions	1 Months Ended
	May 31, 2024 USD ($)	Dec. 31, 2024 USD ($) LegalProceedings
Commitments And Contingencies [Line Items]
Other material legal proceedings pending | LegalProceedings		0
Decrease in ROU	$ 7
Decrease in operating lease liability	$ 7
MBIA Corp [Member] | Fully Drawn [Member]
Commitments And Contingencies [Line Items]
Other Commitment		$ 15

X

- Definition

CommitmentsAndContingenciesDisclosureAbstract

+ References

No definition available.

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Namespace Prefix:	mbi_
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- Definition

Increase (decrease) in right of use assets.

+ References

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- Definition

Other material legal proceedings pending.

+ References

No definition available.

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X

- Definition

Amount of increase (decrease) in obligation for operating lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (g)(1)
-SubTopic 20
-Topic 842
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-4

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- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

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Period Type:	instant

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