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Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Detail) (Successor [Member], USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | $ 4,958,298 us-gaap_AvailableForSaleSecuritiesAmortizedCost | $ 4,939,325 us-gaap_AvailableForSaleSecuritiesAmortizedCost
Gross Unrealized Gains | 222,608 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax | 242,962 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 29,363 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax | 32,269 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Estimated Fair Value | 5,151,543 us-gaap_AvailableForSaleSecurities | 5,150,018 us-gaap_AvailableForSaleSecurities
Non - credit other - than - temporary Impairments | 9,844 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments | 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments
Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Estimated Fair Value | 2,704,657 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 2,743,050 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Short-Term [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 220,980 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 360,069 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 4 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 220,980 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 360,065 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 4,672,886 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 4,514,878 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 222,227 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 242,962 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 29,363 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 32,154 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 4,865,750 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 4,725,686 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 9,844 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Securities Pledged as Collateral [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 64,432 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 64,378 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 381 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 111 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 64,813 us-gaap_AvailableForSaleSecurities / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 64,267 us-gaap_AvailableForSaleSecurities / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 517,256 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 523,019 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 12,136 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 9,769 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 4,204 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 6,996 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 525,188 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 525,792 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 1,588,962 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,382,195 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 24,097 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 12,815 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 3,290 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 9,416 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 1,609,769 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,385,594 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Foreign Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 123,601 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 126,041 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 4,038 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 3,060 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 2,475 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,344 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 125,164 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 127,757 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | U.S. Government Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 28,983 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 42,328 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 1,418 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,078 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 104 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 427 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 30,297 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 42,979 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | U.S. Government Obligations [Member] | Securities Pledged as Collateral [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 64,432 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 64,378 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 381 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 111 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 64,813 us-gaap_AvailableForSaleSecurities / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 64,267 us-gaap_AvailableForSaleSecurities / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 4,438 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 29,524 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 11 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 38 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 4,427 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 29,486 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 1,705,246 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,557,059 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 159,388 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 167,396 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 18,157 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 13,500 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 1,846,477 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,710,955 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 9,844 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 88,569 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 21,346 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 102 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 50 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 433 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 274 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 88,238 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 21,122 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 615,831 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 833,366 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 21,048 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 48,794 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 689 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 159 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 636,190 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 882,001 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Fixed Income Investments And Other Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 4,893,866 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 4,874,947 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 222,227 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 242,962 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 29,363 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 32,158 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 5,086,730 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 5,085,751 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | $ 9,844 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | $ 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember

X
- Definition Non credit other than temporary impairments on investments. + References No definition available. + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References 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 + Details
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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 + Details
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- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + 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 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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