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Background and Business Description - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2014 | Jun. 30, 2018 | Feb. 12, 2018 | May 01, 2013 | Apr. 30, 2013
Background And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |
Entity Incorporation, Date of Incorporation | Apr. 29, 1991 |  |  |  |  |  |  |
Minimum surplus amount | $ 100,000 |  |  |  |  |  |  |
Gain Contingency, Unrecorded Amount |  |  |  |  | $ 1,400,000 |  |  |
Amount of Senior Surplus Notes Outstanding on June 8, 2020 |  | 25.00% |  |  |  |  |  |
Tier 2 Notes |  |  |  |  |  | $ 240,000 |  |
Tier 2 Note Security in RMBS Litigation Settlement Proceeds |  |  |  |  |  | $ 1,600,000 |  |
Accrued rate of interest on outstanding policy obligations (percent) |  | 5.10% |  |  |  |  |  |
Common stock, shares authorized | 130,000,000 | 130,000,000 |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ 0.01 | $ 0.01 |  |  |  |  |  | $ 0.01
Preferred stock, shares authorized | 20,000,000 | 20,000,000 |  |  |  |  |  |
Preferred Stock, Par or Stated Value Per Share | $ 0.01 | $ 0.01 |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  |  |  |  | $ 16.67 |
Junior surplus note of Ambac Assurance Segregated Account |  |  |  |  |  |  | $ 350,000 |
Common Stock Voting Restrictions |  |  |  | 10.00% |  |  |  |
Common Stock Voting Restriction Less One Vote |  |  |  | 10.00% |  |  |  |
Common Stock Transfer Restrictions |  |  |  | 5.00% |  |  |  |
Common Stock Additional Transfer Restrictions |  |  |  | 5.00% |  |  |  |
Litigation Settlement, Amount Awarded from Other Party |  |  | $ 995,000 |  |  |  |  |
Financial Guarantee Insurance Contracts, Accelerated Premium Revenue, Amount | $ 32,482 | $ 64,494 | $ 52,416 |  |  |  |  |
Ambac UK [Member] |  |  |  |  |  |  |  |
Background And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |
Total Benefit Related to Ballantyne Settlement |  | $ 144,600 |  |  |  |  |  |

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- Definition Junior Surplus Notes issued by the Segregated Account of Ambac Assurance to Ambac upon Ambac's emergence from bankruptcy. These Junior Surplus notes will be includable in surplus for statutory accounting purposes as prescribed or permitted by state laws and regulations. + References No definition available. + Details
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- Definition Amount of Senior Surplus Notes Outstanding on June 8, 2020 + References No definition available. + Details
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- Definition Ability to vote has been restricted for any person owning at least this percentage of common stock to be this percentage minus one vote. + References No definition available. + Details
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- Definition Reflects the effective interest rate on Deferred Amounts and Junior Deferred Amounts of the Segregated Account of Ambac as directed by the Rehabilitator of the Segregated Account. + References No definition available. + Details
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