Basis of Presentation and Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Consolidation

Consolidation:

The consolidated financial statements include the accounts of Ambac and all other entities in which Ambac (directly or through its subsidiaries) has a controlling financial interest, including variable interest entities (“VIEs”) for which Ambac or an Ambac subsidiary is deemed the primary beneficiary in accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"). All significant intercompany balances have been eliminated. The usual condition for a controlling financial interest is ownership of a majority of the voting interests of an entity. However, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests. A VIE is an entity: a) that lacks enough equity investment at risk to permit the entity to finance its activities without additional subordinated financial support from other parties; or b) where the group of equity holders does not have: (1) the power, through voting rights or similar rights, to direct the activities of an entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb the entity’s expected losses; or (3) the right to receive the entity’s expected residual returns. The determination of whether a variable interest holder is the primary beneficiary involves performing a qualitative analysis of the VIE that includes, among other factors, its capital structure, contractual terms including the rights of each variable interest holder, the activities of the VIE, whether the variable interest holder has the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, whether the variable interest holder has the obligation to absorb losses of the VIE that could potentially be significant to the VIE or the right to receive benefits from the VIE that could potentially be significant to the VIE, related party relationships and the design of the VIE. An entity that is deemed the primary beneficiary of a VIE is required to consolidate the VIE. Refer to Note 3. Special Purpose Entities, Including Variable Interest Entities, for a detailed discussion of Ambac’s involvement in VIEs, Ambac’s methodology for determining whether Ambac is required to consolidate a VIE and the effects of VIEs being consolidated.

Unconsolidated Financial Information

Ambac Unconsolidated Financial Information:

Financial information of Ambac is presented in Schedule II to this Form 10-K as of December 31, 2017 and 2016 and for the years ended December 31, 2017, 2016 and 2015. Investments in subsidiaries are accounted for using the equity method of accounting.

Investments

Investments:

The Investments - Debt and Equity Securities Topic of the ASC requires that all debt instruments and certain equity instruments be classified in Ambac’s Consolidated Balance Sheets according to their purpose and, depending on that classification, be carried at either cost or fair market value. Ambac’s non-VIE investment portfolio is accounted for on a trade-date basis and consists primarily of investments in fixed income securities that are considered available-for-sale as defined by the Investments - Debt and Equity Securities Topic of the ASC. Available-for-sale securities are reported in the financial statements at fair value with unrealized gains and losses, net of deferred taxes, reflected in Accumulated Other Comprehensive Income in Stockholders’ Equity and computed using amortized cost as the basis. For purposes of computing amortized cost, premiums and discounts are accounted for using the effective interest method over the remaining term of the securities. For structured securities with a large underlying pool of homogenous loans, such as mortgage-backed and asset-backed securities, premiums and discounts are adjusted for the effects of actual and anticipated prepayments on a retrospective basis. For other fixed income securities, such as corporate and municipal bonds, premiums and discounts are amortized or accreted over the remaining term of the securities even if they are callable.

Ambac’s non-VIE investment portfolio also includes equity interests in pooled investment funds. Such equity interests in the form of common stock or in-substance common stock are classified as trading securities. Equity interests in pooled funds organized as limited liability companies are recorded under the fair value option in accordance with the Financial Instruments Topic of the ASC. Investments classified either as trading or fair value option securities are reported as Other investments on the Consolidated Balance Sheet at fair value with changes in fair value reported through Net investment income on the Statement of Comprehensive Income. Investments in pooled funds have been classified as trading or fair value option securities so that any undistributed earnings of the funds may be reflected in Net investment income as they occur.

Fair value is based primarily on quotes obtained from independent market sources. When quotes are not available or cannot be reasonably corroborated, valuation models are used to estimate fair value. These models include estimates, made by management, which utilize current market information. The quotes received or modeled valuations could differ materially from amounts that would actually be realized in the market. Realized gains and losses on the sale of investments are determined on the basis of specific identification.

VIE investments in fixed income securities are carried at fair value under the fair value option. For additional information about VIE investments, including fair value by asset-type, see Note 3. Special Purpose Entities, Including Variable Interest Entities.

Ambac has a formal impairment review process for fixed income available for sale securities in its investment portfolio. Ambac conducts a review each quarter to identify and evaluate investments that have indications of impairment that may be other than temporary in accordance with the Investments - Debt and Equity Securities Topic of the ASC. Factors considered to identify and assess securities for other than temporary impairment include: (i) fair values that have declined by 20% or more below amortized cost; (ii) market values that have declined by 5% or more but less than 20% below amortized cost for a continuous period of at least six months; (iii) recent downgrades by rating agencies; (iv) the financial condition of the issuer and financial guarantor, as applicable, and an analysis of projected defaults on the underlying collateral; (v) scheduled interest payments are past due; (vi) whether Ambac has the intent to sell the security; and (vii) whether it is more likely than not that Ambac will be required to sell a security before the anticipated recovery of its amortized cost basis. If we believe a decline in the fair value of a particular investment is temporary, we record the decline as an unrealized loss net of tax in Accumulated Other Comprehensive Income in Stockholders’ Equity on our Consolidated Balance Sheets. If management either: (i) has the intent to sell its investment in a debt security or (ii) determines that the Company more likely than not will be required to sell the debt security before its anticipated recovery of the amortized cost basis less any current period credit impairment, then an other-than-temporary impairment charge is recognized in earnings, with the amortized cost of the security being written-down to fair value. If these conditions are not met, but it is determined that a credit loss exists, the credit impairment loss is recognized in earnings, and the other-than-temporary amount related to all other factors is recognized in other comprehensive income. For fixed income securities that have other-than-temporary impairments in a period, the previous amortized cost of the security less the amount of the other-than-temporary impairment recorded through earnings becomes the investment’s new cost basis. Ambac accretes the new cost basis to par or to the estimated future cash flows to be recovered over the expected remaining life of the security.

The evaluation of securities for impairment is a quantitative and qualitative process, which is subject to risks and uncertainties and is intended to determine whether, and to what extent, declines in the fair value of investments should be recognized in current period earnings. The risks and uncertainties include changes in general economic conditions, the issuer’s or guarantor’s financial condition and/or future prospects, the impact of regulatory actions on the investment portfolio, the performance of the underlying collateral, the effects of changes in interest rates or credit spreads and the expected recovery period. With respect to Ambac insured securities owned, future cash flows used to measure credit impairment represents the sum of (i) the bond’s intrinsic cash flows and (ii) the estimated Ambac Assurance claim payments. For Ambac-insured securities owned and guaranteed under policies that were allocated to the Segregated Account, the estimate of Ambac Assurance claim payments included interest on Deferred Amounts, which were discharged on February 12, 2018. Ambac estimated the timing of claim payment receipts on all Ambac-insured securities owned, but the actual timing of such amounts for Segregated Account securities was at the sole discretion of the Rehabilitator. Refer to Note 1. Background and Business Description for more information on the Segregated Account and the Segregated Account Rehabilitation Proceedings. Ambac’s assessment about whether a decline in value is other-than-temporary reflects management’s current judgment regarding facts and circumstances specific to a security and the factors noted above, including Ambac's intention to sell securities and ability to hold temporarily impaired securities until recovery. If that judgment changes, Ambac may ultimately record a charge for other-than-temporary impairment in future periods.

Net Premiums Earned

Net Premiums:

Gross premiums are received either upfront or in installments. For premiums received upfront, an unearned premium revenue (“UPR”) liability is established, which is initially recorded as the cash amount received. For installment premium transactions, a premium receivable asset and offsetting UPR liability is initially established in an amount equal to: (i) the present value of future contractual premiums due (the “contractual” method) or (ii) if the underlying insured obligation is a homogenous pool of assets which are contractually prepayable, the present value of premiums to be collected over the expected life of the transaction (the “expected” method). An appropriate risk-free rate corresponding to the weighted average life of each policy and currency is used to discount the future premiums contractually due or expected to be collected. For example, U.S. dollar exposures are discounted using U.S. Treasury rates while exposures denominated in a foreign currency are discounted using the appropriate risk-free rate for the respective currency. The weighted average risk-free rate at December 31, 2017 and 2016, was 2.5%. and 2.6%, respectively, and the weighted average period of future premiums used to estimate the premium receivable at December 31, 2017 and 2016, was 9.8 years and 9.0 years, respectively.

Insured obligations consisting of homogeneous pools for which Ambac uses expected future premiums to estimate the premium receivable and UPR include residential mortgage-backed securities. As prepayment assumptions change for homogenous pool transactions, or if there is an actual prepayment for a “contractual” method installment transaction, the related premium receivable and UPR are adjusted in equal and offsetting amounts with no immediate effect on earnings using new premium cash flows and the then current risk-free rate corresponding to the initial weighted average life of the related policy.

For both upfront and installment premium policies, premium revenues are earned over the life of the financial guarantee contract in proportion to the insured principal amount outstanding at each reporting date (referred to as the level-yield method). For installment paying policies, the premium receivable discount, equating to the difference between the undiscounted future installment premiums and the present value of future installment premiums, is accreted as premiums earned in proportion to the premium receivable balance at each reporting date.

Similar to gross premiums, premiums ceded to reinsurers are paid either upfront or in installments. For premiums paid upfront, a deferred ceded premium asset is established which is initially recorded as the cash amount paid. For installment premiums, a ceded installment premiums payable liability and offsetting deferred ceded premium asset are initially established in an amount equal to: i) the present value of future contractual premiums due or ii) if the underlying insured obligation is a homogenous pool of assets which are contractually pre-payable, the present value of expected premiums to be paid over the life of the transaction. An appropriate risk-free rate corresponding to the weighted average life of each policy and exposure currency is used to discount the future premiums contractually due or expected to be collected. Premiums ceded to reinsurers reduce the amount of premiums earned by Ambac from its financial guarantee insurance policies. For both upfront and installment premiums, ceded premiums written are primarily recognized in earnings in proportion to and at the same time as the related gross premium revenue is recognized. For premiums paid to reinsurers on an installment basis, Ambac records the present value of future ceding commissions as an offset to ceded premiums payable, using the same assumptions noted above for installment premiums.

When a bond issue insured by Ambac has been retired early, typically due to an issuer call, any remaining UPR is recognized at that time to the extent the financial guarantee contract is legally extinguished, causing accelerated premium revenue. For installment premium paying transactions, we offset the recognition of any remaining UPR by the reduction of the related premium receivable to zero (as it will not be collected as a result of the retirement), which may cause negative accelerated premium revenue. Certain obligations insured by Ambac have been legally defeased whereby government securities are purchased by the issuer with the proceeds of a new bond issuance, or less frequently with other funds of the issuer, and held in escrow. The principal and interest received from the escrowed securities are then used to retire the Ambac-insured obligations at a future date either to their maturity date (a refunding) or a specified call date (a pre-refunding). Ambac has evaluated the provisions in policies issued on these obligations and determined those insurance policies have not been legally extinguished. For policies with refunding securities, premium revenue recognition is not impacted as the escrowed maturity date is the same as the previous legal maturity date. For policies with pre-refunding securities, the maturity date of the pre-refunded security has been shortened from its previous legal maturity. Although premium revenue recognition has not been accelerated in the period of the pre-refunding, it results in an increase in the rate at which the policy's remaining UPR is to be recognized.

Loans

Loans:

Loans are reported at either their outstanding principal balance less unamortized discount or at fair value. For loans reported at their outstanding principal balance less unamortized discount (non-VIE loans), interest income is earned using the effective interest method based upon interest accrued on the unpaid principal balance adjusted for accretion of discounts. A loan is considered impaired when, based on the financial condition of the borrower, it is probable that Ambac will be unable to collect all principal and interest due according to the contractual terms of the loan agreement. Loans held by VIEs consolidated as required under the Consolidation Topic of the ASC are carried at fair value, with changes in fair value recorded in Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income.

Derivative Contracts

Derivative Contracts:

The Company has entered into derivative contracts both for trading purposes and to hedge certain economic risks inherent in its financial asset and liability portfolios. None of Ambac’s derivative contracts are designated as hedges under the Derivatives and Hedging Topic of the ASC. Ambac's derivatives consist primarily of credit derivatives, interest rate swaps and futures contracts. Ambac’s credit derivative contracts are accounted for at fair value since they do not qualify for the financial guarantee scope exception under the Derivatives and Hedging Topic of the ASC. Changes in fair value of credit derivatives are recorded in Net change in fair value of credit derivatives on the Consolidated Statements of Total Comprehensive Income. Ambac maintains a derivatives portfolio consisting primarily of interest rate swaps and futures contracts to economically hedge interest rate risk in the financial guarantee and investment portfolios. This portfolio also includes legacy interest rate swaps with asset-backed securitization issuers, states, municipalities and their authorities which were written in connection with their financings. Changes in fair value of all interest rate derivatives are recorded in net gains (losses) on interest rate derivatives on the Consolidated Statements of Total Comprehensive Income. VIEs consolidated under the Consolidation Topic of the ASC entered into derivative contracts to meet specified purposes within their securitization structure. Changes in fair value of consolidated VIE derivatives are included within Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income.

All derivatives are recorded on the Consolidated Balance Sheets at fair value on a gross basis; assets and liabilities are netted by counterparty only when a legal right of offset exists. Ambac has determined that the amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral may not be used to offset amounts due under the derivative instruments in the normal course of settlement. Therefore, such amounts are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement. Effective January 3, 2017, as a result of rule changes by the central clearing party ("CCP"), variation payments are considered settlements of the associated derivative balance and are reflected as a reduction to derivative liabilities on the Consolidated Balance Sheet at December 31, 2017. For periods presented prior to this rule change, variation payments were included in "Other assets" on the Consolidated Balance Sheet. Refer toNote 11. Derivative Instrumentsfor further discussion of the Company’s use of derivative instruments and their impact of the consolidated financial statements, including details of the CCP rule change. Refer to Note 9. Fair Value Measurements for further description of the methodologies used to determine the fair value of derivative contracts, including model inputs and assumptions where applicable.

Goodwill

Goodwill:

Under the Reorganization Topic of the ASC, the Company determined that fresh start financial statement reporting was to be applied upon our emergence from Chapter 11 because (i) the reorganization value of the emerging entity was less than total post-petition liabilities and allowed claims, and (ii) the holders of existing voting shares immediately before the confirmation of the Reorganization Plan received less than 50% of the voting shares of the emerging entity. Specifically, fresh start reporting was applied upon confirmation of the Reorganization Plan by the Bankruptcy Court and the satisfaction of the remaining material contingencies necessary to complete implementation of the Reorganization Plan. All conditions required for the adoption of fresh start reporting were satisfied by the Company on April 30, 2013 (“Fresh Start Reporting Date”) when Ambac executed a closing agreement with the United States Internal Revenue Service (the "IRS") to conclude the settlement of a dispute. As such, fresh start financial statement reporting ("Fresh Start") was adopted by the Company on April 30, 2013, incorporating, among other things, the discharge of debt obligations, issuance of new common stock and fair value adjustments. 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 ("fair value of net 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.

We tested goodwill for impairment as of October 1^st of each year. Goodwill is also tested more frequently if indicators of impairment exist for each reporting unit. During the third quarter of 2015, Ambac determined sufficient indicators of potential impairment existed to perform an interim goodwill impairment evaluation for the reporting unit to which goodwill was assigned. Those indicators included the trading values of Ambac stock and changes in Ambac credit spreads. In conducting the goodwill impairment analysis, we performed step one of the goodwill impairment test where we estimated the fair value of the reporting unit using a market approach, which was derived using: i) Ambac’s common stock and warrant market capitalization, ii) fair value estimates of Ambac Assurance preferred shares (reported as noncontrolling interests on Ambac's balance sheet) and iii) an estimated control premium. Step one of the impairment test indicated the reporting unit's carrying value exceeded its fair value.

Accordingly, the Company performed step two of the impairment test, which indicated the implied fair value of goodwill was zero. This was the result of substantial decreases in the reporting unit's fair value and substantial increases in the fair value of its net assets. The fair value of the reporting unit decreased significantly due to a material decrease in Ambac's market capitalization components (described above). The reporting unit's fair value of net assets increased significantly primarily as a result of a decrease in the estimated fair value of financial guarantee liabilities and, to a lesser extent, a decrease in the fair value of long-term debt. The fair value decrease in financial guarantee liabilities, which is a Level 3 estimate, was primarily driven by wider Ambac credit spreads and positive loss and loss expense reserves development. Please refer to Note 9. Fair Value Measurements for further discussion on the fair value model for financial guarantee liabilities. The fair value decrease in long-term debt was driven by lower market pricing on surplus notes and junior surplus notes.

As a result, the Company recorded a full non-cash, non-tax deductible goodwill impairment charge of $514,511 in 2015.

Intangible Assets

Insurance Intangible Asset:

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 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 is amortized using a level yield method based on par exposure of the related financial guarantee insurance or reinsurance contracts and is applied to groups of contracts with similar characteristics.

Restricted Cash

Restricted Cash:

Cash that we do not have the right to use for general purposes is recorded as restricted cash in our consolidated balance sheets. Restricted cash includes consolidated variable interest entity cash restricted to fund the obligations of the consolidated VIEs.

Loss Reserves

Loss and Loss Expenses:

The loss and loss expense reserve (“loss reserve”) policy relates only to Ambac’s non-derivative insurance business for insurance policies issued to beneficiaries, including VIEs, for which we do not consolidate the VIE. Losses and loss expenses are based upon estimates of the ultimate aggregate losses inherent in the non-derivative financial guarantee portfolio as of the reporting date. The policy for derivative contracts is discussed in the “Derivative Contracts” section above. A loss reserve is recorded on the balance sheet on a policy-by-policy basis. Loss reserve components of an insurance policy include unpaid claims and the present value ("PV") of expected net cash flows required to be paid under an insurance contract, further described below:

• Unpaid claims represent the sum of (i) claims not yet paid for policies allocated to the Segregated Account, including Deferred Amounts (as defined in Note 1. Background and Business Description) and (ii) accrued interest on Deferred Amounts (generally at an effective rate of 5.1%.) as required by the Segregated Account Rehabilitation Plan. Refer to Note 1. Background and Business Descriptionfor further discussion of the Segregated Account Rehabilitation Plan. Unpaid claims are measured based on the cost of settling the claims, which is principal plus accrued interest.

• The PV of expected net cash flows represents the PV of expected cash outflows less the PV of expected cash inflows. The PV of expected net cash flows are impacted by: (i) expected future claims to be paid under an insurance contract, including the impact of potential settlement outcomes upon future installment premiums, (ii) expected recoveries from contractual breaches of RMBS representations and warranties by transaction sponsors, which is discussed further in the “RMBS Representation and Warranty Subrogation Recoveries” section below, (iii) excess spread within the underlying transaction's cash flow structure, and (iv) other subrogation recoveries, including expected receipts from third parties within the underlying transaction's cash flow structure. Ambac’s approach to resolving disputes involving contractual breaches by transaction sponsors or other third parties has included negotiations and/or pursuing litigation. Ambac does not include potential recoveries attributed solely to fraudulent inducement claims in our estimate of subrogation recoveries, since any remedies under such claims would be non-contractual.

Net cash outflow policies represent contracts where the sum of unpaid claims plus the PV of expected cash outflows are greater than the PV of expected cash inflows. For such policies, a “Loss and loss expense reserves” liability is recorded for the sum of: (i) unpaid claims plus (ii) the excess of the PV of expected net cash outflows over the unearned premium revenue. Net cash inflow policies represent contracts where losses have been paid, but not yet recovered, such that the PV of expected cash inflows are greater than the sum of unpaid claims plus the PV of expected cash outflows. For such policies, a “Subrogation recoverable” asset is recorded for the difference between (i) the PV of expected net cash inflows and (ii) unpaid claims.

The approaches used to estimate expected future losses and recoveries considers the likelihood of all possible outcomes. The evaluation process for determining expected losses is subject to certain judgments based on our assumptions regarding the probability of default by the issuer of the insured security, probability of settlement outcomes (which may include commutation settlements, refinancing and/or other settlement outcomes) and expected severity of credits for each insurance contract. Ambac’s loss reserves are based on management’s ongoing review of the financial guarantee credit portfolio. Active surveillance of the insured portfolio enables Ambac’s Risk Management Group ("RMG") to track credit migration of insured obligations from period to period and update internal classifications and credit ratings for each transaction. Non-adversely classified credits are assigned a Class I rating while adversely classified credits are assigned a rating of Class IA through Class V. The criteria for an exposure to be assigned an adversely classified credit rating includes the deterioration of an issuer’s financial condition, underperformance of the underlying collateral (for collateral dependent transactions such as mortgage-backed or student loan securitizations), poor performance by the servicer of the underlying collateral and other adverse economic events or trends. The servicer of the underlying collateral of an insured securitization transaction is a consideration in assessing credit quality because the servicer’s performance can directly impact the performance of the related issue. For example, a servicer of a mortgage-backed securitization that does not remain current in its collection loss mitigation efforts could cause an increase in the delinquency and potential default of the underlying obligation. Similarly, loss severities increase when a servicer does not effectively handle loss mitigation activities such as (i) the advancing of delinquent principal and interest and of default related expenses which are deemed to be recoverable by the servicer, (ii) pursuit of loan charge-offs which maximize cash flows from the mortgage loan pool, and (iii) foreclosure and real estate owned disposition strategies and timelines. All credits are assigned risk classifications by RMG using the following guidelines:

CLASS I - “Fully Performing - Meets Ambac Criteria with Remote Probability of Claim” - Credits that demonstrate adequate security and structural protection with a strong capacity to pay interest, repay principal and perform as underwritten. Factors supporting debt service payment and performance are considered unlikely to change and any such change would not have a negative impact upon the fundamental credit quality. Through ongoing surveillance, Ambac may also designate Class I credits into one or more of the following categories:

• Survey list - credits that may lack information or demonstrate a weakness but further deterioration is not expected.

• Watch list - credits that demonstrate the potential for future material adverse development due to such factors as long-term uncertainty about a particular sector, a certain structural element related to the issuer or transaction or overall financial and economic sustainability.

CLASS IA - “Potential Problem with Risks to be Dimensioned”- Credits that are fully current and monetary default or claims-payment are not anticipated. The payor’s or issuer’s financial condition may be deteriorating or the credits may lack adequate collateral. A structured financing may also evidence weakness in its fundamental credit quality as evidenced by its under-performance relative to its modeled projections at underwriting, issues related to the servicer’s ability to perform or questions about the structural integrity of the transaction. While certain of these credits may still retain an investment grade rating, they usually have experienced or are vulnerable to a ratings downgrade. Further investigation is required to dimension and correct any deficiencies. A complete legal review of documents may be required. An action plan should be developed with triggers for future classification changes upward or downward.

CLASS II - “Substandard Requiring Intervention”- Credits whose fundamental credit quality has deteriorated to the point that timely payment of debt service may be jeopardized by adversely developing trends of a financial, economic, structural, managerial or political nature. No claim payment is currently foreseen but the probability of loss or claim payment over the life of the transaction is now existent (generally 10% or greater probability). Class II credits may be border-line or below investment grade (BBB- to B). Prompt and sustained action must be taken to execute a comprehensive loss mitigation plan and correct deficiencies.

CLASS III - “Doubtful with Clear Potential for Loss” - Credits whose fundamental credit quality has deteriorated to the point that timely payment of debt service has been or will be jeopardized by adverse trends of a financial, economic, structural, managerial or political nature which, in the absence of positive change or corrective action, are likely to result in a loss. The probability of monetary default or claims paying over the life of the transaction is generally 50% or greater. Full exercise of all available remedial actions is required to avert or minimize losses. Class III credits will generally be rated below investment grade (B to CCC).

CLASS IV - “Imminent Default or Defaulted” - Monetary default or claim payments have occurred or are expected imminently. Class IV credits are generally rated D.

CLASS V - “Fully Reserved” - The credit has defaulted and payments have occurred. The claim payments are scheduled and known, reserves have been established to fully cover such claims, and no claim volatility is expected.

The population of credits evaluated in Ambac’s loss reserve process are: (i) all adversely classified credits (Class IA through V) and ii) non-adversely classified credits which had an internal Ambac rating downgrade since the transaction’s inception. One of two approaches is then utilized to estimate losses to ultimately determine if a loss reserve should be established. The first approach is a statistical expected loss approach, which considers the likelihood of all possible outcomes. The “base case” statistical expected loss is the product of: (i) the par outstanding on the credit; (ii) internally developed historical default information (taking into consideration internal ratings and average life of an obligation); (iii) internally developed loss severities; and (iv) a discount factor. The loss severities and default information are based on rating agency information, are specific to each bond type and are established and approved by senior RMG officers. For certain credit exposures, Ambac’s additional monitoring, loss remediation efforts and probabilities of potential settlement outcomes may provide information relevant to adjust this estimate of “base case” statistical expected losses. Analysts may accept the “base case” statistical expected loss as the best estimate of expected loss or assign multiple probability weighted scenarios to determine an adjusted statistical expected loss that better reflects management’s view of a given transaction’s expected losses, as well as the potential for additional remediation activities (i.e., commutations).

The second approach entails the use of cash-flow based models to estimate expected losses (future claims, net of potential recoveries, expected to be paid to the holder of the insured financial obligation). Ambac’s RMG group will consider the likelihood of all possible outcomes and develop appropriate cash flow scenarios. This approach can include the utilization of internal or third party models to project future losses and resultant claim payment estimates. We utilize cash flow models for residential mortgage-backed (RMBS), student loan, and other exposures. RMBS and student loan models use historical performance of the collateral pools in order to then derive future performance characteristics, such as default and voluntary prepayment rates, which in turn determine projected future claim payments. In other cases, such as many public finance exposures, including our Puerto Rico exposures, we do not specifically forecast resources available to pay debt service in the cash flow model itself. Rather, we consider the issuers’ overall ability and willingness to pay, including the fiscal, economic, legal and political framework. In this approach a probability-weighted expected loss estimate is developed based on assigning probabilities to multiple claim payment scenarios and applying an appropriate discount factor. Additionally, we assign a probability to the issuer’s ability to refinance an insured issue and/or Ambac’s ability to execute a potential settlement (i.e., commutation) of the insurance policy, including the impact on future installment premiums. The commutation scenarios and the related probabilities of occurrence vary by transaction, depending on our view of the likelihood of negotiating such a transaction with issuers and/or investors.

The discount factor applied to the statistical expected loss approach is based on a risk-free discount rate corresponding to the remaining expected weighted-average life of the exposure and the exposure currency. For the cash flow scenario approach, discount factors are applied based on a risk-free discount rate term structure and correspond to the date of each respective cash flow payment or recovery and the exposure currency. Discount factors are updated for the current risk-free rate each reporting period.

Ambac establishes loss expense reserves based on our estimate of expected net cash outflows for loss expenses, such as legal and consulting costs.

RMBS Representation and Warranty Subrogation Recoveries:

Ambac records as a component of its loss reserve estimate, subrogation recoveries related to securitized loans in RMBS transactions that breached certain representations and warranties described herein. Generally, the sponsor of a RMBS transaction provided representations and warranties with respect to the securitized loans, including representations and warranties with respect to loan characteristics, the absence of borrower fraud in the underlying loan pools and other misconduct in the origination process and attesting to the compliance of loans with the prevailing underwriting policies. In such cases, the sponsor of the transaction is contractually obligated to repurchase, cure or substitute collateral for any loan that breaches the representations or warranties. Ambac or its counsel have engaged consultants with significant mortgage underwriting experience to review the underwriting documentation for mortgage loans underlying certain insured RMBS transactions which exhibited exceptionally poor performance. Factors which Ambac believes to be indicative of poor performance include (i) increased levels of early payment defaults, (ii) significant numbers of loan liquidations or charge-offs and resulting high levels of losses, and (iii) rapid elimination of credit protections inherent in the transactions’ structures. With respect to item (ii), “loan liquidations” refers to loans for which the servicer has liquidated the related collateral and the securitization has realized losses on the loan; “charge-offs” refers to loans which have been written off as uncollectible by the servicer, generating no recoveries to the securitization, and may also refer to the unrecovered balance of liquidated loans. In either case, the servicer has taken actions to recover against the collateral, and the securitization has incurred losses to the extent such actions did not result in full repayment of the borrower’s obligations.

Generally, subsequent to the forensic exercise of examining loan files to ascertain whether the loans conformed to the representations and warranties, we submit nonconforming loans for repurchase to the contractual counterparty bearing the repurchase obligation, which is typically the transaction sponsor. To effect a repurchase, depending on the transaction, the sponsor is obligated to repurchase the loan at (a) for loans which have not been liquidated or charged off, either (i) the current unpaid principal balance of the loan, (ii) the current unpaid principal balance plus accrued unpaid interest, or (iii) the current unpaid principal balance plus accrued interest plus unreimbursed servicer advances/expenses and/or trustee expenses resulting from the breach of representations and warranties that trigger the repurchase, and (b) for a loan that has already been liquidated or charged-off, the amount of the realized loss (which in certain cases may exclude accrued unpaid interest). In cases where loans are repurchased by a sponsor, the effect is typically to offset current period losses and then to increase the over-collateralization of the securitization, depending on the extent of loan repurchases and the structure of the securitization. Specifically, the repurchase price is paid by the sponsor to the securitization trust which holds the loan. The cash becomes an asset of the trust, replacing the loan that was repurchased by the sponsor. On a monthly basis the cash received related to loan repurchases by the sponsor is aggregated with cash collections from the underlying mortgages and applied in accordance with the trust indenture payment waterfall. This payment waterfall typically includes principal and interest payments to the note holders, various expenses of the trust and reimbursements to Ambac, as financial guarantor, for previously paid claims. Notwithstanding the reimbursement of previous claim payments, to the extent there continues to be insufficient cash in the waterfall in the current month to make scheduled principal and interest payments to the note holders, Ambac is required to make additional claim payments to cover this shortfall. Ambac may also receive payments directly from transaction sponsors in settlement of their repurchase obligations pursuant to negotiated settlement agreements or otherwise as a result of related litigation.

While the obligation by sponsors to repurchase loans with material breaches is clear, generally the sponsors have not yet honored those obligations without actual or threatened litigation. Ambac has utilized the results of the above described loan file examinations to make demands for loan repurchases from sponsors or their successors and, in certain instances, as a part of the basis for litigation. Ambac’s approach to resolving these disputes has included negotiating with individual sponsors at the transaction level and in some cases at the individual loan level and has resulted in the repurchase of some loans. Ambac has initiated and will continue to pursue lawsuits seeking compliance with the repurchase obligations in the securitization documents.

Ambac has performed the above-mentioned, detailed examinations on a variety of second-lien and first-lien transactions that have experienced exceptionally poor performance. However, the loan file examinations and related estimated recoveries we have reviewed and recorded to date have been limited to only those transactions whose sponsors (or their successors) are subsidiaries of large financial institutions, all of which carry an investment grade rating from at least one nationally recognized rating agency, or are otherwise deemed to have the financial wherewithal to live up to their repurchase obligations. While our contractual recourse is generally to the sponsor/subsidiary, rather than to the parent, each of these large institutions has significant financial resources and may have an ongoing interest in mortgage finance, and we therefore believe that the financial institution/parent would ultimately assume financial responsibility for these obligations if the sponsor/subsidiary is unable to honor its contractual obligations or pay a judgment that we may obtain in litigation. Additionally, in the case of successor institutions, we are not aware of any provisions that explicitly preclude or limit the successors’ ability to honor the obligations of the original sponsor. Certain successor financial institutions have made significant payments to certain claimants to settle breaches of representations and warranties perpetrated by sponsors that have been acquired by such financial institutions. In addition, Ambac received a significant payment in 2016 from JP Morgan to settle RMBS-related litigation. As a result of these factors, we did not make significant adjustments to our estimated subrogation recoveries with respect to the credit risk of these sponsors or their successors.

Our ability to recover the RMBS subrogation recoveries is subject to significant uncertainty, including risks inherent in litigation, collectability of such amounts from counterparties and/or their respective parents and affiliates, timing of receipt of any such recoveries, intervention by OCI which could impede our ability to take actions required to realize such recoveries and uncertainties inherent in the assumptions used in estimating such recoveries.

The approach used to estimate subrogation recoveries is based on obtaining a random sample of the original loans in the pool, using a protocol developed by a statistical expert. The ratio of: (a) loans identified in the sample as having materially breached representations and warranties to (b) the total loan sample size, is applied (extrapolated) to the sum of realized and estimated future collateral pool losses to determine an estimated repurchase obligation. We limit the estimated repurchase obligation by ever-to-date incurred losses, with respect to the remaining steps in this approach.

Multiple probability-weighted scenarios are developed by applying various realization factors to the estimated repurchase obligation. The realization factors in these scenarios were developed using Ambac’s own assumptions about the likelihood of outcomes based on all the information available to it including, but not limited to, (i) discussions with external legal counsel and their views on ultimate settlement and/or litigation outcomes, (ii) experience with loan put back negotiations where the existence of a material breach was debated and negotiated at the loan level, (iii) the pervasiveness of the breach rates and (iv) experience in settling similar claims. The probability weightings are developed based on the unique facts and circumstances for each transaction. The sum of these probability-weighted scenarios represents the undiscounted subrogation recovery, which is then discounted using a factor derived from a risk-free discount rate term structure that corresponds to the date of each respective recovery. Discount factors are updated for the current risk-free rate each reporting period.

Obligations Under Investment Agreements and Investment Repurchase Agreements

Obligations under Investment Agreements:

Ambac's investment agreements were written principally to asset-backed and structured finance issuers, states, municipalities and municipal authorities, and required Ambac to pay an agreed-upon rate of interest based on funds deposited. Proceeds from these investment agreement obligations were used to invest in fixed income investments. Interest income from these investments was included in Net investment income on the Consolidated Statements of Total Comprehensive Income. The principal amount outstanding under investment agreements of $82,358, with a variable interest rate of 0.94%, at December 31, 2016 was repaid during the first quarter of 2017.

Obligations under investment agreements are reported as liabilities on the Consolidated Balance Sheets at their principal value less unamortized discount. The carrying value of these obligations is adjusted for principal paid and interest credited to the account. Interest expense is computed based upon daily outstanding liability balances at rates and periods specified in the agreements adjusted for accretion of discount, and is included in Interest expense on the Consolidated Statements of Total Comprehensive Income.

Debt, Policy

Long-Term Debt:

Long-term debt issued by Ambac is carried at par value less unamortized discount. Accrued interest and discount accretion on long-term debt is reported as Interest expense on the Consolidated Statements of Total Comprehensive Income. To the extent Ambac repurchases or redeems its long-term debt, such repurchases or redemptions may be settled for an amount different than the carrying value of the obligation. Any difference between the settlement payment and carrying value of the obligation is reported in Net realized gains (losses) on extinguishment of debt on the Consolidated Statements of Total Comprehensive Income.

Long-term debt issued by VIEs consolidated as a result of Ambac's variable interest arising from financial guarantees written by Ambac's subsidiaries, is carried at fair value with changes in fair value recorded as Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income.

Noncontrolling Interest Policy [Policy Text Block]

Noncontrolling Interest:

At December 31, 2016 and 2017, Ambac Assurance had 26,411 shares of issued and outstanding auction rate preferred shares with a liquidation preference of $660,300 (reported as noncontrolling interest of $264,110 on Ambac's balance sheet). The auction occurs every 28 days. Due to the dislocation in the auction rate markets and the Company’s financial condition, the dividend rate on the auction market preferred has continuously been reset at the maximum rate of one-month LIBOR plus 200 basis points.

Under the terms of the preferred stock, dividends may not be paid on the common stock of Ambac Assurance unless all accrued and unpaid dividends on the preferred stock for the then current dividend period have been paid, provided, that dividends on the common stock may be made at all times for the purpose of, and only in such amounts as are necessary for, enabling Ambac (i) to service its indebtedness for borrowed money as such payments become due or (ii) to pay its operating expenses. If dividends are paid on the common stock as provided in the prior sentence, dividends on the preferred stock become cumulative until the date that all accumulated and unpaid dividends have been paid on the preferred stock. Ambac Assurance has not paid dividends on its preferred stock since 2010.

Postretirement and Postemployment Benefits

Postretirement and Postemployment Benefits:

Ambac provides postretirement and postemployment benefits, including health and life benefits covering employees who meet certain age and service requirements. Ambac accounts for these benefits under the accrual method of accounting. Amounts related to the postretirement health benefits liability are established and charged to expense based on actuarial determinations.

Long Term Incentive and Stock Compensation Plan

Incentive Compensation:

Incentive compensation is a key component of our compensation strategy. Our incentive compensation awards generally have two components: short term incentive compensation (consisting of an annual cash bonus and deferred stock units for certain officers) and long term incentive plan awards (consisting of cash awards and performance stock units). Annual decisions with regard to incentive compensation are generally made in the first quarter of each year and are based on Company performance and individual and business unit performance of the prior year.

The Ambac 2013 Incentive Compensation Plan (the “Equity Plan”) provides for the granting of stock options, restricted stock, stock appreciation rights, restricted and performance units and other awards that are valued or determined by reference to Ambac's common stock to employees and directors. In March 2014, Ambac developed a long term incentive compensation plan (“LTIP”) as a sub-plan of the 2013 Plan. This LTIP allows for both cash and equity performance awards to US employees. In 2015, Ambac UK 's Board of Directors adopted a long term incentive plan which provides cash based performance awards to Ambac UK employees.

Prior to the adoption of ASU 2016-09 (as noted below), Ambac recognized compensation costs for all equity classified awards granted at fair value with an estimation of forfeitures for all unvested shares. As a result of the adoption of ASU 2016-09 in 2017, Ambac recognizes compensation costs for all equity classified awards granted at fair value and records forfeitures for unvested shares only when they occur.

• Deferred stock units granted vest upon grant and will settle and convert to Ambac common stock annually over a two-year period (50% on the first anniversary of the grant date and 50% on the second anniversary of the grant date). The fair value of these grants is recognized as compensation expense on the date of grant since no future service is required.

• Restricted stock units granted only require future service and accordingly the respective fair value is amortized into compensation expense over the relevant service period.

• Performance stock units granted and performance cash awards require both future service and achieving specified performance targets to vest and accordingly compensation costs are only recognized when the achievement of the performance conditions are considered probable. Once deemed probable, such compensation costs are amortized over the relevant service period. Compensation costs are initially based on the probable outcome of the performance conditions and adjusted for subsequent changes in the estimated or actual outcome each reporting period as necessary. Changes in the estimated or actual outcome of a performance condition are recognized by reflecting a retrospective adjustment to compensation cost in the current period.

Depreciation and Amortization

Depreciation and Amortization:

Depreciation of furniture and fixtures and electronic data processing equipment is charged over the estimated useful lives of the respective assets, ranging from three to five years, using the straight-line method. Amortization of leasehold improvements is charged over the remaining term of the respective operating lease using the straight-line method.

Foreign Currency

Foreign Currency:

Financial statement accounts expressed in foreign currencies are translated into U.S. dollars in accordance with the Foreign Currency Matters Topic of the ASC. The functional currencies of Ambac's subsidiaries are the local currencies of the country where the respective subsidiaries are based, which are also the primary operating environments in which the subsidiaries operate.

Foreign currency translation: Functional currency assets and liabilities of Ambac’s foreign subsidiaries are translated into U.S. dollars using exchange rates in effect at the balance sheet dates and the related translation adjustments, net of deferred taxes, are included as a component of Accumulated Other Comprehensive Income in Stockholders' Equity. Consolidated Statements of Total Comprehensive Income (Loss) accounts expressed in functional currencies are translated using average exchange rates.

Foreign currency transactions: The impact of non-functional currency transactions and the remeasurement of non-functional currency assets and liabilities into the respective subsidiaries' functional currency (collectively "foreign currency transactions gains/(losses)") are $21,116, $(39,128) and $(17,010) for the years ended December 31, 2017, 2016 and 2015, respectively. Foreign currency transactions gains/(losses) are primarily the result of remeasuring Ambac UK's assets and liabilities denominated in currencies other than its functional currency, primarily the U.S. dollar and the Euro. The significant components of foreign currency transaction gains/(losses), including the respective classifications in the Consolidated Statement of Total Comprehensive Income, are as follows:

• Remeasurement of loss reserves, classified in Loss and loss expenses, in the amount of $28,939, $(77,578) and $(24,838) for the years ended December 31, 2017, 2016 and 2015, respectively;

• Realized gain (loss) from the sale of investment securities and the unrealized gains (losses) of trading and short-term investment securities, classified in Net realized investment gains, in the amount of $(4,769), $30,179 and $5,816 for the years ended December 31, 2017, 2016 and 2015, respectively;

• Remeasurement of premium receivables, classified in Other income, in the amount of $(1,904), $8,003 and $(2,555) for the years ended December 31, 2017, 2016 and 2015, respectively; and

• Remeasurement of credit derivative liabilities, classified in Net change in fair value of credit derivative, in the amount of $(1,150), $32 and $3,981 for the years ended December 31, 2017, 2016 and 2015, respectivel

Income Taxes

Income Taxes:

Ambac files a consolidated U.S. Federal income tax return with its subsidiaries. Ambac UK files tax returns in both the United Kingdom and Italy (for its Milan branch). Current tax assets and liabilities are recognized for taxes refundable or payable for the current year. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on current and deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. In December 2017, the Tax Cut and Jobs Act ("TCJA") was enacted that introduces significant changes that impact U.S. corporate tax rates, business-related exclusions, and deductions and credits effective January 1, 2018. As such, we incorporated the effects of the TCJA in our current and deferred tax evaluation for the year ended December 31, 2017.

Ambac evaluates our deferred income taxes quarterly to determine if valuation allowances are required. The Income Taxes Topic of the ASC requires that companies assess whether valuation allowances should be established against their deferred tax assets based on the consideration of all available evidence using a ‘more likely than not” standard. In making such judgments, significant weight is given to evidence that can be objectively verified.

The level of deferred tax asset recognition is influenced by management’s assessment of future profitability, which depends on the existence of sufficient taxable income of the appropriate character (ordinary vs. capital) within the carry forward periods available under the tax law. We determined that we would not be able to realize all of our deferred tax assets in the future, and therefore we reduced such amounts through a charge to the Statement of Total Comprehensive Income in the period in which that determination was made. Refer to Note 14. Income Taxes for further discussion of the Company's tax positions, including the impact of the TCJA.

The Income Taxes Topic of the ASC provides a framework to determine the appropriate level of tax reserves for uncertain tax positions. This framework prescribes a more-likely-than-not threshold for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Ambac also accrues interest and penalties related to these unrecognized tax benefits in the provision for income taxes.

Net Income Per Share

Net Income Per Share:

Basic net income per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares outstanding and vested restricted stock units. Diluted net income per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares used for basic earnings per share plus all potential dilutive common shares outstanding during the period. All potential dilutive common shares outstanding consider common stock deliverable pursuant to warrants issued under the Reorganization Plan, vested and unvested options, unvested restricted stock units and unvested performance stock units granted under employee and director compensation plans.

Reclassifications

Reclassifications:

Reclassifications may have been made to prior years' amounts to conform to the current year's presentation.

Adoption of New Accounting Standards

Recently Adopted Accounting Standards:

Effective December 31, 2017, Ambac early adopted the following accounting standard:

Reclassification of Shareholders' Equity items related to the TCJA

In February 2018, the FASB issued ASU 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. Current GAAP requires the effect of a change in tax laws or rates which impact deferred tax assets and liabilities to be recorded as income tax expense within net income. This guidance is applicable even in situations where the related income tax effects of items in accumulated other comprehensive income ("AOCI") were originally charged or credited directly to AOCI as required by GAAP. As a result, when tax laws or rates change, the tax effects of certain items (referred to as "stranded tax effects") in AOCI may not reflect the appropriate tax rate. This ASU eliminates the stranded tax effects by allowing a reclassification of those items from AOCI to retained earnings that resulted from the recently enacted TCJA. Ambac early adopted this standard effective December 31, 2017. Adoption of this ASU resulted in a decrease to AOCI of $6,588 and offsetting increase to retained earnings of $6,588 with no change to total shareholders' equity.

Effective January 1, 2017, Ambac adopted the following accounting standards:

Consolidation of Variable Interest Entities - Decision Makers

In October 2016, the FASB issued ASU 2016-17, Consolidation (Topic 810) - Interests Held through Related Parties That Are under Common Control. The new guidance changes how a reporting entity that is a single decision maker for a VIE will consider its indirect interests in that VIE when determining whether the reporting entity is the primary beneficiary and should consolidate the VIE. Under previous GAAP, a single decision maker in a VIE is required to consider an indirect interest held by a related party under common control in its entirety. Under the new ASU, the single decision maker will consider the indirect interest on a proportionate basis. Adoption of this ASU did not have an impact on Ambac's financial statements.

Improvements to Employee Share-Based Payment Accounting

In March 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation (Topic 718) - Improvements to Employee Share-Based Payment Accounting. The objective of this ASU is to improve and simplify the accounting for employee share-based payment accounting. The amendments are as follows: (i) recognizing excess tax benefits and tax deficiencies as income tax expense, (ii) recognizing excess tax benefits regardless of whether it reduces taxes payable in the current period, (iii) classifying excess tax benefits related to share-based payments along with other income tax cash flows as an operating activity on the statement of cash flows, (iv) for purposes of accruing compensation costs, allowing companies to make an accounting policy election to either: a) estimate forfeitures or b) account for forfeitures as they occur, which Ambac elected to do upon adoption, (v) to qualify for equity classification treatment, permitting tax withholding by employees up to the maximum statutory tax rate and (vi) classifying cash paid by an employer to a taxing authority when directly withholding shares as a financing activity on the statement of cash flows. Adoption of this ASU did not have a material impact on Ambac's financial statements.

Equity Method of Accounting

In March 2016, the FASB issued ASU 2016-07, Investments-Equity Method and Joint Ventures (Topic 323) - Simplifying the Transition to the Equity Method of Accounting. This ASU eliminates the requirement that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, an investor must adjust the investment, results of operations, and retained earnings retroactively as if the equity method had been in effect during all previous periods that the investment had been owned. The ASU will now require that at the date an available-for-sale equity security becomes qualified for the equity method of accounting, the reporting entity will recognize through earnings the unrealized holding gain or loss in accumulated other comprehensive income. Adoption of this ASU did not have an impact on Ambac's financial statements.

Contingent Put and Call Options in Debt Instruments

In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging (Topic 815) - Contingent Put and Call Options in Debt Instruments. Previous accounting rules required that embedded derivatives be separated from the host contract in a financial instrument and accounted for separately as derivatives if certain criteria are met. One of these criteria is that the economic characteristics and risks of the embedded derivatives are not "clearly and closely related" to the host contract. The objective of the ASU is to resolve diversity in practice in assessing embedded contingent put and call options. The ASU clarifies what steps are required when assessing whether the economic characteristics and risk of put and call options are clearly and closely related to their debt host contracts. Adoption of this ASU did not have an impact on Ambac's financial statements.