Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2013
Accounting Policies [Abstract]
Goodwill	Goodwill At the Fresh Start Reporting Date, we revalued our assets and liabilities to current estimated fair value. The excess reorganization value which could not be attributed to the fair value of specific identified tangible and intangible assets was recorded as goodwill. Pursuant to the Intangibles—Goodwill and Other Topic of the ASC, goodwill is not amortized but is subject to annual impairment testing and more frequently if indicators of impairment exist for each reporting unit. The Company has an option to first assess qualitative factors, in their totality, to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a goodwill impairment test as described below. If the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the Company is required to perform the goodwill impairment test. Goodwill impairment is determined using a two-step approach. In the first step of the goodwill impairment test, the fair value of a reporting unit is compared with its carrying amount, including goodwill. In performing the first step, the market capitalization of Ambac is considered in management’s estimate of the fair value of the reporting unit. Determining the allocation of the market capitalization of Ambac to the reporting unit requires the exercise of significant judgment. If the fair value is in excess of the carrying amount, including goodwill, the reporting unit’s goodwill is considered not to be impaired. If the carrying amount, including goodwill of a reporting unit exceeds its fair value, the second step of the goodwill impairment test is performed to measure the amount of impairment loss, if any. In the second step, the implied fair value of a reporting unit’s goodwill is compared with the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination and is defined as the excess of the fair value of a reporting unit over the fair value of the net assets of a reporting unit. If the carrying amount of goodwill exceeds its implied fair value, an impairment loss is recognized for the excess. If the carrying amount of goodwill is less than its implied fair value, no goodwill impairment is recognized. We have assigned all goodwill recorded at the Fresh Start Reporting Date to the Financial Guarantee reporting unit, which corresponds to the Financial Guarantee reportable segment as further described in Note 13—Segment Information. For the five months ended September 30, 2013, there was no goodwill impairment recorded. As a result, initial goodwill of $514,511 recorded at the Fresh Start Reporting Date remains the same at September 30, 2013.
Intangible assets	Intangible assets Insurance intangible: At the Fresh Start Reporting Date, an insurance intangible asset was recorded which represented the difference between the fair value and aggregate carrying value of the financial guarantee insurance and reinsurance assets and liabilities. The carrying values of our financial guarantee insurance and reinsurance contracts will continue to be reported and measured in accordance with existing accounting policies. Pursuant to the Financial Services—Insurance Topic of the ASC, the insurance intangible is to be measured on a basis consistent with the related financial guarantee insurance and reinsurance contracts. The insurance intangible asset will be amortized using a level yield method based on par exposure of the related financial guarantee insurance or reinsurance contracts and will be applied to groups of contracts with similar characteristics. VIE intangible: Effective April 30, 2013, Ambac consolidated a VIE which had assets that included finite lived intangible assets associated with its operations. The intangible assets were recorded at their fair value on the consolidation date in the amount of $164,520. Pursuant to the Intangible—Goodwill and Other Topic of the ASC, the intangibles will be amortized over their useful lives. The useful lives are determined after considering the specific facts and circumstances including, contractual term of any agreement, the long-term strategy for the use of the asset and other economic factors. Furthermore, the VIE intangible is tested for impairment if conditions exist that might indicate the carrying amount of the intangible is not recoverable and exceeds its fair value. Such conditions may include an economic downturn in a geographic market or a change in the assessment of future operations. If such conditions are present, a two-step impairment evaluation is performed. In the first step, a recoverability test is performed by comparing the sum of the estimated undiscounted future cash flows attributable to the intangible asset to its carrying amount. If the undiscounted cash flows are less than the carrying amount, the second step of the test is performed to measure the impairment amount, if any. In the second step, an impairment loss would be recognized to the extent the carrying amount of the intangible exceeds its fair value. For the five months ended September 30, 2013, no VIE intangible impairment was recorded.
Adoption of New Accounting Standards	Adopted: Effective January 1, 2013, Ambac adopted ASU No. 2011-11, Disclosures about Offsetting Assets and Liabilities, and ASU No. 2013-01, Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities retrospectively for all periods presented. Upon the adoption of these ASUs, Ambac presented the offsetting disclosure requirements in Note 10, Derivative Instruments. Effective January 1, 2013, Ambac adopted ASU No. 2013-02, Reporting of Amounts Reclassified out of Accumulated Other Comprehensive Income. Upon the adoption of this ASU, Ambac presented the changes in the accumulated balances by component of other comprehensive income and the corresponding effects on net income by line item for the reclassifications out of accumulated other comprehensive income, in Note 5, Comprehensive Income.
Recently Issued Accounting Standards	Issued: In July 2013, the FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. The objective of this ASU is to eliminate diversity in practice in the presentation of unrecognized tax benefits. The ASU requires an entity to present an unrecognized tax benefit in the financial statements as a reduction to a deferred tax asset for an NOL carryforward, a similar tax loss, or a tax credit carryforward except when: i) an NOL carryforward, a similar tax loss, or a tax credit carryforward is not available as of the reporting date under the governing tax law to settle taxes that would result from the disallowance of the tax position and ii) the entity does not intend to use the deferred tax asset for this purpose. If either of these conditions exists, an entity should present an unrecognized tax benefit in the financial statements as a liability and should not net the unrecognized tax benefit with a deferred tax asset. The ASU is effective prospectively for reporting periods beginning after December 15, 2013, with early adoption permitted. Ambac will adopt the ASU on January 1, 2014. The adoption of this ASU will not have a material effect on Ambac’s financial statements.