| Organization and Summary of Significant Accounting Policies (Policies) | 12 Months Ended |
| Dec. 31, 2016 |
| Accounting Policies [Abstract] | |
| Basis of Consolidation | Basis of Consolidation The accompanying consolidated financial statements have been prepared 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 prior period amounts have been reclassified to conform with current period presentation. During 2016, each of current and non-current marketable securities were reclassified from "Other assets" to its own line item within each section on the balance sheet. In addition, foreign exchange translation adjustments and unrealized loss on investments were reclassified as "Other comprehensive loss" on the Statement of Convertible Preferred Stock and Stockholders' Equity. |
| 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 stock, (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 generates revenue from buyers and sellers who use its solution for the purchase and sale of advertising inventory. The Company's solution enables buyers and sellers to purchase and sell advertising inventory, by matching buyers and sellers, and establishing rules and parameters for open and transparent auctions of advertising inventory. Buyers use the Company's solution to reach their intended audiences by buying advertising inventory that the Company makes available from sellers through its solution or advertising inventory the Company purchases from third-party exchanges. Sellers use the Company's solution to monetize their inventory. The Company recognizes revenue upon fulfillment of its contractual obligations in connection with a completed transaction, subject to satisfying all other revenue recognition criteria, including (i) persuasive evidence of an arrangement existing, (ii) delivery having occurred or services having been rendered, (iii) the fees being fixed or determinable, and (iv) collectability being reasonably assured. The Company generally bills and collects the full purchase price of impressions from buyers, together with other fees, if applicable. The Company reports revenue on a net basis for arrangements in which it has determined that it does not act as the principal in the purchase and sale of advertising inventory because pricing is determined through the Company's auction process and it is not the primary obligor. In some cases, the Company generates revenue directly from sellers who maintain the primary relationship with buyers and utilize the Company's solution to transact and increase the monetization of their activities. The Company reports revenue on a net basis for these activities. The Company reports revenue on a gross basis for arrangements in which it has determined that the Company acts as the principal in the purchase and sale of advertising inventory because the Company has direct contractual relationships with and manages advertising campaigns on behalf of the buyer by acting as the primary obligor in the purchase of advertising inventory, the Company exercises discretion in establishing prices, the Company has credit risk, and the Company independently selects and purchases inventory from the seller. The Company's accounts receivable are recorded at the amount of gross billings to buyers, net of allowances, for the amounts the Company is responsible to collect, and the Company's accounts payable are recorded at the net amount payable to sellers. Accordingly, both accounts receivable and accounts payable appear large in relation to revenue reported on a net basis. |
| 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. Personnel costs included in cost of revenue include salaries, bonuses, stock-based compensation, and employee benefit costs, and are primarily attributable to personnel in the Company's 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 its revenue-producing platform in cost of revenue over their estimated useful lives. The Company amortizes acquired developed technologies over their estimated useful lives. |
| Sales and Marketing | Sales and Marketing. The Company's sales and marketing expenses consist primarily of personnel costs, including stock-based compensation and 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 the Company's business acquisitions and, to a lesser extent, facilities-related costs and depreciation and amortization. The Company's sales organization focuses on increasing the adoption of the Company's solution by existing and new buyers and sellers. The Company amortizes acquired intangibles associated with customer relationships and backlog from its 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 bonuses, 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, net on the Company's consolidated balance sheet. The Company amortizes internal use software development costs that relate to its revenue-producing activities on the Company's 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 its 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 and bonuses, 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 amortization of 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 acquisitions. |
| Restructuring and Other Exit Costs | Restructuring and other exit costs. The Company's restructuring and other exit costs are cash and non-cash charges consisting primarily of employee termination costs, facility closure and relocation costs, and contract termination costs. |
| Impairment of Intangible Assets | Impairment of intangible assets. The Company's impairment charges are non-cash charges related to its intangible assets. Intangible assets are reviewed for impairment annually in the fourth quarter and whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Conditions that would necessitate an impairment assessment include a significant decline in the observable market value of an asset, a significant change in the extent or manner in which an asset is used, or any other significant adverse change that would indicate that the carrying amount of an asset or group of assets may not be recoverable. For intangible assets used in operations, impairment losses are only recorded if the asset’s carrying amount is not recoverable through its undiscounted, probability-weighted future cash flows. The Company measures the impairment loss based on the difference between the carrying amount and estimated fair value. Intangible assets are considered held for sale when certain criteria are met, including when management has committed to a plan to sell the asset, the asset is available for sale in its immediate condition, and the sale is probable within one year of the reporting date. Assets held for sale are reported at the lower of cost or fair value less costs to sell. The Company had no assets held for sale as of December 31, 2016 and 2015 . |
| 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 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 . 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, 2016 , 2015 and 2014 . |
| 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. |
| 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), unrealized gains (losses) on investments 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 prepaid expenses and other current assets on the consolidated balance sheets based upon the term of the remaining restrictions. At December 31, 2016 and 2015 , restricted cash was held as collateral for credit cards. At December 31, 2016 and 2015 , restricted cash totaling $0.1 million and $0.3 million , respectively, was included in prepaid expenses and other current assets. |
| 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 $0.7 million , $1.0 million and $0.3 million at December 31, 2016 , 2015 and 2014 respectively. During the years ended December 31, 2016 , 2015 and 2014 , the Company wrote-off $1.1 million , $0.2 million and $0.6 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. 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. |
| 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. Testing goodwill for impairment involves a two-step quantitative process. However, prior to performing the two-step quantitative goodwill impairment test, the Company has the option to first assess qualitative factors to determine whether or not it is necessary to perform the two-step quantitative goodwill impairment test for selected reporting units. If the Company chooses the qualitative option, the Company is not required to perform the two-step quantitative goodwill impairment test unless it has determined, based on the qualitative assessment, that it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If the two-step quantitative impairment test is required or chosen, the first step of the impairment test involves comparing the estimated fair value of the reporting unit with its respective carrying amount, including goodwill. If the estimated fair value of the reporting unit exceeds its carrying amount, including goodwill, goodwill is considered not to be impaired and no additional steps are necessary. If, however, the estimated fair value of the reporting unit is less than its carrying amount, including goodwill, then the carrying amount of the goodwill is compared with its implied fair value, and an impairment loss is recognized in an amount equal to the excess. The Company operates as a single operating segment and has identified a single reporting unit. The Company performed the annual quantitative goodwill impairment assessment for its reporting unit in the fourth quarter of 2016. The first step of the quantitative goodwill impairment test resulted in the determination that the fair value of the Company's reporting unit substantially exceeded its carrying amount, including goodwill. Accordingly, the second step was not required for the Company's reporting unit. |
| 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. 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. 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 amounts of cash equivalents are classified as Level 1 or Level 2 depending on whether or not their fair values are based on quoted market prices for identical securities that are traded in active markets, rather derived from similar securities. Corporate debt securities, included in marketable securities on the balance sheet, whose fair values are not based on quoted market prices for identical securities that are traded in an active market, rather derived from similar securities, are classified as Level 2 as well. 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, 2016 , two buyers accounted for 12% and 11% , respectively, of consolidated accounts receivable. At December 31, 2015 , two buyers accounted for 14% and 10% , respectively, of consolidated accounts receivable. For the years ended December 31, 2016 , 2015 and 2014 , no buyer or seller of advertising inventory comprised 10% or more of consolidated revenue. At December 31, 2016 , no seller of advertising inventory comprised 10% of consolidated accounts payable. At December 31, 2015 , one seller of advertising inventory comprised 10% 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 $0.9 million , $1.4 million and $1.1 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, 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 amends the guidance for revenue recognition to replace numerous, industry-specific requirements and converges areas under the "Revenue from Contracts with Customers" topic with those of the International Financial Reporting Standards. The guidance implements a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. The amendment also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. Other major provisions include the capitalization and amortization of certain contract costs, ensuring the time value of money is considered in the transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. These amendments were effective for reporting periods beginning after December 15, 2016, with early adoption prohibited. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. Subsequent to issuing the May 2014 guidance, in August 2015, the FASB issued amendments that deferred the effective date one year. As a result, the guidance is effective for reporting periods beginning after December 15, 2017, with early adoption permitted only as of annual reporting periods beginning after December 15, 2016. Since its issuance, the FASB has amended several aspects of the new guidance including provisions that clarify the implementation guidance on principal versus agent considerations in the new revenue recognition standard. The amendments clarify how an entity should identify the unit of accounting (i.e. the specified good or service) for the principal versus agent evaluation and how it should apply the control principle to certain types of arrangements. The Company has not yet selected a transition method, but is currently evaluating the new principle vs. agent guidance with respect to its revenue arrangements and assessing the impact this guidance will have on the Company's consolidated financial statements. In January 2016, the FASB issued new accounting guidance that 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 its consolidated financial statements. In February 2016, the FASB issued new accounting guidance that 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. Although the Company is currently evaluating the effect this guidance will have on its consolidated financial statements and related disclosures. The Company anticipates the guidance to have an impact on its assets and liabilities, as most of its operating lease commitments will be subject to the new standard and recognized as right-of-use assets and lease liabilities. In June 2016, the FASB issued new guidance that changes the accounting for recognizing impairments of financial assets. Under the new guidance, credit losses for certain types of financial instruments will be estimated based on expected losses. The new guidance also modifies the impairment models for available-for-sale debt securities and for purchased financial assets with credit deterioration since their origination. The new guidance will be effective for the Company starting in the first quarter of fiscal 2021. Early adoption is permitted starting in the first quarter of fiscal 2020. The Company is currently assessing the impact this guidance will have on its consolidated financial statements. In August 2016, the FASB issued new guidance intended to reduce diversity in practice in how certain cash receipts and payments are classified in the statement of cash flows, including debt prepayment or extinguishment costs, the settlement of contingent liabilities arising from a business combination, proceeds from insurance settlements, and distributions from certain equity method investees. The new guidance will be effective for interim and annual periods beginning after December 15, 2017, and early adoption is permitted. The guidance requires application using a retrospective transition method. The Company is currently assessing the impact this guidance will have on its consolidated financial statements. In October 2016, the FASB issued new guidance intended to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. Under the new guidance, entities should recognize the income tax consequences of such transfers when the transfers occur. The new guidance will be effective for interim and annual periods beginning after December 15, 2017, and early adoption is permitted. The guidance requires application using a modified retrospective transition method. The Company is currently assessing the impact this guidance will have on its consolidated financial statements. In January 2017, the FASB issued new guidance intended to simplify the test for goodwill impairment. The new guidance removes the requirement to perform a hypothetical purchase price allocation to measure goodwill impairment (Step 2). Under the new guidance, a goodwill impairment is calculated as the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill in the reporting unit. All other goodwill impairment guidance will remain largely unchanged. The guidance is effective on a prospective basis beginning after December 15, 2019, with early adoption permitted for interim or annual goodwill impairment tests performed after January 1, 2017. The Company expects to update its methodology for assessing goodwill impairment as a result of this guidance. In January 2017, the FASB issued amended guidance for business combinations. The new pronouncement changes the definition of a business with the objective of adding guidance to assist companies with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, and will be applied prospectively to any transactions occurring within the period of adoption. Early adoption is permitted, including for interim or annual periods in which the financial statements have not been issued or made available for issuance. Subsequent to adoption, the Company will apply this guidance to acquisitions or disposals occurring in the period of adoption and thereafter. |
