XML 112 R101.htm IDEA: XBRL DOCUMENT v3.25.0.1

Insurance Regulations And Dividends (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Insurance Regulations And Dividends [Line Items]
Percentage of policyholders' surplus	10.00%
Percentage of adjusted net investment income	100.00%
Policyholders Surplus [Member] | Minimum [Member]
Insurance Regulations And Dividends [Line Items]
Policyholders' surplus	$ 65
MBIA Corp [Member]
Insurance Regulations And Dividends [Line Items]
Unassigned surplus	1,900	$ 1,900
Statutory net loss	64	28
Statutory capital	88	152
Policyholders' surplus	83
Contingency reserves	5
Statutory net income			$ 46
National [Member]
Insurance Regulations And Dividends [Line Items]
Dividends from subsidiaries	69		72
Statutory net loss	133	142
Statutory capital	912	1,100
Policyholders' surplus	602
Contingency reserves	$ 310
Statutory net income			$ 75
National [Member] | S 2023 A Dividends [Member]
Insurance Regulations And Dividends [Line Items]
Dividends from subsidiaries		550
National [Member] | O 2023 A Right Dividends [Member]
Insurance Regulations And Dividends [Line Items]
Dividends from subsidiaries		$ 97

X

- Definition

Insurance Regulations And Dividends Line Items

+ References

No definition available.

+ Details

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

X

- Definition

Percentage of adjusted net investment income.

+ References

No definition available.

+ Details

Name:	mbi_PercentageOfAdjustedNetInvestmentIncome
Namespace Prefix:	mbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage of policyholders surplus.

+ References

No definition available.

+ Details

Name:	mbi_PercentageOfPolicyholdersSurplus
Namespace Prefix:	mbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Statutory Accounting Practices defined as policyholders' surplus plus contingency reserves.

+ References

No definition available.

+ Details

Name:	mbi_StatutoryAccountingPracticesCapital
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Statutory accounting practices, contingency reserves.

+ References

No definition available.

+ Details

Name:	mbi_StatutoryAccountingPracticesContingencyReserves
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount of net loss for the period determined using accounting principles prescribed or permitted by insurance regulators.

+ References

No definition available.

+ Details

Name:	mbi_StatutoryAccountingPracticesStatutoryNetLossAmount
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Statutory accounting practices, surplus.

+ References

No definition available.

+ Details

Name:	mbi_StatutoryAccountingPracticesSurplus
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Statutory accounting practices, unassigned surplus.

+ References

No definition available.

+ Details

Name:	mbi_StatutoryAccountingPracticesUnassignedSurplus
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3

+ Details

Name:	us-gaap_CashDividendsPaidToParentCompanyByConsolidatedSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of net income for the period determined using accounting principles prescribed or permitted by insurance regulators.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Name:	us-gaap_StatutoryAccountingPracticesStatutoryNetIncomeAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_StatementEquityComponentsAxis=mbi_PolicyholdersSurplusMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ConsolidatedEntitiesAxis=mbi_MbiaCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ConsolidatedEntitiesAxis=mbi_NationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DividendsAxis=mbi_S2023ADividendsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DividendsAxis=mbi_O2023ARightDividendsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: