Name:	ambc_DerivativesCreditRiskValuationAdjustmentDerivativeLiabilitiesOtherThanCreditDerivatives
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Weighted average discounted rate of estimated future premium payments to be paid by the VIEs.

No definition available.

Name:	ambc_EstimatedFuturePremiumPaymentsWeightedAverageDiscountedRate
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Fair value inputs coupon rate.

No definition available.

Name:	ambc_FairValueInputsCouponRate
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Fair value inputs maturity.

No definition available.

Name:	ambc_FairValueInputsMaturity
Namespace Prefix:	ambc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Fair value inputs yield.

No definition available.

Name:	ambc_FairValueInputsYield
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Hypothetical base fee received on a credit derivative contract used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesBaseFee
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Hypothetical base reference obligation spread used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesBaseReferenceObligationSpread
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Hypothetical base relative change ratio for a credit derivative contract used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesBaseRelativeChangeRatio
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Full relative change ratio comparable to certain default used in the description of the valuation processes in place for fair value measurement of credit derivative.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesFullRelativeChangeRatio
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Hypothetical incremental credit derivative fee used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesHypotheticalIncrementalFee
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Hypothetical incremental credit derivative fee given a certain credit downgrade used in the description of the valuation processes in place for fair value measurement of credit derivative.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesHypotheticalIncrementalFeeWithCreditDeterioration
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Hypothetical remaining contract life used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesRemainingLife
Namespace Prefix:	ambc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Hypothetical revised fee required on credit derivative contract used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesRevisedHypotheticalFee
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Hypothetical revised fee required on credit derivative given a certain credit downgrade used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesRevisedHypotheticalFeeWithCreditDownGrade
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Hypothetical revised reference obligation spread (second example) used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesRevisedHypotheticalReferenceObligationSpreadTwo
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Hypothetical revised relative change ratio used in the description of the valuation processes in place for fair value measurement of credit derivatives.

No definition available.

Name:	ambc_FairValueMeasurementProcessDescriptionForCreditDerivativesRevisedRelativeChangeRatio
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Name:	ambc_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems
Namespace Prefix:	ambc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair Value of consolidated VIE debt obligations valued using unobservable inputs by asset class

No definition available.

Name:	ambc_FairValueOfConsolidatedVariableInterestEntityDebtObligationsValuedUsingUnobservableInputsByAssetClass
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value of investments in securities valued using unobservable inputs by asset class.

No definition available.

Name:	ambc_FairValueOfInvestmentsInSecuritiesValuedUsingUnobservableInputsByAssetClass
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of credit derivative gross par outstanding using internally estimated reference obligation prices in determination of fair value.

No definition available.

Name:	ambc_PercentageOfCreditDerivativeGrossParOutstandingUsingInternallyEstimatedReferenceObligationPricesInDeterminationOfFairValue
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of credit derivative liability using internally estimated reference obligation prices in determination of fair value.

No definition available.

Name:	ambc_PercentageOfCreditDerivativeLiabilityUsingInternallyEstimatedReferenceObligationPricesInDeterminationOfFairValue
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of credit derivatives gross par outstanding using third party reference obligation quotes in determination of fair value.

No definition available.

Name:	ambc_PercentageOfCreditDerivativesGrossParOutstandingUsingThirdPartyReferenceObligationQuotesInDeterminationOfFairValue
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of credit derivatives liability using third party reference obligation quotes ion determination of fair value.

No definition available.

Name:	ambc_PercentageOfCreditDerivativesLiabilityUsingThirdPartyReferenceObligationQuotesInDeterminationOfFairValue
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Credit valuation adjustment (CVA) as a percentage of the credit derivative liability calculated excluding the CVA.

No definition available.

Name:	ambc_PercentageOfCreditValueAdjustment
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Investment portfolio valued using dealer quotes.

No definition available.

Name:	ambc_PercentageOfInvestmentPortfolioValuedUsingDealerQuotes
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of investment portfolio valued using external pricing services.

No definition available.

Name:	ambc_PercentageOfInvestmentPortfolioValuedUsingExternalPricingServices
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of investment portfolio valued using internal valuation models.

No definition available.

Name:	ambc_PercentageOfInvestmentPortfolioValuedUsingInternalValuationModels
Namespace Prefix:	ambc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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

Amount of credit risk valuation adjustment to derivative liabilities to properly reflect the credit quality of the entity.

No definition available.

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

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624163-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226000-175313

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

Ratio of an entity's operating income net of tax to its revenue, used as an input to measure fair value.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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

Name:	dei_LegalEntityAxis=ambc_VariableInterestEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	invest_CreditRatingSourceAxis=us-gaap_InternalCreditAssessmentDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_CreditDerivativesByContractTypeAxis=ambc_CreditDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FairValueByAssetClassAxis=ambc_EuropeanTransactionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FairValueByAssetClassAxis=ambc_UnitedStatesTransactionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: