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

This element represents the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration, net of reinsurance.

No definition available.

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

The increase (decrease) during the reporting period in the loss and loss expense reserve accounts, net of subrogation and reinsurance.

No definition available.

Name:	ambc_ChangeInLossAndLossExpenseReservesNet
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Financial Guarantee Insurance Contracts Premium Receivable Deemed Uncollectible

No definition available.

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

Total provision in the period for loss adjustment expenses incurred in the claim settlement process.

No definition available.

Name:	ambc_LossAdjustmentExpenseIncurred
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer.

No definition available.

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

Percentage of financial guarantee premiums receivable related to RMBS insured transactions with non-investment grade internal ratings.

No definition available.

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

Percentage of financial guarantee premiums receivable related to Student Loan insured transactions with non-investment grade internal ratings.

No definition available.

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

Percentage Premiums Receivable Related To Asset Backed Transactions

No definition available.

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

Percentage of financial guarantee premiums receivable related to insured transactions with non-investment grade internal ratings.

No definition available.

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

Past due premiums on policies insuring internally rated non-investment grade obligations.

No definition available.

Name:	ambc_PremiumsPastDueOnNonInvestmentGradeObligation
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Loss adjustment expense reserves, net of reinsurance, represent the costs estimated to be incurred in the settlement of unpaid claims.

No definition available.

Name:	ambc_ReserveForLossAdjustmentExpenses
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

This element represents the amount of premium revenue on financial guarantee insurance contracts recognized during the period that was accelerated for revenue recognition purposes.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 605

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 163

-Paragraph 30

-Subparagraph d

-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.

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

This element represents the weighted average risk free rate used to discount the claim liability related to financial guarantee insurance contracts.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 9

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 163

-Paragraph 30

-Subparagraph f(1)

-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.

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

Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 310

-Section 50

-Paragraph 3

-Subparagraph (a)(5)

-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageCollectionPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The reduction in the amount of the provision for the period for claims and benefits incurred on contract risks ceded to other insurers under reinsurance arrangements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27, 113

-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.