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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 | Dec. 31, 2014 | Dec. 31, 2013
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Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | $ 4,939,325 us-gaap_AvailableForSaleSecuritiesAmortizedCost | $ 6,324,568 us-gaap_AvailableForSaleSecuritiesAmortizedCost
Gross Unrealized Gains | 242,962 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax | 74,724 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 32,269 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax | 116,634 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Estimated Fair Value | 5,150,018 us-gaap_AvailableForSaleSecurities | 6,282,658 us-gaap_AvailableForSaleSecurities
Non - credit other - than - temporary Impairments | 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments | 852 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments
Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Estimated Fair Value | 2,743,050 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 2,475,182 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Residential Mortgage-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 1,557,059 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember |
Estimated Fair Value | 1,710,955 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember |
Collateralized Debt Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 21,346 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember |
Estimated Fair Value | 21,122 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember |
Asset-backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 833,366 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember |
Estimated Fair Value | 882,001 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember |
Short-Term [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 360,069 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 271,118 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 | 1 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 | 4 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 360,065 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 271,119 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 | 4,514,878 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 5,927,254 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 242,962 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 74,696 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 | 32,154 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 116,634 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 4,725,686 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 5,885,316 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 852 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 | 64,378 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 126,196 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 27 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 | 111 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 64,267 us-gaap_AvailableForSaleSecurities / us-gaap_FinancialInstrumentAxis = us-gaap_SecuritiesPledgedAsCollateralMember / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 126,223 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 | 523,019 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,405,293 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 9,769 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 857 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 | 6,996 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 28,427 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 525,792 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,377,723 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 | 1,382,195 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,508,377 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 12,815 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 4,886 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 | 9,416 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 23,894 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 1,385,594 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,489,369 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 | 126,041 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 131,709 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 3,060 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 69 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 | 1,344 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 6,901 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 127,757 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ForeignGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 124,877 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 | 42,328 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 128,415 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 1,078 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 9 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 | 427 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 2,176 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 42,979 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 126,248 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 | 64,378 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 | 126,196 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 | 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 | 27 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 | 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 | 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
Estimated Fair Value | 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 | 126,223 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 | 29,524 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 32,214 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 | 10 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 | 38 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 70 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 29,486 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 32,154 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 | 1,557,059 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,516,877 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 167,396 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 59,853 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 | 13,500 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 18,105 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 1,710,955 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,558,625 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 | 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ResidentialMortgageBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 852 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 | 21,346 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 184,118 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 50 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 217 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 | 274 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 463 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 21,122 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CollateralizedDebtObligationsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 183,872 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 | 833,366 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 1,020,251 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 48,794 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 8,795 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 | 159 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 36,598 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 882,001 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 992,448 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 | 4,874,947 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 6,198,372 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Gross Unrealized Gains | 242,962 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 74,697 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 32,158 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 116,634 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Estimated Fair Value | 5,085,751 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | 6,156,435 us-gaap_AvailableForSaleSecurities / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember
Non - credit other - than - temporary Impairments | $ 7,773 ambc_NonCreditOtherThanTemporaryImpairmentsOnInvestments / us-gaap_InvestmentTypeAxis = ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember / us-gaap_StatementScenarioAxis = us-gaap_SuccessorMember | $ 852 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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