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Insurance Regulatory Restrictions Additional Details (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Statutory Accounting Practices Capital $ 268,353ambc_StatutoryAccountingPracticesCapital  
Average Annual Rate Of Return 7.87%ambc_AverageAnnualRateOfReturn 9.80%ambc_AverageAnnualRateOfReturn
Prescribed Discount Rate Percentage   5.10%ambc_PrescribedDiscountRatePercentage
Quarterly Dividend Increase Limitation Percentage 15.00%ambc_QuarterlyDividendIncreaseLimitationPercentage  
Percentage Of Policy Holders Surplus 10.00%ambc_PercentageOfPolicyHoldersSurplus  
Minimum [Member]    
Settlement Agreement Annual Restricted Payment Amount 5,000ambc_SettlementAgreementAnnualRestrictedPaymentAmount
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Maximum [Member]    
Settlement Agreement Annual Restricted Payment Amount 7,500ambc_SettlementAgreementAnnualRestrictedPaymentAmount
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Ambac Assurance [Member]    
Statutory Accounting Practices, Statutory Capital and Surplus, Balance 100,000us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
/ dei_LegalEntityAxis
= ambc_AmbacAssuranceMember
840,262us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
/ dei_LegalEntityAxis
= ambc_AmbacAssuranceMember
Statutory Accounting Practices Capital   905,065ambc_StatutoryAccountingPracticesCapital
/ dei_LegalEntityAxis
= ambc_AmbacAssuranceMember
Ambac Assurance [Member] | Prescribed Or Permitted Additional Accounting Practices [Member]    
Statutory Accounting Practices, Prescribed Practice, Amount 168,085us-gaap_StatutoryAccountingPracticesPrescribedPracticeAmount
/ dei_LegalEntityAxis
= ambc_AmbacAssuranceMember
/ us-gaap_PublicUtilitiesRegulatoryProceedingAxis
= ambc_PrescribedOrPermittedAdditionalAccountingPracticesMember
227,334us-gaap_StatutoryAccountingPracticesPrescribedPracticeAmount
/ dei_LegalEntityAxis
= ambc_AmbacAssuranceMember
/ us-gaap_PublicUtilitiesRegulatoryProceedingAxis
= ambc_PrescribedOrPermittedAdditionalAccountingPracticesMember
Segregated Account [Member]    
Statutory Accounting Practices, Statutory Capital and Surplus, Balance 239,280us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
/ dei_LegalEntityAxis
= ambc_SegregatedAccountMember
442,639us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
/ dei_LegalEntityAxis
= ambc_SegregatedAccountMember
Insurance Liabilities Not Assumed $ 149,482ambc_Ambc_InsuranceLiabilitiesNotAssumed
/ dei_LegalEntityAxis
= ambc_SegregatedAccountMember