Amount of insured par outstanding ceded to reinsurer.

No definition available.

Name:	ambc_AmountOfInsuredParOutstandingCededToReinsurer
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration, net of reinsurance.

+ References

No definition available.

+ Details

Name:	ambc_BalanceOfRmbsSubrogationRecoveriesNetOfReinsurance
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Ceded Loss And Loss Expenses Paid Not Yet Recovered

+ References

No definition available.

+ Details

Name:	ambc_CededLossAndLossExpensesPaidNotYetRecovered
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Ceded Principal Outstanding Major Reinsurer Percentage.

+ References

No definition available.

+ Details

Name:	ambc_CededPrincipalOutstandingMajorReinsurerPercentage
Namespace Prefix:	ambc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average discounted rate of estimated future premium payments to be paid by the VIEs.

+ References

No definition available.

+ Details

Name:	ambc_EstimatedFuturePremiumPaymentsWeightedAverageDiscountedRate
Namespace Prefix:	ambc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Financial Guarantee Outstanding Principal Ceded to third parties.

+ References

No definition available.

+ Details

Name:	ambc_FinancialGuaranteeOutstandingPrincipalCededToThirdParties
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Insurance [Line Items]

+ References

No definition available.

+ Details

Name:	ambc_InsuranceLineItems
Namespace Prefix:	ambc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims expected to be paid or incurred by the ceding insurer.

+ References

No definition available.

+ Details

Name:	ambc_LossReservesCededToReinsurers
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Net Incurred RMBS Subrogation Recoveries

+ References

No definition available.

+ Details

Name:	ambc_NetIncurredRMBSSubrogationRecoveries
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Reinsurance Recoverable, Gross, All Other

+ References

No definition available.

+ Details

Name:	ambc_ReinsuranceRecoverableGrossAllOther
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unsecured Reinsurance Recoverable, All Other

+ References

No definition available.

+ Details

Name:	ambc_UnsecuredReinsuranceRecoverableAllOther
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents reinsurance recoverables on paid and unpaid losses and deferred ceded premiums, net of ceded premiums payables due to reinsurers, letters of credit, and collateral posted for the benefit of the cedant.

+ References

No definition available.

+ Details

Name:	ambc_UnsecuredReinsuranceRecoverables
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The valuation allowance as of the balance sheet date to reduce the gross amount of receivables to estimated net realizable value, which would be presented in parentheses on the face of the balance sheet.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524

+ Details

Name:	us-gaap_AllowanceForDoubtfulAccountsPremiumsAndOtherReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI https://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

+ Details

Name:	us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the amount of premium revenue on financial guarantee insurance contracts recognized during the period that was accelerated for revenue recognition purposes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291

+ Details

Name:	us-gaap_FinancialGuaranteeInsuranceContractsAcceleratedPremiumRevenueAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the weighted average risk free rate used to discount the claim liability related to financial guarantee insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 9
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=99382878&loc=SL5749324-161292

+ Details

Name:	us-gaap_FinancialGuaranteeInsuranceContractsClaimLiabilityWeightedAverageRiskFreeDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the premium receivable for financial guarantee insurance contracts reported in the statement of financial position. This element primarily would consist of those financial guarantee insurance contracts which premiums are to be collected over the contract period, but may, on occasion, include premiums which are to be collected in full at inception, but which straddle a financial reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (c)(1),(5)
-URI https://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

+ Details

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (a)(5)
-URI https://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

+ Details

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumReceivedOverContractPeriodPremiumReceivableWeightedAverageCollectionPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph ((a)(1),(b))
-URI https://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274

+ Details

Name:	us-gaap_IntangibleAssetsNetExcludingGoodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of participating insurance in force.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 50
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6483535&loc=d3e16392-158451

+ Details

Name:	us-gaap_ParticipatingPoliciesAmountInForce
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of expense (reversal of expense) for expected credit loss on premium receivable.

+ References

+ Details

Name:	us-gaap_PremiumReceivableCreditLossExpenseReversal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(5))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524

+ Details

Name:	us-gaap_PremiumsReceivableAllowanceForDoubtfulAccounts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of writeoff of premium receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Gross amount, as of the balance sheet date, due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, before deducting the allowance for doubtful accounts.

+ 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 210.7-03.5)
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

+ Details

Name:	us-gaap_PremiumsReceivableGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387

+ Details

Name:	us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements.

+ References

No definition available.

+ Details

Name:	us-gaap_ReinsurancePayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of allowance for credit loss on reinsurance recoverable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

+ Details

Name:	us-gaap_ReinsuranceRecoverablesAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524

+ Details

Name:	us-gaap_ReinsuranceRecoverablesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of risk undertaken originally by insurer ceded to reinsurer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387

+ Details

Name:	us-gaap_ReinsuranceRetentionPolicyReinsuredRiskPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ambc_SpecialtyPropertyCasualtyProgramDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfMalpracticeInsuranceTypeAndTierIdentifierAxis=us-gaap_FinancialGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=ambc_AssuredGuarantyReLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfMalpracticeInsuranceTypeAndTierIdentifierAxis=us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=ambc_QBEInsuranceCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=ambc_GeneralReinsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ambc_SurveillanceCategoryOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ambc_SurveillanceCategoryOneaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ambc_SurveillanceCategoryTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ambc_SurveillanceCategoryThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ambc_SurveillanceCategoryFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_FurnitureAndFixturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=ambc_LossReservesClaimLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_GBP
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_EUR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=ambc_PublicFinanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_StructuredFinanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=ambc_InternationalFinanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_HousingRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ambc_SecuritiesFinancingTransactionDetailAxis=ambc_MilitaryHousingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_OtherPublicFinanceSectorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_MortgageBackedAndHomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_StructuredInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_StudentLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_OtherStructuredFinanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_SovereignAndSubSovereignMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_InvestorOwnedAndPublicUtilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=ambc_OtherInternationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Financial Guarantee Insurance Contracts - Additional Information (Detail) € in Millions, £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 EUR (€)	Dec. 31, 2020 GBP (£)	Dec. 31, 2020 EUR (€)	Dec. 31, 2019 USD ($)
Insurance [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered		$ 0	$ 0
Net par amount of financial guarantees	$ 22,613	$ 28,020
Estimated Future Premium Payments Weighted Average Discounted Rate	3.00%	2.20%		3.00%	3.00%	2.20%	2.20%
Financial Guarantee Insurance Contracts, Premium Receivable	$ 254	$ 320	370							$ 416
Amount Of Insured Par Outstanding Ceded To Reinsurer	$ 2,187
Ceded Principal Outstanding Major Reinsurer Percentage	7.90%
Reinsurance Payable	$ 39	$ 33
Weighted average period of future premiums	8 years	8 years
Uncollectable premium receivables	$ 5	$ 9
Accelerated premium revenue for retired obligations	8	1	12
Reinsurance recoveries of losses included in losses and loss expenses	(41)	5	(7)
Losses and loss expense reserves ceded to reinsurers		24
Subrogation recoveries, net of reinsurance	(140)	(1,704)
Amortization of intangible assets	47	55	57
Intangible assets	326	362
Financial Guarantee Outstanding Principal Ceded To Third Parties	4,938
Premiums Receivable, Gross	259	329
Allowance for Doubtful Accounts, Premiums and Other Receivables	5	9	17
Premium Receivable, Credit Loss Expense (Reversal)	(4)	(6)
Premium Receivable, Allowance for Credit Loss, Writeoff	0	(2)
Reinsurance Recoverable, Allowance for Credit Loss	0	0
Net Incurred RMBS Subrogation Recoveries	(123)	20	(23)
Reinsurance Recoverables, Gross	115
Net unsecured reinsurance recoverable	60
Reinsurance Recoverable, Gross, All Other	18
Unsecured Reinsurance Recoverable, All Other	7
Specialty Property & Casualty Program [Domain]
Insurance [Line Items]
Premiums Receivable, Gross	$ 16	2
Property and Casualty, Commercial Insurance
Insurance [Line Items]
Reinsurance, Reinsured Risk, Percentage	70.00%
Financial Guarantee
Insurance [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 0
Losses and loss expense reserves ceded to reinsurers	33
Financial Guarantee \| Assured Guaranty Re Ltd [Member]
Insurance [Line Items]
Reinsurance Recoverables, Gross	30
Net unsecured reinsurance recoverable	0
Property and Casualty, Commercial Insurance \| QBE Insurance Corporation
Insurance [Line Items]
Reinsurance Recoverables, Gross	41
Net unsecured reinsurance recoverable	41
Property and Casualty, Commercial Insurance \| General Reinsurance Company
Insurance [Line Items]
Reinsurance Recoverables, Gross	25
Net unsecured reinsurance recoverable	11
Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	217	277
IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	10	12
II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	6
III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	16	22
IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	$ 11	$ 12
Maximum [Member] \| Furniture and Fixtures [Member]
Insurance [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Loss Reserves [Member]
Insurance [Line Items]
Weighted average risk-free rate used to discount loss reserves	3.90%	1.20%
United Kingdom, Pounds
Insurance [Line Items]
Financial Guarantee Insurance Contracts, Premium Receivable	$ 71	$ 108	117	£ 59		£ 80		£ 86
Euro Member Countries, Euro
Insurance [Line Items]
Financial Guarantee Insurance Contracts, Premium Receivable	14	16	$ 19		€ 13		€ 14		€ 16
Public Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	10,547	12,360
Premiums Receivable, Gross	150	159
Public Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	142	151
Public Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	3	3
Public Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	5
Public Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Public Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Structured Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	3,612	4,904
Premiums Receivable, Gross	24	45
Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	19
Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	1	1
Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	1
Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	12
Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	11	12
International Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	8,454	10,756
Premiums Receivable, Gross	85	125
International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	70	107
International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	8
International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	9	11
International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Housing Revenue [Member] \| Public Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	5,491	5,610
Premiums Receivable, Gross	148	157
Housing Revenue [Member] \| Public Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	140	149
Housing Revenue [Member] \| Public Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	3	3
Housing Revenue [Member] \| Public Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	5
Housing Revenue [Member] \| Public Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Housing Revenue [Member] \| Public Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Housing Revenue [Member] \| Military Housing [Member] \| Public Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	5,400	5,490
Other Public Finance Sectors [Member] \| Public Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	2	2
Other Public Finance Sectors [Member] \| Public Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	2	2
Other Public Finance Sectors [Member] \| Public Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	1,930	2,724
Premiums Receivable, Gross	11	16
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	1
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	1
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	2
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	11	12
Structured Insurance [Member] \| Structured Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	10
Structured Insurance [Member] \| Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	10
Structured Insurance [Member] \| Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Structured Insurance [Member] \| Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Structured Insurance [Member] \| Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Structured Insurance [Member] \| Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Student Loan [Member] \| Structured Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	8	12
Student Loan [Member] \| Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	1	1
Student Loan [Member] \| Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	1	1
Student Loan [Member] \| Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Student Loan [Member] \| Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	9
Student Loan [Member] \| Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	579	624
Premiums Receivable, Gross	4	7
Other Structured Finance [Member] \| Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	4	7
Other Structured Finance [Member] \| Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	4,077	5,141
Premiums Receivable, Gross	64	93
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	49	74
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	8
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	9	11
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member]
Insurance [Line Items]
Net par amount of financial guarantees	2,583	3,283
Premiums Receivable, Gross	18	28
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	18	28
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	2	5
Other International [Member] \| International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	2	5
Other International [Member] \| International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	$ 0	$ 0