XML 48 R92.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Investments - Additional Information (Detail) - USD ($) $ in Millions | Dec. 31, 2019 | Sep. 30, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | --- | ---
Investment [Line Items] |  |  |  |
Other Investments | $ 478 |  | $ 391 |
Securities fair value | 6 |  | 6 |
Market Value of Secured Note Collateral | 197 |  | 210 |
Real Estate [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 16 |  | 16 |
Hedge Funds, Multi-strategy [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments |  | $ 65 | 0 |
Interest Rate Contract [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 176 |  | 114 |
Illiquid Investments [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 51 |  | 84 |
Insurance Linked [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 3 |  | 29 |
Equity [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 55 |  | 44 |
Credit Index Product [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 66 |  | 63 |
Equity investments in pooled funds [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 432 |  |  | $ 351
Reported Value Measurement [Member] | Interest Rate Contract [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 81 |  | 27 |
Priced Through Pricing Vendors [Member] | Equity [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 55 |  | 44 |
Investment Portfolio [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Fair Value of Cash and Securities Pledged to Derivative Counterparties | 85 |  | 103 |
Ambac Assurance [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Unsettled Amounts Secured Notes from LSNI | 55 |  | $ 19 |
Commitments [Member] | Partnership Interest [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | 41 |  |  |
Commitments [Member] | Capital of Dislocations [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other Investments | $ 48 |  |  |

X
- Definition Fair value of cash and securities pledged to derivative counterparties. + References No definition available. + Details
Name: | ambc_FairValueOfCashAndSecuritiesPledgedToDerivativeCounterparties
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of securities deposited with governmental authorities. + References No definition available. + Details
Name: | ambc_FairValueOfSecuritiesDepositedWithGovernmentalAuthorities
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Market Value of Secured Note Collateral + References No definition available. + Details
Name: | ambc_MarketValueofSecuredNoteCollateral
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Unsettled Amounts Secured Notes from LSNI + References No definition available. + Details
Name: | ambc_UnsettledAmountsSecuredNotesfromLSNI
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | invest_InvestmentLineItems
Namespace Prefix: | invest_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investments classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_OtherInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_RealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_HedgeFundsMultistrategyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_InterestRateContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ambc_IlliquidInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ambc_InsuranceLinkedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_EquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CreditIndexProductMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ambc_EquityinvestmentsinpooledfundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=ambc_PricedThroughPricingVendorsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ambc_InvestmentPortfolioMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=ambc_AmbacAssuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_OtherCommitmentsAxis=us-gaap_CommitmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=srt_PartnershipInterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ambc_CapitalofDislocationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |