Name:	mbi_InsuranceRegulationsAndDividendsLineItems
Namespace Prefix:	mbi_
Data Type:	xbrli:stringItemType
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Percentage required to be invested in certain qualifing assets.

+ References

No definition available.

+ Details

Name:	mbi_InvestmentsInCertainQualifingAssets
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum percentage of admitted assets the asset swap can be without three month notice to initiate cash dividends.

+ References

No definition available.

+ Details

Name:	mbi_MaximumPercentageOfNotionalAssetSwap
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum percentage of statutory admitted assets allowed to be invested in subsidaries under New York insurance laws.

+ References

No definition available.

+ Details

Name:	mbi_MaximumPercentageOfStatutoryAdmittedAssetsInvestedInSubsidiaries
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of adjusted net investment income.

+ References

No definition available.

+ Details

Name:	mbi_PercentageOfAdjustedNetInvestmentIncome
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Policyholders Surplus

+ References

No definition available.

+ Details

Name:	mbi_PercentageOfPolicyholdersSurplus
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of contingency reserve requested to be released to surplus.

+ References

No definition available.

+ Details

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

- 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:	duration

- 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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Statutory accounting practices, surplus.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Impact on statutory surplus due to maximum amount of investment in subsidiaries.

+ References

No definition available.

+ Details

Name:	mbi_StatutorySurplusNegativeImpact
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 235

-Section S99

-Paragraph 2

-Subparagraph (SX 210.9-06)

-URI http://asc.fasb.org/extlink&oid=6882215&loc=d3e537971-122884

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 06

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph b

-Article 12

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 3

-Subparagraph (SX 210.12-04.(b))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.23(c))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 24

-Subparagraph c

-Article 7

+ Details

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

- Details

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Insurance Regulations And Dividends (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2012
Insurance Regulations And Dividends [Line Items]
Percentage of policyholders' surplus	10.00%mbi_PercentageOfPolicyholdersSurplus
Percentage of adjusted net investment income	100.00%
Maximum percentage of notional asset swap	5.00%
Minimum [Member]
Insurance Regulations And Dividends [Line Items]
Policyholders' surplus	$ 65,000,000
MBIA Corp [Member]
Insurance Regulations And Dividends [Line Items]
Requested contingency reserve release to surplus			1,100,000,000
Statutory net loss	35,000,000	494,000,000
Statutory capital	859,000,000	825,000,000
Policyholders' surplus	542,000,000
Contingency reserves	317,000,000
MBIA Corp [Member] \| Minimum Surplus And Contingency Reserves [Member]
Insurance Regulations And Dividends [Line Items]
Investments in certain qualifing assets	100.00%
MBIA Corp [Member] \| Loss Reserves And Unearned Premium Reserves [Member]
Insurance Regulations And Dividends [Line Items]
Investments in certain qualifing assets	50.00%
MBIA Corp [Member] \| Policyholders Surplus [Member]
Insurance Regulations And Dividends [Line Items]
Statutory surplus negative impact	106,000,000
Maximum percentage of statutory admitted assets invested in subsidiaries	50.00%
MBIA Corp [Member] \| Surplus [Member]
Insurance Regulations And Dividends [Line Items]
Maximum percentage of statutory admitted assets invested in subsidiaries	60.00%
National [Member]
Insurance Regulations And Dividends [Line Items]
Dividends from subsidiaries	220,000,000
Statutory capital	3,300,000,000	3,300,000,000
Policyholders' surplus	2,200,000,000
Contingency reserves	1,100,000,000
Statutory net income	$ 238,000,000	$ 256,000,000