XML 99 R76.htm IDEA: XBRL DOCUMENT
v3.20.1

Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Detail) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
AFS [Member] | Interest Rate Swap [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | $ 328 | $ 332
AFS [Member] | Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | 1,261 | 1,261
AFS [Member] | Futures Contracts [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | 240 | 755
Variable Interest Entity, Primary Beneficiary [Member] | Other Credit Derivatives [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | 8 | 9
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Swap [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | 1,121 | 1,194
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | 1,093 | 1,176
Other Credit Derivatives [Member] |  |
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] |  |
Derivative products, Notional Amount | $ 275 | $ 280

X
- Definition Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items] + References No definition available. + Details
Name: | ambc_ScheduleOfLoansAndAllowanceForLoanByClassIndividuallyAndCollectivelyEvaluatedForImpairmentLineItems
Namespace Prefix: | ambc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959 + Details
Name: | us-gaap_DerivativeNotionalAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

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

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=ambc_InterestRateSwapOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_FutureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_OtherCreditDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_OtherCreditDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |