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v3.8.0.1

Subsequent Events (Details) - Subsequent Event [Member] - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Feb. 12, 2018
Discount on Deferred Amounts Resulting in Adjustment to Loss Reserves |  | $ 288,000,000
Cancellation of Surplus Notes and Accrued Interest |  | 809,520,000
Debt Modification Criteria, Change in Cash Flows | 10.00% |
Deferred Payment Obligation [Member] |  |
One Dollar Outstanding |  | 1.00
Cash Payment Amount |  | 0.40
Payment Amount in New Secured Notes |  | 0.41
Payment Amount in Existing Surplus Notes |  | 0.125
Discount Amount |  | 0.065
Ambac [Member] | Deferred Payment Obligation [Member] |  |
One Dollar Outstanding |  | 1.00
Payment Amount in New Secured Notes |  | 0.91
Discount Amount |  | $ 0.09

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- Definition Cancellation of Surplus Notes and Accrued Interest + References No definition available. + Details
Name: | ambc_CancellationofSurplusNotesandAccruedInterest
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Cash Payment Amount + References No definition available. + Details
Name: | ambc_CashPaymentAmount
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Debt Modification Criteria, Change in Cash Flows + References No definition available. + Details
Name: | ambc_DebtModificationCriteriaChangeinCashFlows
Namespace Prefix: | ambc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Discount Amount + References No definition available. + Details
Name: | ambc_DiscountAmount
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Discount on Deferred Amounts Resulting in Adjustment to Loss Reserves + References No definition available. + Details
Name: | ambc_DiscountonDeferredAmountsResultinginAdjustmenttoLossReserves
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition One Dollar Outstanding + References No definition available. + Details
Name: | ambc_OneDollarOutstanding
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Payment Amount in Existing Surplus Notes + References No definition available. + Details
Name: | ambc_PaymentAmountinExistingSurplusNotes
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Payment Amount in New Secured Notes + References No definition available. + Details
Name: | ambc_PaymentAmountinNewSecuredNotes
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DebtSecurityAxis=ambc_DeferredPaymentObligationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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