Debt (Narrative) (Detail) (USD $)	0 Months Ended	6 Months Ended
May 06, 2013	Jun. 30, 2013
Bank Of America [Member]
Debt Instrument [Line Items]
Amount received on litigation settlement	$ 1,700,000,000
Line of credit maximum amount	500,000,000
Liquidity requirements period	0 years 0 months 30 days
Equity interest collateral pledged percentage	65.00%
Line of credit commitment fee percentage	2.00%
Line of credit commitment fee	1,000,000
Line of credit term	3 years
Putback recoveries collateral percentage	100.00%
Other prepayment collateral percentage after year one to year two	50.00%
Other prepayment collateral percentage after year two to year three	100.00%
Disposal of assets collateral percentage	100.00%
Liquidity borrowings repayment period	0 years 0 months 30 days
Minimum statutory capital required	750,000,000
Bank Of America [Member] \| Libor Rate Loans [Member] \| Applicable Margin [Member]
Debt Instrument [Line Items]
Line of credit interest rate	7.50%
Bank Of America [Member] \| Base Rate Loans [Member] \| Applicable Margin [Member]
Debt Instrument [Line Items]
Line of credit interest rate	6.50%
Bank Of America [Member] \| Base Rate Loans [Member] \| Federal Funds Rate Margin [Member]
Debt Instrument [Line Items]
Line of credit interest rate	0.50%
Bank Of America [Member] \| Base Rate Loans [Member] \| Adjusted Libor Rate Margin [Member]
Debt Instrument [Line Items]
Line of credit interest rate	1.00%
Mbia Inc [Member]
Debt Instrument [Line Items]
MBIA debt coupon rate		5.70%
Maximum [Member] \| Bank Of America [Member]
Debt Instrument [Line Items]
General corporate purposes limit	50,000,000
Disposal of assets maximum collateral	1,000,000
Remediation efforts maximum amount		260,000,000
Remediation efforts loans outstanding maximum amount	200,000,000
Remediation efforts statutory capital reduction maximum	100,000,000
Minimum [Member] \| Bank Of America [Member]
Debt Instrument [Line Items]
Secured line of credit collateral	1,000,000,000
Fair Value [Member] \| Bank Of America [Member]
Debt Instrument [Line Items]
Secured line of credit collateral	2,500,000,000
Corporate Obligations [Member] \| Bank Of America [Member]
Debt Instrument [Line Items]
Amount received on litigation settlement	136,000,000
MBIA Inc Senior Notes Due 2034 [Member] \| Mbia Inc [Member]
Debt Instrument [Line Items]
MBIA debt coupon rate		5.70%
MBIA Corp Surplus Notes Due 2033 [Member] \| Mbia Corp [Member]
Debt Instrument [Line Items]
MBIA debt coupon rate		14.00%
Accrued interest on surplus notes		117,000,000
Medium Term Notes [Member] \| Conduits [Member]
Debt Instrument [Line Items]
Par value redeemed		336,000,000
Weighted average percent of par		100.00%
Medium Term Notes [Member] \| Global Funding Limited [Member]
Debt Instrument [Line Items]
Par value redeemed		$ 38,000,000
Weighted average percent of par		97.00%

Debt instruments repurchased weighted average percent of par value.

No definition available.

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

- Definition

The maximum amount of assets that can be disposed without requiring repayment of the secured loan.

+ References

No definition available.

+ Details

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

- Definition

The mandatory percentage of proceeds from disposals of assets required to repay the secured loan.

+ References

No definition available.

+ Details

Name:	mbi_DisposalOfAssetsCollateralPercentage
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The secured loan limit that can be used for general corporate purposes.

+ References

No definition available.

+ Details

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

- Definition

The period in which liquidity borrowings on the secured loan must be repaid if in fact the borrowings are not used for such purposes.

+ References

No definition available.

+ Details

Name:	mbi_LiquidityBorrowingsRepaymentPeriod
Namespace Prefix:	mbi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The period of projected ordinary course liquidity requirements that secured loan proceeds must be used for after meeting the general corporate purposes limit.

+ References

No definition available.

+ Details

Name:	mbi_LiquidityRequirementsPeriod
Namespace Prefix:	mbi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the minimum statutory requirement required under the secured loan.

+ References

No definition available.

+ Details

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

- Definition

The mandatory percentage of proceeds from other prepayment collateral required to repay the secured loan after year one to year two.

+ References

No definition available.

+ Details

Name:	mbi_OtherPrepaymentCollateralPercentageAfterYearOneToYearTwo
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The mandatory percentage of proceeds from other prepayment collateral required to repay the secured loan after year two to year three.

+ References

No definition available.

+ Details

Name:	mbi_OtherPrepaymentCollateralPercentageAfterYearTwoToYearThree
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The mandatory percentage of proceeds from put-back recoveries required to repay the secured loan.

+ References

No definition available.

+ Details

Name:	mbi_PutbackRecoveriesCollateralPercentage
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The maximum amount of secured loans outstanding with regard to remediation efforts without consent.

+ References

No definition available.

+ Details

Name:	mbi_RemediationEffortsLoansOutstandingMaximumAmount
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum amount of remediation efforts with respect to insurance obligations and settlements of litigation that can be entered into without requiring consent.

+ References

No definition available.

+ Details

Name:	mbi_RemediationEffortsMaximumAmount
Namespace Prefix:	mbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum amount statutory capital can decline due to remediation efforts without consent.

+ References

No definition available.

+ Details

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

- Definition

The collateral required under terms of the line of credit agreement.

+ References

No definition available.

+ Details

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

- Definition

Term of secured revolving credit agreement.

+ References

No definition available.

+ Details

Name:	mbi_SecuredRevolvingCreditAgreementTerm
Namespace Prefix:	mbi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the percentage of the Company's equity interest in a subsidiary that is pledged as collateral.

+ References

No definition available.

+ Details

Name:	mbi_SubsidiaryCollateralPercentage
Namespace Prefix:	mbi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Interest rate stated in the contractual debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.15(a))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph a

-Article 7

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

+ Details

Name:	us-gaap_InterestPayableCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received for the settlement of litigation during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 27

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585

+ Details

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