| Organization and Summary of Significant Accounting Policies (Policies) | 12 Months Ended |
| Dec. 31, 2015 |
| Accounting Policies [Abstract] | |
| Basis of Consolidation | Basis of Consolidation The accompanying consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States of America, or GAAP, and include the operations of the Company and its wholly owned subsidiaries. All significant inter-company transactions and balances have been eliminated in consolidation. |
| Segments | Segments Management has determined that the Company operates as one segment. The Company’s chief operating decision maker reviews financial information on an aggregated and consolidated basis, together with certain operating and performance measures principally to make decisions about how to allocate resources and to measure the Company’s performance. |
| Stock Split | Stock Split On March 18, 2014 , the Company effected a 1-for-2 reverse stock split of its common stock. The convertible preferred stock was not split at March 18, 2014 ; instead the convertible preferred stock conversion ratio was adjusted to effect the stock split at the time of conversion of the preferred stock to common stock. All share, per share and related information presented in the consolidated financial statements and accompanying notes has been retroactively adjusted, where applicable, to reflect the reverse stock split. |
| Reclassifications | Reclassifications Certain amounts related to deferred tax liabilities in the consolidated balance sheet for December 31, 2014 have been reclassified to conform with current-period presentation. Certain amounts related to the income tax disclosure for December 31, 2014 and 2013 have been reclassified to conform to current period presentation. |
| Use of Estimates | Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported and disclosed financial statements and accompanying footnotes. Actual results could differ materially from these estimates. On an ongoing basis, management evaluates its estimates, primarily those related to: (i) revenue recognition criteria, including the determination of revenue reporting as net versus gross in the Company’s revenue arrangements, (ii) accounts receivable and allowances for doubtful accounts, (iii) the useful lives of intangible assets and property and equipment, (iv) valuation of long-lived assets and their recoverability, including goodwill, (v) the realization of tax assets and estimates of tax liabilities, (vi) the valuation of common and preferred stock and preferred stock warrants prior to the Company’s IPO, (vii) assumptions used in valuation models to determine the fair value of stock-based awards, (viii) fair value of financial instruments, (ix) the recognition and disclosure of contingent liabilities, and (x) the assumptions used in valuing acquired assets and assumed liabilities in business combinations. These estimates are based on historical data and experience, as well as various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Estimates relating to the valuation of stock and business combinations require the selection of appropriate valuation methodologies and models, and significant judgment in evaluating ranges of assumptions and financial inputs. Actual results may differ materially from those estimates under different assumptions or circumstances. |
| Revenue Recognition | Revenue Recognition The Company updated its revenue recognition policy to include transactions for which the Company manages campaigns on behalf of buyers, function as principal, and reports the related revenue on a gross basis. The Company generates revenue from buyers and sellers in transactions in which they use the Company’s solution for the purchase and sale of advertising inventory, and also in transactions in which the Company manages ad campaigns on behalf of buyers. The Company recognizes revenue when four basic criteria are met: (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered, (iii) the fees are fixed or determinable, and (iv) collectibility is reasonably assured. The Company maintains separate arrangements with each buyer and seller either in the form of a master agreement, which specifies the terms of the relationship and access to the Company’s solution, or by insertion orders, which specify price and volume requests and other terms. The Company recognizes revenue upon the completion of a transaction, that is, when an impression has been delivered to the consumer viewing a website or mobile application. The Company assesses whether fees are fixed or determinable based on impressions delivered and the contractual terms of the arrangements. Historically, any refunds and adjustments have not been material. The Company assesses collectibility based on a number of factors, including the creditworthiness of a buyer and seller and payment and transaction history. The Company’s revenue arrangements generally do not include multiple deliverables. Revenue is reported depending on whether the Company functions as principal or agent. The determination of whether the Company acts as the principal or the agent requires the Company to evaluate a number of indicators, none of which is presumptive or determinative. For transactions in which the Company is the principal, revenue is reported on a gross basis for the amount paid by buyers for the purchase of advertising inventory and related services and the Company records the amounts paid to sellers as cost of revenue. For transactions in which the Company is the agent, revenue is reported on a net basis for the amount of fees charged to the buyer (if any), and fees retained from or charged to the seller. The Company enters into arrangements for which it manages advertising campaigns on behalf of buyers. The Company is the principal in these arrangements as it: (i) is the primary obligor in the advertising inventory purchase transaction; (ii) establishes the purchase prices paid by the buyer; (iii) performs all billing and collection activities including the retention of credit risk; (iv) has latitude in selecting suppliers; (v) negotiates the price it pays to suppliers of inventory; and (vi) makes all inventory purchasing decisions. Accordingly, for these arrangements the Company reports revenue on a gross basis. For the Company's other arrangements, in which the Company’s solution matches buyers and sellers, enables them to purchase and sell advertising inventory, and establishes rules and parameters for advertising inventory transactions, the Company reports revenue on a net basis because the Company: (i) is not the primary obligor for the purchase of advertising inventory but rather provides a platform to facilitate the buying and selling of advertising; (ii) does not have pricing latitude as pricing is generally determined through the Company’s auction process and/or the Company’s fees are based on a percentage of advertising spend; and (iii) does not directly select suppliers. |
| Cost of Revenue | Cost of Revenue The Company’s cost of revenue consists primarily of amounts the Company pays sellers for transactions for which the Company is the principal and reports revenues on a gross basis, data center costs, bandwidth costs, depreciation and maintenance expense of hardware supporting the Company’s revenue-producing platform, amortization of software costs for the development of the Company’s revenue-producing platform, amortization expense associated with acquired developed technologies, personnel costs, and facilities-related costs. Amounts the Company pays sellers includes the cost of advertising impressions the Company purchases from sellers through third-party exchanges in transactions for which the Company is the principal. Personnel costs included in cost of revenue include salaries, bonuses, stock-based compensation, and employee benefit costs, and are primarily attributable to personnel in our network operations group who support the Company’s platform. The Company capitalizes costs associated with software that is developed or obtained for internal use and amortizes the costs associated with the Company’s revenue-producing platform in cost of revenue over their estimated useful lives. The Company amortizes acquired developed technologies over their estimated useful lives. Many of these expenses are generally fixed and do not increase or decrease in direct proportion to increases or decreases in our revenue. |
| Sales and Marketing | Sales and Marketing The Company’s sales and marketing expenses consist primarily of personnel costs, including stock-based compensation and the sales bonuses paid to the Company’s sales organization, marketing expenses such as brand marketing, travel expenses, trade shows and marketing materials, professional services, and amortization expense associated with customer relationships and backlog from our business acquisitions, and to a lesser extent, facilities-related costs and depreciation and amortization. The Company's sales organization focuses on marketing the Company's solution to increase the adoption of the solution by existing and new buyers and sellers. The Company amortizes acquired intangibles associated with customer relationships and backlog from the Company's business acquisitions over their estimated useful lives. |
| Technology and Development | Technology and Development The Company’s technology and development expenses consist primarily of personnel costs, including stock-based compensation, and professional services associated with the ongoing development and maintenance of the Company’s solution, and to a lesser extent, facilities-related costs and depreciation and amortization, including amortization expense associated with acquired intangible assets from the Company's business acquisitions that are related to technology and development functions. These expenses include costs incurred in the development, implementation, and maintenance of internal use software, including platform and related infrastructure. Technology and development costs are expensed as incurred, except to the extent that such costs are associated with internal use software development that qualifies for capitalization, which are then recorded as internal use software development costs on the Company’s consolidated balance sheet. The Company amortizes internal use software development costs that relate to its revenue-producing activities on its platform to cost of revenue and amortizes other internal use software development costs to technology and development costs or general and administrative expenses, depending on the nature of the related project. The Company amortizes acquired intangibles associated with technology and development functions from the Company's business acquisitions over their estimated useful lives. |
| General and Administrative | General and Administrative The Company’s general and administrative expenses consist primarily of personnel costs, including stock-based compensation, associated with the Company’s executive, finance, legal, human resources, compliance, and other administrative personnel, as well as accounting and legal professional services fees, facilities-related costs and depreciation, and other corporate-related expenses. General and administrative expenses also include internal use software development costs and acquired intangible assets from the Company's business acquisitions over their estimated useful lives that relate to general and administrative functions and changes in fair value associated with the liability-classified contingent consideration related to business acquisitions. |
| Stock-Based Compensation | Stock-Based Compensation Compensation expense related to employee stock-based awards is measured and recognized in the consolidated financial statements based on the fair value of the awards granted. The Company has granted awards to employees that vest based solely on continued service, or service conditions, awards that vest based on the achievement of performance targets, or performance conditions, and awards that vest based on the Company's stock price exceeding a peer index, or market conditions. The fair value of each option award containing service and/or performance conditions is estimated on the grant date using the Black-Scholes option-pricing model. The fair value of awards containing market conditions is estimated using a Monte-Carlo lattice model. For service condition awards, stock-based compensation expense is recognized on a straight-line basis, net of forfeitures, over the requisite service periods of the awards, which is generally four years. For performance condition and market condition awards, stock-based compensation expense is recognized using a graded vesting model over the requisite service period of the awards. For market condition awards, expense recognized is not subsequently reversed if the market conditions are not achieved. Stock-based awards issued to non-employees are accounted for at fair value determined by using the Black-Scholes option-pricing model. The Company believes that the fair value of the stock options is more reliably measured than the fair value of the services received. The fair value of each non-employee stock-based compensation award is re-measured each period until a commitment date is reached, which is generally the vesting date. Determining the fair value of stock-based awards at the grant date requires judgment. The Company’s use of the Black-Scholes option-pricing model and Monte-Carlo lattice model requires the input of subjective assumptions such as the expected term of the option, the expected volatility of the price of the Company’s common stock, risk-free interest rates, the expected dividend yield of the Company’s common stock, and for periods prior to the Company's IPO, the fair value of the Company's common stock. The assumptions used in the Company’s valuation models represent management’s best estimates. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, the Company’s stock-based compensation expense could be materially different in the future. These assumptions and estimates are as follows: Fair Value of Common Stock. For stock options granted subsequent to the Company's IPO, the fair value of common stock is based on the closing price of the Company's common stock as reported on the New York Stock Exchange, or the NYSE, on the date of grant. Prior to the IPO, the board of directors determined the fair value of the common stock at the time of the grant of options and restricted stock awards by considering a number of objective and subjective factors. The fair value was determined in accordance with applicable elements of the practice aid issued by the American Institute of Certified Public Accountants titled Valuation of Privately Held Company Equity Securities Issued as Compensation. Risk-Free Interest Rate. The Company bases the risk-free interest rate used in the Black-Scholes option-pricing model on the yields of U.S. Treasury securities with maturities appropriate for the term of employee stock option awards. Expected Term. For employee options that contain service conditions, the Company applies the simplified approach, in which the expected term of an award is presumed to be the mid-point between the vesting date and the expiration date of the award. The expected term of employee stock options that contain performance conditions represents the weighted-average period that the stock options are estimated to remain outstanding. Volatility. Because the Company does not have significant trading history for the Company’s common stock, the Company determines the price volatility based on the historical volatilities of a publicly traded peer group based on daily price observations over a period equivalent to the expected term of the stock option grants. Dividend Yield. The dividend yield assumption is based on the Company’s history and current expectations of dividend payouts. The Company has never declared or paid any cash dividends on its common stock and does not anticipate paying any cash dividends in the foreseeable future, so the Company used an expected dividend yield of zero . In addition to the above assumptions, the Company also estimates a forfeiture rate to calculate the stock-based compensation expense for stock-based awards. The Company’s forfeiture rate is based on an analysis of the Company’s historical forfeitures and estimated future forfeitures. Changes in the estimated forfeiture rate may have a significant impact on the Company’s stock-based compensation expense as the cumulative effect of adjusting the rate is recognized in the period the forfeiture estimate is changed. The Company will continue to use judgment in evaluating the assumptions related to the Company’s stock-based compensation. Future expense amounts for any particular period could be affected by changes in the Company’s assumptions or market conditions. Due to the full valuation allowance provided on its net deferred tax assets, the Company has not recorded any tax benefit attributable to stock-based awards for the years ended December 31, 2015 , 2014 and 2013 . |
| Income Taxes | Income Taxes Deferred income tax assets and liabilities are determined based upon the net tax effects of the differences between the Company’s consolidated financial statements carrying amounts and the tax basis of assets and liabilities and are measured using the enacted tax rate expected to apply to taxable income in the years in which the differences are expected to be reversed. A valuation allowance is used to reduce some or all of the deferred tax assets if, based upon the weight of available evidence, it is more likely than not that those deferred tax assets will not be realized. The Company has established a full valuation allowance to offset its domestic net deferred tax assets due to the uncertainty of realizing future tax benefits from the net operating loss carryforwards and other deferred tax assets. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the consolidated financial statements from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties accrued related to its uncertain tax positions in its income tax provision (benefit) in the consolidated statements of operations. The Company recognizes excess tax benefits associated with stock-based compensation to stockholders’ equity only when realized based on applying a with-and-without approach. |
| Net Income (Loss) Per Share Attributable to Common Stockholders | Net Income (Loss) Per Share Attributable to Common Stockholders Basic net income (loss) per share of common stock is calculated by dividing the net income (loss) attributable to common stockholders by the weighted-average number of shares of common stock outstanding. Net income (loss) attributable to common stockholders is equal to net income (loss) adjusted for declared or cumulative preferred stock dividends for the period. Prior to the IPO, because the holders of the Company’s convertible preferred stock were entitled to participate in dividends, the Company applied the two-class method in calculating earnings per share for periods when the Company generated net income. The two-class method requires net income to be allocated between the common and preferred stockholders based on their respective rights to receive dividends, whether or not declared. However, because the convertible preferred stock was not contractually obligated to share in the Company’s income (losses), no such allocation was made for any period presented given the Company’s net income (losses). Diluted income (loss) per share attributable to common stockholders adjusts the basic weighted-average number of shares of common stock outstanding for the effect of potentially dilutive securities during the period. Potentially dilutive securities consist of stock options, restricted stock awards, restricted stock units, potential shares issued under the Company's Employee Stock Purchase Plan, shares held in escrow and potential shares issuable as part of contingent consideration as a result of business combinations, warrants and convertible preferred stock. For purposes of this calculation, potentially dilutive securities are excluded from the calculation of diluted net income (loss) per share attributable to common stockholders if their effect is anti-dilutive. Prior to the Company's IPO, the Company had two classes of stock, Class A and Class B. Basic and diluted net income (loss) per share attributable to common stockholders were the same for Class A and Class B common stock because they were entitled to the same liquidation and dividend rights. In connection with the IPO, the outstanding shares of Class A common stock and Class B common stock were converted into shares of a single class of common stock on a one -for-one basis. See Note 12. |
| Comprehensive Income (Loss) | Comprehensive Income (Loss) Comprehensive income (loss) encompasses all changes in equity other than those arising from transactions with stockholders, and consists of net income (loss) and foreign currency translation adjustments. |
| Cash, Cash Equivalents, and Marketable Securities | Cash, Cash Equivalents, and Marketable Securities The Company invests excess cash primarily in money market funds, corporate debt securities, and highly liquid debt instruments of the U.S. government and its agencies. The Company classifies investments held in money market funds as cash equivalents included in cash and cash equivalents as they have weighted-average maturities at the date of purchase of less than 90 days, U.S. government and agency bonds and corporate debt securities with stated maturities of less than one year as short-term investments included in marketable securities, prepaid expenses, and other current assets, and U.S. government and agency bonds and corporate debt securities with stated maturities of over a year as long-term investments included in marketable securities and other assets, non-current on the Company’s consolidated balance sheets, as the Company does not expect to redeem or sell these securities within one year from the balance sheet date. The Company determines the appropriate classification of investments in marketable securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company classifies and accounts for the Company’s marketable securities as available-for-sale, and as a result carries the securities at fair value and reports the unrealized gains and losses in the consolidated statements of comprehensive income (loss) and as a component of stockholders’ equity. The Company determines any realized gains or losses on the sale of marketable securities on a specific identification method, and the Company records such gains and losses as a component of other income, net on the Company’s consolidated statements of operations. |
| Restricted Cash | Restricted Cash The Company classifies certain restricted cash balances within marketable securities, prepaid expenses and other current assets and marketable securities and other assets, non-current on the consolidated balance sheets based upon the term of the remaining restrictions. At December 31, 2015 , restricted cash was held as collateral for credit cards. At December 31, 2014 , restricted cash was held as security under certain building leases and as collateral for credit cards. At December 31, 2015 and 2014 , restricted cash included in prepaid expenses and other current assets was $0.3 million and $0.4 million , respectively. At December 31, 2015 and 2014 , restricted cash included in other assets, non-current was zero and $1.0 million , respectively. |
| Accounts Receivable Allowance for Doubtful Accounts | Accounts Receivable Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount, are unsecured, and do not bear interest. The allowance for doubtful accounts is based on the best estimate of the amount of probable credit losses in existing accounts receivable. The allowance for doubtful accounts is determined based on historical collection experience and the review in each period of the status of the then-outstanding accounts receivable, while taking into consideration current customer information, subsequent collection history and other relevant data. The Company reviews the allowance for doubtful accounts on a quarterly basis. Account balances are charged off against the allowance when the Company believes it is probable the receivable will not be recovered. The Company’s allowance for doubtful accounts was approximately $1.0 million and $0.3 million at December 31, 2015 and 2014 , respectively. During the years ended December 31, 2015 and 2014 , the Company reserved an additional $0.9 million and $0.2 million , respectively, for doubtful accounts. During the years ended December 31, 2015 , 2014 , and 2013 , the Company wrote-off $0.2 million , $0.6 million , and $0.4 million , respectively, of accounts receivable. |
| Property and Equipment, Net | Property and Equipment, Net Property and equipment are recorded at historical cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method based upon the estimated useful lives of the assets. The estimated useful lives of the Company’s property and equipment are as follows: Years Computer equipment and network hardware 3 Furniture, fixtures and office equipment 5 to 7 Leasehold improvements Shorter of useful Computer equipment under capital leases Shorter of useful Repair and maintenance costs are charged to expense as incurred, while renewals and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in the Company’s results of operations. |
| Internal Use Software Development Costs | Internal Use Software Development Costs The Company capitalizes certain internal use software development costs associated with creating and enhancing internally developed software related to the Company’s technology infrastructure. These costs include personnel and related employee benefits expenses for employees who are directly associated with and who devote time to software projects, and external direct costs of materials and services consumed in developing or obtaining the software. Software development costs that do not meet the qualification for capitalization, as further discussed below, are expensed as incurred and recorded in technology and development expenses in the results of operations. Software development activities generally consist of three stages, (i) the planning stage, (ii) the application and infrastructure development stage, and (iii) the post implementation stage. Costs incurred in the planning and post implementation stages of software development, including costs associated with the post-configuration training and repairs and maintenance of the developed technologies, are expensed as incurred. The Company capitalizes costs associated with software developed for internal use when both the preliminary project stage is completed, management has authorized further funding for the completion of the project, and it is probable that the project will be completed and perform as intended. Costs incurred in the application and infrastructure development stages, including significant enhancements and upgrades, are capitalized. Capitalization ends once a project is substantially complete and the software and technologies are ready for their intended purpose. Internal use software development costs are amortized using a straight-line method over the estimated useful life of three years, commencing when the software is ready for its intended use. The straight-line recognition method approximates the manner in which the expected benefit will be derived. The Company does not transfer ownership of its software, or lease its software, to third parties. |
| Intangible Assets | Intangible Assets Intangible assets primarily consist of acquired developed technology, customer relationships and non-compete agreements resulting from business combinations, which are recorded at acquisition-date fair value, less accumulated amortization. The Company determines the appropriate useful life of its intangible assets by performing an analysis of expected cash flows of the acquired assets. Intangible assets are amortized over their estimated useful lives using a straight-line method, which approximates the pattern in which the economic benefits are consumed. The estimated useful lives of the Company’s intangible assets are as follows: Years Developed technology 3 to 5 Customer relationships 2.5 to 5 Non-compete agreements 2 to 3 Other intangible assets 0.5 to 1 |
| Impairment of Long-Lived Assets including Internal Use Capitalized Software Costs | Impairment of Long-Lived Assets including Internal Use Capitalized Software Costs The Company assesses the recoverability of its long-lived assets when events or changes in circumstances indicate their carrying value may not be recoverable. Such events or changes in circumstances may include: a significant adverse change in the extent or manner in which a long-lived asset is being used, significant adverse change in legal factors or in the business climate that could affect the value of a long-lived asset, an accumulation of costs significantly in excess of the amount originally expected for the acquisition or development of a long-lived asset, current or future operating or cash flow losses that demonstrate continuing losses associated with the use of a long-lived asset, or a current expectation that, more likely than not, a long-lived asset will be sold or otherwise disposed of significantly before the end of its previously estimated useful life. The Company performs impairment testing at the asset group level that represents the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. The Company assesses recoverability of a long-lived asset by determining whether the carrying value of the asset group can be recovered through projected undiscounted cash flows over their remaining lives. If the carrying value of the asset group exceeds the forecasted undiscounted cash flows, an impairment loss is recognized, measured as the amount by which the carrying amount exceeds estimated fair value. An impairment loss is charged to operations in the period in which management determines such impairment. |
| Business Combinations | Business Combinations The results of businesses acquired in a business combination are included in the Company’s consolidated financial statements from the date of acquisition. The Company allocates the purchase price, which is the sum of the consideration provided, which may consist of cash, equity or a combination of the two, in a business combination to the identifiable assets and liabilities of the acquired business at their acquisition date fair values. The excess of the purchase price over the amount allocated to the identifiable assets and liabilities, if any, is recorded as goodwill. Determining the fair value of assets acquired and liabilities assumed requires management to use significant judgment and estimates including the selection of valuation methodologies, estimates of future revenues and cash flows, discount rates and selection of comparable companies. When the Company issues stock-based or cash awards to an acquired company’s stockholders, the Company evaluates whether the awards are contingent consideration or compensation for post-business combination services. The evaluation includes, among other things, whether the vesting of the awards is contingent on the continued employment of the selling stockholder beyond the acquisition date. If continued employment is required for vesting, the awards are treated as compensation for post-acquisition services and recognized as expense over the requisite service period. The Company estimates the fair value of intangible assets acquired generally using a discounted cash flow approach, which includes an analysis of the future cash flows expected to be generated by the asset and the risk associated with achieving these cash flows. The key assumptions used in the discounted cash flow model include the discount rate that is applied to the forecasted future cash flows to calculate the present value of those cash flows and the estimate of future cash flows attributable to the acquired intangible asset, which include revenue, expenses and taxes. The carrying value of acquired working capital assets and liabilities approximates its fair value, given the short-term nature of these assets and liabilities. Acquisition-related transaction costs are not included as a component of consideration transferred, but are accounted for as an expense in the period in which the costs are incurred. |
| Goodwill | Goodwill Goodwill represents the excess of the aggregate fair value of the consideration transferred in a business combination over the fair value of the assets acquired, net of liabilities assumed. Goodwill is not amortized, but is subject to an annual impairment test. The Company tests for impairment of goodwill annually during the fourth quarter or more frequently if events or changes in circumstances indicate that the goodwill may be impaired. For purposes of goodwill impairment testing, the Company has one reporting unit. Events or changes in circumstances which could trigger an impairment review include a significant adverse change in legal factors or in the business climate, an adverse action or assessment by a regulator, unanticipated competition, a loss of key personnel, significant changes in the manner of the Company’s use of the acquired assets or the strategy for the Company’s overall business, significant negative industry or economic trends, or significant underperformance relative to expected historical or projected future results of operations. The Company has the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then additional impairment testing is not required. However, if an entity concludes otherwise, then it is required to perform the first of a two-step impairment test. The first step involves comparing the estimated fair value of a reporting unit with its respective book value, including goodwill. If the estimated fair value exceeds book value, goodwill is considered not to be impaired and no additional steps are necessary. If, however, the fair value of the reporting unit is less than book value, then a second step is required which requires the carrying amount of the goodwill be compared with its implied fair value. The estimate of implied fair value of goodwill may require valuations of certain internally generated and unrecognized intangible and tangible net assets. If the carrying amount of goodwill exceeds the implied fair value of the goodwill, an impairment loss is recognized in an amount equal to the excess. |
| Operating and Capital Leases | Operating and Capital Leases The Company records rent expense for operating leases, some of which have escalating rent payments on a straight-line basis over the lease term. The Company begins recognition of rent expense on the date of initial possession, which is generally when the Company enters the leased premises and begins to make improvements in preparation for its intended use. Some of the Company’s lease arrangements provide for concessions by the landlords, including payments for leasehold improvements and rent-free periods. The Company accounts for the difference between the straight-line rent expense and rent paid as a deferred rent liability. The Company leases equipment under capital lease arrangements. The assets and liabilities under capital lease are recorded at the lesser of present value of aggregate future minimum lease payments, including estimated bargain purchase options, or the fair value of the asset under lease. Assets under capital lease are amortized using the straight-line method over the estimated useful lives of the assets. |
| Preferred Stock Warrant Liabilities | Preferred Stock Warrant Liabilities The Company issued warrants to purchase preferred stock in connection with professional services and financing arrangements and accounted for these warrants as liabilities at fair value because the underlying shares of convertible preferred stock were contingently redeemable, including in the case of a deemed liquidation, which may have obligated the Company to transfer assets to the warrant holders. The preferred stock warrants were recorded at fair value at the time of issuance and changes in the fair value of the preferred stock warrants each reporting period were recorded as part of other expense, net in the Company’s consolidated statements of operations until the earlier of the exercise or expiration of the warrants or the warrants’ conversion to warrants to purchase common stock, at which time any remaining liability was reclassified to additional paid-in capital. Following the closing of the Company's IPO, the Company was no longer required to re-measure the warrants to fair value and record any changes in the fair value of these liabilities in the consolidated statement of operations, and accordingly, the Company did not record any related expenses subsequent to the closing of the IPO. |
| Fair Value of Financial Instruments | Fair Value of Financial Instruments Fair value represents the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy is based on the following three levels of inputs, of which the first two are considered observable and the last one is considered unobservable: • Level 1 – Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. • Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. • Level 3 – Unobservable inputs. Observable inputs are based on market data obtained from independent sources. The Company's contingent consideration liabilities were measured using unobservable inputs that required a high level of judgment to determine fair value, and thus classified as Level 3. The Company's contingent consideration liabilities were re-measured to fair value through the date they were converted to equity. See Note 9. At December 31, 2013, the Company’s warrants to purchase preferred stock were measured using unobservable inputs that required a high level of judgment to determine fair value, and thus classified as Level 3. The Company's warrants to purchase preferred stock were re-measured to fair value through closing of the IPO. See Note 9. The carrying amounts of cash equivalents, accounts receivable, accounts payable, accrued expenses, and seller payables approximate fair value due to the short-term nature of these instruments. The carrying value of the line of credit approximates fair value based on borrowing rates currently available to the Company for financing with similar terms. The carrying amounts of marketable securities are based on quoted market prices, and thus classified as Level 1. See Note 9. Certain assets, including goodwill and intangible assets are also subject to measurement at fair value on a non-recurring basis if they are deemed to be impaired as a result of an impairment review. |
| Concentration of Risk | Concentration of Risk Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash, cash equivalents, restricted cash and accounts receivable. The Company maintains its cash and cash equivalents with financial institutions which exceed the federally insured limits. Accounts receivable include amounts due from buyers with principal operations primarily in the United States. The Company performs ongoing credit evaluations of its buyers. At December 31, 2015 , two buyers accounted for 14% and 10% , respectively, of consolidated accounts receivable. At December 31, 2014 , two buyers accounted for 15% and 11% , respectively, of consolidated accounts receivable. For the years ended December 31, 2015 , 2014 and 2013 , no buyer or seller of advertising inventory comprised 10% or more of consolidated revenue. At December 31, 2015 , one seller of advertising inventory comprised 10% of consolidated accounts payable. At December 31, 2014 , one seller of advertising inventory comprised 14% of consolidated accounts payable. |
| Foreign Currency Transactions and Translations | Foreign Currency Transactions and Translation Transactions in foreign currencies are translated into the functional currency of the applicable entity at the rates of exchange in effect at the date of the transaction. Foreign exchange gains, net were approximately $1.4 million and $1.1 million for the years ended December 31, 2015 and 2014 , respectively, and foreign exchange losses, net was approximately $0.7 million for the year ended December 31, 2013 and are included in other expense, net in the accompanying consolidated statements of operations. To the extent that the functional currency is different than the U.S Dollar, the financial statements have then been translated into U.S. Dollars using period-end exchange rates for assets and liabilities and average exchanges rates for the results of operations. Foreign currency translation gains and losses are included as a component of accumulated other comprehensive loss on the consolidated balance sheet. |
| Recent Accounting Pronouncements | Recent Accounting Pronouncements Under the Jumpstart Our Business Startups Act, or the JOBS Act, the Company meets the definition of an emerging growth company. The Company has irrevocably elected to opt out of the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. In May 2014, the Financial Accounting Standards Board, or FASB, issued new accounting guidance that requires an entity to recognize the amount of revenue it expects to earn from the transfer of promised goods or services to customers. The new accounting guidance will replace most existing GAAP revenue recognition guidance when it becomes effective. The new guidance is effective for annual reporting periods (including interim periods within those periods) beginning after December 15, 2016. In August 2015, the FASB issued an amendment deferring the effective date by one year making it effective for annual reporting periods beginning on or after December 15, 2017, while also providing for early adoption but not before the original effective date. The Company has not yet selected a transition method and is currently assessing the impact this guidance will have on the Company's consolidated financial statements. In April 2015, the FASB issued new accounting guidance that simplified the presentation of debt issuance costs by requiring debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. In August 2015, the FASB issued an amendment to this guidance stating an entity may defer and present debt issuing costs associated with line of credit arrangements as an asset and subsequently amortize the deferred debt issuance costs ratably over the term of the line of credit arrangement, regardless of whether there are any outstanding borrowings on the line of credit arrangement. The new guidance is effective for fiscal years beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The adoption of this guidance is not expected to have a material impact on the Company's consolidated financial statements. In April 2015, the FASB issued new accounting guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. The new guidance is effective for fiscal years beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The adoption of this guidance is not expected to have a material impact on the Company's consolidated financial statements. In September 2015, the FASB issued new accounting guidance, which requires an acquirer in a business combination to recognize adjustments to the provisional amounts identified during the measurement period in the reporting period in which the adjustment amounts are determined. The acquirer is also required to either present separately on the face of the income statement or disclose in the notes to the financial statements the portion of the amounts recorded in the current-period earnings by line item that would have been recorded in previous periods if the adjustment to the provisional amounts had been recognized as of the acquisition date. The new guidance is effective for annual periods beginning after December 31, 2015, with early application permitted, and shall apply to adjustments to provisional amounts that occur after the effective date. The Company is currently assessing the impact this guidance will have on the Company's consolidated financial statements. In November 2015, the FASB issued new accounting guidance, which simplifies the presentation of deferred income taxes by requiring deferred tax assets and liabilities be classified as non-current on the balance sheet. The new guidance is effective for annual and interim periods for fiscal years beginning after December 15, 2016. Early adoption is permitted for financial statements that have not been previously issued and can be applied on either a prospective or retrospective basis. The Company has elected to early adopt and prospectively apply the provisions of this new guidance beginning in the fourth quarter of 2015. As the Company adopted the new guidance on a prospective basis, no adjustments were made to prior period balance sheets. In January 2016, the FASB issued new accounting guidance, which changes certain recognition, measurement, presentation, and disclosure requirements for financial instruments. The new guidance requires all equity investments, except those accounted for under the equity method of accounting or resulting in consolidation, to be measured at fair value with changes in fair value recognized in net income. The guidance also simplifies the impairment assessment for equity investments without readily determinable fair values, amends the presentation requirements for changes in the fair value of financial liabilities, requires presentation of financial instruments by measurement category and form of financial asset, and eliminates the requirement to disclose the methods and significant assumptions used in estimating the fair value of financial instruments. The new guidance is effective for interim and annual periods beginning after December 15, 2017, and early adoption is not permitted except for the amended presentation requirements for changes in the fair value of financial liabilities. The Company is currently assessing the impact this guidance will have on the Company's consolidated financial statements. In February 2016, the FASB issued new accounting guidance, which requires an entity to recognize right-of-use assets and lease liabilities on its balance sheet and disclose key information about leasing arrangements. This guidance offers specific accounting guidance for a lessee, a lessor, and sale and leaseback transactions. Lessees and lessors are required to disclose qualitative and quantitative information about leasing arrangements to enable a user of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. This guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, and requires a modified retrospective adoption, with early adoption permitted. The Company is currently assessing the impact this guidance will have on the Company's consolidated financial statements. |
