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

Financial guarantee insurance contracts, the amount of premium revenue expected to be recognized during the sixteenth year and thereafter following the statement of financial position reporting date.

No definition available.

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

Financial guarantee insurance contracts, the amount of premium revenue expected to be recognized during the sixth through tenth year following the statement of financial position reporting date

No definition available.

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

- References

No definition available.

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

Amount of unearned premium revenue under contracts issued by an insurance entity that provide protection to the holder of a financial obligation from a financial loss in the event of a default.

No definition available.

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in next fiscal quarter following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in fourth fiscal quarter following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in second fiscal quarter following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in third fiscal quarter following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Amount of premium revenue under financial guarantee insurance contract to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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

Carrying amount of premiums written on insurance contracts that have not been earned as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(13)(a)(2))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mbi_UnearnedPremiumRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_MarchThirtyOneTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_JuneThirtyTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_SeptemberThirtyTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandTwentyFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandTwentyFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandTwentySixMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandThirtyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandTwentyThirtySixMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=mbi_DecemberThirtyOneTwoThousandFourtyOneAndThereafterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mbi_UpfrontMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=mbi_InstallmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: