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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 21, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	RUBICON PROJECT, INC.
Entity Central Index Key	0001595974
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q4
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		51,734,264
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 138,653,552

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 80,452	$ 76,642
Marketable securities	7,524	52,504
Accounts receivable, net	205,683	165,890
Prepaid expenses and other current assets	6,882	9,620
TOTAL CURRENT ASSETS	300,541	304,656
Property and equipment, net	33,487	47,393
Internal use software development costs, net	14,570	12,734
Other assets, non-current	1,240	5,493
Intangible assets, net	10,174	13,359
TOTAL ASSETS	360,012	383,635
Current liabilities:
Accounts payable and accrued expenses	239,678	214,103
Other current liabilities	1,304	3,141
TOTAL CURRENT LIABILITIES	240,982	217,244
Other liabilities, non-current	1,017	1,780
TOTAL LIABILITIES	241,999	219,024
Commitments and contingencies (Note 16)
STOCKHOLDERS' EQUITY
Preferred stock, $0.00001 par value, 10,000 shares authorized at December 31, 2018 and 2017; 0 shares issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, $0.00001 par value; 500,000 shares authorized at December 31, 2018 and 2017; 51,159 and 50,239 shares issued and outstanding at December 31, 2018 and 2017, respectively	1	0
Additional paid-in capital	433,877	418,354
Accumulated other comprehensive loss	(259)	41
Accumulated deficit	(315,606)	(253,784)
TOTAL STOCKHOLDERS' EQUITY	118,013	164,611
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 360,012	$ 383,635

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, par or stated value per share (usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par or stated value per share	$ 0.00001	$ 0.00001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares, issued	51,159,000	50,239,000
Common stock, shares, outstanding	51,159,000	50,239,000

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 124,685	$ 155,545
Expenses:
Cost of revenue	60,003	56,836
Sales and marketing	44,556	51,794
Technology and development	37,863	47,500
General and administrative	42,431	55,596
Restructuring and other exit costs	3,440	5,959
Impairment of intangible assets and internal use software	0	4,585
Impairment of goodwill	0	90,251
Total expenses	188,293	312,521
Loss from operations	(63,608)	(156,976)
Other (income) expense:
Interest income, net	(988)	(908)
Other income	(766)	(688)
Foreign exchange (gain) loss, net	(389)	1,165
Total other income, net	(2,143)	(431)
Loss before income taxes	(61,465)	(156,545)
Provision (benefit) for income taxes	357	(1,762)
Net loss	$ (61,822)	$ (154,783)
Net loss per share:
Basic and Diluted (usd per share)	$ (1.23)	$ (3.17)
Weighted average shares used to compute net loss per share:
Basic and Diluted (in shares)	50,259	48,869

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (61,822)	$ (154,783)
Other comprehensive income (loss):
Unrealized gain (loss) on investments	27	(28)
Foreign currency translation adjustments	(327)	342
Other comprehensive income (loss)	(300)	314
Comprehensive loss	$ (62,122)	$ (154,469)

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance (in shares) at Dec. 31, 2016		49,378,000
Beginning Balance at Dec. 31, 2016	$ 299,513	$ 0	$ 398,787	$ (273)	$ (99,001)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		106,000
Exercise of common stock options	394		394
Restricted stock awards, net (in shares)		(189,000)
Restricted stock awards, net	0	$ 0
Issuance of common stock related to employee stock purchase plan (in shares)		200,000
Issuance of common stock related to employee stock purchase plan	629		629
Issuance of common stock related to RSU vesting (in shares)		1,273,000
Issuance of common stock related to RSU vesting	0	$ 0
Shares withheld related to net share settlement (in shares)		(529,000)
Shares withheld related to net share settlement	(2,403)		(2,403)
Stock-based compensation	20,947		20,947
Other comprehensive loss	314			314
Net loss	$ (154,783)				(154,783)
Ending Balance (in shares) at Dec. 31, 2017	50,239,000	50,239,000
Ending Balance at Dec. 31, 2017	$ 164,611	$ 0	418,354	41	(253,784)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		50,000
Exercise of common stock options	45		45
Restricted stock awards, net (in shares)		(156,000)
Restricted stock awards, net	0	$ 0
Issuance of common stock related to employee stock purchase plan (in shares)		174,000
Issuance of common stock related to employee stock purchase plan	314		314
Issuance of common stock related to RSU vesting (in shares)		1,367,000
Issuance of common stock related to RSU vesting	1	$ 1
Shares withheld related to net share settlement (in shares)		(515,000)
Shares withheld related to net share settlement	(1,638)		(1,638)
Stock-based compensation	16,802		16,802
Other comprehensive loss	(300)			(300)
Net loss	$ (61,822)				(61,822)
Ending Balance (in shares) at Dec. 31, 2018	51,159,000	51,159,000
Ending Balance at Dec. 31, 2018	$ 118,013	$ 1	$ 433,877	$ (259)	$ (315,606)

Consolidated Statement of Cash Flows - USD ($)	12 Months Ended
Consolidated Statement of Cash Flows - USD ($)	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES:
Net loss	$ (61,822,000)	$ (154,783,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	35,338,000	36,225,000
Stock-based compensation	16,282,000	20,504,000
Impairment of intangible assets and internal use software	0	4,585,000
Impairment of goodwill	0	90,251,000
Loss on disposal of property and equipment	243,000	195,000
Provision for doubtful accounts	758,000	580,000
Accretion of available for sale securities	(412,000)	(276,000)
Unrealized foreign currency gains, net	(897,000)	970,000
Deferred income taxes	(42,000)	(1,564,000)
Changes in operating assets and liabilities, net of effect of business acquisitions:
Accounts receivable	(40,688,000)	26,051,000
Prepaid expenses and other assets	4,519,000	(224,000)
Accounts payable and accrued expenses	26,612,000	(502,000)
Other liabilities	(2,577,000)	(477,000)
Net cash provided by (used in) operating activities	(22,686,000)	21,535,000
INVESTING ACTIVITIES:
Purchases of property and equipment	(11,433,000)	(32,438,000)
Capitalized internal use software development costs	(8,507,000)	(7,988,000)
Acquisitions, net of cash acquired	0	(38,610,000)
Investments in available-for-sale securities	(23,991,000)	(95,224,000)
Maturities of available-for-sale securities	62,650,000	81,050,000
Sales of available-for-sale securities	9,228,000	0
Net cash provided by (used in) investing activities	27,947,000	(93,210,000)
FINANCING ACTIVITIES:
Proceeds from exercise of stock options	45,000	394,000
Proceeds from issuance of common stock under employee stock purchase plan	314,000	629,000
Taxes paid related to net share settlement	(1,638,000)	(2,403,000)
Net cash used in financing activities	(1,279,000)	(1,380,000)
EFFECT OF EXCHANGE RATE CHANGES ON CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(172,000)	199,000
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	3,810,000	(72,856,000)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of period	76,642,000	149,498,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of period	80,452,000	76,642,000
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	379,000	382,000
Cash paid for interest	46,000	61,000
Capitalized assets financed by accounts payable and accrued expenses	6,000	109,000
Capitalized stock-based compensation	$ 520,000	$ 443,000

Nature of Operations

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Operations

Company Overview

The Rubicon Project, Inc., or Rubicon Project (the "Company"), was formed on April 20, 2007 in Delaware and began operations in April 2007. The Company is headquartered in Los Angeles, California.

The Company provides a technology solution to automate the purchase and sale of digital advertising inventory for buyers and sellers. The Company's platform features applications and services for digital advertising sellers, including websites, mobile applications and other digital media properties, and their representatives, to sell their digital advertising inventory; applications and services for buyers, including advertisers, agencies, agency trading desks, and demand side platforms, or DSPs, to buy digital advertising inventory; and a marketplace over which such transactions are executed. Together, these features power and enhance a comprehensive, transparent, independent advertising marketplace that brings buyers and sellers together and facilitates intelligent decision making and automated transaction execution for the digital advertising inventory managed on the Company's platform. The Company's clients include many of the world's leading publishers of websites and mobile applications and buyers of digital advertising inventory.

Advertising inventory takes different forms, referred to as advertising units, is purchased and sold through different transactional methodologies, and allows advertising content to be presented to consumers through different channels. The Company's solution enables buyers and sellers to purchase and sell:


•	a comprehensive range of advertising units, including display, audio and video;


•	that are transacted through real-time bidding ("RTB"), which includes (i) direct sale of premium inventory, which the Company refers to as private marketplace ("PMP"), and (ii) open auction bidding, which the Company refers to as open marketplace ("OMP"); and


•	that are displayed across digital channels, including mobile web, mobile application, and desktop, as well as across various out-of-home channels, such as digital billboards.

Risks and Uncertainties

The Company has been negatively impacted by rapid changes in the ad tech industry, including demand by ad tech buyers for more efficiency and lower costs, changes in bidding technologies, and increased competition. In response to these challenges, the Company made significant reductions in fees charged to buyers during 2017 and in November 2017 eliminated its buyer fees altogether. The competitive pressures and reduced take rate resulted in lower revenue on an annual basis in 2018 compared to the prior year. In an effort to bring its costs into better alignment with reduced take rates, the Company has undertaken restructuring activities to reduce headcount and related operating costs, and has also reduced its capital expenditures. Unless and until the Company is able to compensate for the fee reductions and reduced margins by continuing to increase advertising spending on its platform, or sufficiently reducing costs, it may not be able to grow its business and may continue to operate at a loss, depleting its cash resources and liquidity. If the Company continues to experience significant operating losses in the future, the Company may require additional liquidity to fund its operations.

Net Income (Loss) Per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

The following table presents the basic and diluted net loss per share:



	Year Ended
	December 31, 2018			December 31, 2017
	(in thousands, except per share data)
Basic and Diluted EPS:
Net loss	$	(61,822	)	$	(154,783	)
Weighted-average common shares outstanding	50,602			49,720
Weighted-average unvested restricted shares	(343		)	(851		)
Weighted-average common shares outstanding used to compute net loss per share	50,259			48,869
Basic and diluted net loss per share	$	(1.23	)	$	(3.17	)

The following weighted-average shares have been excluded from the calculation of diluted net loss per share attributable to common stockholders for each period presented because they are anti-dilutive:



	Year Ended
	December 31, 2018	December 31, 2017
	(in thousands)
Options to purchase common stock	128	120
Unvested restricted stock awards	218	297
Unvested restricted stock units	2,029	556
ESPP	55	50
Total shares excluded from net loss per share	2,430	1,023

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Organization and Summary of Significant Accounting Policies

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

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.

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) assumptions used in valuation models to determine the fair value of stock-based awards, (vii) fair value of financial instruments, (viii) the recognition and disclosure of contingent liabilities, and (ix) 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, as well as the recoverability of long-lived assets and goodwill, 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

The Company generates revenue from transactions where it provides a platform for the purchase and sale of digital advertising inventory between buyers and sellers of advertising inventory. Digital advertising inventory is created when consumers access sellers’ content. Sellers provide digital advertising inventory to our platform in the form of advertising requests, or ad requests. When the Company receives ad requests from sellers, it sends bid requests to buyers, which enable buyers to bid on sellers’ digital advertising inventory. Winning bids can create advertising, or paid impressions, for the seller to present to the consumer.

The total volume of spending between buyers and sellers on the Company's platform is referred to as advertising spend. The Company keeps a percentage of that advertising spend as a fee, and remits the remainder to the seller. The fee that the Company retains from the gross advertising spend on its platform is recognized as revenue. The fee earned on each transaction is based on the pre-existing agreement with the seller and the clearing price of the winning bid. The Company recognizes revenue upon fulfillment of its performance obligation to a client, which occurs at the point in time an ad renders and is counted as a paid impression, subject to a contract existing with the client and a fixed or determinable transaction price. Performance obligations for all transactions are satisfied, and the corresponding revenue is recognized, at a distinct point in time; the Company has no arrangements with multiple performance obligations. The Company considers the following when determining if a contract exists (i) contract approval by all parties, (ii) identification of each party’s rights regarding the goods or services to be transferred, (iii) specified payment terms, (iv) commercial substance of the contract, and (v) collectability of substantially all of the consideration is probable.

The Company evaluates whether it acts as the principal in the purchase and sale of digital advertising inventory to determine whether revenue should be reported on a gross or net basis. The Company has determined that it does not act as the principal in the purchase and sale of digital advertising inventory because it does not have control of the digital advertising inventory and does not set prices agreed upon within the auction marketplace, and therefore reports revenue on a net basis. In periods prior to the second quarter of 2017, the Company reported revenue on a gross basis for revenue associated with its intent marketing solution, as the Company determined that it acted as the principal in the purchase and sale of digital advertising inventory. The Company ceased offering its intent marketing solution after the first quarter of 2017, after which time, all of the Company’s revenues have been recorded on a net basis. See Note 4 for additional disclosure of our revenue policies and disaggregated presentation of our revenues.

Expenses

The Company classifies its expenses into the following seven categories:

Cost of Revenue. The Company's cost of revenue consists of 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. For intent marketing transactions conducted in the first quarter of 2017 in which the Company was the principal and reported revenues on a gross basis, cost of revenue also included amounts the Company paid to sellers for their inventory. 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. 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 client 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 client relationships and backlog from its business acquisitions over their estimated useful lives.

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. 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. 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 and Internal Use Software. The Company's impairment charges are non-cash charges related to its intangible assets. Intangible assets are reviewed for impairment indicators at least annually and whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Refer to the "Intangible Assets" policy within this footnote for additional information regarding the determination of impairment charges related to intangible assets.

Impairment of Goodwill. The Company's goodwill impairment charges are non-cash charges related to its goodwill asset. Goodwill is tested annually for impairment during the fourth quarter or more frequently if events or changes in circumstances indicate that goodwill may be impaired. Refer to the "Goodwill" policy within this footnote for additional information regarding the determination of goodwill impairment charges.

Stock-Based Compensation

Compensation expense related to 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 restricted stock awards, restricted stock units, and stock option awards that vest based solely on continued service, or service conditions, to employees and non-employees. The fair value of each share-based award containing service conditions is based on the Company's grant date common share price for restricted stock awards and restricted stock units and is estimated using the Black-Scholes option-pricing model for stock option awards. For service condition awards, stock-based compensation expense is recognized on a straight-line basis over the requisite service periods of the awards, or the vesting period, which is generally four years.

As of July 1, 2018, the Company prospectively adopted ASU 2018-07—Stock Compensation (Topic 718) ("ASU 2018-07"), which updated the treatment of non-employee share-based awards to conform with the existing guidance under Accounting Standards Codification Topic 718, Compensation—Stock Compensation that was already applicable to share-based awards granted to employees. Prior to this adoption, the Company remeasured the fair value of each non-employee stock-based award each period until a commitment date was reached, which was generally the vesting date. As of the adoption date, the fair value of existing unvested awards held by non-employees was determined based on the adoption date fair value, which will be recognized over the remaining service period. For employees that transition into a non-employee contractor relationship with the Company subsequent to the adoption date their existing awards will continue to be recognized at the original grant date fair value. There was no impact to the Company's consolidated financial statements resulting from the adoption of ASU 2018-07.

The assumptions and estimates used in the Black-Scholes pricing model are as follows:

Fair Value of Common Stock. 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.

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 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.

Determining the fair value of stock-based awards using a pricing model requires judgment. The Company’s use of the Black-Scholes option-pricing model requires the input of subjective assumptions such as the expected term of the award, the expected volatility of the price of the Company’s common stock, risk-free interest rates, and the expected dividend yield of the Company’s common stock. The assumptions used in the Company’s valuation model 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.

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, 2018 and 2017.

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 statement 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 Tax Cuts and Jobs Act (“the Tax Act”) was enacted in December 2017. The Tax Act significantly changes U.S. tax law by, among other things, lowering U.S. corporate income tax rates, implementing a territorial tax system and imposing a one-time transition tax on deemed repatriated earnings of foreign subsidiaries. The Tax Act reduces the U.S. corporate income tax rate from 34% to 21%, effective January 1, 2018. The Company recognized the impact of the revaluation of deferred tax balances and the provisional impact related to the one-time transition tax in its consolidated financial statements for the year ended December 31, 2017. The Company completed its analysis of the impact of U.S. tax reform during 2018 in accordance with the SAB 118 measurement period and there were no changes to the amounts recorded.

Capital Stock

The Company has authorized capital stock of 500,000,000 shares of common stock and 10,000,000 shares of preferred stock. The Company has issued common stock, which is included in outstanding common stock on the Company's Consolidated Balance Sheets. The Company has not issued any shares of its preferred stock subsequent to the Company's IPO and does not have any preferred stock outstanding.

The Company is required to reserve and keep available out of its authorized but unissued shares of common stock such number of shares sufficient to effect any of the Company's contingent consideration liabilities and the conversion of all shares granted and available for grant under the Company’s stock award plans. The number of shares of the Company's stock reserved for these purposes at December 31, 2018 was 18,094,154.

The board of directors is authorized to establish, from time to time, the number of shares to be included in each series of preferred stock, and to fix the designation, powers, privileges, preferences, and relative participating, optional or other rights, if any, of the shares of each series of preferred stock, and any of its qualifications, limitations or restrictions.

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) by the weighted-average number of shares of common stock outstanding. 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 ("ESPP"), shares held in escrow and potential shares issuable as part of contingent consideration as a result of business combinations. For purposes of this calculation, potentially dilutive securities are excluded from the calculation of diluted net income (loss) per share if their effect is anti-dilutive.

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

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 because the money market funds have weighted-average maturities at the date of purchase of less than 90 days. Investments held in U.S. government and agency bonds and corporate debt securities with stated maturities of less than one year are classified as short-term investments included in marketable securities and prepaid expenses and other current assets. Investments held in U.S. government and agency bonds and corporate debt securities with stated maturities of over a year are classified as long-term investments included in 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

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, 2018 and 2017 the Company had no restricted cash.

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 client 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 $1.3 million and $0.5 million at December 31, 2018 and 2017, respectively. During the years ended December 31, 2018 and 2017, the Company wrote-off $0.6 million and $0.7 million, respectively, of accounts receivable.

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 life or life of lease
Computer equipment under capital leases	Shorter of useful life or life of lease

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

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 the planning 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 primarily consist of acquired developed technology, client 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 Company’s intangible assets are being amortized over their estimated useful lives as follows:



	Years
Developed technology	3 to 5
Client relationships	2.5 to 3
Non-compete agreements	2 to 3
Other intangible assets	1 to 1.5

Intangible assets are reviewed for impairment indicators at least annually 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.

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

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 of a business combination, which is the sum of the consideration provided, which may consist of cash, equity or a combination of the two, 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 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 impairment testing conducted annually during the fourth quarter or more frequently if events or changes in circumstances indicate that goodwill may be impaired.

The Company adopted Accounting Standards Update ("ASU") 2017-04—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment during the first quarter of 2017. In accordance with the guidance, the Company has the option to first assess qualitative factors to determine whether or not it is necessary to perform the quantitative goodwill impairment test. If the qualitative assessment option is not elected, or if the qualitative assessment indicates that it is more likely than not that the fair value is less than its carrying amount, a quantitative analysis is then performed. The quantitative analysis, if performed, compares the estimated fair value of the Company with its respective carrying amount, including goodwill. If the estimated fair value of the Company exceeds its carrying amount, including goodwill, goodwill is considered not to be impaired and no additional steps are necessary. If the fair value is less than the carrying amount, including goodwill, then an impairment adjustment must be recorded up to the carrying amount of goodwill.

The Company operates as a single operating segment and has identified a single reporting unit. In the third quarter of 2017, the Company identified potential indications of impairment and performed a quantitative goodwill impairment assessment and determined that the fair value of the Company was less than the carrying value, including goodwill. As a result, the Company recorded a goodwill impairment charge of $90.3 million during the third quarter of 2017. Refer to Note 5 for a description of the methods used to compute the goodwill impairment charge in the third quarter of 2017.

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. The Company has no capital leases at December 31, 2018.

Fair Value of Financial Instruments

The carrying amounts of the Company's cash equivalents, accounts receivable, accounts payable, accrued expenses, and seller payables approximate fair value due to the short-term nature of these instruments. Certain assets of the Company are recorded at their fair value, using the fair value hierarchy, on a recurring basis, and other assets and liabilities, including goodwill and intangible assets are 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 (see Note 5).

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. Cash and cash equivalents maintained with financial institutions exceed applicable 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, 2018, two buyers accounted for 21% and 13%, respectively, of consolidated accounts receivable. At December 31, 2017, two buyers accounted for 20% and 15%, respectively, of accounts receivable.

The Company recognizes revenue from its contracts with sellers, and no seller of advertising inventory comprised 10% or more of revenue in 2018 or 2017.

At December 31, 2018 and 2017, no seller of advertising inventory comprised 10% or more of accounts payable.

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 or losses were included in foreign exchange (gain) loss, 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 income (loss) on the consolidated balance sheet.

Recently Adopted Accounting Pronouncements

On January 1, 2018, the Company adopted the following accounting pronouncements, using a prospective adoption method, which did not have an impact on the Company's consolidated financial statements and did not result in any significant policy changes:


•	Accounting Standards Update ("ASU") 2017-01—Business Combinations (Topic 805): Clarifying the Definition of a Business; and


•	ASU 2017-09—Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting.

The Company has also adopted ASU 2016-15—Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, although the retrospective adoption method did not have an impact on periods presented. The Company will apply this guidance to applicable future transactions.

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 February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02—Leases (Topic 842) ("ASU 2016-02"), which requires an entity to recognize right-of-use assets and lease liabilities on its balance sheet and disclose key information about leasing arrangements. ASU 2016-02 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. ASU 2016-02 is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early adoption permitted. ASU 2016-02 required a modified retrospective adoption approach, however subsequent guidance (discussed below) provides an additional option for adoption approach.

In July 2018, the FASB issued ASU 2018-11—Leases (Topic 842): Targeted Improvements ("ASU 2018-11"), which updates some of the implementation requirements under Accounting Standards Codification Topic 842 on leases. ASU 2018-11 provides for an additional adoption approach that was not previously included in ASU 2016-02 that allows for a prospective application. This guidance eliminates the requirement to present prior year comparative lease disclosures once ASU 2016-02 is adopted, and must be adopted concurrently with ASU 2016-02. The Company plans to apply the adoption method made available by ASU 2018-11.

Although the Company is evaluating the impact of adopting ASU 2016-02 on its consolidated financial statements, the Company expects that most of its operating lease commitments will be recognized as operating lease liabilities and right-of-use assets upon adoption of the new guidance. The adoption date of this guidance is January 1, 2019 in accordance with ASU 2018-11 and prior periods will not be adjusted. The Company continues to implement changes to its systems, processes and controls, in conjunction with its review of existing lease agreements. The Company’s leases primarily include, real estate leases (office space), equipment leases, and data center leases. The adoption of the new accounting guidance will have a material, although largely offsetting, impact on its consolidated balance sheet in future periods, with increases to both its total assets and total liabilities by establishing right-of-use assets and lease liabilities, respectively. The adoption of this guidance will not have a material impact to the Company's consolidated statements of operations and the Company does not expect it to have any impact on its total cash flows from operating, investing or financing activities.

In August 2018, the FASB issued ASU 2018-13—Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13"), to streamline the disclosure requirements of ASC Topic 820—Fair Value Measurement. ASU 2018 removes certain disclosure requirements, including the valuation process for Level 3 fair value measurements, and adds certain quantitative disclosures around Level 3 fair value measurements. This ASU is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period, with early adoption permitted. The provisions of ASU 2018-13 are required to be adopted retrospectively, with the exception of disclosure of

the range and weighted average of significant unobservable inputs used to develop Level 3 measurements, which can be adopted prospectively. The Company is currently evaluating the effect this guidance will have on its consolidated financial statements and related disclosures.

In August 2018, the FASB issued ASU 2018-15—Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15"). ASU 2018-15 was issued to clarify the requirements of ASC 350-40—Intangibles—Goodwill and Other—Internal-Use Software ("ASC 350-40"). The ASU clarifies that implementation, setup and other upfront costs related to cloud hosting agreements should be accounted for under ASC 350-40. This ASU is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period, with early adoption permitted. ASU 2018-15 can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is currently evaluating the effect this guidance will have on its consolidated financial statements.

In December 2018, the FASB issued ASU 2018-20—Leases (Topic 842): Narrow-Scope Improvements for Lessors ("ASU 2018-20"). ASU 2018-20 was issued to clarify the requirements for lessors under ASC 842—Leases ("ASC 842"). The ASU clarifies the recognition timing and requirements of certain payments made by lessees to either the lessor or a third party. This ASU is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with its adoption aligned with the adoption of ASU 2016-02. The Company functions as the sublessor for a limited number of real estate leases, however ASU 2018-20 is not applicable to these subleases.

Revenues

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Revenues

On January 1, 2018, the Company adopted Accounting Standards Update 2014-09—Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09") using a modified retrospective approach applied to all contracts that generated revenue in the preceding year. The adoption of this guidance did not have an impact on the amount or timing of revenue recognized by the Company.

The Company generates revenue from transactions where it provides a platform for the purchase and sale of digital advertising inventory. The Company’s advertising automation solution is a marketplace for sellers of digital advertising inventory (providers of websites, mobile applications and other digital media properties, and their representatives) and buyers of digital advertising inventory (including advertisers, agencies, agency trading desks, and demand-side platforms). This solution incorporates proprietary machine-

learning algorithms, sophisticated data processing, high-volume storage, detailed analytics capabilities, and a distributed infrastructure. Together, these features form the basis for the Company’s automated advertising solution that brings buyers and sellers together and facilitates intelligent decision-making and automated transaction execution for the digital advertising inventory managed on the Company's platform. Digital advertising inventory is created when consumers access sellers’ content. Sellers provide digital advertising inventory to the Company’s platform in the form of advertising requests, or ad requests. When the Company receives ad requests from sellers, it sends bid requests to buyers, which enable buyers to bid on sellers’ digital advertising inventory. Winning bids can create advertising, or paid impressions, for the seller to present to the consumer.

The total volume of spending between buyers and sellers on the Company’s platform is referred to as advertising spend. The Company keeps a percentage of that advertising spend as a fee, and remits the remainder to the seller. The fee that the Company retains from the gross advertising spend on its platform is recognized as revenue. The fee earned on each transaction is based on the pre-existing agreement between the Company and the seller and the clearing price of the winning bid. The Company recognizes revenue upon fulfillment of its performance obligation to a client, which occurs at the point in time an ad renders and is counted as a paid impression, subject to an underlying agreement existing with the client and a fixed or determinable transaction price. Performance obligations for all transactions are satisfied, and the corresponding revenue is recognized, at a distinct point in time when an ad renders. The Company does not have arrangements with multiple performance obligations.

The Company reports revenue on a net basis as it does not act as the principal in the purchase and sale of digital advertising inventory because it does not have control of the digital advertising inventory and does not set prices agreed upon within the auction marketplace. In periods prior to the second quarter of 2017, the Company reported revenue on a gross basis for revenue associated with its intent marketing solution, as the Company determined that it acted as the principal in the purchase and sale of digital advertising inventory. The Company ceased offering its intent marketing solution after the first quarter of 2017, after which time, all of the Company’s revenues have been recorded on a net basis. Revenue generated by the Company’s intent marketing solution in 2017 prior to its cessation was $1.3 million, which is included in total revenue for the year ended December 31, 2017.

Payment terms are specified in agreements between the Company and the buyers and sellers on its exchange platform. The Company generally bills buyers at the end of each month for the full purchase price of impressions filled in that month. The Company recognizes volume discounts as a reduction of revenue as they are incurred. Specific payment terms may vary by agreement, but are generally seventy-five days or less. 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. The Company's accounts payable related to amounts due to sellers are recorded at the net amount payable to sellers (see Note 11). Accordingly, both accounts receivable and accounts payable appear large in relation to revenue reported on a net basis.

The following table presents our revenue by channel for the years ended December 31, 2018 and 2017:



	Year Ended
	December 31, 2018				December 31, 2017
	(in thousands, except percentages)
Channel:
Desktop	$	59,039	47	%	$	84,327	54	%
Mobile	65,646		53		71,218		46
Total	$	124,685	100	%	$	155,545	100	%

The following table presents our revenue disaggregated by geographic location, based on the location of the Company's sellers:



	Year Ended
	December 31, 2018		December 31, 2017
	(in thousands)
United States	$	83,020	$	95,567
International	41,665		59,978
Total	$	124,685	$	155,545

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

Recurring Fair Value Measurements

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. Observable inputs are based on market data obtained from independent sources. 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.

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2018:



	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	13,692	$	13,692	$	—	$	—
U.S. Treasury, government and agency debt securities	$	7,524	$	7,524	$	—	$	—

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2017:



	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	1,807	$	210	$	1,597	$	—
Corporate debt securities	$	25,098	$	—	$	25,098	$	—
U.S. Treasury, government and agency debt securities	$	29,901	$	29,901	$	—	$	—

At December 31, 2018 and 2017, cash equivalents of $13.7 million and $1.8 million, respectively, consisted of money market funds and commercial paper, with original maturities of three months or less. 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 an active market. The commercial paper included in cash equivalents at December 31, 2017 is classified as Level 2 since its fair value is not based on quoted market prices for identical securities that are traded in an active market, but rather is derived from similar securities. Corporate debt securities (which are included in marketable securities on the balance sheet) with fair values derived from similar securities rather than based on quoted market prices for identical securities, are classified as Level 2 as well. The fair values of the Company's U.S. treasury, government and agency debt securities are based on quoted market prices and classified as Level 1, and are included within marketable securities.

There were no transfers between Level 1 and Level 2 fair value measurements during the year ended December 31, 2018 and 2017.

Non-Recurring Fair Value Measurements

Impairment of Goodwill

During the third quarter of 2017, the Company identified potential indications of impairment, which triggered a quantitative goodwill impairment assessment. The Company compared the fair value of its net assets, calculated using three valuation methodologies, to the carrying value of the net assets. The fair value of the Company's net assets falls within Level 3 of

the fair value hierarchy, as it was determined using unobservable inputs and relied on assumptions and estimates made by the Company's management. The valuation process is described below:

Income Approach. The Company first estimated the fair value of its net assets based on an income approach using the 2017 remaining year forecast, projections for growth from that base, and a terminal growth rate. The cash flows were discounted using the Company's estimated weighted average cost of capital rate of 16.2%. The value of net operating losses and the excess working capital were then added to the discounted cash flows to arrive at the income approach fair value of the Company's net assets.

Market Approach. The market approach used to determine the fair value of the Company's net assets was based upon a review of private and public company control transactions involving comparable companies. The Company performed two analyses under the market approach—a control premium analysis and a similar transaction analysis. In each of these analyses, the Company identified merger or acquisition transactions that were completed over the past three years involving targets that operate within the “Advertising” or “Internet Software and Services” industries and where the buyer was a strategic buyer. In the control premium analysis, the Company calculated a control premium paid in each of these transactions. After analyzing the comparable transactions, the Company applied a control premium of 15% to its adjusted public equity value to derive the fair value of its net assets. An additional method under the market approach, the similar transactions method, was utilized to determine the fair value of the Company's net assets under a strategic buyer purchase scenario. In this analysis, target companies were compared to the Company and multiples paid in transactions, specifically EBITDA, were analyzed and applied to the Company's adjusted EBITDA for the twelve months ended September 30, 2017. Based on the results of this analysis, an adjusted EBITDA multiple of 2.0x was applied to calculate the fair value of the Company's net assets. In determining the comparability of publicly-traded companies, several factors were analyzed, including products and solutions, markets, growth patterns, relative size, earnings trends and other financial characteristics.

The Company compared the fair value of its net assets using the three methodologies (one income approach and two market approaches) described above, to the carrying value and determined that its goodwill was fully impaired. The Company recorded an impairment of $90.3 million to adjust its goodwill balance to its fair value of zero.

Impairment of Intangible Assets and Internal Use Software

The Company measures impairment loss based on the difference between the carrying amount and estimated fair value. In the fourth quarter of 2017, we performed a cash flow analysis of our Guaranteed Orders workflow tool that resulted in impairment charges of the related intangible assets and long lived assets totaling $3.5 million and $1.1 million, respectively. The intangible assets included developed technology and client relationships acquired as part of an acquisition completed in 2014. The fair value of the asset group was determined based on a discounted cash flow method, which reflected estimated future cash flows associated with the identified asset group at the measurement date, and falls within Level 3 of the fair value hierarchy. The asset group was determined to be fully impaired and the assets were written down to their fair values of zero.

For the year ended December 31, 2018, no impairments were recorded on the Company's assets required to be measured at fair value on a non-recurring basis.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Investments Investments (Notes)

12 Months Ended

Dec. 31, 2018

Investments, Fair Value Disclosure [Abstract]

Investments

Investments in marketable securities as of December 31, 2018 consisted of the following:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
Available-for-sale—short-term:
U.S. Treasury, government and agency debt securities	$	7,526	$	—	$	(2	)	$	7,524

The Company's available-for-sale securities had a weighted remaining contractual maturity of 0.1 years as of December 31, 2018. During the year ended December 31, 2018, the Company sold $9.2 million of available-for-sale investments, on which the realized gains were de minimis and there were no unrealized holding gains (losses) reclassified out of accumulated other comprehensive loss into the consolidated statements of operations. The Company had no sales of available-for-sale investments in 2017. As of December 31, 2018, all of the Company's marketable securities had contractual maturities of less than one year.

Investments in marketable securities as of December 31, 2017 consisted of the following:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
Available-for-sale—short-term:
U.S. Treasury, government and agency debt securities	$	27,426	$	—	$	(20	)	$	27,406
Corporate debt securities	25,098		—		—			25,098
Total	$	52,524	$	—	$	(20	)	$	52,504
Available-for-sale—long-term:
U.S. Treasury, government and agency debt securities	$	2,504	$	—	$	(9	)	$	2,495

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property and Equipment

Major classes of property and equipment were as follows:



	December 31, 2018			December 31, 2017
	(in thousands)
Purchased software	$	1,254		$	1,985
Computer equipment and network hardware	98,884			90,695
Furniture, fixtures and office equipment	1,973			2,165
Leasehold improvements	2,571			3,325
Gross property and equipment	104,682			98,170
Accumulated depreciation	(71,195		)	(50,777		)
Net property and equipment	$	33,487		$	47,393

Depreciation expense on property and equipment totaled $25.0 million and $20.3 million for the years ended December 31, 2018 and 2017, respectively. There were no impairment charges to property and equipment for the years ended December 31, 2018 and 2017.

At December 31, 2018 and 2017, the Company had no property and equipment under capital leases.

The Company's property and equipment, net by geographical region was as follows:



	December 31, 2018		December 31, 2017
	(in thousands)
United States	$	24,928	$	37,566
International	8,559		9,827
Total	$	33,487	$	47,393

Internal Use Software Development Costs

12 Months Ended

Dec. 31, 2018

Research and Development [Abstract]

Internal Use Software Development Costs

Internal use software development costs were as follows:



	December 31, 2018			December 31, 2017
	(in thousands)
Internal use software development costs, gross	41,882			$	33,414
Accumulated amortization	(27,312		)	(20,680		)
Internal use software development costs, net	$	14,570		$	12,734

During the years ended December 31, 2018 and 2017, the Company capitalized $9.0 million and $8.4 million, respectively, of internal use software development costs. Amortization expense was $7.2 million and $11.1 million for the years ended December 31, 2018 and 2017, respectively. In the years ended December 31, 2018 and 2017, amortization expense included the write-off of software development costs of $0.5 million and $1.6 million, in the respective periods. Based on the Company’s internal

use software development costs at December 31, 2018, estimated amortization expense of $7.0 million, $5.1 million and $2.5 million is expected to be recognized in 2019, 2020 and 2021, respectively.

In the fourth quarter of 2017, the Company recognized an impairment of the remaining capitalized software asset related to its Guaranteed Orders workflow tool of $1.1 million, which is included within impairment of intangible assets and internal use software on the consolidated statements of operations (see Note 5 for additional valuation details). There were no impairment charges to internal use software development costs for the year ended December 31, 2018.

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

Throughout 2017, the Company experienced a decrease in its stock price and market capitalization. During the third quarter of 2017, there were also certain developments that negatively impacted the Company's near-term business outlook, including the strategic decision to make reductions in the fees the Company charges buyers in open market waterfall RTB transactions, header bidding, and direct pressure from buyers and sellers, which accelerated dramatically in 2017. The Company concluded that these developments, together with the continued decline in the Company's market capitalization below the carrying value of its net assets, represented an indication of impairment that triggered the Company to perform a quantitative valuation assessment of its goodwill. The Company, with the assistance of a valuation consultant, performed a fair value assessment of its net assets using fair values derived from income and market approaches and weighted the outcomes. The fair value of its net assets was compared to the carrying value of $274.4 million and, as the carrying value exceeded the estimated fair value, the Company recorded an impairment charge of $90.3 million during the third quarter of 2017. For additional details regarding the valuation assessment process, refer to Note 5.

The Company no longer had a goodwill balance following the goodwill impairment. Activity of the Company’s goodwill for the year ended December 31, 2017 was as follows:



	December 31, 2017
	(in thousands)
Beginning balance	$	65,705
Additions from the acquisition of nToggle (See Note 10)	24,546
Impairment of goodwill	(90,251		)
Ending balance	$	—

The Company’s intangible assets as of December 31, 2018 and 2017 included the following:



	December 31, 2018			December 31, 2017
	(in thousands)
Amortizable intangible assets:
Developed technology	$	16,878		$	16,878
Non-compete agreements	690			690
Trademarks	20			20
Total identifiable intangible assets, gross	17,588			17,588
Accumulated amortization—intangible assets:
Developed technology	(6,888		)	(4,062		)
Non-compete agreements	(506		)	(161		)
Trademarks	(20		)	(6		)
Total accumulated amortization—intangible assets	(7,414		)	(4,229		)
Total identifiable intangible assets, net	$	10,174		$	13,359

Amortization of intangible assets for the years ended December 31, 2018 and 2017 was $3.2 million and $4.8 million, respectively.

In the fourth quarter of 2017, the Company recognized an impairment charge of the remaining intangible assets associated with its Guaranteed Orders workflow tool, totaling $3.5 million. These intangible assets included developed technology and client relationships acquired as part of an acquisition completed in 2014. See Note 5 for additional information.

The estimated remaining amortization expense associated with the Company's intangible assets was as follows as of December 31, 2018:



Fiscal Year	Amount
	(in thousands)
2019	$	3,010
2020	2,826
2021	2,826
2022	1,512
2023	—
Thereafter	—
Total	$	10,174

Business Combinations

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Business Combinations

2017 Acquisition—nToggle, Inc.

On July 14, 2017, the Company completed the merger of nToggle, Inc. ("nToggle") with Caviar Acquisition Corp., a wholly owned subsidiary of the Company, with nToggle surviving as a wholly owned subsidiary of Rubicon Project. nToggle was a Boston, Massachusetts based programmatic advertising company with traffic-shaping technology. The primary reason for the acquisition was to acquire technology, know-how and personnel that will enable the Company to offer services that make it easier and more cost-effective for buyers to find the inventory they seek among the billions of bid requests they receive. At closing, the Company paid net cash consideration of $38.6 million, which represents total purchase consideration of $40.6 million less acquired cash and cash equivalents of $2.0 million, to the stockholders, warrantholders, and holders of vested in-the-money options of nToggle. In addition, the Company assumed 432,482 outstanding unvested in-the-money options and 77,499 shares of restricted stock held by continuing employees, and issued an aggregate of 174,117 restricted stock units to the continuing employees under the Company's 2014 Inducement Grant Equity Incentive Plan. The financial results of nToggle have been included in our consolidated financial statements since the date of the acquisition.

The major classes of assets and liabilities to which the Company allocated the purchase price were as follows as of the acquisition date:



	Amount
	(in thousands)
Cash and cash equivalents	$	1,953
Accounts receivable	256
Prepaid and other assets	18
Fixed assets	763
Other non-current assets	82
Intangible assets	14,840
Goodwill	24,546
Total assets acquired	42,458
Accounts payable and accrued expenses	78
Deferred revenue	91
Deferred tax liability, net	1,719
Total liabilities assumed	1,888
Total net assets acquired	$	40,570

The Company recognized approximately $0.3 million of acquisition-related costs during the year ended December 31, 2017 that are included within general and administrative expenses in the Company’s consolidated statements of operations. As part of the acquisition of nToggle, the Company acquired nToggle's net operating losses of approximately $9.3 million. In addition, the Company recorded deferred tax liabilities related to acquired intangibles of $5.5 million net of deferred tax assets of $3.8 million primarily related to net operating loss carryforwards.

The following table summarizes the components of the acquired intangible assets and estimated useful lives (in thousands, except for estimated useful life):



	December 31, 2017		Estimated Useful Life
Developed technology	$	14,130	5 years
Non-compete agreements	690		2 years
Trademark & trade name	20		1.5 years
Total intangible assets acquired	$	14,840

The intangible assets are amortized on a straight-line basis, which approximates the pattern in which the economic benefits are consumed, over their estimated useful lives. Amortization of developed technology is included in cost of revenue, the amortization related to non-compete agreements is included in technology and development, and amortization related to trademark and trade name is included in general and administrative.

Goodwill resulting from the acquisition was primarily attributable to acquired workforce, an increase in development capabilities, increased offerings to clients, and enhanced opportunities for growth and innovation. Refer to Note 5 for a description of the methods used to compute the charge for the impairment of consolidated goodwill of $90.3 million recorded in the third quarter of 2017. The acquired intangibles and goodwill resulting from the nToggle acquisition are not amortizable for tax purposes.

Unaudited Pro Forma Information - nToggle Acquisition

The following table provides unaudited condensed pro forma information to give effect to the nToggle acquisition as if it had occurred on January 1, 2017. The unaudited pro forma information reflects adjustments for additional amortization resulting from the fair value adjustments to assets acquired and liabilities assumed. The pro forma results do not include any anticipated cost synergies or other effects of the integration of nToggle. Accordingly, pro forma amounts are not necessarily indicative of the results that actually would have occurred had the acquisition been completed on the date indicated, nor are they indicative of the actual or future operating results of the combined company.



	Year Ended
	December 31, 2017
	(in thousands)
Pro forma revenues	$	156,480
Pro forma net loss	$	(158,443	)
Pro forma net loss per share, basic	$	(3.24	)
Pro forma net loss per share, diluted	$	(3.24	)

nToggle's technology was fully integrated into the Company's platform, and its pre-acquisition product is not offered on a stand-alone basis. As a result, the determination of nToggle's post-acquisition revenue and operating results on a stand-alone basis was impracticable.

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Accounts Payable and Accrued Expense

Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses included the following:



	December 31, 2018		December 31, 2017
	(in thousands)
Accounts payable—seller	$	230,423	$	203,694
Accounts payable—trade	3,122		3,764
Accrued employee-related payables	6,133		6,645
Total	$	239,678	$	214,103

Accumulated Other Comprehensive Loss

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Accumulated Other Comprehensive Loss

Accumulated Other Comprehensive Income (Loss)

The components of accumulated other comprehensive income (loss) were as follows (in thousands):



	Unrealized Gain (Loss) on Investments, net of tax			Foreign Currency Translation			Accumulated Other Comprehensive Income (Loss)
Balance at December 31, 2016	$	(1	)	$	(272	)	$	(273	)
Other comprehensive income (loss)	(28		)	342			314
Balance at December 31, 2017	(29		)	70			41
Other comprehensive income (loss)	27			(327		)	(300		)
Balance at December 31, 2018	$	(2	)	$	(257	)	$	(259	)

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

In connection with its IPO, the Company implemented its 2014 Equity Incentive Plan, which governs equity awards made to employees and directors of the Company since the IPO. Prior to the IPO, the Company granted equity awards under its 2007 Stock Incentive Plan, which governs equity awards made to employees and contractors under the plan. In November 2014, the Company approved the 2014 Inducement Grant Equity Incentive Plan (the "Inducement Plan"), which governs certain equity awards made to certain employees in connection with commencement of employment. In connection with the Company's acquisitions of Chango Inc. ("Chango") and iSocket, Inc. ("iSocket"), it assumed the existing employee equity award plans, the 2009 Chango Stock Option Plan (the "Chango Plan") and the 2009 Equity Incentive Plan - iSocket (the "iSocket Plan"). As part of the nToggle acquisition in July 2017, the Company assumed all unvested in-the-money options and restricted stock held by continuing employees under the nToggle, Inc. 2014 Equity Incentive Plan ("nToggle Plan") (see Note 10). All compensatory equity awards outstanding at December 31, 2018 were issued pursuant to the 2014 Equity Incentive Plan, the iSocket Plan, the Chango Plan, the nToggle Plan, the Inducement Plan, or the Company's 2007 Stock Incentive Plan.

The Company’s equity incentive plans provide for the grant of equity awards, including non-statutory or incentive stock options, restricted stock awards, and restricted stock units, to the Company's employees, officers, directors, and consultants. The Company's board of directors administers the plans. Options outstanding vest based upon continued service at varying rates, but generally over four years from issuance with 25% vesting after one year of service and the remainder vesting monthly thereafter. Restricted stock awards and restricted stock units vest at varying rates, typically approximately 25% vesting after approximately one year of service and the remainder vesting semi-annually thereafter. The restricted stock units granted in 2018 included 2,800,000 restricted stock units that vest 50% on each of the first and second anniversaries of the grant date. Options, restricted stock awards, and restricted stock units granted under the plans accelerate under certain circumstances for certain participants upon on a change in control, as defined in the governing plan. No further awards were made under the iSocket Plan, the Chango Plan, the nToggle Plan, or the 2007 Stock Incentive Plan; available shares under the iSocket Plan, the Chango Plan, and the nToggle Plan were rolled into the available share pool under the 2014 Equity Incentive Plan at the time of acquisition of each company, and available shares under the 2007 Stock Incentive Plan were rolled into the available share pool under the 2014 Equity Incentive Plan at the time of the IPO. An aggregate of 6,701,872 shares remained available for future issuance at December 31, 2018 under the plans. The 2014 Equity Incentive Plan has an evergreen provision pursuant to which the share reserve will automatically increase on January 1^st of each year in an amount equal to 5% of the total number of shares of capital stock outstanding on December 31^st of the preceding calendar year, although the Company’s board of directors may provide for a lesser increase, or no increase, in any year. The 2014 Inducement Grant Equity Incentive Plan has a provision pursuant to which the share reserve may be increased at the discretion of the Company's board of directors.

Stock Options

A summary of stock option activity for the year ended December 31, 2018 is as follows:



	Shares Under Option		Weighted- Average Exercise Price		Weighted- Average Contractual Life	Aggregate Intrinsic Value
	(in thousands)					(in thousands)
Outstanding at December 31, 2017	4,363		$	8.75
Granted	706		$	2.09
Exercised	(50	)	$	0.91
Expired	(1,438	)	$	10.17
Forfeited	(93	)	$	3.83
Outstanding at December 31, 2018	3,488		$	7.06	7.09 years	$	2,354
Exercisable at December 31, 2018	2,114		$	9.29	6.07 years	$	765

The total intrinsic values of options exercised during the year ended December 31, 2018 was $0.1 million. At December 31, 2018, the Company had unrecognized employee stock-based compensation expense relating to nonvested stock options of approximately $3.2 million, which is expected to be recognized over a weighted-average period of 2.5 years. The weighted-average grant date fair value per share of stock options granted during the year ended December 31, 2018 was $1.15. Total fair value of options vested during the year ended December 31, 2018 was $3.3 million.

The Company estimates the fair value of stock options that contain service and/or performance conditions using the Black-Scholes option pricing model. The weighted-average input assumptions used by the Company were as follows:



	Year Ended
	December 31, 2018		December 31, 2017
Expected term (in years)	6.0		5.8
Risk-free interest rate	2.67	%	2.03	%
Expected volatility	57	%	57	%
Dividend yield	—	%	—	%

Restricted Stock Awards

A summary of restricted stock activity for the year ended December 31, 2018 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested shares of restricted stock outstanding at December 31, 2017	558		$	12.60
Granted	—		$	—
Canceled	(156	)	$	13.82
Vested	(205	)	$	12.19
Nonvested shares of restricted stock outstanding at December 31, 2018	197		$	12.06

The aggregate fair value of restricted stock awards with service conditions that vested during the year ended December 31, 2018 was $0.6 million. At December 31, 2018, the Company had unrecognized stock-based compensation expense for restricted stock awards with service conditions of $0.9 million, which is expected to be recognized over a weighted-average period of 1.1 years.

Restricted Stock Units

A summary of restricted stock unit activity for the year ended December 31, 2018 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested restricted stock units outstanding at December 31, 2017	3,609		$	7.55
Granted	4,976		$	2.30
Canceled	(1,118	)	$	5.32
Vested	(1,367	)	$	8.06
Nonvested restricted stock units outstanding at December 31, 2018	6,100		$	3.56

The weighted-average grant date fair value per share of restricted stock units granted during the year ended December 31, 2018 was $2.30. The aggregate fair value of restricted stock units that vested during year ended December 31, 2018 was $4.3 million. At December 31, 2018, the intrinsic value of nonvested restricted stock units was $22.8 million. At December 31, 2018, the Company had unrecognized stock-based compensation expense relating to nonvested restricted stock units of approximately $17.3 million, which is expected to be recognized over a weighted-average period of 2.1 years.

Employee Stock Purchase Plan

In November 2013, the Company adopted the Company's 2014 Employee Stock Purchase Plan ("ESPP"). The ESPP is designed to enable eligible employees to periodically purchase shares of the Company's common stock at a discount through payroll deductions of up to 10% of their eligible compensation, subject to any plan limitations. At the end of each six-month offering period, employees are able to purchase shares at a price per share equal to 85% of the lower of the fair market value of the Company's common stock on the first trading day of the offering period or on the last trading day of the offering period. Offering periods generally commence and end in May and November of each year.

As of December 31, 2018, the Company has reserved 1,607,646 shares of its common stock for issuance under the ESPP. The ESPP has an evergreen provision pursuant to which the share reserve will automatically increase on January 1^st of each year in an amount equal to 1% of the total number of shares of capital stock outstanding on December 31^st of the preceding calendar year, although the Company’s board of directors may provide for a lesser increase, or no increase, in any year.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded in the consolidated statements of operations was as follows:



	Year Ended
	December 31, 2018		December 31, 2017
	(in thousands)
Cost of revenue	$	321	$	404
Sales and marketing	4,557		4,582
Technology and development	2,867		4,034
General and administrative	8,139		9,924
Restructuring and other exit costs	398		1,560
Total stock-based compensation expense	$	16,282	$	20,504

Restructuring and Other Exit Costs

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring and Other Exit Costs

As part of its on-going efforts to control costs and create efficiencies, the Company underwent restructuring events throughout 2017 and in the first quarter of 2018. The objective of these restructuring activities was to streamline operations, prioritize resources for growth initiatives and increase profitability.

For the year ended December 31, 2017, the Company recognized $6.0 million of restructuring and other exit costs expenses related to the cessation of it's intent marketing solution, including the closure of the Toronto office, as well as the realignment of the management team to a more cost efficient structure (collectively, the "2017 Restructuring Events"). A majority of

the costs incurred in the year ended December 31, 2017 were severance and one-time termination benefit costs, of which $1.6 million related to non-cash stock-based compensation, the remainder of which related to facility closure costs.

In the first quarter of 2018, the Company announced its restructuring plan to reduce headcount to bring the Company's general and administrative operations into better alignment with the current size of the business and de-layer certain functions, and to reduce its investment in unprofitable projects (the "2018 Restructuring Events"). During the year ended December 31, 2018, the Company incurred restructuring and other exit costs expenses of $3.4 million for severance and one-time termination benefits.

The following table summarizes restructuring and other exit cost activity for the 2018 Restructuring Events (in thousands):



Accrued restructuring and other exit costs at December 31, 2017	$	—
Restructuring and other exit costs	3,440
Cash paid for restructuring and other exit costs	(2,975		)
Non-cash stock-based compensation for restructuring and other exit costs	(398		)
Accrued restructuring and other exit costs at December 31, 2018	$	67

Accrued restructuring costs related to the 2017 Restructuring Events were $0.1 million at December 31, 2017 and were paid in the first half of 2018. Accrued restructuring costs are included within other liabilities on the Company's consolidated balance sheets.

The following table presents the components of restructuring and other exit costs for the years ended December 31, 2018 and 2017 (in thousands):



	Year Ended
	December 31, 2018		December 31, 2017
Employee termination costs	$	3,440	$	5,753
Facility closing costs	—		206
Total restructuring and other exit costs	$	3,440	$	5,959

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

The following are the domestic and foreign components of the Company’s income (loss) before income taxes for the years ended December 31, 2018 and 2017:



	Year Ended
	December 31, 2018			December 31, 2017
	(in thousands)
Domestic	$	(62,292	)	$	(104,750	)
International	827			(51,795		)
Loss before income taxes	$	(61,465	)	$	(156,545	)

The following are the components of the provision (benefit) for income taxes for the years ended December 31, 2018 and 2017:



	Year Ended
	December 31, 2018			December 31, 2017
	(in thousands)
Current:
Federal	$	(23	)	$	(140	)
State	41			78
Foreign	388			(250		)
Total current provision	406			(312		)
Deferred:
Federal	—			(1,877		)
State	2			288
Foreign	(51		)	139
Total deferred benefit	(49		)	(1,450		)
Total provision (benefit) for income taxes	$	357		$	(1,762	)

The Company recorded an income tax expense of $0.4 million for the year ended December 31, 2018 and an income tax benefit of $1.8 million for the year ended December 31, 2017. The tax provision for the year ended December 31, 2018 is primarily the result of the domestic valuation allowance and the tax liability associated with the foreign subsidiaries.

During the fourth quarter of 2017, the Company recorded a tax deduction of $145.8 million and increased its valuation allowance by a corresponding amount, resulting in no net tax benefit related to a worthless stock deduction generated by the Company's exit from its intent marketing business activities in Canada.

On December 22, 2017, the U.S. government enacted the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act includes significant changes to the U.S. corporate income tax system including the following: a federal corporate rate reduction from 34% to 21%; limitations on the deductibility of executive compensation and research and development (“R&D”) expenditures; temporary immediate expensing of qualified property; the creation of new minimum taxes such as the base erosion anti-abuse tax (“BEAT”) and Global Intangible Low Taxed Income (“GILTI”) tax; and the transition of U.S. international taxation from a worldwide tax system to a modified territorial tax system, which resulted in a one time U.S. tax liability on those earning which had not previously been repatriated to the U.S. (the “Transition Tax”).

The Tax Act imposes a Transition Tax on previously untaxed accumulated and current earnings and profits (“E&P”) of certain of our foreign subsidiaries. To determine the amount of the Transition Tax, the Company determined, among other things, the amount of post-1986 E&P of the relevant subsidiaries. The Company recorded a provisional Transition Tax of $0.6 million, which reduced its U.S. net deferred tax assets for the year ended December 31, 2017. We completed our analysis of the impact of U.S. tax reform during 2018, and for the year ended December 31, 2018, there was no change to the Transaction Tax recorded in the prior period.

The Tax Act also reduced the U.S. corporate tax rate from 34% to 21%, effective January 1, 2018. Consequently, the Company recorded a decrease to its tax effected U.S. net deferred tax assets of $31.6 million, with a corresponding decrease to the U.S. valuation allowance for the year ended December 31, 2017 as a result of re-measuring net deferred tax assets at the new lower corporate tax rate of 21%.

The Tax Act requires certain GILTI income earned by controlled foreign corporations (“CFCs”) to be included in the gross income of the CFCs’ U.S. shareholder (for tax years beginning after December 31, 2017). For the year ended December 31, 2018, the Company has included a GILTI inclusion of $1.3 million, which was incorporated in the calculation of the tax provision.

Set forth below is a reconciliation of the components that caused the Company’s provision (benefit) for income taxes to differ from amounts computed by applying the U.S. Federal statutory rate of 21% for the year ended December 31, 2018 and 34% for the year ended December 31, 2017:



	Year Ended
	December 31, 2018		December 31, 2017
U.S. federal statutory income tax rate	21.0	%	34.0	%
State income taxes, net of federal benefit	(0.1	)%	—	%
Foreign income (loss) at other than U.S. rates	—	%	0.2	%
Stock-based compensation expense	(5.3	)%	(3.8	)%
Meals and entertainment	(0.4	)%	(0.1	)%
Goodwill impairment	—	%	(19.0	)%
Research and development tax credits	—	%	0.8	%
Debt cancellation	(1.2	)%	—	%
Worthless stock	—	%	31.7	%
Other permanent items	(0.5	)%	(0.5	)%
Change in valuation allowance	(14.1	)%	(22.0	)%
Tax rate change; U.S. tax reform	—	%	(20.2	)%
Effective income tax rate	(0.6	)%	1.1	%

Set forth below are the tax effects of temporary differences that give rise to a significant portion of the deferred tax assets and deferred tax liabilities as of December 31, 2018 and 2017:



	December 31, 2018			December 31, 2017
	(in thousands)
Deferred Tax Assets:
Accrued liabilities	$	916		$	2,648
Stock-based compensation	2,623			3,685
Net operating loss carryovers	76,098			65,648
Tax credit carryovers	13,206			13,494
Other	1,053			1,502
Total deferred tax assets	93,896			86,977
Less valuation allowance	(90,959		)	(81,767		)
Deferred tax assets, net of valuation allowance	2,937			5,210
Deferred Tax Liabilities:
Fixed assets	(2,352		)	(3,864		)
Intangible assets	(152		)	(955		)
Other	—			—
Total deferred tax liabilities	(2,504		)	(4,819		)
Net deferred tax assets (liability)	$	433		$	391

The change in valuation allowance for the years ended December 31, 2018 and 2017 was $9.2 million and $42.3 million, respectively.

At December 31, 2018, the Company had U.S. federal net operating loss carryforwards, or NOLs, of approximately $285.5 million, which will begin to expire in 2027. At December 31, 2018, the Company had state NOLs of approximately $167.0 million, which will begin to expire in 2027. At December 31, 2018, the Company had foreign NOLs of approximately $20.5 million, which will begin to expire in 2026. At December 31, 2018, the Company had federal research and development tax credit carryforwards, or credit carryforwards, of approximately $10.2 million, which will begin to expire in 2027. At December 31, 2018, the Company had state research and development tax credits of approximately $8.0 million, which carry forward indefinitely. No amounts for any federal or state research and development tax credits for the year ended December 31, 2018 are included herein.

Utilization of certain NOLs and credit carryforwards may be subject to an annual limitation due to ownership change limitations set forth in the Internal Revenue Code of 1986, as amended, or the Code, and comparable state income tax laws. Any future annual limitation may result in the expiration of NOLs and credit carryforwards before utilization. A prior ownership change and certain acquisitions resulted in the Company having NOLs subject to insignificant annual limitations.

Additionally, for tax years beginning after December 31, 2017, the Tax Act limits the NOL deduction to 80% of taxable income, repeals carryback of all NOLs arising in a tax year ending after 2017, and permits indefinite carryforward for all such NOLs. NOL’s arising in a tax year ending in or before 2017 can offset 100% of taxable income, are available for carryback, and expire 20 years after they arise.

At December 31, 2018, unremitted earnings of the subsidiaries outside of the United States were approximately $7.6 million, on which the Company recorded a transition tax of $0.6 million, as discussed above. The Company’s intention is to indefinitely reinvest these earnings outside the United States. Upon distribution of those earnings in the form of a dividend or otherwise, the Company would be subject to withholding taxes payable to various foreign countries and, potentially, various state taxes. The amounts of such tax liabilities that might be payable upon actual repatriation of foreign earnings, after consideration of corresponding foreign tax credits, are not material.

The following table summarizes the activity related to the unrecognized tax benefits (in thousands):



	Amount
	(in thousands)
Balance as of December 31, 2016	$	5,027
Increases related to 2017 tax positions	619
Decreases related to prior year tax positions	—
Balance as of December 31, 2017	5,646
Increases related to current year tax positions	—
Decreases related to current year tax positions	—
Decreases related to prior year tax positions	(929		)
Balance as of December 31, 2018	$	4,717

Interest and penalties related to the Company’s unrecognized tax benefits accrued at December 31, 2018 and 2017 were not material.

Due to the net operating loss carryforwards, the Company's United States federal and a majority of its state returns are open to examination by the Internal Revenue Service and state jurisdictions for all years since inception. For Australia, Brazil, Canada, Germany, Italy, Japan, Singapore, and the United Kingdom, all tax years remain open for examination by the local country tax authorities, while for France only 2014 forward are open for examination. During the first quarter of 2017, the Internal Revenue Service ("IRS") commenced an examination of the 2015 tax year. During 2018, the Company received an IRS Letter 1226 indicating no change to the 2015 tax return as filed and concluded the examination.

The Company does not expect its uncertain income tax positions to have a material impact on its consolidated financial statements within the next twelve months.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

The Company has commitments under non-cancelable operating leases for facilities, certain equipment, and its managed data center facilities. Total rental expenses were $12.6 million and $12.7 million for the years ended December 31, 2018 and 2017, respectively. Additionally, expenses for cloud-based services related to data centers were $7.1 million and $4.9 million for the years ended December 31, 2018 and 2017, respectively. As of December 31, 2018 and December 31, 2017, the Company had $2.9 million of letters of credit associated with office leases available for borrowing, on which there were no outstanding borrowings as of either date.

The following table summarizes the Company's future minimum lease payments under non-cancelable operating leases and related sublease income at December 31, 2018:



	2019			2020			2021			2022			2023			Total
	(in thousands)
Operating lease expense	$	6,773		$	3,880		$	1,734		$	1,019		$	597		$	14,003
Operating sublease income	(285		)	(194		)	(194		)	(194		)	(145		)	(1,012		)
Total	$	6,488		$	3,686		$	1,540		$	825		$	452		$	12,991

Guarantees and Indemnification

The Company’s agreements with sellers, buyers, and other third parties typically obligate it to provide indemnity and defense for losses resulting from claims of intellectual property infringement, damages to property or persons, business losses, or other liabilities. Generally, these indemnity and defense obligations relate to the Company’s own business operations, obligations, and acts or omissions. However, under some circumstances, the Company agrees to indemnify and defend contract counterparties against losses resulting from their own business operations, obligations, and acts or omissions, or the business operations, obligations, and acts or omissions of third parties. For example, because the Company’s business interposes the Company between buyers and sellers in various ways, buyers often require the Company to indemnify them against acts and omissions of sellers, and sellers often require the Company to indemnify them against acts and omissions of buyers. In addition, the Company’s agreements with sellers, buyers, and other third parties typically include provisions limiting the Company’s liability to the counterparty, and the counterparty’s liability to the Company. These limits sometimes do not apply to certain liabilities, including indemnity obligations. These indemnity and limitation of liability provisions generally survive termination or expiration of the agreements in which they appear. The Company has also entered into indemnification agreements with its directors, executive officers and certain other officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. No material demands have been made upon the Company to provide indemnification under such agreements and there are no claims that the Company is aware of that could have a material effect on the Company’s consolidated financial statements.

Litigation

The Company and its subsidiaries may from time to time be parties to legal or regulatory proceedings, lawsuits and other claims incident to their business activities and to the Company’s status as a public company. Such matters may include, among other things, assertions of contract breach or intellectual property infringement, claims for indemnity arising in the course of the Company’s business, regulatory investigations or enforcement proceedings, and claims by persons whose employment has been terminated. Such matters are subject to many uncertainties, and outcomes are not predictable with assurance. Consequently, management is unable to ascertain the ultimate aggregate amount of monetary liability, amounts which may be covered by insurance or recoverable from third parties, or the financial impact with respect to such matters as of December 31, 2018. However, based on management’s knowledge as of December 31, 2018, management believes that the final resolution of these matters known at such date, individually and in the aggregate, will not have a material adverse effect upon the Company’s consolidated financial position, results of operations or cash flows.

On March 31, 2017, Guardian News & Media Limited ("Guardian") issued proceedings (the "Complaint") against the Company in the Chancery Division of the High Court of Justice in England & Wales. The Complaint alleged that the Company underpaid Guardian for digital advertising inventory sold by Guardian through the Company's platform as a result of the fact that the Company charged fees to buyers of that inventory. Guardian claimed the Company was precluded from charging buyer fees as a result of the contractual arrangements with Guardian and English agency law principles, as well as representations it allegedly made to Guardian. The Complaint claimed damages including loss of revenue, interest, and costs. On October 11, 2018, the Company and Guardian mutually agreed to resolve their dispute and the High Court proceedings have been discontinued. Though the terms of the settlement agreement are confidential, the settlement is immaterial to the Company from a financial standpoint.

Employment Contracts

The Company has entered into severance agreements with certain employees and officers. The Company may be required to pay severance and accelerate the vesting of certain equity awards in the event of involuntary terminations.

Debt	12 Months Ended
Debt	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt On September 26, 2018, the Company amended and restated its loan and security agreement with Silicon Valley Bank (the "Loan Agreement"), which was scheduled to expire on September 27, 2018. The Loan Agreement provides a senior secured revolving credit facility of up to $40.0 million with a maturity date of September 26, 2020. The amount available for borrowing as of December 31, 2018 is $30.0 million due to a $10.0 million reserve that will be released if the Company maintains positive Adjusted EBITDA for any trailing twelve-month period. The Company incurred $0.1 million of debt issuance fees that were capitalized and are being amortized over the term of the Loan Agreement. An unused revolver fee in the amount of 0.15% per annum of the average unused portion of the revolver line is charged and is payable monthly in arrears. The Company may elect for advances to bear interest calculated by reference to prime or LIBOR. If the Company elects LIBOR, amounts outstanding under the amended credit facility bear interest at a rate per annum equal to LIBOR plus 2.50% if a streamline period applies or LIBOR plus 4.00% if a streamline period does not apply. If the Company elects prime, advances bear interest at a rate of prime plus 0.50% if a streamline period applies or prime plus 2.00% if a streamline period does not apply. A streamline period is any period during which an event of default does not exist and the Company's Adjusted Quick Ratio (as defined in the Loan Agreement) is at least 1.05 for each day in the preceding month. The Loan Agreement is collateralized by security interests in substantially all of the Company's assets. Subject to certain exceptions, the Loan Agreement restricts the Company's ability to, among other things, pay dividends, sell assets, make changes to the nature of the business, engage in mergers or acquisitions, incur, assume or permit to exist, additional indebtedness and guarantees, create or permit to exist, liens, make distributions or redeem or repurchase capital stock, or make other investments, engage in transactions with affiliates, make payments with respect to subordinated debt, and enter into certain transactions without the consent of the financial institution. If a streamline period is not in effect, the Company is required to maintain a lockbox arrangement where clients payments received in the lockbox will immediately reduce the amounts outstanding on the credit facility. The Loan Agreement requires the Company to comply with financial covenants, including a minimum Adjusted Quick Ratio and the achievement of certain Adjusted EBITDA targets. On a monthly basis, or quarterly if there were no advances outstanding during the calendar quarter, the Company is required to maintain a minimum Adjusted Quick Ratio of: (i) 1.00 if the trailing six month adjusted EBITDA is $0 or less, or (ii) 0.90 if the trailing six month adjusted EBITDA is greater than $0. If the Company’s Adjusted Quick Ratio is 1.05 or greater, a streamline period applies. As of December 31, 2018, the Company's Adjusted Quick Ratio was 1.16, which is in compliance with its covenant requirement and is higher than the minimum Adjusted Quick Ratio required to qualify for a streamline period. The Company must also maintain the following trailing twelve month Adjusted EBITDA targets as of the end of each quarter as follows: (1) September 30, 2018 through June 30, 2019 Adjusted EBITDA must be within 20% of the Adjusted EBITDA projections that were delivered to Silicon Valley Bank; (2) September 30, 2019 Adjusted EBITDA of $1 or greater; and (3) December 31, 2019 and thereafter, Adjusted EBITDA of $5.0 million or greater. As of December 31, 2018, the Company was in compliance with the Adjusted EBITDA covenant. The Loan Agreement also includes customary representations and warranties, affirmative covenants, and events of default, including events of default upon a change of control and material adverse change (as defined in the Loan Agreement). Following an event of default, SVB would be entitled to, among other things, accelerate payment of amounts due under the credit facility and exercise all rights of a secured creditor. As of December 31, 2018, there were no amounts outstanding under the Loan Agreement. Future availability under the credit facility is dependent on several factors including the available borrowing base and compliance with future covenant requirements.

Related Party Transaction	12 Months Ended
Related Party Transaction	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsAs of December 31, 2018 and 2017, there were no holders of more than 10% of the Company’s outstanding common stock that were considered to be related parties. During the years ended December 31, 2018 and 2017, the Company did not enter into transactions with any of its related parties.

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

The following tables set forth our quarterly consolidated statements of operations data for each of the eight quarters in the two-year period ended December 31, 2018. We have prepared the quarterly unaudited consolidated statements of operations data on a basis consistent with the audited consolidated financial statements included elsewhere in this Annual Report on Form 10-K. In the opinion of management, the financial information in these tables reflects all adjustments, consisting only of normal recurring adjustments, which management considers necessary for a fair statement of this data. This information should be read in conjunction with the audited consolidated financial statements and related notes included elsewhere in this Annual Report on Form 10-K. The results of historical periods are not necessarily indicative of the results for any future period.



	Three Months Ended
	Mar. 31, 2017			June 30, 2017			Sept. 30, 2017			Dec. 31, 2017			Mar. 31, 2018			June 30, 2018			Sept. 30, 2018			Dec. 31, 2018
	(in thousands, except per share amounts)
Revenue	$	46,015		$	42,922		$	35,211		$	31,397		$	24,876		$	28,648		$	29,729		$	41,432
Expenses:
Cost of revenue	14,688			13,698			12,985			15,465			14,783			15,044			14,687			15,489
Sales and marketing	14,628			12,529			12,503			12,134			12,257			11,135			10,654			10,510
Technology and development	12,753			12,044			11,580			11,123			10,494			9,245			9,299			8,825
General and administrative	15,080			14,355			13,644			12,517			12,544			11,441			9,355			9,091
Restructuring and other exit costs	4,338			1,621			—			—			2,466			974			—			—
Impairment of intangible assets and internally developed software	—			—			—			4,585			—			—			—			—
Impairment of goodwill	—			—			90,251			—			—			—			—			—
Total expenses	61,487			54,247			140,963			55,824			52,544			47,839			43,995			43,915
Loss from operations	(15,472		)	(11,325		)	(105,752		)	(24,427		)	(27,668		)	(19,191		)	(14,266		)	(2,483		)
Other (income) expense, net	(7		)	84			(150		)	(358		)	73			(1,281		)	(558		)	(377		)
Loss before income taxes	(15,465		)	(11,409		)	(105,602		)	(24,069		)	(27,741		)	(17,910		)	(13,708		)	(2,106		)
Provision (benefit) for income taxes	375			146			(2,031		)	(252		)	75			74			84			124
Net loss	$	(15,840	)	$	(11,555	)	$	(103,571	)	$	(23,817	)	$	(27,816	)	$	(17,984	)	$	(13,792	)	$	(2,230	)
Net loss per share:
Basic and diluted	$	(0.33	)	$	(0.24	)	$	(2.11	)	$	(0.48	)	$	(0.56	)	$	(0.36	)	$	(0.27	)	$	(0.04	)
Weighted-average shares used to compute net loss per share:
Basic and diluted	48,332			48,783			49,055			49,293			49,692			50,071			50,513			50,746

Organization and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

Basis of ConsolidationThe 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

SegmentsManagement 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.

Use of Estimates

materially from these estimates.

Revenue Recognition

Cost of Revenue

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 client 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 client relationships and backlog from its business acquisitions over their estimated useful lives.

Technology and Development

General and Administrative

Restructuring and Other Exit Costs

Impairment of Intangible Assets and Internal Use Software

Impairment of Goodwill

Stock-Based Compensation

The assumptions and estimates used in the Black-Scholes pricing model are as follows:

Fair Value of Common Stock. 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.

Income Taxes

Capital Stock

Net Income (Loss) Per Share Attributable to Common Stockholders

Net Income (Loss) Per Share Attributable to Common StockholdersBasic net income (loss) per share of common stock is calculated by dividing the net income (loss) by the weighted-average number of shares of common stock outstanding. 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 ("ESPP"), shares held in escrow and potential shares issuable as part of contingent consideration as a result of business combinations. For purposes of this calculation, potentially dilutive securities are excluded from the calculation of diluted net income (loss) per share if their effect is anti-dilutive.

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.

Restricted Cash

Cash, Cash Equivalents, and Marketable Securities

Restricted Cash

Accounts Receivable Allowance for Doubtful Accounts

Property and Equipment, Net



	Years
Computer equipment and network hardware	3
Furniture, fixtures and office equipment	5 to 7
Leasehold improvements	Shorter of useful life or life of lease
Computer equipment under capital leases	Shorter of useful life or life of lease

Internal Use Software Development Costs

The Company does not transfer ownership of its software, or lease its software, to third parties.

Intangible Assets

The Company’s intangible assets are being amortized over their estimated useful lives as follows:



	Years
Developed technology	3 to 5
Client relationships	2.5 to 3
Non-compete agreements	2 to 3
Other intangible assets	1 to 1.5

Impairment of Long-Lived Assets and including Internal Use Capitalized Software Costs

Impairment of Long-Lived Assets including Internal Use Capitalized Software CostsThe 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

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

Operating and Capital Leases

Fair Value of Financial Instruments

Fair Value of Financial InstrumentsThe carrying amounts of the Company's cash equivalents, accounts receivable, accounts payable, accrued expenses, and seller payables approximate fair value due to the short-term nature of these instruments. Certain assets of the Company are recorded at their fair value, using the fair value hierarchy, on a recurring basis, and other assets and liabilities, including goodwill and intangible assets are 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 (see Note 5).

Concentration of Risk

Accounts receivable include amounts due from buyers with principal operations primarily in the United States. The Company performs ongoing credit evaluations of its buyers.

The Company recognizes revenue from its contracts with sellers, and no seller of advertising inventory comprised 10% or more of revenue in 2018 or 2017.

At December 31, 2018 and 2017, no seller of advertising inventory comprised 10% or more of accounts payable.

Foreign Currency Transactions and Translation

Foreign Currency Transactions and TranslationTransactions 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 or losses were included in foreign exchange (gain) loss, 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 income (loss) on the consolidated balance sheet.

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements


•	Accounting Standards Update ("ASU") 2017-01—Business Combinations (Topic 805): Clarifying the Definition of a Business; and


•	ASU 2017-09—Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting.

Recent Accounting Pronouncements

Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table presents the basic and diluted net loss per share:



	Year Ended
	December 31, 2018			December 31, 2017
	(in thousands, except per share data)
Basic and Diluted EPS:
Net loss	$	(61,822	)	$	(154,783	)
Weighted-average common shares outstanding	50,602			49,720
Weighted-average unvested restricted shares	(343		)	(851		)
Weighted-average common shares outstanding used to compute net loss per share	50,259			48,869
Basic and diluted net loss per share	$	(1.23	)	$	(3.17	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share



	Year Ended
	December 31, 2018	December 31, 2017
	(in thousands)
Options to purchase common stock	128	120
Unvested restricted stock awards	218	297
Unvested restricted stock units	2,029	556
ESPP	55	50
Total shares excluded from net loss per share	2,430	1,023

Organization and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Property, Plant and Equipment

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 life or life of lease
Computer equipment under capital leases	Shorter of useful life or life of lease

Major classes of property and equipment were as follows:



	December 31, 2018			December 31, 2017
	(in thousands)
Purchased software	$	1,254		$	1,985
Computer equipment and network hardware	98,884			90,695
Furniture, fixtures and office equipment	1,973			2,165
Leasehold improvements	2,571			3,325
Gross property and equipment	104,682			98,170
Accumulated depreciation	(71,195		)	(50,777		)
Net property and equipment	$	33,487		$	47,393

The Company's property and equipment, net by geographical region was as follows:



	December 31, 2018		December 31, 2017
	(in thousands)
United States	$	24,928	$	37,566
International	8,559		9,827
Total	$	33,487	$	47,393

Finite-lived Intangible Assets Amortization

The Company’s intangible assets are being amortized over their estimated useful lives as follows:



	Years
Developed technology	3 to 5
Client relationships	2.5 to 3
Non-compete agreements	2 to 3
Other intangible assets	1 to 1.5

Revenues (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table presents our revenue by channel for the years ended December 31, 2018 and 2017:



	Year Ended
	December 31, 2018				December 31, 2017
	(in thousands, except percentages)
Channel:
Desktop	$	59,039	47	%	$	84,327	54	%
Mobile	65,646		53		71,218		46
Total	$	124,685	100	%	$	155,545	100	%

The following table presents our revenue disaggregated by geographic location, based on the location of the Company's sellers:



	Year Ended
	December 31, 2018		December 31, 2017
	(in thousands)
United States	$	83,020	$	95,567
International	41,665		59,978
Total	$	124,685	$	155,545

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring Basis

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2018:



	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	13,692	$	13,692	$	—	$	—
U.S. Treasury, government and agency debt securities	$	7,524	$	7,524	$	—	$	—

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2017:



	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	1,807	$	210	$	1,597	$	—
Corporate debt securities	$	25,098	$	—	$	25,098	$	—
U.S. Treasury, government and agency debt securities	$	29,901	$	29,901	$	—	$	—

Investments (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Fair Value Disclosure [Abstract]

Investments in Marketable Securities

Investments in marketable securities as of December 31, 2018 consisted of the following:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
Available-for-sale—short-term:
U.S. Treasury, government and agency debt securities	$	7,526	$	—	$	(2	)	$	7,524

Investments in marketable securities as of December 31, 2017 consisted of the following:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
Available-for-sale—short-term:
U.S. Treasury, government and agency debt securities	$	27,426	$	—	$	(20	)	$	27,406
Corporate debt securities	25,098		—		—			25,098
Total	$	52,524	$	—	$	(20	)	$	52,504
Available-for-sale—long-term:
U.S. Treasury, government and agency debt securities	$	2,504	$	—	$	(9	)	$	2,495

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

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 life or life of lease
Computer equipment under capital leases	Shorter of useful life or life of lease

Major classes of property and equipment were as follows:



	December 31, 2018			December 31, 2017
	(in thousands)
Purchased software	$	1,254		$	1,985
Computer equipment and network hardware	98,884			90,695
Furniture, fixtures and office equipment	1,973			2,165
Leasehold improvements	2,571			3,325
Gross property and equipment	104,682			98,170
Accumulated depreciation	(71,195		)	(50,777		)
Net property and equipment	$	33,487		$	47,393

The Company's property and equipment, net by geographical region was as follows:



	December 31, 2018		December 31, 2017
	(in thousands)
United States	$	24,928	$	37,566
International	8,559		9,827
Total	$	33,487	$	47,393

Internal Use Software Development Costs (Tables)

12 Months Ended

Dec. 31, 2018

Research and Development [Abstract]

Schedule Of Internal Use Software Costs

Internal use software development costs were as follows:



	December 31, 2018			December 31, 2017
	(in thousands)
Internal use software development costs, gross	41,882			$	33,414
Accumulated amortization	(27,312		)	(20,680		)
Internal use software development costs, net	$	14,570		$	12,734

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The Company no longer had a goodwill balance following the goodwill impairment. Activity of the Company’s goodwill for the year ended December 31, 2017 was as follows:



	December 31, 2017
	(in thousands)
Beginning balance	$	65,705
Additions from the acquisition of nToggle (See Note 10)	24,546
Impairment of goodwill	(90,251		)
Ending balance	$	—

Schedule of Finite-Lived Intangible Assets

The Company’s intangible assets as of December 31, 2018 and 2017 included the following:



	December 31, 2018			December 31, 2017
	(in thousands)
Amortizable intangible assets:
Developed technology	$	16,878		$	16,878
Non-compete agreements	690			690
Trademarks	20			20
Total identifiable intangible assets, gross	17,588			17,588
Accumulated amortization—intangible assets:
Developed technology	(6,888		)	(4,062		)
Non-compete agreements	(506		)	(161		)
Trademarks	(20		)	(6		)
Total accumulated amortization—intangible assets	(7,414		)	(4,229		)
Total identifiable intangible assets, net	$	10,174		$	13,359

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

The estimated remaining amortization expense associated with the Company's intangible assets was as follows as of December 31, 2018:



Fiscal Year	Amount
	(in thousands)
2019	$	3,010
2020	2,826
2021	2,826
2022	1,512
2023	—
Thereafter	—
Total	$	10,174

Business Combinations (Tables)

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Schedule of Business Acquisitions, by Acquisition

The major classes of assets and liabilities to which the Company allocated the purchase price were as follows as of the acquisition date:



	Amount
	(in thousands)
Cash and cash equivalents	$	1,953
Accounts receivable	256
Prepaid and other assets	18
Fixed assets	763
Other non-current assets	82
Intangible assets	14,840
Goodwill	24,546
Total assets acquired	42,458
Accounts payable and accrued expenses	78
Deferred revenue	91
Deferred tax liability, net	1,719
Total liabilities assumed	1,888
Total net assets acquired	$	40,570

Schedule of Finite-lived Intangible Assets Acquired as Part of Business Combination

The following table summarizes the components of the acquired intangible assets and estimated useful lives (in thousands, except for estimated useful life):



	December 31, 2017		Estimated Useful Life
Developed technology	$	14,130	5 years
Non-compete agreements	690		2 years
Trademark & trade name	20		1.5 years
Total intangible assets acquired	$	14,840

Business Acquisition, Pro Forma Information



	Year Ended
	December 31, 2017
	(in thousands)
Pro forma revenues	$	156,480
Pro forma net loss	$	(158,443	)
Pro forma net loss per share, basic	$	(3.24	)
Pro forma net loss per share, diluted	$	(3.24	)

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Liabilities

Accounts payable and accrued expenses included the following:



	December 31, 2018		December 31, 2017
	(in thousands)
Accounts payable—seller	$	230,423	$	203,694
Accounts payable—trade	3,122		3,764
Accrued employee-related payables	6,133		6,645
Total	$	239,678	$	214,103

Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The components of accumulated other comprehensive income (loss) were as follows (in thousands):



	Unrealized Gain (Loss) on Investments, net of tax			Foreign Currency Translation			Accumulated Other Comprehensive Income (Loss)
Balance at December 31, 2016	$	(1	)	$	(272	)	$	(273	)
Other comprehensive income (loss)	(28		)	342			314
Balance at December 31, 2017	(29		)	70			41
Other comprehensive income (loss)	27			(327		)	(300		)
Balance at December 31, 2018	$	(2	)	$	(257	)	$	(259	)

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity

A summary of stock option activity for the year ended December 31, 2018 is as follows:



	Shares Under Option		Weighted- Average Exercise Price		Weighted- Average Contractual Life	Aggregate Intrinsic Value
	(in thousands)					(in thousands)
Outstanding at December 31, 2017	4,363		$	8.75
Granted	706		$	2.09
Exercised	(50	)	$	0.91
Expired	(1,438	)	$	10.17
Forfeited	(93	)	$	3.83
Outstanding at December 31, 2018	3,488		$	7.06	7.09 years	$	2,354
Exercisable at December 31, 2018	2,114		$	9.29	6.07 years	$	765

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions



	Year Ended
	December 31, 2018		December 31, 2017
Expected term (in years)	6.0		5.8
Risk-free interest rate	2.67	%	2.03	%
Expected volatility	57	%	57	%
Dividend yield	—	%	—	%

Nonvested Restricted Stock Shares Activity

A summary of restricted stock activity for the year ended December 31, 2018 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested shares of restricted stock outstanding at December 31, 2017	558		$	12.60
Granted	—		$	—
Canceled	(156	)	$	13.82
Vested	(205	)	$	12.19
Nonvested shares of restricted stock outstanding at December 31, 2018	197		$	12.06

Schedule of Nonvested Restricted Stock Units Activity

A summary of restricted stock unit activity for the year ended December 31, 2018 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested restricted stock units outstanding at December 31, 2017	3,609		$	7.55
Granted	4,976		$	2.30
Canceled	(1,118	)	$	5.32
Vested	(1,367	)	$	8.06
Nonvested restricted stock units outstanding at December 31, 2018	6,100		$	3.56

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs for all Plans

Total stock-based compensation expense recorded in the consolidated statements of operations was as follows:



	Year Ended
	December 31, 2018		December 31, 2017
	(in thousands)
Cost of revenue	$	321	$	404
Sales and marketing	4,557		4,582
Technology and development	2,867		4,034
General and administrative	8,139		9,924
Restructuring and other exit costs	398		1,560
Total stock-based compensation expense	$	16,282	$	20,504

Restructuring and Other Exit Costs (Tables)

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Schedule of Restructuring and Other Exit Costs



Accrued restructuring and other exit costs at December 31, 2017	$	—
Restructuring and other exit costs	3,440
Cash paid for restructuring and other exit costs	(2,975		)
Non-cash stock-based compensation for restructuring and other exit costs	(398		)
Accrued restructuring and other exit costs at December 31, 2018	$	67

The following table presents the components of restructuring and other exit costs for the years ended December 31, 2018 and 2017 (in thousands):



	Year Ended
	December 31, 2018		December 31, 2017
Employee termination costs	$	3,440	$	5,753
Facility closing costs	—		206
Total restructuring and other exit costs	$	3,440	$	5,959

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign

The following are the domestic and foreign components of the Company’s income (loss) before income taxes for the years ended December 31, 2018 and 2017:



	Year Ended
	December 31, 2018			December 31, 2017
	(in thousands)
Domestic	$	(62,292	)	$	(104,750	)
International	827			(51,795		)
Loss before income taxes	$	(61,465	)	$	(156,545	)

Schedule of Components of Income Tax Expense (Benefit)

The following are the components of the provision (benefit) for income taxes for the years ended December 31, 2018 and 2017:



	Year Ended
	December 31, 2018			December 31, 2017
	(in thousands)
Current:
Federal	$	(23	)	$	(140	)
State	41			78
Foreign	388			(250		)
Total current provision	406			(312		)
Deferred:
Federal	—			(1,877		)
State	2			288
Foreign	(51		)	139
Total deferred benefit	(49		)	(1,450		)
Total provision (benefit) for income taxes	$	357		$	(1,762	)

Schedule of Effective Income Tax Rate Reconciliation



	Year Ended
	December 31, 2018		December 31, 2017
U.S. federal statutory income tax rate	21.0	%	34.0	%
State income taxes, net of federal benefit	(0.1	)%	—	%
Foreign income (loss) at other than U.S. rates	—	%	0.2	%
Stock-based compensation expense	(5.3	)%	(3.8	)%
Meals and entertainment	(0.4	)%	(0.1	)%
Goodwill impairment	—	%	(19.0	)%
Research and development tax credits	—	%	0.8	%
Debt cancellation	(1.2	)%	—	%
Worthless stock	—	%	31.7	%
Other permanent items	(0.5	)%	(0.5	)%
Change in valuation allowance	(14.1	)%	(22.0	)%
Tax rate change; U.S. tax reform	—	%	(20.2	)%
Effective income tax rate	(0.6	)%	1.1	%

Schedule of Deferred Tax Assets and Liabilities

Set forth below are the tax effects of temporary differences that give rise to a significant portion of the deferred tax assets and deferred tax liabilities as of December 31, 2018 and 2017:



	December 31, 2018			December 31, 2017
	(in thousands)
Deferred Tax Assets:
Accrued liabilities	$	916		$	2,648
Stock-based compensation	2,623			3,685
Net operating loss carryovers	76,098			65,648
Tax credit carryovers	13,206			13,494
Other	1,053			1,502
Total deferred tax assets	93,896			86,977
Less valuation allowance	(90,959		)	(81,767		)
Deferred tax assets, net of valuation allowance	2,937			5,210
Deferred Tax Liabilities:
Fixed assets	(2,352		)	(3,864		)
Intangible assets	(152		)	(955		)
Other	—			—
Total deferred tax liabilities	(2,504		)	(4,819		)
Net deferred tax assets (liability)	$	433		$	391

Schedule of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns Roll Forward

The following table summarizes the activity related to the unrecognized tax benefits (in thousands):



	Amount
	(in thousands)
Balance as of December 31, 2016	$	5,027
Increases related to 2017 tax positions	619
Decreases related to prior year tax positions	—
Balance as of December 31, 2017	5,646
Increases related to current year tax positions	—
Decreases related to current year tax positions	—
Decreases related to prior year tax positions	(929		)
Balance as of December 31, 2018	$	4,717

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

The following table summarizes the Company's future minimum lease payments under non-cancelable operating leases and related sublease income at December 31, 2018:



	2019			2020			2021			2022			2023			Total
	(in thousands)
Operating lease expense	$	6,773		$	3,880		$	1,734		$	1,019		$	597		$	14,003
Operating sublease income	(285		)	(194		)	(194		)	(194		)	(145		)	(1,012		)
Total	$	6,488		$	3,686		$	1,540		$	825		$	452		$	12,991

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

The results of historical periods are not necessarily indicative of the results for any future period.



	Three Months Ended
	Mar. 31, 2017			June 30, 2017			Sept. 30, 2017			Dec. 31, 2017			Mar. 31, 2018			June 30, 2018			Sept. 30, 2018			Dec. 31, 2018
	(in thousands, except per share amounts)
Revenue	$	46,015		$	42,922		$	35,211		$	31,397		$	24,876		$	28,648		$	29,729		$	41,432
Expenses:
Cost of revenue	14,688			13,698			12,985			15,465			14,783			15,044			14,687			15,489
Sales and marketing	14,628			12,529			12,503			12,134			12,257			11,135			10,654			10,510
Technology and development	12,753			12,044			11,580			11,123			10,494			9,245			9,299			8,825
General and administrative	15,080			14,355			13,644			12,517			12,544			11,441			9,355			9,091
Restructuring and other exit costs	4,338			1,621			—			—			2,466			974			—			—
Impairment of intangible assets and internally developed software	—			—			—			4,585			—			—			—			—
Impairment of goodwill	—			—			90,251			—			—			—			—			—
Total expenses	61,487			54,247			140,963			55,824			52,544			47,839			43,995			43,915
Loss from operations	(15,472		)	(11,325		)	(105,752		)	(24,427		)	(27,668		)	(19,191		)	(14,266		)	(2,483		)
Other (income) expense, net	(7		)	84			(150		)	(358		)	73			(1,281		)	(558		)	(377		)
Loss before income taxes	(15,465		)	(11,409		)	(105,602		)	(24,069		)	(27,741		)	(17,910		)	(13,708		)	(2,106		)
Provision (benefit) for income taxes	375			146			(2,031		)	(252		)	75			74			84			124
Net loss	$	(15,840	)	$	(11,555	)	$	(103,571	)	$	(23,817	)	$	(27,816	)	$	(17,984	)	$	(13,792	)	$	(2,230	)
Net loss per share:
Basic and diluted	$	(0.33	)	$	(0.24	)	$	(2.11	)	$	(0.48	)	$	(0.56	)	$	(0.36	)	$	(0.27	)	$	(0.04	)
Weighted-average shares used to compute net loss per share:
Basic and diluted	48,332			48,783			49,055			49,293			49,692			50,071			50,513			50,746

Net Income (Loss) Per Share (Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Basic and Diluted EPS:
Net loss	$ (2,230)	$ (13,792)	$ (17,984)	$ (27,816)	$ (23,817)	$ (103,571)	$ (11,555)	$ (15,840)	$ (61,822)	$ (154,783)
Weighted-average common shares outstanding									50,602	49,720
Weighted-average unvested restricted shares									(343)	(851)
Weighted-average common shares outstanding used to compute net loss per share	50,746	50,513	50,071	49,692	49,293	49,055	48,783	48,332	50,259	48,869
Basic and diluted net loss per share	$ (0.04)	$ (0.27)	$ (0.36)	$ (0.56)	$ (0.48)	$ (2.11)	$ (0.24)	$ (0.33)	$ (1.23)	$ (3.17)

Net Income (Loss) Per Share (Shares Excluded and Included in Calculation of Diluted Earnings Per Share) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share (in shares)	2,430	1,023
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share (in shares)	128	120
Unvested restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share (in shares)	218	297
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share (in shares)	2,029	556
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share (in shares)	55	50

Organization and Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($) shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment shares	Dec. 31, 2017 USD ($) shares
Concentration Risk [Line Items]
Number of Operating Segments \| segment									1
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period									4 years
Fair Value Assumptions, Expected Dividend Rate									0.00%
Common Stock, Shares Authorized \| shares	500,000,000				500,000,000				500,000,000	500,000,000
Preferred stock, shares authorized \| shares	10,000,000				10,000,000				10,000,000	10,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized \| shares	18,094,154								18,094,154
Allowance for Doubtful Accounts Receivable \| $	$ 1,300				$ 500				$ 1,300	$ 500
Allowance for Doubtful Accounts Receivable, Write-offs \| $									600	700
Impairment of goodwill \| $	$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251	$ 0	$ 0	$ 0	$ 90,251
Customer One \| Customer concentration risk, accounts receivable
Concentration Risk [Line Items]
Concentration risk, percentage									21.00%	20.00%
Customer Two \| Customer concentration risk, accounts receivable
Concentration Risk [Line Items]
Concentration risk, percentage									13.00%	15.00%

Organization and Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Impairment of goodwill	$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251	$ 0	$ 0	$ 0	$ 90,251
Computer equipment and network hardware
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life									3 years
Furniture, fixtures and office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life									5 years
Furniture, fixtures and office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life									7 years

Organization and Summary of Significant Accounting Policies - Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2018
Minimum \| Developed technology
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum \| Client relationships
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years 6 months
Minimum \| Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years
Minimum \| Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Maximum \| Developed technology
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum \| Client relationships
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Maximum \| Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Maximum \| Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year 6 months

Revenues (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Revenues (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 41,432	$ 29,729	$ 28,648	$ 24,876	$ 31,397	$ 35,211	$ 42,922	$ 46,015	$ 124,685	$ 155,545
Payment terms									75 days
Intent Marketing Solution
Disaggregation of Revenue [Line Items]
Revenue										$ 1,300

Revenues (Revenue Disaggregated by Sales Distribution Channel) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 41,432	$ 29,729	$ 28,648	$ 24,876	$ 31,397	$ 35,211	$ 42,922	$ 46,015	$ 124,685	$ 155,545
Revenues, percent									100.00%	100.00%
Desktop
Disaggregation of Revenue [Line Items]
Revenues									$ 59,039	$ 84,327
Revenues, percent									47.00%	54.00%
Mobile
Disaggregation of Revenue [Line Items]
Revenues									$ 65,646	$ 71,218
Revenues, percent									53.00%	46.00%

Revenues (Revenue Disaggregated by Geographic Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 41,432	$ 29,729	$ 28,648	$ 24,876	$ 31,397	$ 35,211	$ 42,922	$ 46,015	$ 124,685	$ 155,545
United States
Disaggregation of Revenue [Line Items]
Revenue									83,020	95,567
International
Disaggregation of Revenue [Line Items]
Revenue									$ 41,665	$ 59,978

Fair Value Measurements (Financial Instruments) (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 13,692	$ 1,807
Cash equivalents \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	13,692	210
Cash equivalents \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	1,597
Cash equivalents \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		25,098
Corporate debt securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Corporate debt securities \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		25,098
Corporate debt securities \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
U.S. Treasury, government and agency debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	7,524	29,901
U.S. Treasury, government and agency debt securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	7,524	29,901
U.S. Treasury, government and agency debt securities \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
U.S. Treasury, government and agency debt securities \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 0	$ 0

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
EBITDA multiple used for fair value										2.0
Impairment of goodwill	$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251	$ 0	$ 0	$ 0	$ 90,251
Goodwill					0					0	$ 65,705
Impairment of intangible assets and internal use software	0	$ 0	$ 0	$ 0	4,585	$ 0	$ 0	$ 0	0	4,585
Cash equivalents \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 13,692				$ 1,807				$ 13,692	$ 1,807
Income Approach Valuation Technique [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate					16.20%
Market Approach Valuation Technique [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Control Premium										15.00%
Finite-Lived Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of intangible assets and internal use software					$ 3,500					$ 3,500
Software Development [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of intangible assets and internal use software										$ 1,100

Investments - Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale—short-term
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 52,524
Gross Unrealized Gains		0
Gross Unrealized Losses		(20)
Fair Value		52,504
Available-for-sale—short-term \| U.S. Treasury, government and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 7,526	27,426
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2)	(20)
Fair Value	$ 7,524	27,406
Available-for-sale—short-term \| Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		25,098
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		25,098
Available-for-sale — long-term \| U.S. Treasury, government and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,504
Gross Unrealized Gains		0
Gross Unrealized Losses		(9)
Fair Value		$ 2,495

Investments - Narrative (Details) - USD ($)	12 Months Ended
Investments - Narrative (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Investments, Fair Value Disclosure [Abstract]
Weighted remaining contractual maturity	1 month 6 days
Sales of available-for-sale securities	$ 9,228,000	$ 0
Unrealized gain (loss)	0
Realized gain (loss)	$ 0

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 104,682	$ 98,170
Accumulated depreciation	(71,195)	(50,777)
Property and equipment, net	33,487	47,393
Purchased software
Property, Plant and Equipment [Line Items]
Gross property and equipment	1,254	1,985
Computer equipment and network hardware
Property, Plant and Equipment [Line Items]
Gross property and equipment	98,884	90,695
Furniture, fixtures and office equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	1,973	2,165
Leasehold improvements
Property, Plant and Equipment [Line Items]
Gross property and equipment	2,571	3,325
United States
Property, Plant and Equipment [Line Items]
Property and equipment, net	24,928	37,566
International
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 8,559	$ 9,827

Property and Equipment (Narrative) (Details) - USD ($)	12 Months Ended
Property and Equipment (Narrative) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense on property and equipment	$ 25,000,000.0	$ 20,300,000
Impairment of long-lived assets	0	0
Property and equipment under capital leases	$ 0	$ 0

Internal Use Software Development Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Research and Development [Abstract]
Internal use software development costs, gross	$ 41,882	$ 33,414
Accumulated amortization	(27,312)	(20,680)
Internal use software development costs, net	$ 14,570	$ 12,734

Internal Use Software Development Costs (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Research and Development [Abstract]
Capitalized computer software, additions		$ 9.0	$ 8.4
Capitalized computer software, amortization		7.2	11.1
Internal use software development costs, write-offs		0.5	$ 1.6
Estimated amortization expense, 2019		7.0
Estimated amortization expense, 2020		5.1
Estimated amortization expense, 2021		2.5
Capitalized computer software, impairments	$ 1.1	$ 0.0

Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Net Asset Carrying Value Prior to Impairment						$ 274,400
Impairment of goodwill	$ 0	$ 0	$ 0	$ 0	$ 0	90,251	$ 0	$ 0	$ 0	$ 90,251
Amortization expense of intangible assets									3,200	4,800
Impairment of intangible assets	$ 0	$ 0	$ 0	$ 0	4,585	$ 0	$ 0	$ 0	$ 0	4,585
Finite-Lived Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets					$ 3,500					$ 3,500

Goodwill and Intangible Assets (Finite-Lived Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	$ 17,588	$ 17,588
Total accumulated amortization—intangible assets	(7,414)	(4,229)
Total	10,174	13,359
Developed technology
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	16,878	16,878
Total accumulated amortization—intangible assets	(6,888)	(4,062)
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	690	690
Total accumulated amortization—intangible assets	(506)	(161)
Trademarks
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	20	20
Total accumulated amortization—intangible assets	$ (20)	$ (6)

Goodwill and Intangible Assets (Finite-Lived Intangible Assets, Future Amortization Expense) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
2019	$ 3,010
2020	2,826
2021	2,826
2022	1,512
2023	0
Thereafter	0
Total	$ 10,174	$ 13,359

Goodwill and Intangible Assets (Goodwill Activity) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, Beginning balance				$ 0				$ 65,705	$ 0	$ 65,705
Goodwill, Acquired During Period										24,546
Impairment of goodwill	$ 0	$ 0	$ 0	$ 0	$ 0	$ (90,251)	$ 0	$ 0	$ 0	(90,251)
Goodwill, Ending balance					$ 0					$ 0

Business Combinations - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Jul. 14, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired										$ 0	$ 38,610
Business Combination, Acquisition Related Costs											300
Business Combination, Net Operating Loss Acquired											9,300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	$ 5,500
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	3,800
Impairment of goodwill		$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251	$ 0	$ 0	$ 0	$ 90,251
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Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	38,600
Business Combination, Consideration Transferred	40,600
Cash Acquired from Acquisition	$ (2,000)
Business Combination, In-The-Money Options Assumed	432,482
Business Combination, Restricted Stock Assumed	77,499
Equity interest issued, number of shares	174,117

Business Combinations - Allocation of Total Purchase Considerations (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 14, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 0		$ 65,705
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Business Acquisition [Line Items]
Cash and cash equivalents		$ 1,953
Accounts receivable		256
Prepaid and other assets		18
Fixed assets		763
Other non-current assets		82
Intangible assets		14,840
Goodwill		24,546
Total assets acquired		42,458
Accounts payable and accrued expenses		78
Deferred revenue		91
Deferred tax liability, net		1,719
Total liabilities assumed		1,888
Total net assets acquired		$ 40,570

Business Combinations - Acquired Intangible Assets and Estimated Useful Lives (Details) - nToggle $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 14,840
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 14,130
Estimated Useful Life	5 years
Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 690
Estimated Useful Life	2 years
Trademark & trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 20
Estimated Useful Life	1 year 6 months

Business Combinations - Pro Forma Information (Details) - nToggle $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares
Business Acquisition [Line Items]
Pro forma revenues \| $	$ 156,480
Pro forma net loss \| $	$ (158,443)
Pro forma net loss per share, basic (in usd per share) \| $ / shares	$ (3.24)
Pro forma net loss per share, diluted (in usd per share) \| $ / shares	$ (3.24)

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts payable—seller	$ 230,423	$ 203,694
Accounts payable—trade	3,122	3,764
Accrued employee-related payables	6,133	6,645
Accounts payable and accrued expenses	$ 239,678	$ 214,103

Accumulated Other Comprehensive Loss - Schedule of Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 164,611	$ 299,513
Unrealized gain (loss) on investments	27	(28)
Foreign currency translation adjustments	(327)	342
Other comprehensive income (loss)	(300)	314
Ending Balance	118,013	164,611
Unrealized Gain (Loss) on Investments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(29)	(1)
Ending Balance	(2)	(29)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	70	(272)
Ending Balance	(257)	70
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	41	(273)
Other comprehensive income (loss)	(300)	314
Ending Balance	$ (259)	$ 41

Stock-Based Compensation (Details)	12 Months Ended
Stock-Based Compensation (Details)	Dec. 31, 2018 shares
Number of Shares
Evergreen Annual % Increase	5.00%
Equity plans other than ESPP
Number of Shares
Number of shares available for grant	6,701,872
Stock Option
Number of Shares
Vesting period	4 years
Award vesting rights, percentage	25.00%
Restricted awards
Number of Shares
Award vesting rights, percentage	25.00%
Two Year RSUs [Member] \| Unvested restricted stock units
Number of Shares
Award vesting rights, percentage	50.00%
RSUs granted	2,800,000

Stock-Based Compensation (Stock Options Outstanding) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares) \| shares	4,363
Granted (in shares) \| shares	706
Exercised (in shares) \| shares	(50)
Expired (in shares) \| shares	(1,438)
Forfeited (in shares) \| shares	(93)
Ending balance (in shares) \| shares	3,488
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (usd per share) \| $ / shares	$ 8.75
Granted (usd per share) \| $ / shares	2.09
Exercised (usd per share) \| $ / shares	0.91
Expired (usd per share) \| $ / shares	10.17
Forfeited (usd per share) \| $ / shares	3.83
Ending balance (usd per share) \| $ / shares	$ 7.06
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding	7 years 1 month 2 days
Outstanding, aggregate intrinsic value \| $	$ 2,354
Exercisable (in shares) \| shares	2,114
Exercisable (usd per share) \| $ / shares	$ 9.29
Exercisable	6 years 25 days
Exercisable, aggregate intrinsic value \| $	$ 765

Stock-Based Compensation (Stock Options Narrative) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares
Number of Shares
Intrinsic values of options exercised	$ 0.1
Unrecognized employee stock-based compensation	$ 3.2
Weighted average grant date fair value \| $ / shares	$ 1.15
Fair value of options vested in period	$ 3.3
Stock Option
Number of Shares
Unrecognized employee stock-based compensation, period for recognition	2 years 6 months

Stock-Based Compensation (Valuation Assumptions) (Details) - Stock Option	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Expected term (in years)	6 years	5 years 9 months 18 days
Risk-free interest rate	2.67%	2.03%
Expected volatility	57.00%	57.00%
Dividend yield	0.00%	0.00%

Stock-Based Compensation (Restricted Stock Activity) (Details) - Restricted Stock Awards shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of Shares
Beginning balance \| shares	558
Granted \| shares	0
Canceled \| shares	(156)
Vested \| shares	(205)
Ending balance \| shares	197
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) \| $ / shares	$ 12.60
Granted (in dollars per share) \| $ / shares	0
Canceled (in dollars per share) \| $ / shares	13.82
Vested (in dollars per share) \| $ / shares	12.19
Ending balance (in dollars per share) \| $ / shares	$ 12.06

Stock-Based Compensation (Restricted Stock Narrative) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares
Unvested restricted stock awards
Number of Shares
Fair value of restricted stock	$ 0.6
Unrecognized employee stock-based compensation	$ 0.9
Unrecognized employee stock-based compensation, period for recognition	1 year 1 month 6 days
Granted (in dollars per share) \| $ / shares	$ 0
Restricted Stock Units (RSUs)
Number of Shares
Fair value of restricted stock	$ 4.3
Unrecognized employee stock-based compensation	$ 17.3
Unrecognized employee stock-based compensation, period for recognition	2 years 1 month 6 days
Granted (in dollars per share) \| $ / shares	$ 2.30
Intrinsic value of nonvested unit	$ 22.8

Stock-Based Compensation (Restricted Stock Units Activity) (Details) - Restricted Stock Units (RSUs) shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of Shares
Beginning balance \| shares	3,609
Granted \| shares	4,976
Canceled \| shares	(1,118)
Vested \| shares	(1,367)
Ending balance \| shares	6,100
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) \| $ / shares	$ 7.55
Granted (in dollars per share) \| $ / shares	2.30
Canceled (in dollars per share) \| $ / shares	5.32
Vested (in dollars per share) \| $ / shares	8.06
Ending balance (in dollars per share) \| $ / shares	$ 3.56

Stock-Based Compensation (Employee Stock Purchase Plan Narrative) (Details)	12 Months Ended
	Dec. 31, 2018 shares
Number of Shares
Number of shares reserved	18,094,154
Evergreen Annual % Increase	5.00%
Employee Stock
Number of Shares
Evergreen Annual % Increase	1.00%
2014 Employee Stock Purchase Plan \| Employee Stock
Number of Shares
Maximum employee subscription rate	10.00%
Purchase price of common stock, percent	85.00%
Number of shares available for grant	1,607,646

Stock-Based Compensation (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 16,282	$ 20,504
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	321	404
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,557	4,582
Technology and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	2,867	4,034
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	8,139	9,924
Restructuring and other exit costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 398	$ 1,560

Restructuring and Other Exit Costs - Schedule of Restructuring and Other Exit Costs (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Restructuring and other exit costs		$ 0	$ (974)	$ (2,466)	$ 0	$ 0	$ (1,621)	$ (4,338)	$ (3,440)	$ (5,959)
Severance costs									3,440	5,753
Business exit costs									0	206
The 2018 Restructuring Events
Restructuring Reserve [Roll Forward]
Accrued restructuring and other exit costs at December 31, 2017				0					0
Restructuring and other exit costs	$ 0								(3,440)
Cash paid for restructuring and other exit costs									(2,975)
Accrued restructuring and other exit costs at December 31, 2018	$ 67				0				67	0
The 2017 Restructuring Events
Restructuring Reserve [Roll Forward]
Accrued restructuring and other exit costs at December 31, 2017				$ 100					100
Restructuring and other exit costs										(6,000)
Accrued restructuring and other exit costs at December 31, 2018					$ 100					100
Non-cash stock-based compensation \| The 2017 Restructuring Events
Restructuring Reserve [Roll Forward]
Restructuring and other exit costs									$ (398)	$ (1,600)

Restructuring and Other Exit Costs - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and other exit costs		$ 0	$ 974	$ 2,466	$ 0	$ 0	$ 1,621	$ 4,338	$ 3,440	$ 5,959
The 2017 Restructuring Events
Restructuring Cost and Reserve [Line Items]
Restructuring and other exit costs										6,000
Accrued restructuring costs					100					100
The 2018 Restructuring Events
Restructuring Cost and Reserve [Line Items]
Restructuring and other exit costs	$ 0								3,440
Accrued restructuring costs	$ 67				$ 0				67	0
Non-cash stock-based compensation \| The 2017 Restructuring Events
Restructuring Cost and Reserve [Line Items]
Restructuring and other exit costs									$ 398	$ 1,600

Income Taxes (Income before Income Tax, Domestic and Foreign) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (62,292)	$ (104,750)
International	827	(51,795)
Loss before income taxes	$ (61,465)	$ (156,545)

Income Taxes (Components of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal									$ (23)	$ (140)
State									41	78
Foreign									388	(250)
Total current provision									406	(312)
Deferred:
Federal									0	(1,877)
State									2	288
Foreign									(51)	139
Total deferred benefit									(49)	(1,450)
Total provision (benefit) for income taxes	$ 124	$ 84	$ 74	$ 75	$ (252)	$ (2,031)	$ 146	$ 375	$ 357	$ (1,762)

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ 124	$ 84	$ 74	$ 75	$ (252)	$ (2,031)	$ 146	$ 375	$ 357	$ (1,762)
Income Tax Expense (Benefit) Related To Worthless Stock					$ 145,800
Tax Cuts And Jobs Act Of 2017 Incomplete Accounting Transition Tax For Accumulated Foreign Earnings Provisional Income Tax Expense										600
Tax Cuts And Jobs Act Of 2017 Incomplete Accounting Change In Tax Rate Deferred Tax Asset Provisional Income Tax Expense										$ 31,600
Provisional GILTI inclusion for ASC Topic 740									$ 1,300

Income Taxes (Effective Income Tax Rate Reconciliation) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	21.00%	34.00%
State income taxes, net of federal benefit	(0.10%)	0.00%
Foreign income at other than U.S. rates	0.00%	0.20%
Stock-based compensation expense	(5.30%)	(3.80%)
Meals and entertainment	(0.40%)	(0.10%)
Goodwill impairment	0.00%	(19.00%)
Research and development tax credits	0.00%	(0.80%)
Other permanent items	(0.50%)	(0.50%)
Debt cancellation	(1.20%)	0.00%
Worthless stock	0.00%	31.70%
Change in valuation allowance	(14.10%)	(22.00%)
Tax rate change; U.S. tax reform	0.00%	(20.20%)
Effective income tax rate	(0.60%)	1.10%

Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Accrued liabilities	$ 916	$ 2,648
Stock-based compensation	2,623	3,685
Net operating loss carryovers	76,098	65,648
Research tax credit carryovers	13,206	13,494
Other	1,053	1,502
Total deferred tax assets	93,896	86,977
Less valuation allowance	(90,959)	(81,767)
Deferred tax assets, net of valuation allowance	2,937	5,210
Deferred Tax Liabilities:
Fixed assets	(2,352)	(3,864)
Intangible assets	(152)	(955)
Other	0	0
Total deferred tax liabilities	(2,504)	(4,819)
Net deferred tax assets (liability)	$ 433	$ 391

Income Taxes (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ 124	$ 84	$ 74	$ 75	$ (252)	$ (2,031)	$ 146	$ 375	$ 357	$ (1,762)
Tax Credit Carryforward [Line Items]
U.S. federal statutory income tax rate									21.00%	34.00%
Operating Loss Carryforwards [Line Items]
Change in valuation allowance									$ 9,200	$ 42,300
Unremitted earnings of the subsidiaries outside of the United States	7,600								7,600
Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	10,200								10,200
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	20,500								20,500
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	285,500								285,500
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	167,000								167,000
State and Local Jurisdiction \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 8,000								$ 8,000

Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Beginning balance	$ 5,646	$ 5,027
Increases related to 2017 tax positions		619
Decreases related to prior year tax positions	(929)	0
Increases related to current year tax positions	0
Decreases related to current year tax positions	0
Ending balance	$ 4,717	$ 5,646

Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Rental expense	$ 12,600	$ 12,700
Operating lease expense
2019	6,773
2020	3,880
2021	1,734
2022	1,019
2023	597
Total	14,003
Operating sublease income
2019	(285)
2020	(194)
2021	(194)
2022	(194)
2023	(145)
Total	(1,012)
Total lease obligations and sublease income
2019	6,488
2020	3,686
2021	1,540
2022	825
2023	452
Total	12,991
Data Centers For Cloud-Based Services
Other Commitments [Line Items]
Rental expense	7,100	4,900
Office Lease \| Financial Standby Letter of Credit
Other Commitments [Line Items]
Letters of credit outstanding, amount	$ 2,900	$ 2,900

Debt (Narrative) (Details) - Revolving Credit Facility	12 Months Ended
Debt (Narrative) (Details) - Revolving Credit Facility	Dec. 31, 2018 USD ($)	Sep. 26, 2018 USD ($)
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 40,000,000.0
Line Of Credit Facility Borrowing Capacity Reserve		10,000,000.0
Line of credit facility, unused capacity, commitment fee percentage	0.15%
Line of credit facility, remaining borrowing capacity		30,000,000.0
Debt Issuance Costs, Net		$ 100,000
Debt Instrument Adjusted Quick Ratio Requirement In Streamline Period	1.05
Debt Instrument Adjusted Quick Ratio	1.16
2011 Loan Agreement
Line of Credit Facility [Line Items]
Adjusted EBITDA Threshold	20.00%
Streamline Period Applies \| Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.50%
Streamline Period Applies \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.50%
Streamline Period Does Not Apply \| Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Streamline Period Does Not Apply \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	4.00%
Covenant Term, Scenario One
Line of Credit Facility [Line Items]
Debt Instrument Adjusted Quick Ratio Requirement	1.00
Debt Instrument Covenant Compliance Adjusted Earnings Before Interest Taxes Depreciation And Amortization Maximum	$ 0
Covenant Term, Scenario Two
Line of Credit Facility [Line Items]
Debt Instrument Adjusted Quick Ratio Requirement	0.90
Debt Instrument, Covenant Compliance, Adjusted Earnings Before Interest Taxes Depreciation And Amortization Minimum	$ 0
Covenant Compliance Period Two \| 2011 Loan Agreement
Line of Credit Facility [Line Items]
Debt Instrument Covenant Compliance Adjusted Earnings Before Interest Taxes Depreciation And Amortization Maximum	1
Covenant Compliance Period Three \| 2011 Loan Agreement
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Adjusted Earnings Before Interest Taxes Depreciation And Amortization Minimum	$ 5,000,000.0

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 41,432	$ 29,729	$ 28,648	$ 24,876	$ 31,397	$ 35,211	$ 42,922	$ 46,015	$ 124,685	$ 155,545
Cost of revenue	15,489	14,687	15,044	14,783	15,465	12,985	13,698	14,688	60,003	56,836
Sales and marketing	10,510	10,654	11,135	12,257	12,134	12,503	12,529	14,628	44,556	51,794
Technology and development	8,825	9,299	9,245	10,494	11,123	11,580	12,044	12,753	37,863	47,500
General and administrative	9,091	9,355	11,441	12,544	12,517	13,644	14,355	15,080	42,431	55,596
Restructuring and other exit costs		0	974	2,466	0	0	1,621	4,338	3,440	5,959
Impairment of intangible assets and internal use software	0	0	0	0	4,585	0	0	0	0	4,585
Impairment of goodwill	0	0	0	0	0	90,251	0	0	0	90,251
Total expenses	43,915	43,995	47,839	52,544	55,824	140,963	54,247	61,487	188,293	312,521
Loss from operations	(2,483)	(14,266)	(19,191)	(27,668)	(24,427)	(105,752)	(11,325)	(15,472)	(63,608)	(156,976)
Total other income, net	(377)	(558)	(1,281)	73	(358)	(150)	84	(7)	(2,143)	(431)
Loss before income taxes	(2,106)	(13,708)	(17,910)	(27,741)	(24,069)	(105,602)	(11,409)	(15,465)	(61,465)	(156,545)
Provision (benefit) for income taxes	124	84	74	75	(252)	(2,031)	146	375	357	(1,762)
Net loss	$ (2,230)	$ (13,792)	$ (17,984)	$ (27,816)	$ (23,817)	$ (103,571)	$ (11,555)	$ (15,840)	$ (61,822)	$ (154,783)
Basic and Diluted (usd per share)	$ (0.04)	$ (0.27)	$ (0.36)	$ (0.56)	$ (0.48)	$ (2.11)	$ (0.24)	$ (0.33)	$ (1.23)	$ (3.17)
Basic and Diluted (in shares)	50,746	50,513	50,071	49,692	49,293	49,055	48,783	48,332	50,259	48,869