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Background and Business Description - Additional Information (Detail) (USD $) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2015 Segment | Dec. 31, 2014 | Apr. 30, 2013
Background And Basis Of Presentation [Line Items] |  |  |
Entity Incorporation, Date of Incorporation | Apr. 29, 1991 |  |
Number of reportable segments | 2 us-gaap_NumberOfReportableSegments |  |
Investment Warrants Expiration Date |  | Apr. 30, 2023 |
Payment of permitted policy claim (percent) |  | 25.00%ambc_PaymentAsPercentageOfPermittedPolicyClaim |
Common stock, shares authorized | 130,000,000 us-gaap_CommonStockSharesAuthorized | 130,000,000 us-gaap_CommonStockSharesAuthorized |
Common Stock, Par or Stated Value Per Share | $ 0.01 us-gaap_CommonStockParOrStatedValuePerShare | $ 0.01 us-gaap_CommonStockParOrStatedValuePerShare | $ 0.01 us-gaap_CommonStockParOrStatedValuePerShare
Preferred stock, shares authorized | 20,000,000 us-gaap_PreferredStockSharesAuthorized | 20,000,000 us-gaap_PreferredStockSharesAuthorized |
Preferred Stock, Par or Stated Value Per Share | $ 0.01 us-gaap_PreferredStockParOrStatedValuePerShare | $ 0.01 us-gaap_PreferredStockParOrStatedValuePerShare |
Common stock, shares issued | 45,006,057 us-gaap_CommonStockSharesIssued | 45,005,932 us-gaap_CommonStockSharesIssued |
Warrants Distributed In Bankruptcy |  |  | 5,047,138 us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Warrants issued exercise price |  |  | $ 16.67 us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Ambac Assurance [Member] |  |  |
Background And Basis Of Presentation [Line Items] |  |  |
Net par exposure for policies allocated to the Segregated Account | $ 18,052,539,000 ambc_NetParExposureForPoliciesAllocatedToSegregatedAccount / dei_LegalEntityAxis = ambc_AmbacAssuranceMember |  |
Minimum surplus amount | 100,000,000 ambc_MinimumSurplusAmount / dei_LegalEntityAxis = ambc_AmbacAssuranceMember |  |
Segregated Account [Member] |  |  |
Background And Basis Of Presentation [Line Items] |  |  |
Insurance Liabilities Not Assumed | $ 26,169,000 ambc_Ambc_InsuranceLiabilitiesNotAssumed / dei_LegalEntityAxis = ambc_SegregatedAccountMember |  |
Successor [Member] |  |  |
Background And Basis Of Presentation [Line Items] |  |  |
Common stock, shares issued |  |  | 45,000,000 us-gaap_CommonStockSharesIssued / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Warrants Distributed In Bankruptcy |  |  | 5,047,138 us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember

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- Definition Ambac Assurance is not obligated to make payments under the Reinsurance Agreement or Cooperation Agreement if its surplus as regards to policyholders is less than $100,000 (the “Minimum Surplus Amount”). This amount represents the Segregated Account’s insurance liabilities that were not assumed by Ambac Assurance. + References No definition available. + Details
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- Definition Minimum surplus amount that will cap the benefits of the Reinsurance Agreement between Ambac Assurance and the Segregated Account of Ambac Assurance. + References No definition available. + Details
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- Definition Net par outstanding for policies allocated to the Segregated Account of Ambac Assurance. + References No definition available. + Details
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- Definition Percentage of the Segregated Account of Ambac Assurance's permitted policy claims that were paid in cash from September 2012 through June 2014. + References No definition available. + Details
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- Definition Expiration date of warrants held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column A + Details
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- Definition Exercise price per share or per unit of warrants or rights outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(i)(4)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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- Definition Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(i)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph i -Subparagraph 2 -Article 4 + Details
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- Definition Face amount or stated value per share of common stock. + 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 210.5-02.29) -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 30 -Article 5 + Details
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- Definition Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer. + 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 210.5-02.28) -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 29 -Article 5 + Details
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