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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2017	Mar. 08, 2018	Jun. 30, 2017
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, 2017
Amendment Flag	false
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		50,254,718
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 228.2

Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 76,642,000	$ 149,423,000
Marketable securities	52,504,000	40,550,000
Accounts receivable, net	165,890,000	192,064,000
Prepaid expenses and other current assets	9,620,000	9,540,000
TOTAL CURRENT ASSETS	304,656,000	391,577,000
Property and equipment, net	47,393,000	36,246,000
Internal use software development costs, net	12,734,000	16,522,000
Other assets, non-current	5,493,000	2,921,000
Intangible assets, net	13,359,000	6,804,000
Goodwill	0	65,705,000
TOTAL ASSETS	383,635,000	519,775,000
Current liabilities:
Accounts payable and accrued expenses	214,103,000	214,903,000
Other current liabilities	3,141,000	3,534,000
TOTAL CURRENT LIABILITIES	217,244,000	218,437,000
Deferred tax liability, net	1,780,000	1,783,000
Deferred tax liability, net	0	42,000
TOTAL LIABILITIES	219,024,000	220,262,000
Commitments and contingencies (Note 17)
STOCKHOLDERS' EQUITY
Common stock, $0.00001 par value; 500,000 shares authorized at December 31, 2017 and 2016; 50,239 and 49,378 shares issued and outstanding at December 31, 2017 and 2016, respectively	0	0
Additional paid-in capital	418,354,000	398,787,000
Accumulated other comprehensive loss	41,000	(273,000)
Accumulated deficit	(253,784,000)	(99,001,000)
TOTAL STOCKHOLDERS' EQUITY	164,611,000	299,513,000
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 383,635,000	$ 519,775,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
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	50,239,000	49,378,000
Common stock, shares, outstanding	50,239,000	49,378,000

Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 155,545,000	$ 278,221,000	$ 248,484,000
Expenses:
Cost of revenue	56,836,000	73,247,000	58,495,000
Sales and marketing	51,794,000	83,328,000	83,333,000
Technology and development	47,500,000	51,184,000	42,055,000
General and administrative	55,596,000	68,570,000	70,199,000
Restructuring and other exit costs	5,959,000	3,316,000	0
Impairment of intangible assets and internal use software	4,585,000	23,473,000	0
Impairment of goodwill	90,251,000	0	0
Total expenses	312,521,000	303,118,000	254,082,000
Loss from operations	(156,976,000)	(24,897,000)	(5,598,000)
Other (income) expense:
Interest income, net	(908,000)	(491,000)	(59,000)
Other income	688,000	554,000	0
Foreign exchange (gain) loss, net	1,165,000	(939,000)	(1,400,000)
Total other income, net	(431,000)	(1,984,000)	(1,459,000)
Loss before income taxes	(156,545,000)	(22,913,000)	(4,139,000)
Benefit for income taxes	(1,762,000)	(4,860,000)	(4,561,000)
Net income (loss)	$ (154,783,000)	$ (18,053,000)	$ 422,000
Net income (loss) per share:
Basic (usd per share)	$ (3.17)	$ (0.39)	$ 0.01
Diluted (usd per share)	$ (3.17)	$ (0.39)	$ 0.01
Weighted-average shares used to compute net income (loss) per share:
Basic (in shares)	48,869	46,655	39,663
Diluted (in shares)	48,869	46,655	44,495

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (154,783)	$ (18,053)	$ 422
Other comprehensive income (loss):
Unrealized gain (loss) on investments	(28)	67	(68)
Foreign currency translation adjustments	342	(325)	61
Other comprehensive income (loss)	314	(258)	(7)
Comprehensive income (loss)	$ (154,469)	$ (18,311)	$ 415

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	New Accounting Pronouncement, Early Adoption, Effect [Member] Additional Paid-In Capital	New Accounting Pronouncement, Early Adoption, Effect [Member] Accumulated Deficit
Beginning Balance (in shares) at Dec. 31, 2014		37,192
Beginning Balance at Dec. 31, 2014	$ 128,752	$ 0	$ 209,472	$ (8)	$ (80,712)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		2,552
Exercise of common stock options	13,533		13,533
Restricted stock awards, net (in shares)		479
Issuance of common stock related to RSU vesting (in shares)		229
Issuance of common stock related to RSU vesting	2,040		2,040
Issuance of common stock related to employee stock purchase plan (in shares)		170
Issuance of common stock related to acquisition (in shares)		4,425
Issuance of common stock related to acquisition	76,350		76,350
Issuance of common stock for contingent consideration associated with acquisitions (in shares)		1,553
Issuance of common stock for contingent consideration associated with acquisitions	25,608		25,608
Stock-based compensation	31,403		31,403
Other comprehensive loss	(7)			(7)
Net income (loss)	422				422
Ending Balance (in shares) at Dec. 31, 2015		46,600
Ending Balance at Dec. 31, 2015	278,101	$ 0	358,406	(15)	(80,290)
Ending Balance (Accounting Standards Update 2016-09 [Member]) at Dec. 31, 2015						$ 359,064	$ (80,948)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment \| Accounting Standards Update 2016-09 [Member]						$ 658	$ (658)
Exercise of common stock options (in shares)		2,026
Exercise of common stock options	14,249		14,249
Restricted stock awards, net (in shares)		92
Shares withheld related to net share settlement (in shares)		(493)
Shares withheld related to net share settlement	(6,058)		(6,058)
Issuance of common stock related to RSU vesting (in shares)		945
Issuance of common stock related to RSU vesting	1,886		1,886
Issuance of common stock related to employee stock purchase plan (in shares)		208
Issuance of common stock related to acquisition (in shares)		0
Issuance of common stock related to acquisition			0
Stock-based compensation	29,646		29,646
Other comprehensive loss	(258)			(258)
Net income (loss)	$ (18,053)				(18,053)
Ending Balance (in shares) at Dec. 31, 2016	49,378	49,378
Ending 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
Exercise of common stock options	394		394
Restricted stock awards, net (in shares)		(189)
Shares withheld related to net share settlement (in shares)		(529)
Shares withheld related to net share settlement	(2,403)		(2,403)
Issuance of common stock related to RSU vesting (in shares)		1,273
Issuance of common stock related to RSU vesting	629		629
Issuance of common stock related to employee stock purchase plan (in shares)		200
Stock-based compensation	20,947		20,947
Other comprehensive loss	314			314
Net income (loss)	$ (154,783)
Ending Balance (in shares) at Dec. 31, 2017	50,239	50,239
Ending Balance at Dec. 31, 2017	$ 164,611	$ 0	$ 418,354	$ 41	$ (253,784)

Consolidated Statement of Cash Flows - USD ($)	12 Months Ended
Consolidated Statement of Cash Flows - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING ACTIVITIES:
Net income (loss)	$ (154,783,000)	$ (18,053,000)	$ 422,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	36,225,000	42,763,000	31,010,000
Stock-based compensation	20,504,000	28,694,000	30,584,000
Loss on disposal of property and equipment	195,000	214,000	58,000
Provision for doubtful accounts	580,000	540,000	664,000
Accretion of available for sale securities	(276,000)	(82,000)	57,000
Change in fair value of contingent consideration	0	0	306,000
Unrealized foreign currency gains, net	970,000	(1,122,000)	(72,000)
Impairment of intangible assets and internal use software	4,585,000	23,473,000	0
Impairment of goodwill	90,251,000	0	0
Deferred income taxes	(1,564,000)	(6,635,000)	(5,286,000)
Changes in operating assets and liabilities, net of effect of business acquisitions:
Accounts receivable	26,051,000	25,303,000	(72,460,000)
Prepaid expenses and other assets	(224,000)	(2,956,000)	(1,130,000)
Accounts payable and accrued expenses	(502,000)	(32,965,000)	93,135,000
Other liabilities	(477,000)	947,000	(432,000)
Net cash provided by operating activities	21,535,000	60,121,000	76,856,000
INVESTING ACTIVITIES:
Purchases of property and equipment	(32,438,000)	(23,479,000)	(20,104,000)
Capitalized internal use software development costs	(7,988,000)	(9,922,000)	(8,333,000)
Acquisitions, net of cash acquired	(38,610,000)	(238,000)	(8,647,000)
Investments in available-for-sale securities	(95,224,000)	(41,096,000)	(48,801,000)
Maturities of available-for-sale securities	81,050,000	37,360,000	12,001,000
Net cash used in investing activities	(93,210,000)	(37,375,000)	(73,884,000)
FINANCING ACTIVITIES:
Proceeds from exercise of stock options	394,000	14,249,000	13,533,000
Proceeds from issuance of common stock under employee stock purchase plan	629,000	1,886,000	2,040,000
Taxes paid related to net share settlement	(2,403,000)	(6,058,000)	0
Repayment of debt and capital lease obligations	0	0	(105,000)
Net cash provided by (used in) financing activities	(1,380,000)	10,077,000	15,468,000
EFFECT OF EXCHANGE RATE CHANGES ON CASH, CASH EQUIVALENTS AND RESTRICTED CASH	199,000	(157,000)	(160,000)
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(72,856,000)	32,666,000	18,280,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of period	149,498,000	116,832,000	98,552,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of period	76,642,000	149,498,000	116,832,000
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	382,000	1,285,000	1,069,000
Cash paid for interest	61,000	61,000	62,000
Capitalized assets financed by accounts payable and accrued expenses	109,000	1,627,000	342,000
Capitalized stock-based compensation	443,000	952,000	819,000
Common stock and options issued for business acquisitions	0	0	76,534,000
Conversion of contingent consideration to common stock	$ 0	$ 0	$ 25,608,000

Nature of Operations	12 Months Ended
Nature of Operations	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations Company Overview The Rubicon Project, Inc., or Rubicon Project or the Company, was formed on April 20, 2007 in Delaware and began operations in April 2007. The Company is headquartered in Los Angeles, California, and completed its initial public offering ("IPO") in April 2014. The Company is one of the world's largest advertising exchanges. The Company helps websites and apps thrive by giving them tools and expertise to sell ads easily and safely. In addition, the world’s leading agencies and brands rely on Rubicon Project’s technology to execute billions of advertising transactions each month. The Company provides a technology solution to automate the purchase and sale of digital advertising 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, to sell their advertising inventory; applications and services for buyers, including advertisers, agencies, agency trading desks, demand side platforms, or DSPs, to buy 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 advertising inventory we manage on our platform. The Company’s clients include many of the world’s leading publishers of websites and mobile applications and buyers of digital advertising. 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. As a result, the Company’s take rate, which was 25.0% for the full year 2016, dropped to 18.5% for the full year 2017, and was 11.6% exiting 2017. The reduced take rate and competitive pressures resulted in the Company experiencing lower advertising spending on its platform in 2017 as compared to 2016 and also resulted in lower operating results and cash flows in 2017. In an effort to bring its costs into better alignment with reduced revenue, the Company has undertaken restructuring activities to reduce headcount and related operating costs, and has also reduced its capital expenditures, which may make execution against its strategic business plans more difficult. Unless and until the Company is able to compensate for the buyer fee reductions and reduced gross 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. The Company’s current credit facility expires in September 2018. There can be no guarantee that additional financing will be available on commercially reasonable terms, if at all.

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

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.

Reclassifications

Certain prior period amounts have been reclassified to conform with current period presentation. Specifically, this includes amounts reclassified to conform to the current year presentation in the consolidated statement of cash flows.

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 the buying and selling of digital advertising inventory transacted on its platform. The Company's solution enables buyers and sellers to purchase and sell digital advertising inventory by matching buyers and sellers, and by establishing rules and parameters for auctions of advertising inventory. Buyers use the Company's solution to reach their intended audiences by buying advertising inventory that the Company makes available from sellers through its solution. Sellers use the Company's solution to monetize their inventory. The Company recognizes revenue upon fulfillment of its contractual obligations in connection with a completed transaction, subject to satisfying all other revenue recognition criteria, including (i) persuasive evidence of an arrangement existing, (ii) delivery having occurred or services having been rendered, (iii) the fees being fixed or determinable, and (iv) collectability being reasonably assured. The Company (or in some cases, the provider of inventory that the Company accesses via xAPI connection) generally bills and collects the full purchase price of impressions from buyers, together with other fees, if applicable. The Company reports revenue on a net basis for arrangements in which it has determined that it does not act as the principal in the purchase and sale of advertising inventory because pricing is determined through the Company's auction process or directly between a buyer and a seller and the Company is not the primary obligor. In some cases, the Company generates revenue directly from sellers who maintain the primary relationship with buyers and utilize the Company's solution to transact and increase the monetization of their activities. The Company reports revenue on a net basis for these activities. The Company reported revenue on a gross basis for revenue associated with its intent marketing solution, which the Company ceased providing in the first quarter of 2017. For its intent marketing solution, the Company determined that it acted as the principal in the purchase and sale of advertising inventory because the Company had direct contractual relationships with and managed advertising campaigns on behalf of the buyer by acting as the primary obligor in the purchase of advertising inventory, the Company exercised discretion in establishing prices, the Company had credit risk, and the Company independently selected and purchased inventory from the seller. For periods ending after March 31, 2017, all the Company’s revenue is reported on a net basis.

The Company's accounts receivable are recorded at the amount of gross billings to buyers, net of allowances, for the amounts the Company is responsible to collect, and the Company's accounts payable related to amounts due to sellers are recorded at the net amount payable to sellers. Accordingly, both accounts receivable and accounts payable appear large in relation to revenue reported on a net basis.

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 customer relationships and backlog from the Company's business acquisitions and, to a lesser extent, facilities-related costs and depreciation and amortization. The Company's sales organization focuses on increasing the adoption of the Company's solution by existing and new buyers and sellers. The Company amortizes acquired intangibles associated with customer relationships and backlog from its business acquisitions over their estimated useful lives.

Technology and Development. 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 employee stock-based awards is measured and recognized in the consolidated financial statements based on the fair value of the awards granted. The Company has granted awards to employees that vest based solely on continued service, or service conditions, awards that vest based on the achievement of performance targets, or performance conditions, and awards that vest based on the Company's stock price exceeding a peer index, or market conditions. The fair value of each option award containing service and/or performance conditions is estimated on the grant date using the Black-Scholes option-pricing model. The fair value of awards containing market conditions is estimated using a Monte-Carlo lattice model. For service condition awards, stock-based compensation expense is recognized on a straight-line basis over the requisite service periods of the awards, which is generally four years. For performance condition and market condition awards, stock-based compensation expense is recognized using a graded vesting model over the requisite service period of the awards. For market condition awards, expense recognized is not subsequently reversed if the market conditions are not achieved.

Option awards issued to non-employees are accounted for at fair value determined by using the Black-Scholes option-pricing model. The fair value of restricted stock issued to non-employees is based on the market value of the Company's common stock as of the measurement date. The Company believes that the fair value of the stock-based awards is more reliably measured than the fair value of the services received. The fair value of each non-employee stock-based award is re-measured each period until a commitment date is reached, which is generally the vesting date.

Determining the fair value of stock-based awards using a pricing model requires judgment. The Company’s use of the Black-Scholes option-pricing model and Monte-Carlo lattice model requires the input of subjective assumptions such as the expected term of the 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 models represent management’s best estimates. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, the Company’s stock-based compensation expense could be materially different in the future.

These assumptions and estimates are as follows:

Fair Value of Common Stock. 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.

The Company will continue to use judgment in evaluating the assumptions related to the Company’s stock-based compensation. Future expense amounts for any particular period could be affected by changes in the Company’s assumptions or market conditions.

Due to the full valuation allowance provided on its net deferred tax assets, the Company has not recorded any tax benefit attributable to stock-based awards for the years ended December 31, 2017, 2016 and 2015.

Income Taxes

Deferred income tax assets and liabilities are determined based upon the net tax effects of the differences between the Company’s consolidated financial statements carrying amounts and the tax basis of assets and liabilities and are measured using the enacted tax rate expected to apply to taxable income in the years in which the differences are expected to be reversed.

A valuation allowance is used to reduce some or all of the deferred tax assets if, based upon the weight of available evidence, it is more likely than not that those deferred tax assets will not be realized. The Company has established a full valuation allowance to offset its domestic net deferred tax assets due to the uncertainty of realizing future tax benefits from the net operating loss carryforwards and other deferred tax assets.

The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the consolidated financial statements from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties accrued related to its uncertain tax positions in its income tax provision (benefit) in the consolidated statements of operations.

The 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 SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared or analyzed in reasonable detail to complete the accounting for certain income tax effects of the Tax Act and allows the registrant to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. The Company has recognized the impact of the revaluation of deferred tax balances and the provisional impact related to the one-time transition tax. These amounts are included in the Company's consolidated financial statements for the year ended December 31, 2017. The ultimate impact may materially differ from these provisional amounts, due to, among other things, additional analysis, changes in interpretations and assumptions that have been made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the Tax Act. The Company expects to complete our analysis within the measurement period in accordance with SAB 118.

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, 2017 was 15,881,965.

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, 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, 2016, restricted cash totaling $0.1 million was held as collateral for credit cards and is included in prepaid expenses and other current assets on the consolidated balance sheets. At December 31, 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 customer information, subsequent collection history and other relevant data. The Company reviews the allowance for doubtful accounts on a quarterly basis. Account balances are charged off against the allowance when the Company believes it is probable the receivable will not be recovered. The Company’s allowance for doubtful accounts was approximately $0.5 million, $0.7 million and $1.0 million at December 31, 2017, 2016 and 2015 respectively. During the years ended December 31, 2017, 2016 and 2015, the Company wrote-off $0.7 million, $1.1 million and $0.2 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, customer relationships, and non-compete agreements resulting from business combinations, which are recorded at acquisition-date fair value, less accumulated amortization. The Company determines the appropriate useful life of its intangible assets by performing an analysis of expected cash flows of the acquired assets. Intangible assets are amortized over their estimated useful lives using a straight-line method, which approximates the pattern in which the economic benefits are consumed.

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



	Years
Developed technology	3 to 5
Customer 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 9 for a description of the methods used to compute the goodwill impairment charge in the third quarter of 2017. There was no impairment of goodwill recorded during the years ended December 31, 2016 and 2015.

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, 2017.

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 9).

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, 2017, two buyers accounted for 20% and 15%, respectively, of consolidated accounts receivable. At December 31, 2016, two buyers accounted for 12% and 11%, respectively, of consolidated accounts receivable.

For the years ended December 31, 2017, 2016 and 2015, no buyer or seller of advertising inventory comprised 10% or more of consolidated revenue.

At December 31, 2017 and 2016, no seller of advertising inventory comprised 10% or more of consolidated 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 loss on the consolidated balance sheet.

Recent Accounting Pronouncements

Under the Jumpstart Our Business Startups Act, or the JOBS Act, the Company meets the definition of an emerging growth company. The Company has irrevocably elected to opt out of the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act.

In May 2014, the Financial Accounting Standards Board ("FASB"), issued ASU 2014-09—Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"). ASU 2014-09 amends the guidance for revenue recognition to replace numerous industry-specific requirements and converges areas under the "Revenue from Contracts with Customers" topic with those of the International Financial Reporting Standards. The guidance implements a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. The amendment also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. Other major provisions include the capitalization and amortization of certain contract costs, ensuring the time value of money is considered in the transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption ("modified retrospective"). The guidance is effective for reporting periods beginning after December 15, 2017, with early adoption permitted only as of annual reporting periods beginning after December 15, 2016. Since its issuance, the FASB has amended several aspects of the new guidance including provisions that clarify the implementation guidance on principal versus agent considerations in the new revenue recognition standard. The amendments clarify how an entity should identify the unit of accounting (i.e., the specified good or service) for the principal versus agent evaluation and how it should apply the control principle to certain types of arrangements. Management has completed an assessment to determine the impact on the Company's consolidated financial statements by analyzing the Company's primary revenue generating transaction types, and concluded that there was no impact on the Company's results of operations as a result of adopting this standard. The Company will adopt the new standard on a modified retrospective basis as of January 1, 2018.

In January 2016, the FASB issued ASU 2016-01—Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01"). ASU 2016-01 changes certain recognition, measurement, presentation, and disclosure requirements for financial instruments. The new guidance requires all equity investments, except those accounted for under the equity method of accounting or resulting in consolidation, to be measured at fair value with changes in fair value recognized in net income. The guidance also simplifies the impairment assessment for equity investments without readily determinable fair values, amends the presentation requirements for changes in the fair value of financial liabilities, requires presentation of financial instruments by measurement category and form of financial asset, and eliminates the requirement to disclose the methods and significant assumptions used in estimating the fair value of financial instruments. The new guidance is effective for interim and annual periods beginning after December 15, 2017, and early adoption is not permitted except for the amended presentation requirements for changes in the fair value of financial liabilities. The Company is currently assessing the impact this guidance will have on its consolidated financial statements.

In February 2016, the FASB issued 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, and requires a modified retrospective adoption, with early adoption permitted. The Company is currently evaluating the effect this guidance will have on its consolidated financial statements and related disclosures, and anticipates the guidance to result in increases in its assets and liabilities as most of its operating lease commitments will be subject to the new standard and recognized as right-of-use assets and lease liabilities.

In June 2016, the FASB issued ASU 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), which changes the accounting for recognizing impairments of financial assets. Under ASU 2016-13, credit losses for certain types of financial instruments will be estimated based on expected losses. The new guidance also modifies the impairment models for available-for-sale debt securities and for purchased financial assets with credit deterioration since their origination. The new guidance will be effective for the Company starting in the first quarter of fiscal 2021. Early adoption is permitted starting in the first quarter of fiscal 2020. The Company is currently assessing the impact this guidance will have on its consolidated financial statements.

In August 2016, the FASB issued ASU 2016-15—Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"). ASU 2016-15 is intended to reduce diversity in practice in how certain cash receipts and payments are classified in the statement of cash flows, including debt prepayment or extinguishment costs, the settlement of contingent liabilities arising from a business combination, proceeds from insurance settlements, and distributions from certain equity method investees. The new guidance will be effective for interim and annual periods beginning after December 15, 2017, and early adoption is permitted. The guidance requires application using a retrospective transition method. The Company is currently assessing the impact this guidance will have on its consolidated financial statements.

In October 2016, the FASB issued ASU 2016-16—Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory ("ASU 2016-16"), which is intended to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. Under the new guidance, entities should recognize the income tax consequences of such transfers when the transfers occur. The new guidance will be effective for interim and annual periods beginning after December 15, 2017, and early adoption is permitted. The guidance requires application using a modified retrospective transition method. The Company does not expect the guidance to have a material impact on its consolidated financial statements.

In January 2017, the FASB issued ASU 2017-01—Business Combinations (Topic 805): Clarifying the Definition of a Business ("ASU 2017-01"). ASU 2017-01 changes the definition of a business with the objective of adding guidance to assist companies with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, and will be applied prospectively to any transactions occurring within the period of adoption. Early adoption is permitted, including for interim or annual periods in which the financial statements have not been issued or made available for issuance. Subsequent to adoption, the Company will apply this guidance to acquisitions or disposals occurring in the period of adoption and thereafter. The Company does not expect the guidance to have a material impact on its consolidated financial statements.

In May 2017, the FASB issued ASU 2017-09—Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting ("ASU 2017-09") to provide guidance about which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting. The guidance notes that an entity should account for the effects of a modification unless the fair value of the modified award is the same as the fair value of the original award immediately before the original award was modified and it did not change any of the inputs to the valuation technique used to value the award, the vesting conditions did not change, and the classification of the award as either equity or liability did not change. The guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, and will be applied prospectively to any transactions occurring within the period of adoption. Early adoption is permitted, including for interim or annual periods in which the financial statements have not been issued or made available for issuance. The Company is currently assessing the impact this guidance will have on its consolidated financial statements.

Net Income (Loss) Per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

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



	Year Ended
	December 31, 2017			December 31, 2016			December 31, 2015
	(In thousands, except per share data)
Basic EPS:
Net income (loss)	$	(154,783	)	$	(18,053	)	$	422
Weighted-average common shares outstanding	49,720			48,512			42,067
Weighted-average unvested restricted shares	(851		)	(1,857		)	(1,677		)
Weighted-average escrow shares	—			—			(727		)
Weighted-average common shares outstanding used to compute net income (loss) per share	48,869			46,655			39,663
Basic net income (loss) per share	$	(3.17	)	$	(0.39	)	$	0.01
Diluted EPS:
Net income (loss)	$	(154,783	)	$	(18,053	)	$	422
Weighted-average common shares used in basic EPS	48,869			46,655			39,663
Dilutive effect of weighted-average common stock options	—			—			2,510
Dilutive effect of weighted-average restricted stock awards	—			—			532
Dilutive effect of weighted-average restricted stock units	—			—			426
Dilutive effect of weighted-average ESPP	—			—			25
Dilutive effect of weighted-average escrow shares	—			—			591
Dilutive effect of weighted-average contingent shares	—			—			748
Weighted-average shares used to compute diluted net income (loss) per share	48,869			46,655			44,495
Diluted net income (loss) per share	$	(3.17	)	$	(0.39	)	$	0.01

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



	December 31, 2017	December 31, 2016	December 31, 2015
	(in thousands)
Options to purchase common stock	120	951	—
Unvested restricted stock awards	297	414	—
Unvested restricted stock units	556	611	—
Shares held in escrow	—	392	—
ESPP	50	30	—
Contingent shares	—	—	704
Total shares excluded from net income (loss) per share	1,023	2,398	704

In connection with the acquisition of Chango, which occurred during the year ended December 31, 2015, the Company issued 971,481 shares in connection with the contingent consideration and released 126,098 shares from escrow. These shares were included in the calculation of basic net income (loss) per share effective December 31, 2015, the date of issuance, and were included in the calculation of diluted net income (loss) per share for periods between the date of acquisition and immediately prior to December 31, 2015.

In connection with the acquisition of iSocket, Inc. ("iSocket"), which occurred in 2014, the Company issued 585,170 shares in connection with the contingent consideration on December 31, 2015. These shares were included in the calculation of basic net income (loss) per share effective December 31, 2015, the date of issuance.

Investments

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Investments

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

As of December 31, 2017, the Company's available-for-sale securities had a weighted remaining contractual maturity of 0.3 years. For the year ended December 31, 2017, there were no realized gains (losses) and there were no unrealized holding gains (losses) reclassified out of accumulated other comprehensive income (loss) into the consolidated statements of operations for the sale of available-for-sale investments.

Investments in marketable securities as of December 31, 2016 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	$	23,237	$	1	$	(2	)	$	23,236
Corporate debt securities	17,314		—		—			17,314
Total	$	40,551	$	1	$	(2	)	$	40,550

The amortized cost and fair value of the Company's marketable securities at December 31, 2017, by contractual years-to-maturity are as follows:



	Amortized Cost		Fair Value
	(in thousands)
Due in less than 1 year	$	52,524	$	52,504
Due within 1-2 years	2,504		2,495
Total	$	55,028	$	54,999

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment

Major classes of property and equipment were as follows:



	December 31, 2017			December 31, 2016
	(in thousands)
Purchased software	$	1,985		$	1,777
Computer equipment and network hardware	90,695			62,084
Furniture, fixtures and office equipment	2,165			2,194
Leasehold improvements	3,325			3,385
Gross property and equipment	98,170			69,440
Accumulated depreciation	(50,777		)	(33,194		)
Net property and equipment	$	47,393		$	36,246

Depreciation expense on property and equipment totaled $20.3 million, $13.7 million and $8.6 million for the years ended December 31, 2017, 2016 and 2015, respectively. There were no impairment charges to property and equipment for the years ended December 31, 2017, 2016 and 2015.

At December 31, 2017 and 2016, the Company had no property and equipment under capital leases.

Internal Use Software Development Costs

12 Months Ended

Dec. 31, 2017

Research and Development [Abstract]

Internal Use Software Development Costs

Internal use software development costs were as follows:



	December 31, 2017			December 31, 2016
	(in thousands)
Internal use software development costs, gross	33,414			$	37,032
Accumulated amortization	(20,680		)	(20,510		)
Internal use software development costs, net	$	12,734		$	16,522

During the years ended December 31, 2017, 2016 and 2015, the Company capitalized $8.4 million, $10.9 million, and $9.2 million of internal use software development costs. Amortization expense was $11.1 million, $8.3 million and $6.7 million for the years ended December 31, 2017, 2016 and 2015. In the years ended December 31, 2017, 2016 and 2015, amortization expense included the write-off of software development costs of $1.6 million, $0.8 million and $1.5 million, in the respective periods. Based on the Company’s internal use software development costs at December 31, 2017, estimated amortization expense of $6.2 million, $4.3 million and $2.2 million is expected to be recognized in 2018, 2019 and 2020, 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 9 for additional valuation details). There were no impairment charges to internal use software development costs for the years ended December 31, 2016 and 2015.

Business Combinations

12 Months Ended

Dec. 31, 2017

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 is 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 has 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 revenues, 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 customers, and enhanced opportunities for growth and innovation. Refer to Note 9 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, 2016. 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 dates indicated, nor are they indicative of the actual or future operating results of the combined company.



	Year Ended
	December 31, 2017			December 31, 2016

Pro forma revenues	$	156,480		$	278,995
Pro forma net loss	$	(158,443	)	$	(25,116	)
Pro forma net loss per share, basic	$	(3.24	)	$	(0.54	)
Pro forma net loss per share, diluted	$	(3.24	)	$	(0.54	)

nToggle's technology was fully integrated into the Company's platform, and its pre-acquisition product will not be 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 is impracticable.

2015 Acquisition—Chango Inc.

On April 24, 2015 (the "Acquisition Date"), the Company completed the acquisition of all the issued and outstanding shares of Chango, a Toronto, Canada based intent marketing technology company.

The purchase consideration for the acquisition included 4,191,878 shares of the Company's common stock, with a fair value of approximately $72.5 million, based on the Company's stock price as reported on the NYSE on the Acquisition Date. 639,318 of the 4,191,878 shares of the Company's common stock were placed in escrow to secure post-closing indemnification obligations of the sellers and were released from escrow on July 24, 2016. In addition, the Company issued 106,553 shares of the Company's common stock on the date of the acquisition, which were placed in escrow, related to employee future service requirements which were excluded from the purchase consideration and were expensed in the Company's post acquisition consolidated statement of operations. The Company also used approximately $9.1 million of cash to repay Chango's outstanding debt, including accrued interest, and to pay Chango's outstanding transaction expenses.

The purchase consideration also included contingent consideration of up to approximately $18.2 million worth of cash or shares of the Company's common stock and 126,098 shares held in escrow based upon Chango's performance against certain agreed-upon operating objectives for the year ending December 31, 2015. The Company had the option to pay the contingent consideration in cash or common stock, or a combination thereof. The number of shares issued in connection with the contingent consideration, excluding the escrow shares, was based on a price per share of $18.77. On the Acquisition Date, the fair value was estimated using a Monte-Carlo model as the fair value of the contingent consideration was dependent on both the performance milestones being achieved and the post-acquisition prices of the Company's common stock. The total contingent consideration was recorded at an estimated fair value of $16.2 million. The fair value of the contingent consideration assumed the probability of the performance milestones being achieved and the probability that the Company would settle the contingent consideration in common stock. The contingent consideration was recorded as a non-current liability in the consolidated balance sheet as the contingent consideration was payable in a variable number of shares at the Acquisition Date. Changes in the fair value of the contingent consideration liability were recorded in the Company's consolidated statement of operations. Subsequent to the Acquisition Date, the operations of Chango were fully integrated into the operations of the Company. Accordingly, pursuant to the acquisition agreement, because Chango would no longer be operated separate from the Company's other operations in accordance with the agreed-upon business plan, the entire contingent consideration was deemed earned. As a result, the changes in the fair value of the contingent consideration liability post-acquisition were primarily dependent on prices of the Company's common stock for periods subsequent to the Acquisition Date. On December 31, 2015 the Company converted the contingent consideration to equity and issued 971,481 shares in addition to releasing 126,098 shares from escrow.

As part of the acquisition, existing stock options to purchase common stock of Chango were exchanged for 428,798 options to purchase the Company's common stock. The fair value of stock options exchanged on the Acquisition Date attributable to pre-acquisition services of approximately $4.3 million was recorded as purchase consideration. The fair value of stock options exchanged on the Acquisition Date attributable to post-acquisition services of $2.4 million will be recorded as additional stock-based compensation expense in the Company's consolidated statements of operations over their remaining requisite service (vesting) periods. During the fourth quarter of 2015, the Company recorded a decrease to goodwill related to the Chango acquisition for an insignificant adjustment to purchase price associated with the fair value of stock-based awards exchanged in the amount of $0.3 million and a reduction to the fair value of stock options exchanged on the Acquisition Date attributable to post-acquisition services of $0.7 million.

As part of the acquisition, the Company recorded deferred tax liabilities related to acquired intangibles of $13.9 million net of deferred tax assets of $2.0 million, primarily related to net operating loss carry forwards. During the fourth quarter of 2015, the Company recorded a decrease to goodwill related to the Chango acquisition for a measurement period adjustment for a reduction in deferred tax liabilities in the amount of $0.5 million.

The total purchase consideration and the allocation of the total purchase consideration to assets acquired and liabilities assumed is summarized below (in thousands):



Shares of the Company's common stock	$	72,477
Estimated fair value of contingent consideration	16,171
Fair value of stock-based awards exchanged	4,058
Cash paid	9,097
Working capital adjustment	(184		)
Total purchase consideration	101,619
Cash	450
Accounts receivable	13,333
Prepaid and other assets	1,025
Fixed assets	265
Intangible assets, including in process research and development of $580	52,420
Goodwill	51,732
Total assets acquired	119,225
Accounts payable and accrued expenses	5,825
Other liabilities	443
Deferred tax liability, net	11,338
Total liabilities assumed	17,606
Total net assets acquired	$	101,619

The fair value of the consideration transferred to acquire Chango was allocated to the identifiable assets acquired and liabilities assumed based upon their estimated fair values as of the Acquisition Date. This allocation was final as of December 31, 2015.

Goodwill was primarily attributable to expected synergies from assembled workforce, an increase in development capabilities, increased offerings to customers, and enhanced opportunities for growth and innovation. The goodwill resulting from the Chango acquisition is not tax deductible.

During the year ended December 31, 2015, the Company recognized approximately $1.3 million in professional fees directly related to the acquisition of Chango, primarily composed of legal, accounting, and valuation costs, which are recorded within general and administrative expenses in the Company’s consolidated statements of operations. In addition, as part of the acquisition of Chango, the Company acquired Chango's NOLs of approximately $6.9 million.

Unaudited Pro Forma Information - Chango Acquisition

The following table provides unaudited pro forma information as if Chango had been acquired as of January 1, 2014. 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 Chango or recognition of compensation expense relating to the contingent consideration. Accordingly, pro forma amounts are not necessarily indicative of the results that actually would have occurred had the acquisition been completed on the dates indicated, nor are they indicative of the future operating results of the combined company.



	Year Ended
	December 31, 2015
	(in thousands, except per share data)
Pro forma revenues	$	265,134
Pro forma net income	$	673
Pro forma net income per share, basic	$	0.02
Pro forma net income per share, diluted	$	0.01

Subsequent to the Acquisition Date, the operations of Chango were fully integrated into the operations of the Company and as a result, the determination of Chango’s post-acquisition revenues and operating results on a standalone basis are impracticable given the integration of the Chango operations with the Company's operations.

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

The Company has continued to experience 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. For additional details regarding the valuation assessment process, refer to Note 9.

The Company compared the fair value of its net assets using the three methodologies (one income approach and two market approaches), to the carrying value of $274.4 million. As the carrying value of the Company's net assets exceeded the estimated fair value, the Company recorded an impairment charge of $90.3 million during the third quarter of 2017. No impairment of goodwill was identified for the years ended December 31, 2016 and 2015.

Details of the Company’s goodwill were as follows:



	December 31, 2017			December 31, 2016
	(in thousands)
Beginning balance	$	65,705		$	65,705
Additions from the acquisition of nToggle (See Note 7)	24,546			—
Impairment of goodwill	(90,251		)	—
Ending balance	$	—		$	65,705

As a result of the indications of impairment related to goodwill, the Company also performed an interim impairment assessment of its long-lived assets, including intangible assets. Under this assessment, the carrying value of the Company's long-lived assets was compared to the undiscounted cash flows expected to be generated by the asset group over its remaining life. Based on this assessment, there was no impairment of long-lived assets.

The Company’s intangible assets as of December 31, 2017 and 2016 including the following:



	December 31, 2017			December 31, 2016
	(in thousands)
Amortizable intangible assets:
Developed technology	$	16,878		$	13,418
Customer relationships	—			3,330
Non-compete agreements	690			4,990
Trademarks	20			—
Total identifiable intangible assets, gross	17,588			21,738
Accumulated amortization— intangible assets:
Developed technology	(4,062		)	(7,652		)
Customer relationships	—			(2,837		)
Non-compete agreements	(161		)	(4,445		)
Trademarks	(6		)	—
Total accumulated amortization—intangible assets	(4,229		)	(14,934		)
Total identifiable intangible assets, net	$	13,359		$	6,804

Amortization of intangible assets for the years ended December 31, 2017, 2016 and 2015 was $4.8 million, $20.5 million and $15.7 million, respectively. In 2016, the Company reassessed the remaining estimated useful lives of the developed technology and customer relationships related to the Chango acquisition based on the remaining expected benefit from those assets. The change in the remaining estimated useful lives for developed technology and customer relationships resulted in increased amortization expense of $4.2 million for the year ended December 31, 2016. The increased amortization expense decreased the basic and diluted earnings per share by $0.09 for the year ended December 31, 2016.

In January 2017, the Company announced that it would cease providing intent marketing services. In connection with this decision, the Company assessed the asset group related to the intent marketing services, which consisted of customer relationships and developed technology related to the Chango acquisition, and determined that the asset group was impaired. Accordingly, the Company recorded a charge for the impairment of intangible assets totaling $23.5 million, which is included in the consolidated statement of operations for the year ended December 31, 2016.

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 customer relationships acquired as part of an acquisition completed in 2014. See Note 9 for additional information.

The estimated remaining amortization expense associated with the Company's intangible assets was as follows as of December 31, 2017:



Fiscal Year	Amount
	(in thousands)
2018	$	3,185
2019	3,010
2020	2,826
2021	2,826
2022	1,512
Total	$	13,359

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Fair Value Measurements

12 Months Ended

Dec. 31, 2017

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, 2017:



	December 31, 2017		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	$	—	$	—

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2016:



	December 31, 2016		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	$	15,776	$	7,781	$	7,995	$	—
Corporate debt securities	$	17,314	$	—	$	17,314	$	—
U.S. Treasury, government and agency debt securities	$	23,236	$	23,236	$	—	$	—

At December 31, 2017 and 2016, cash equivalents of $1.8 million and $15.8 million 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 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, rather 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, for securities with maturities of one year or less, or within other assets, non current, for securities with maturities over one year.

There were no transfers between Level 1 and Level 2 fair value measurements during the years ended December 31, 2017 and 2016.

The Company classified its contingent consideration liabilities incurred in connection with the acquisitions of iSocket and Chango within Level 3 of the fair value hierarchy because the valuations relied on unobservable inputs. The fair value of these liabilities was evaluated on a quarterly basis, with changes to the fair value recorded within general and administrative expenses in the Consolidated Statements of Operations. For the year ended December 31, 2015, the Company recognized an expense of $0.3 million related to the change in fair value of the contingent consideration liabilities. On December 31, 2015, the Company settled the remaining liabilities by issuance of shares of its common stock.

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 customer 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, 2016, the Company recorded an impairment of intangible assets totaling $23.5 million related to the exit of its intent marketing product. 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 intangible assets were determined to be fully impaired and were written down to their fair values of zero.

For the year ended December 31, 2015, 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

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Accounts Payable and Accrued Expense

Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses included the following:



	December 31, 2017		December 31, 2016
	(in thousands)
Accounts payable—seller	$	203,694	$	197,261
Accounts payable—trade	3,764		7,930
Accrued employee-related payables	6,645		9,712
Total	$	214,103	$	214,903

Debt	12 Months Ended
Debt	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt The Company has a loan and security agreement with Silicon Valley Bank (the "Loan Agreement") that provides a senior secured revolving credit facility of up to $40.0 million with a maturity date of September 27, 2018. 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 2.0% if the Company maintains a net cash balance exceeding $1. If the Company elects prime, advances bear interest at a rate of prime plus 0% if the Company maintains a net cash balance exceeding $1 or prime plus 1.50% if the Company does not maintain a net cash balance of $1. The Loan Agreement is collateralized by security interests in substantially all of the Company’s assets. The Loan Agreement restricts the Company’s ability to 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. The Company is required to maintain a lockbox arrangement where customer payments received in the lockbox will reduce the amounts outstanding on the credit facility only if the Company does not maintain a net cash balance of $1 or in the event of a default, as defined in the arrangement. The Loan Agreement requires the Company to comply with financial covenants including minimum levels of adjusted tangible net worth and a fixed charge coverage ratio, as well as certain affirmative covenants. In the event the amount available to be drawn is less than 20% of the maximum line amount of the credit facility, or in the event that a default exists, the Company is required to satisfy a minimum fixed charge coverage ratio of no less than 1.10 to 1.00 calculated on a twelve month trailing basis as of the last day of each month on a consolidated basis. The Company was in compliance with the covenants as of December 31, 2017 and 2016. The Loan Agreement includes customary events of defaults, including a change of control default and an event of default in the event a material adverse change occurs. In case of such an event of default, Silicon Valley Bank would be entitled to, among other things, accelerate payment of amounts due under the credit facility and exercise all rights of a secured creditor. At December 31, 2017, there were no amounts outstanding under this loan. Future availability under the credit facility is dependent on several factors including the available borrowing base and compliance with future covenant requirements.

Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

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, 2015	$	(68	)	$	53		$	(15	)
Other comprehensive income (loss)	67			(325		)	(258		)
Balance at December 31, 2016	(1		)	(272		)	(273		)
Other comprehensive income (loss)	(28		)	342			314
Balance at December 31, 2017	$	(29	)	$	70		$	41

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

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, or the 2014 Plan, which governs equity awards made to employees and directors of the Company since the IPO. In connection with the acquisition of iSocket, the Company assumed the iSocket 2009 Equity Incentive Plan, or the iSocket Plan, which governs stock options issued to former iSocket employees and assumed by the Company. In November 2014, the Company approved the 2014 Inducement Grant Equity Incentive Plan, or the Inducement Plan, which governs certain equity awards made to certain employees in connection with commencement of employment. In connection with the acquisition of Chango, the Company assumed Chango's 2009 Stock Option Plan, or the Chango plan, which governs stock options issued to former Chango employees and assumed by the Company. All compensatory equity awards outstanding at December 31, 2017 were issued pursuant to the 2014 Plan, the iSocket Plan, the Chango Plan, the Inducement Plan, or the Company's 2007 Stock Incentive Plan, or the 2007 Plan, which governs equity awards made to employees and contractors of the Company prior to the IPO. The Company’s equity incentive plans provide for the grant of equity awards, including non-statutory or incentive stock options, restricted stock, 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 and restricted stock units vest at varying rates, usually 25% vesting after one year of service and the remainder vesting semi-annually thereafter. Options, restricted stock, and restricted stock units granted under the plans accelerate under certain circumstances on a change in control, as defined in the governing plan. No further awards were made under the iSocket Plan, the Chango Plan, or the 2007 Plan; available shares under the iSocket Plan and the Chango Plan were rolled into the available share pool under the 2014 Plan at the time of acquisition of each company, and available shares under the 2007 Plan were rolled into the available share pool under the 2014 Plan at the time of the IPO. An aggregate of 6,073,370 shares remained available for issuance at December 31, 2017 under the plans. The 2014 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 Inducement Plan has a provision pursuant to which the share reserve may be increased at the discretion of the Company's board of directors.

During the year ended December 31, 2016, the Company early adopted the new accounting guidance that simplifies several aspects of the accounting for share-based payments, including the Company's election to eliminate the requirement to estimate the number of awards that are expected to vest and, instead, account for forfeitures when they occur. The new standard requires the change be adopted using the modified retrospective approach. As such, the Company recorded a cumulative-effect adjustment of $0.7 million to increase the 2016 beginning of period accumulated deficit and additional paid-in capital balances. In addition, the new standard requires income tax benefits and deficiencies to be recognized as income tax expense or benefit in the income statement and the tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. The Company recorded $7.5 million of net deferred tax assets related to net operating losses for income tax benefits as of January 1, 2016. The Company has a full valuation allowance, and thus the income tax consequences of the new standard did not have an impact on the consolidated financial statements. Excess tax benefits should be classified along with other income tax cash flows as an operating activity. The new standard also requires the presentation of cash paid by the employer for employee taxes as a financing activity. The Company has historically presented these items as financing activities, and thus the new standard did not have an impact on the consolidated statement of cash flows.

Stock Options

A summary of stock option activity for the year ended December 31, 2017 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, 2016	3,861		$	11.16
Granted	1,424		$	4.20
Exercised	(106	)	$	3.71
Expired	(506	)	$	12.07
Forfeited	(310	)	$	14.26
Outstanding at December 31, 2017	4,363		$	8.75	5.73 years	$	600
Exercisable at December 31, 2017	2,785		$	10.44	3.92 years	$	99

The total intrinsic values of options exercised during the years ended December 31, 2017, 2016 and 2015 were $0.4 million, $18.5 million and $28.3 million, respectively. At December 31, 2017, the Company had unrecognized employee stock-based compensation expense relating to stock options of approximately $5.4 million, which is expected to be recognized over a weighted-average period of 2.8 years. The weighted-average grant date per share fair values of stock options granted in the years ended December 31, 2017, 2016 and 2015 were $3.55, $6.29 and $9.25, respectively.

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, 2017		December 31, 2016		December 31, 2015
Expected term (in years)	5.8		5.9		4.5
Risk-free interest rate	2.03	%	1.47	%	1.30	%
Expected volatility	57	%	49	%	47	%
Dividend yield	—	%	—	%	—	%

Restricted Stock

A summary of restricted stock activity for the year ended December 31, 2017 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested shares of restricted stock outstanding at December 31, 2016	1,113		$	14.07
Granted	77		$	5.07
Canceled	(267	)	$	13.27
Vested	(365	)	$	15.01
Nonvested shares of restricted stock outstanding at December 31, 2017	558		$	12.60

The weighted-average grant date per share fair values of restricted stock with service conditions granted for the years ended December 31, 2017, 2016 and 2015 were $5.07, $13.26 and $16.75, respectively. The fair values of restricted stock with service conditions that vested during the years ended December 31, 2017, 2016 and 2015 were $1.7 million, $5.7 million and $9.8 million, respectively. At December 31, 2017, the Company had unrecognized stock-based compensation expense for restricted stock with service conditions of $2.6 million, which is expected to be recognized over a weighted-average period of 1.7 years.

In March 2014, the Company granted 280,000 shares of restricted stock to certain executives that vest based on certain stock price performance metrics, beginning on the completion of the Company’s IPO in April 2014 over an estimated weighted-average period of 1.7 years. The grant date fair value per share of the 280,000 shares of restricted stock was $13.15, which was estimated using a Monte-Carlo lattice model. The compensation expense will not be reversed if performance metrics are not obtained. At December 31, 2017, the Company had unrecognized stock-based compensation expense relating to these shares of restricted stock of approximately $0.1 million, which is expected to be recognized over a weighted-average period of 3.4 years.

In May 2015, the Company granted certain executives shares of restricted stock that vest based on certain stock price performance metrics. The grant date fair value per share of restricted stock was $13.81, which was estimated using a Monte-Carlo lattice model. In February 2016, the Company granted certain executives shares of restricted stock that vest based on certain stock price performance metrics. The grant date fair value per share of restricted stock was $11.07, which was estimated using a Monte-Carlo lattice model. At December 31, 2017, the Company had unrecognized employee stock-based compensation expense relating to these shares of restricted stock with market conditions of approximately $0.6 million, which is expected to be recognized over a weighted-average period of 0.6 years. The compensation expense will not be reversed if the performance metrics are not met.

Restricted Stock Units

A summary of restricted stock unit activity for the year ended December 31, 2017 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested shares of restricted stock units outstanding at December 31, 2016	2,903		$	13.63
Granted	3,149		$	5.61
Canceled	(1,170	)	$	12.11
Vested	(1,273	)	$	12.43
Nonvested shares of restricted stock units outstanding at December 31, 2017	3,609		$	7.55

The weighted-average grant date fair values per share of restricted stock units granted for the years ended December 31, 2017, 2016 and 2015 were $5.61, $12.66 and $16.45, respectively. The fair values of restricted stock units that vested during the years ended December 31, 2017, 2016 and 2015 were $5.1 million, $11.5 million and $3.6 million, respectively. At December 31, 2017, the intrinsic value of nonvested restricted stock units was $6.7 million. At December 31, 2017, the Company had unrecognized stock-based compensation expense relating to restricted stock units of approximately $23.9 million, which is expected to be recognized over a weighted-average period of 2.8 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, 2017, the Company has reserved 1,279,464 shares of its common stock for issuance under the ESPP. Shares reserved for issuance will increase on January 1^st of each year by the lesser of (i) a number of shares equal to 1% of the total number of outstanding shares of common stock on the December 31^st immediately prior to the date of increase or (ii) such number of shares as may be determined by the board of directors.

Stock-Based Compensation Expense

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



	Year Ended
	December 31, 2017		December 31, 2016		December 31, 2015
	(in thousands)
Cost of revenue	$	404	$	344	$	240
Sales and marketing	4,582		8,520		7,415
Technology and development	4,034		5,788		4,963
General and administrative	9,924		14,042		17,966
Restructuring and other exit costs	1,560		—		—
Total stock-based compensation expense	$	20,504	$	28,694	$	30,584

Restructuring and Other Exit Costs

12 Months Ended

Dec. 31, 2017

Restructuring and Related Activities [Abstract]

Restructuring and Other Exit Costs

Restructuring And Other Exit Costs

As part of its on-going efforts to control costs and evaluate efficiencies, in January 2017, the Company announced that it would cease providing intent marketing services and would close its Toronto, Canada office as a result. Additional restructuring costs were incurred in the first half of 2017 related to the closure of the Toronto office, as well as a realignment of the management team to a more cost efficient structure. The objective of the restructuring activities was to streamline operations, prioritize resources for growth initiatives and increase profitability. The Company has recognized expenses resulting from these activities as restructuring and other exit costs within its consolidated statement of operations. The remaining liability is included within other liabilities on the Company’s consolidated balance sheets.

The following table summarizes restructuring and other exit cost activity (in thousands):



Accrued restructuring and other exit costs at December 31, 2015	$	—
Restructuring and other exit costs	3,316
Cash paid for restructuring and other exit costs	(2,515		)
Accrued restructuring and other exit costs at December 31, 2016	$	801
Restructuring and other exit costs	5,959
Cash paid for restructuring and other exit costs	(5,059		)
Non-cash stock-based compensation for restructuring and other exit costs	(1,560		)
Accrued restructuring and other exit costs at December 31, 2017	$	141

The following table presents the components of restructuring and other exit costs for the years ended December 31, 2017 and 2016 (in thousands):



	Year Ended
	December 31, 2017		December 31, 2016
Employee termination costs	$	5,753	$	3,270
Facility closing costs	206		46
Total restructuring and other exit costs	$	5,959	$	3,316

Income Taxes

12 Months Ended

Dec. 31, 2017

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, 2017, 2016 and 2015:



	Year Ended
	December 31, 2017			December 31, 2016			December 31, 2015
	(in thousands)
Domestic	$	(104,750	)	$	25,704		$	15,723
International	(51,795		)	(48,617		)	(19,862		)
Loss before income taxes	$	(156,545	)	$	(22,913	)	$	(4,139	)

The following are the components of the provision (benefit) for income taxes for the years ended December 31, 2017, 2016 and 2015:



	Year Ended
	December 31, 2017			December 31, 2016			December 31, 2015
	(in thousands)
Current:
Federal	$	(140	)	$	441		$	196
State	78			713			90
Foreign	(250		)	613			367
Total current provision	(312		)	1,767			653
Deferred:
Federal	(1,877		)	—			—
State	288			(289		)	1
Foreign	139			(6,338		)	(5,215		)
Total deferred benefit	(1,450		)	(6,627		)	(5,214		)
Total provision (benefit) for income taxes	$	(1,762	)	$	(4,860	)	$	(4,561	)

During the year ended December 31, 2016, the Company early adopted the new accounting guidance that simplifies several aspects of the accounting for share-based payments, including the requirement for income tax benefits and deficiencies to be recognized as income tax expense or benefit in the income statement and the tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. The Company recorded $7.5 million of net deferred tax assets related to net operating losses for income tax benefits as of January 1, 2016. The Company has a full valuation allowance, and thus the new standard did not have an impact on the consolidated financial statements. Excess tax benefits should be classified along with other income tax cash flows as an operating activity.

The Company recorded an income tax benefit for the years ended December 31, 2017, 2016 and 2015 of $1.8 million, $4.9 million and $4.6 million, respectively. The tax benefit for the year ended December 31, 2017 is the result of a deferred tax liability associated with the nToggle acquisition, while the benefits for 2016 and 2015 were the result of the net operating loss generated by the Canadian operations.

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: a federal corporate rate reduction from 34% to 21%; limitations on the deductibility of executive compensation and research and development (“R&D”) expenditures, 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 will result in a one time U.S. tax liability on those earning which have 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.

The Tax Act also reduced the U.S. corporate tax rate from 34% to 21%, effective January 1, 2018. Consequently, the Company has 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 SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared or analyzed in reasonable detail to complete the accounting for certain income tax effects of the Tax Act and allows the registrant to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. The Company has recognized the actual impact of the revaluation of deferred tax balances and the provisional impact related to the one-time transition tax. The Company included these amounts in its consolidated financial statements for the year ended December 31, 2017. The ultimate impact may materially differ from these provisional amounts, due to, among other things, additional analysis, changes in interpretations and assumptions that have been made, additional regulatory guidance that may be issued, and actions may be taken as a result of the Tax Act. The Company expects to complete our analysis within the measurement period in accordance with SAB 118.

In addition, it is unclear how many U.S. states will incorporate the federal law changes, or portions thereof, into their tax codes and foreign governments may enact tax laws in response to the Tax Act that could result in further changes to global taxation and materially affect the Company's financial position and results of operations.

The Tax Act allows for the immediate write off (“expensing”) of the cost of qualified property acquired and placed in service after September 27, 2017 and before January 1, 2023. Following January 1, 2023, the expensing phases down 20% annually through January 1, 2027. The Company recorded an immediate write off of $12.4 million for the year ending December 31, 2017.

Additionally, the Tax Act imposes a new BEAT, essentially a 10% minimum tax (5% for tax years beginning after December 31, 2017, increasing to 10% for years beginning after December 31, 2018) calculated on a base equal to taxpayer’s income determined without tax benefits arising from base erosion payments and, also, 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). GAAP allows the Company to either (i) treat taxes due on future U.S. inclusions in taxable income related to BEAT and GILTI as current-period expense when incurred (the “period cost method”); or (ii) factor such amounts into the measurement of deferred taxes (the “deferred method”). The Company elected the period cost method. Given that these new rules are not yet effective, the Company has not made any adjustments to its financial statements for these items for the year ended December 31, 2017.

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 34.0% for the years ended December 31, 2017, 2016 and 2015:



	Year Ended
	December 31, 2017		December 31, 2016		December 31, 2015
U.S. federal statutory income tax rate	34.0	%	34.0	%	34.0	%
State income taxes, net of federal benefit	—	%	(2.1	)%	(1.4	)%
Foreign income (loss) at other than U.S. rates	0.2	%	(14.4	)%	(31.0	)%
Stock-based compensation expense	(3.8	)%	2.1	%	(31.5	)%
Meals and entertainment	(0.1	)%	(1.5	)%	(14.2	)%
Acquisition and related items	—	%	—	%	(8.6	)%
Goodwill impairment	(19.0	)%	—	%	—	%
Non-deductible gifts	—	%	(0.1	)%	(0.8	)%
Research and development tax credits	0.8	%	7.2	%	42.3	%
Tax effect of intercompany financing	—	%	4.9	%	11.2	%
Worthless stock	31.7	%	—	%	—	%
Other permanent items	(0.5	)%	—	%	(0.5	)%
Provision (benefit) to return adjustments	—	%	0.6	%	(9.4	)%
Change in valuation allowance	(22.0	)%	(9.5	)%	120.1	%
Tax rate change; U.S. tax reform	(20.2	)%	—	%	—	%
Effective income tax rate	1.1	%	21.2	%	110.2	%

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, 2017 and 2016:



	December 31, 2017			December 31, 2016
	(in thousands)
Deferred Tax Assets:
Accrued liabilities	$	2,648		$	1,287
Stock-based compensation	3,685			7,381
Net operating loss carryovers	65,648			21,375
Tax credit carryovers	13,494			10,915
Other	1,502			2,360
Total deferred tax assets	86,977			43,318
Less valuation allowance	(81,767		)	(39,491		)
Deferred tax assets, net of valuation allowance	5,210			3,827
Deferred Tax Liabilities:
Fixed assets	(3,864		)	(3,764		)
Intangible assets	(955		)	468
Other	—			—
Total deferred tax liabilities	(4,819		)	(3,296		)
Net deferred tax assets (liability)	$	391		$	531

The change in valuation allowance for the years ended December 31, 2017, 2016 and 2015 was $42.3 million, $10.2 million and $3.2 million, respectively.

At December 31, 2017, the Company had U.S. federal net operating loss carryforwards, or NOLs, of approximately $238.7 million, which will begin to expire in 2027. At December 31, 2017, the Company had state NOLs of approximately $139.8 million, which will begin to expire in 2027. At December 31, 2017, the Company had foreign NOLs of approximately $23.8 million, which will begin to expire in 2026. At December 31, 2017, 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, 2017, the Company had state research and development tax credits of approximately $8.0 million, which carry forward indefinitely. At December 31, 2017, the Company had foreign research tax credits of approximately $0.7 million, which carry forward indefinitely.

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, 2017, unremitted earnings of the subsidiaries outside of the United States were approximately $5.1 million, on which the Company recorded a provisional transaction 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 at January 1, 2015	$	2,131
Increases related to 2015 tax positions	2,194
Decreases related to prior year tax positions	—
Balance as of December 31, 2015	4,325
Increases related to 2016 tax positions	702
Decreases related to prior year tax positions	—
Balance as of December 31, 2016	5,027
Increases related to current year tax positions	550
Increases related to prior year tax positions	69
Decreases related to prior year tax positions	—
Balance as of December 31, 2017	$	5,646

Interest and penalties related to the Company’s unrecognized tax benefits accrued at December 31, 2017, 2016 and 2015 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. The Company has not received and Notice of Proposed Adjustments (“NOPAs”) nor had a discussions with the IRS regarding any potential adjustments.

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.

Geographic Information

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Geographic Information

Revenue by geography are based on the location of the Company's sellers. The Company's revenue by geographical region was as follows:



	Year Ended
	December 31, 2017		December 31, 2016		December 31, 2015
	(in thousands)
United States	$	95,567	$	182,777	$	172,188
United Kingdom	11,140		20,778		20,355
Other international	48,838		74,666		55,941
Total	$	155,545	$	278,221	$	248,484

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



	December 31, 2017		December 31, 2016		December 31, 2015
	(in thousands)
United States	$	37,566	$	29,032	$	21,782
International	9,827		7,214		3,621
Total	$	47,393	$	36,246	$	25,403

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

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 $12.7 million, $11.5 million and $9.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Additionally, expenses for cloud-based services related to data centers were $4.9 million, $5.8 million, and $3.8 million for the years ended December 31, 2017, 2016 and 2015, respectively. Rental expense for sublease rentals were $4.0 million, $3.0 million and $1.7 million for the years ended December 31, 2017, 2016 and 2015, respectively. During the year ended December 31, 2016, in connection with office leases, the Company entered into a new irrevocable letter of credit in the amount of $0.5 million. As of December 31, 2017 and 2016, 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, 2017:



	2018			2019			2020			2021			2022			Thereafter			Total
	(in thousands)
Operating lease obligations	$	9,419		$	7,198		$	3,650		$	1,251		$	438		$	280		$	22,236
Operating sublease income	(766		)	(286		)	(196		)	(196		)	(196		)	(147		)	(1,787		)
Total	$	8,653		$	6,912		$	3,454		$	1,055		$	242		$	133		$	20,449

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, 2017. However, based on management’s knowledge as of December 31, 2017, 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 alleges that the Company underpaid Guardian for inventory sold by Guardian through its platform as a result of the fact that the Company charged fees to buyers of that inventory. Guardian claims the Company was precluded from charging buyer fees as a result of its contractual arrangements with Guardian and English agency law principles, as well as representations it allegedly made to Guardian. The Complaint claims damages including loss of revenue, interest, and costs, without specifying the amount of damages sought. The Company disputes Guardian’s claims and is defending them vigorously, but the Complaint involves disputed facts and complex legal questions, and its outcome is therefore uncertain. Even if Guardian were to prevail in this action, the Company does not believe the payment of the damages it thinks could be recoverable by Guardian would have a material adverse effect upon its consolidated financial position, results of operations, or cash flows. However, pending or in response to the outcome of this action, if the Company faces similar claims from other clients or as a preventative measure, it might decide to provide concessions or make other changes to its business practices that could have such material adverse effects.

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.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions As of December 31, 2017 and 2016, 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, 2017 and 2016, the Company did not enter into transactions with any of its related parties. For the year ended December 31, 2015 the Company recognized revenue of approximately $3.3 million from entities affiliated with a holder of more than 10% of the Company’s outstanding common stock.

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

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, 2017. 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, 2016			June 30, 2016			Sept. 30, 2016			Dec. 31, 2016			Mar. 31, 2017			June 30, 2017			Sept. 30, 2017			Dec. 31, 2017
	(in thousands, except per share amounts)
Revenue	$	69,232		$	70,511		$	65,811		$	72,667		$	46,015		$	42,922		$	35,211		$	31,397
Expenses:
Cost of revenue	16,783			17,540			17,798			21,126			14,688			13,698			12,985			15,465
Sales and marketing	21,278			21,966			21,635			18,449			14,628			12,529			12,503			12,134
Technology and development	12,443			13,294			12,513			12,934			12,753			12,044			11,580			11,123
General and administrative	20,605			16,390			16,238			15,337			15,080			14,355			13,644			12,517
Restructuring and other exit costs	—			—			—			3,316			4,338			1,621			—			—
Impairment of intangible assets and internally developed software	—			—			—			23,473			—			—			—			4,585
Impairment of goodwill	—			—			—			—			—			—			90,251			—
Total expenses	71,109			69,190			68,184			94,635			61,487			54,247			140,963			55,824
Income (loss) from operations	(1,877		)	1,321			(2,373		)	(21,968		)	(15,472		)	(11,325		)	(105,752		)	(24,427		)
Other (income) expense, net	167			(906		)	(346		)	(899		)	(7		)	84			(150		)	(358		)
Income (loss) before income taxes	(2,044		)	2,227			(2,027		)	(21,069		)	(15,465		)	(11,409		)	(105,602		)	(24,069		)
Provision (benefit) for income taxes	(4,328		)	4,904			(5,557		)	121			375			146			(2,031		)	(252		)
Net income (loss)	$	2,284		$	(2,677	)	$	3,530		$	(21,190	)	$	(15,840	)	$	(11,555	)	$	(103,571	)	$	(23,817	)
Net income (loss) per share:
Basic	$	0.05		$	(0.06	)	$	0.07		$	(0.44	)	$	(0.33	)	$	(0.24	)	$	(2.11	)	$	(0.48	)
Diluted	$	0.05		$	(0.06	)	$	0.07		$	(0.44	)	$	(0.33	)	$	(0.24	)	$	(2.11	)	$	(0.48	)
Weighted-average shares used to compute net income (loss) per share:
Basic	44,663			46,341			47,538			48,051			48,332			48,783			49,055			49,293
Diluted	48,676			46,341			48,683			48,051			48,332			48,783			49,055			49,293

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On March 14, 2018, the Company announced that it undertook measures to reduce headcount by approximately 100 people, or 19% of its workforce, and to reduce other operating costs. These actions include reductions in administrative staff to bring its general and administrative operations into better alignment with the current size of the business as well as in sales and technical personnel as a result of offshoring certain development functions, organizational delayering and restructuring, and reducing investment in unprofitable projects. These headcount actions have reduced staff levels from 514 at December 31, 2017 to approximately 415 at March 14, 2018. The reductions will result in approximately $3.0 million in one-time cash severance costs, which will primarily be recognized in the first quarter of 2018. Net of these severance expenses, the workforce reductions undertaken in the first quarter, combined with other non-headcount related operating expense control initiatives, are expected to offset operating expenses in 2018 by approximately $15.0 million. On an annualized basis, the headcount reductions and other cost-control measures announced on March 14, 2018 are expected to offset future cash expenses by approximately $24.0 million.

Organization and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of Consolidation

Technology and Development

General and Administrative

Restructuring and Other Exit Costs

Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block]

Stock-Based Compensation

These assumptions and estimates 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

Comprehensive Income (Loss)

Cash, Cash Equivalents, and Marketable Securities

Restricted Cash

Accounts Receivable Allowance for Doubtful Accounts

Property and Equipment, Net

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
Customer relationships	2.5 to 3
Non-compete agreements	2 to 3
Other intangible assets	1 to 1.5

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

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

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.

For the years ended December 31, 2017, 2016 and 2015, no buyer or seller of advertising inventory comprised 10% or more of consolidated revenue.

At December 31, 2017 and 2016, no seller of advertising inventory comprised 10% or more of consolidated accounts payable.

Foreign Currency Transactions and Translations

Foreign Currency Transactions and Translation

Recent Accounting Pronouncements

Organization and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of Finite-Lived Intangible Assets

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



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

The Company’s intangible assets as of December 31, 2017 and 2016 including the following:



	December 31, 2017			December 31, 2016
	(in thousands)
Amortizable intangible assets:
Developed technology	$	16,878		$	13,418
Customer relationships	—			3,330
Non-compete agreements	690			4,990
Trademarks	20			—
Total identifiable intangible assets, gross	17,588			21,738
Accumulated amortization— intangible assets:
Developed technology	(4,062		)	(7,652		)
Customer relationships	—			(2,837		)
Non-compete agreements	(161		)	(4,445		)
Trademarks	(6		)	—
Total accumulated amortization—intangible assets	(4,229		)	(14,934		)
Total identifiable intangible assets, net	$	13,359		$	6,804

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, 2017			December 31, 2016
	(in thousands)
Purchased software	$	1,985		$	1,777
Computer equipment and network hardware	90,695			62,084
Furniture, fixtures and office equipment	2,165			2,194
Leasehold improvements	3,325			3,385
Gross property and equipment	98,170			69,440
Accumulated depreciation	(50,777		)	(33,194		)
Net property and equipment	$	47,393		$	36,246

Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

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



	Year Ended
	December 31, 2017			December 31, 2016			December 31, 2015
	(In thousands, except per share data)
Basic EPS:
Net income (loss)	$	(154,783	)	$	(18,053	)	$	422
Weighted-average common shares outstanding	49,720			48,512			42,067
Weighted-average unvested restricted shares	(851		)	(1,857		)	(1,677		)
Weighted-average escrow shares	—			—			(727		)
Weighted-average common shares outstanding used to compute net income (loss) per share	48,869			46,655			39,663
Basic net income (loss) per share	$	(3.17	)	$	(0.39	)	$	0.01
Diluted EPS:
Net income (loss)	$	(154,783	)	$	(18,053	)	$	422
Weighted-average common shares used in basic EPS	48,869			46,655			39,663
Dilutive effect of weighted-average common stock options	—			—			2,510
Dilutive effect of weighted-average restricted stock awards	—			—			532
Dilutive effect of weighted-average restricted stock units	—			—			426
Dilutive effect of weighted-average ESPP	—			—			25
Dilutive effect of weighted-average escrow shares	—			—			591
Dilutive effect of weighted-average contingent shares	—			—			748
Weighted-average shares used to compute diluted net income (loss) per share	48,869			46,655			44,495
Diluted net income (loss) per share	$	(3.17	)	$	(0.39	)	$	0.01

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

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



	December 31, 2017	December 31, 2016	December 31, 2015
	(in thousands)
Options to purchase common stock	120	951	—
Unvested restricted stock awards	297	414	—
Unvested restricted stock units	556	611	—
Shares held in escrow	—	392	—
ESPP	50	30	—
Contingent shares	—	—	704
Total shares excluded from net income (loss) per share	1,023	2,398	704

Investments (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Investments in Marketable Securities

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

Investments in marketable securities as of December 31, 2016 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	$	23,237	$	1	$	(2	)	$	23,236
Corporate debt securities	17,314		—		—			17,314
Total	$	40,551	$	1	$	(2	)	$	40,550

Amortized Cost and Fair Value of the Company's Marketable Securities

The amortized cost and fair value of the Company's marketable securities at December 31, 2017, by contractual years-to-maturity are as follows:



	Amortized Cost		Fair Value
	(in thousands)
Due in less than 1 year	$	52,524	$	52,504
Due within 1-2 years	2,504		2,495
Total	$	55,028	$	54,999

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

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, 2017			December 31, 2016
	(in thousands)
Purchased software	$	1,985		$	1,777
Computer equipment and network hardware	90,695			62,084
Furniture, fixtures and office equipment	2,165			2,194
Leasehold improvements	3,325			3,385
Gross property and equipment	98,170			69,440
Accumulated depreciation	(50,777		)	(33,194		)
Net property and equipment	$	47,393		$	36,246

Internal Use Software Development Costs (Tables)

12 Months Ended

Dec. 31, 2017

Research and Development [Abstract]

Schedule Of Internal Use Software Costs

Internal use software development costs were as follows:



	December 31, 2017			December 31, 2016
	(in thousands)
Internal use software development costs, gross	33,414			$	37,032
Accumulated amortization	(20,680		)	(20,510		)
Internal use software development costs, net	$	12,734		$	16,522

Business Combinations (Tables)

12 Months Ended

Dec. 31, 2017

nToggle

Business Acquisition [Line Items]

Schedule of Business Acquisitions, by Acquisition

The major classes of assets and liabilities to which the Company has 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			December 31, 2016

Pro forma revenues	$	156,480		$	278,995
Pro forma net loss	$	(158,443	)	$	(25,116	)
Pro forma net loss per share, basic	$	(3.24	)	$	(0.54	)
Pro forma net loss per share, diluted	$	(3.24	)	$	(0.54	)

Chango

Business Acquisition [Line Items]

Schedule of Business Acquisitions, by Acquisition

The total purchase consideration and the allocation of the total purchase consideration to assets acquired and liabilities assumed is summarized below (in thousands):



Shares of the Company's common stock	$	72,477
Estimated fair value of contingent consideration	16,171
Fair value of stock-based awards exchanged	4,058
Cash paid	9,097
Working capital adjustment	(184		)
Total purchase consideration	101,619
Cash	450
Accounts receivable	13,333
Prepaid and other assets	1,025
Fixed assets	265
Intangible assets, including in process research and development of $580	52,420
Goodwill	51,732
Total assets acquired	119,225
Accounts payable and accrued expenses	5,825
Other liabilities	443
Deferred tax liability, net	11,338
Total liabilities assumed	17,606
Total net assets acquired	$	101,619

Business Acquisition, Pro Forma Information



	Year Ended
	December 31, 2015
	(in thousands, except per share data)
Pro forma revenues	$	265,134
Pro forma net income	$	673
Pro forma net income per share, basic	$	0.02
Pro forma net income per share, diluted	$	0.01

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

Details of the Company’s goodwill were as follows:



	December 31, 2017			December 31, 2016
	(in thousands)
Beginning balance	$	65,705		$	65,705
Additions from the acquisition of nToggle (See Note 7)	24,546			—
Impairment of goodwill	(90,251		)	—
Ending balance	$	—		$	65,705

Schedule of Finite-Lived Intangible Assets

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



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

The Company’s intangible assets as of December 31, 2017 and 2016 including the following:



	December 31, 2017			December 31, 2016
	(in thousands)
Amortizable intangible assets:
Developed technology	$	16,878		$	13,418
Customer relationships	—			3,330
Non-compete agreements	690			4,990
Trademarks	20			—
Total identifiable intangible assets, gross	17,588			21,738
Accumulated amortization— intangible assets:
Developed technology	(4,062		)	(7,652		)
Customer relationships	—			(2,837		)
Non-compete agreements	(161		)	(4,445		)
Trademarks	(6		)	—
Total accumulated amortization—intangible assets	(4,229		)	(14,934		)
Total identifiable intangible assets, net	$	13,359		$	6,804

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, 2017:



Fiscal Year	Amount
	(in thousands)
2018	$	3,185
2019	3,010
2020	2,826
2021	2,826
2022	1,512
Total	$	13,359

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

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, 2017:



	December 31, 2017		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	$	—	$	—

The table below sets forth a summary of financial instruments that are measured at fair value on a recurring basis at December 31, 2016:



	December 31, 2016		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	$	15,776	$	7,781	$	7,995	$	—
Corporate debt securities	$	17,314	$	—	$	17,314	$	—
U.S. Treasury, government and agency debt securities	$	23,236	$	23,236	$	—	$	—

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Liabilities

Accounts payable and accrued expenses included the following:



	December 31, 2017		December 31, 2016
	(in thousands)
Accounts payable—seller	$	203,694	$	197,261
Accounts payable—trade	3,764		7,930
Accrued employee-related payables	6,645		9,712
Total	$	214,103	$	214,903

Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2017

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, 2015	$	(68	)	$	53		$	(15	)
Other comprehensive income (loss)	67			(325		)	(258		)
Balance at December 31, 2016	(1		)	(272		)	(273		)
Other comprehensive income (loss)	(28		)	342			314
Balance at December 31, 2017	$	(29	)	$	70		$	41

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

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, 2017 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, 2016	3,861		$	11.16
Granted	1,424		$	4.20
Exercised	(106	)	$	3.71
Expired	(506	)	$	12.07
Forfeited	(310	)	$	14.26
Outstanding at December 31, 2017	4,363		$	8.75	5.73 years	$	600
Exercisable at December 31, 2017	2,785		$	10.44	3.92 years	$	99

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



	Year Ended
	December 31, 2017		December 31, 2016		December 31, 2015
Expected term (in years)	5.8		5.9		4.5
Risk-free interest rate	2.03	%	1.47	%	1.30	%
Expected volatility	57	%	49	%	47	%
Dividend yield	—	%	—	%	—	%

Nonvested Restricted Stock Shares Activity

A summary of restricted stock activity for the year ended December 31, 2017 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested shares of restricted stock outstanding at December 31, 2016	1,113		$	14.07
Granted	77		$	5.07
Canceled	(267	)	$	13.27
Vested	(365	)	$	15.01
Nonvested shares of restricted stock outstanding at December 31, 2017	558		$	12.60

Schedule of Nonvested Restricted Stock Units Activity

A summary of restricted stock unit activity for the year ended December 31, 2017 is as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
	(in thousands)
Nonvested shares of restricted stock units outstanding at December 31, 2016	2,903		$	13.63
Granted	3,149		$	5.61
Canceled	(1,170	)	$	12.11
Vested	(1,273	)	$	12.43
Nonvested shares of restricted stock units outstanding at December 31, 2017	3,609		$	7.55

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, 2017		December 31, 2016		December 31, 2015
	(in thousands)
Cost of revenue	$	404	$	344	$	240
Sales and marketing	4,582		8,520		7,415
Technology and development	4,034		5,788		4,963
General and administrative	9,924		14,042		17,966
Restructuring and other exit costs	1,560		—		—
Total stock-based compensation expense	$	20,504	$	28,694	$	30,584

Restructuring and Other Exit Costs (Tables)

12 Months Ended

Dec. 31, 2017

Restructuring and Related Activities [Abstract]

Schedule of Restructuring and Other Exit Costs

The following table summarizes restructuring and other exit cost activity (in thousands):



Accrued restructuring and other exit costs at December 31, 2015	$	—
Restructuring and other exit costs	3,316
Cash paid for restructuring and other exit costs	(2,515		)
Accrued restructuring and other exit costs at December 31, 2016	$	801
Restructuring and other exit costs	5,959
Cash paid for restructuring and other exit costs	(5,059		)
Non-cash stock-based compensation for restructuring and other exit costs	(1,560		)
Accrued restructuring and other exit costs at December 31, 2017	$	141

The following table presents the components of restructuring and other exit costs for the years ended December 31, 2017 and 2016 (in thousands):



	Year Ended
	December 31, 2017		December 31, 2016
Employee termination costs	$	5,753	$	3,270
Facility closing costs	206		46
Total restructuring and other exit costs	$	5,959	$	3,316

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

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, 2017, 2016 and 2015:



	Year Ended
	December 31, 2017			December 31, 2016			December 31, 2015
	(in thousands)
Domestic	$	(104,750	)	$	25,704		$	15,723
International	(51,795		)	(48,617		)	(19,862		)
Loss before income taxes	$	(156,545	)	$	(22,913	)	$	(4,139	)

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, 2017, 2016 and 2015:



	Year Ended
	December 31, 2017			December 31, 2016			December 31, 2015
	(in thousands)
Current:
Federal	$	(140	)	$	441		$	196
State	78			713			90
Foreign	(250		)	613			367
Total current provision	(312		)	1,767			653
Deferred:
Federal	(1,877		)	—			—
State	288			(289		)	1
Foreign	139			(6,338		)	(5,215		)
Total deferred benefit	(1,450		)	(6,627		)	(5,214		)
Total provision (benefit) for income taxes	$	(1,762	)	$	(4,860	)	$	(4,561	)

Schedule of Effective Income Tax Rate Reconciliation



	Year Ended
	December 31, 2017		December 31, 2016		December 31, 2015
U.S. federal statutory income tax rate	34.0	%	34.0	%	34.0	%
State income taxes, net of federal benefit	—	%	(2.1	)%	(1.4	)%
Foreign income (loss) at other than U.S. rates	0.2	%	(14.4	)%	(31.0	)%
Stock-based compensation expense	(3.8	)%	2.1	%	(31.5	)%
Meals and entertainment	(0.1	)%	(1.5	)%	(14.2	)%
Acquisition and related items	—	%	—	%	(8.6	)%
Goodwill impairment	(19.0	)%	—	%	—	%
Non-deductible gifts	—	%	(0.1	)%	(0.8	)%
Research and development tax credits	0.8	%	7.2	%	42.3	%
Tax effect of intercompany financing	—	%	4.9	%	11.2	%
Worthless stock	31.7	%	—	%	—	%
Other permanent items	(0.5	)%	—	%	(0.5	)%
Provision (benefit) to return adjustments	—	%	0.6	%	(9.4	)%
Change in valuation allowance	(22.0	)%	(9.5	)%	120.1	%
Tax rate change; U.S. tax reform	(20.2	)%	—	%	—	%
Effective income tax rate	1.1	%	21.2	%	110.2	%

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, 2017 and 2016:



	December 31, 2017			December 31, 2016
	(in thousands)
Deferred Tax Assets:
Accrued liabilities	$	2,648		$	1,287
Stock-based compensation	3,685			7,381
Net operating loss carryovers	65,648			21,375
Tax credit carryovers	13,494			10,915
Other	1,502			2,360
Total deferred tax assets	86,977			43,318
Less valuation allowance	(81,767		)	(39,491		)
Deferred tax assets, net of valuation allowance	5,210			3,827
Deferred Tax Liabilities:
Fixed assets	(3,864		)	(3,764		)
Intangible assets	(955		)	468
Other	—			—
Total deferred tax liabilities	(4,819		)	(3,296		)
Net deferred tax assets (liability)	$	391		$	531

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 at January 1, 2015	$	2,131
Increases related to 2015 tax positions	2,194
Decreases related to prior year tax positions	—
Balance as of December 31, 2015	4,325
Increases related to 2016 tax positions	702
Decreases related to prior year tax positions	—
Balance as of December 31, 2016	5,027
Increases related to current year tax positions	550
Increases related to prior year tax positions	69
Decreases related to prior year tax positions	—
Balance as of December 31, 2017	$	5,646

Geographic Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Revenue from External Customers by Geographic Areas [Table Text Block]

Revenue by geography are based on the location of the Company's sellers. The Company's revenue by geographical region was as follows:



	Year Ended
	December 31, 2017		December 31, 2016		December 31, 2015
	(in thousands)
United States	$	95,567	$	182,777	$	172,188
United Kingdom	11,140		20,778		20,355
Other international	48,838		74,666		55,941
Total	$	155,545	$	278,221	$	248,484

Long-lived Assets by Geographic Areas

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



	December 31, 2017		December 31, 2016		December 31, 2015
	(in thousands)
United States	$	37,566	$	29,032	$	21,782
International	9,827		7,214		3,621
Total	$	47,393	$	36,246	$	25,403

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases

The following table summarizes the Company's future minimum lease payments under non-cancelable operating leases and related sublease income at December 31, 2017:



	2018			2019			2020			2021			2022			Thereafter			Total
	(in thousands)
Operating lease obligations	$	9,419		$	7,198		$	3,650		$	1,251		$	438		$	280		$	22,236
Operating sublease income	(766		)	(286		)	(196		)	(196		)	(196		)	(147		)	(1,787		)
Total	$	8,653		$	6,912		$	3,454		$	1,055		$	242		$	133		$	20,449

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)



	Three Months Ended
	Mar. 31, 2016			June 30, 2016			Sept. 30, 2016			Dec. 31, 2016			Mar. 31, 2017			June 30, 2017			Sept. 30, 2017			Dec. 31, 2017
	(in thousands, except per share amounts)
Revenue	$	69,232		$	70,511		$	65,811		$	72,667		$	46,015		$	42,922		$	35,211		$	31,397
Expenses:
Cost of revenue	16,783			17,540			17,798			21,126			14,688			13,698			12,985			15,465
Sales and marketing	21,278			21,966			21,635			18,449			14,628			12,529			12,503			12,134
Technology and development	12,443			13,294			12,513			12,934			12,753			12,044			11,580			11,123
General and administrative	20,605			16,390			16,238			15,337			15,080			14,355			13,644			12,517
Restructuring and other exit costs	—			—			—			3,316			4,338			1,621			—			—
Impairment of intangible assets and internally developed software	—			—			—			23,473			—			—			—			4,585
Impairment of goodwill	—			—			—			—			—			—			90,251			—
Total expenses	71,109			69,190			68,184			94,635			61,487			54,247			140,963			55,824
Income (loss) from operations	(1,877		)	1,321			(2,373		)	(21,968		)	(15,472		)	(11,325		)	(105,752		)	(24,427		)
Other (income) expense, net	167			(906		)	(346		)	(899		)	(7		)	84			(150		)	(358		)
Income (loss) before income taxes	(2,044		)	2,227			(2,027		)	(21,069		)	(15,465		)	(11,409		)	(105,602		)	(24,069		)
Provision (benefit) for income taxes	(4,328		)	4,904			(5,557		)	121			375			146			(2,031		)	(252		)
Net income (loss)	$	2,284		$	(2,677	)	$	3,530		$	(21,190	)	$	(15,840	)	$	(11,555	)	$	(103,571	)	$	(23,817	)
Net income (loss) per share:
Basic	$	0.05		$	(0.06	)	$	0.07		$	(0.44	)	$	(0.33	)	$	(0.24	)	$	(2.11	)	$	(0.48	)
Diluted	$	0.05		$	(0.06	)	$	0.07		$	(0.44	)	$	(0.33	)	$	(0.24	)	$	(2.11	)	$	(0.48	)
Weighted-average shares used to compute net income (loss) per share:
Basic	44,663			46,341			47,538			48,051			48,332			48,783			49,055			49,293
Diluted	48,676			46,341			48,683			48,051			48,332			48,783			49,055			49,293

Organization and Summary of Significant Accounting Policies -Narrative (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($) shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) shares	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)
Accounting Policies [Abstract]
Number of operating segments \| segment									1
Stock-based compensation award requisite service period									4 years
Tax benefit from compensation expense									$ 0	$ 0	$ 0
Dividend yield									0.00%
Restricted cash included in prepaid expenses and other current assets	$ 0				$ 100,000				$ 0	100,000
Allowance for doubtful accounts	500,000				700,000				500,000	700,000	1,000,000
Allowance for doubtful accounts, write-offs									700,000	1,100,000	200,000
Impairment of goodwill	$ 0	$ 90,251,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251,000	$ 0	$ 0
Class of Stock [Line Items]
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
Number of shares reserved \| shares	15,881,965								15,881,965
Credit Concentration Risk \| Accounts Receivable \| Customer 1
Concentration Risk [Line Items]
Concentration risk, percentage									20.00%	12.00%
Credit Concentration Risk \| Accounts Receivable \| Customer 2
Concentration Risk [Line Items]
Concentration risk, percentage									15.00%	11.00%

Organization and Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Computer equipment and network hardware
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Furniture, fixtures and office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Furniture, fixtures and office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years

Organization and Summary of Significant Accounting Policies - Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2017
Developed technology \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful lives	3 years
Developed technology \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	5 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful lives	2 years 6 months
Customer relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	3 years
Non-compete agreements \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful lives	2 years
Non-compete agreements \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	3 years
Other intangible assets \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful lives	1 year
Other intangible assets \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	1 year 6 months
Software development
Finite-Lived Intangible Assets [Line Items]
Useful lives	3 years

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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic EPS:
Net income (loss)	$ (23,817)	$ (103,571)	$ (11,555)	$ (15,840)	$ (21,190)	$ 3,530	$ (2,677)	$ 2,284	$ (154,783)	$ (18,053)	$ 422
Weighted-average common shares outstanding									49,720	48,512	42,067
Weighted-average unvested restricted shares									(851)	(1,857)	(1,677)
Weighted-average escrow shares									0	0	(727)
Weighted-average common shares outstanding used to compute net income (loss) per share	49,293	49,055	48,783	48,332	48,051	47,538	46,341	44,663	48,869	46,655	39,663
Basic net income (loss) per share (usd per share)	$ (0.48)	$ (2.11)	$ (0.24)	$ (0.33)	$ (0.44)	$ 0.07	$ (0.06)	$ 0.05	$ (3.17)	$ (0.39)	$ 0.01
Diluted EPS:
Net income (loss)	$ (23,817)	$ (103,571)	$ (11,555)	$ (15,840)	$ (21,190)	$ 3,530	$ (2,677)	$ 2,284	$ (154,783)	$ (18,053)	$ 422
Weighted-average common shares used in basic EPS	49,293	49,055	48,783	48,332	48,051	47,538	46,341	44,663	48,869	46,655	39,663
Dilutive effect of weighted-average escrow shares (in shares)									0	0	591
Dilutive effect of weighted-average contingent shares (in shares)									0	0	748
Weighted-average shares used to compute diluted net income (loss) per share attributable to common stockholders (in shares)	49,293	49,055	48,783	48,332	48,051	48,683	46,341	48,676	48,869	46,655	44,495
Diluted net income (loss) per share attributable to common stockholders (usd per share)	$ (0.48)	$ (2.11)	$ (0.24)	$ (0.33)	$ (0.44)	$ 0.07	$ (0.06)	$ 0.05	$ (3.17)	$ (0.39)	$ 0.01
Stock Option
Diluted EPS:
Dilutive effect of weighted-average share-based compensation (in shares)									0	0	2,510
Unvested restricted stock awards
Diluted EPS:
Dilutive effect of weighted-average share-based compensation (in shares)									0	0	532
Restricted Stock Units (RSUs)
Diluted EPS:
Dilutive effect of weighted-average share-based compensation (in shares)									0	0	426
ESPP
Diluted EPS:
Dilutive effect of weighted-average share-based compensation (in shares)									0	0	25

Net Income (Loss) Per Share - Shares Excluded and Included in Calculation of Diluted Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share	1,023,000	2,398,000	704,000
Chango
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Contingent consideration, shares issued			971,481
Contingent consideration, shares released from escrow			126,098
iSocket
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Contingent consideration, shares issued			585,170
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	120,000	951,000	0
Unvested restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share	297,000	414,000	0
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share	556,000	611,000	0
Shares held in escrow
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share	0	392,000	0
Employee Stock Purchase Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share	50,000	30,000	0
Contingent Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net income (loss) per share	0	0	704,000

Investments - Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 52,524	$ 40,551
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(20)	(2)
Fair Value	52,504	40,550
Short-term investments \| U.S. Treasury, government and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,426	23,237
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(20)	(2)
Fair Value	27,406	23,236
Short-term investments \| Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,098	17,314
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	25,098	$ 17,314
Long-term investments \| 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 - Amortized cost and Fair Value of Marketable Securities (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in less than 1 year, Amortized Cost	$ 52,524
Due within 1-2 years, Amortized Cost	2,504
Total, Amortized Cost	55,028
Due in less than 1 year, Fair Value	52,504
Due within 1-2 years, Fair Value	2,495
Total, Fair Value	$ 54,999

Investments - Narrative (Details)	12 Months Ended
Investments - Narrative (Details)	Dec. 31, 2017 USD ($)
Investments, Debt and Equity Securities [Abstract]
Weighted remaining contractual maturity	3 months 5 days
Realized gains (losses)	$ 0
Trading Securities, Unrealized Holding Gain	$ 0

Property and Equipment - Major Classes of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 98,170	$ 69,440
Accumulated depreciation	(50,777)	(33,194)
Property and equipment, net	47,393	36,246	$ 25,403
Purchased software
Property, Plant and Equipment [Line Items]
Gross property and equipment	1,985	1,777
Computer equipment and network hardware
Property, Plant and Equipment [Line Items]
Gross property and equipment	90,695	62,084
Furniture, fixtures and office equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	2,165	2,194
Leasehold improvements
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 3,325	$ 3,385

Property and Equipment - Narrative (Details) - USD ($)	12 Months Ended
Property and Equipment - Narrative (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation expense on property and equipment	$ 20,300,000	$ 13,700,000	$ 8,600,000
Impairment of long-lived assets	0	0	$ 0
Property and equipment under capital leases	$ 0	$ 0

Internal Use Software Development Costs - Internal Use Software Development Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Research and Development [Abstract]
Internal use software development costs, gross	$ 33,414	$ 37,032
Accumulated amortization	(20,680)	(20,510)
Internal use software development costs, net	$ 12,734	$ 16,522

Internal Use Software Development Costs - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Research and Development [Abstract]
Capitalized computer software, additions									$ 8,400,000	$ 10,900,000	$ 9,200,000
Capitalized computer software, amortization									11,100,000	8,300,000	6,700,000
Internal use software development costs, write-offs									1,600,000	800,000	1,500,000
Estimated amortization expense, 2018	$ 6,200,000								6,200,000
Estimated amortization expense, 2019	4,300,000								4,300,000
Estimated amortization expense, 2020	2,200,000								2,200,000
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges	4,585,000	$ 0	$ 0	$ 0	$ 23,473,000	$ 0	$ 0	$ 0	$ 4,585,000	23,473,000	0
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges										23,500,000.0	0
Nonrecurring \| Software development
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges	$ 1,100,000									$ 0	$ 0

Business Combinations (Narrative) (Details) - USD ($)				3 Months Ended									12 Months Ended
Business Combinations (Narrative) (Details) - USD ($)	Jul. 14, 2017	Dec. 31, 2015	Apr. 24, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired													$ 38,610,000	$ 238,000	$ 8,647,000
Impairment of goodwill				$ 0	$ 90,251,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		90,251,000	0	0
Unrecognized employee stock-based compensation				5,400,000									5,400,000
Intangible liabilities				955,000				(468,000)					955,000	(468,000)
Total deferred tax assets				$ 86,977,000				$ 43,318,000					86,977,000	$ 43,318,000
Deferred Taxes, Business Combination, Valuation Allowance, Available to Reduce Income Tax Expense												$ 500,000
nToggle
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ 38,600,000
Business Combination, Consideration Transferred	40,600,000
Cash Acquired from Acquisition	$ 2,000,000
Business Combination, In-The-Money Options Assumed	432,482
Business Combination, Restricted Stock Assumed	77,499
Equity interest issued, number of shares	174,117
Net operating loss acquired													9,300,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	$ 5,500,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	$ 3,800,000
nToggle \| General and Administrative Expense
Business Acquisition [Line Items]
Acquisition related costs													$ 300,000
Chango
Business Acquisition [Line Items]
Net operating loss acquired															6,900,000
Fair value of common stock		$ 72,477,000	$ 72,500,000
Indemnification assets, shares held in escrow			639,318
Business Combination, Future Service, Shares Held in Escrow			106,553
Cash paid for outstanding debt and transaction expenses		9,097,000	$ 9,100,000									9,097,000			9,097,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High			$ 18,200,000
Business Combination, Contingent Consideration, Shares Held in Escrow			126,098
Business Combination, Contingent Consideration, Stock Price Trigger			$ 18.77
Fair value of contingent consideration		16,171,000	$ 16,200,000									16,171,000			$ 16,171,000
Contingent consideration, shares issued															971,481
Fair value attributed to pre-acquisition stock options exchanged		4,058,000	4,300,000									4,058,000			$ 4,058,000
Unrecognized employee stock-based compensation		$ 700,000	2,400,000									700,000			700,000
Goodwill, Other Changes												$ (300,000)
Intangible liabilities			13,900,000
Total deferred tax assets			$ 2,000,000
Chango \| General and Administrative Expense
Business Acquisition [Line Items]
Acquisition related costs															$ 1,300,000
Chango \| Stock Option
Business Acquisition [Line Items]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Options Issued			428,798
Chango \| Common Stock
Business Acquisition [Line Items]
Equity interest issued, number of shares			4,191,878

Business Combinations (Allocation of Total Purchase Considerations) (Details) - USD ($)	Dec. 31, 2015	Apr. 24, 2015	Dec. 31, 2017	Jul. 14, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 65,705,000		$ 0		$ 65,705,000
nToggle
Business Acquisition [Line Items]
Cash acquired				$ 1,953,000
Accounts receivable				256,000
Prepaid and other assets				18,000
Fixed assets				763,000
Other non-current assets				82,000
Intangible assets				14,840,000
Goodwill				24,546,000
Total assets acquired				42,458,000
Accounts payable and accrued expenses				78,000
Deferred revenue				91,000
Deferred tax liability, net				1,719,000
Total liabilities assumed				1,888,000
Net assets acquired				$ 40,570,000
Chango
Business Acquisition [Line Items]
Shares of the Company's common stock	72,477,000	$ 72,500,000
Estimated fair value of contingent consideration	16,171,000	16,200,000
Fair value of stock-based awards exchanged	4,058,000	4,300,000
Cash paid	9,097,000	$ 9,100,000
Working capital adjustment	(184,000)
Total purchase consideration	101,619,000
Cash acquired	450,000
Accounts receivable	13,333,000
Prepaid and other assets	1,025,000
Fixed assets	265,000
Intangible assets	52,420,000
Goodwill	51,732,000
Total assets acquired	119,225,000
Accounts payable and accrued expenses	5,825,000
Other liabilities	443,000
Deferred tax liability, net	11,338,000
Total liabilities assumed	17,606,000
Net assets acquired	$ 101,619,000

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]
Acquired intangible assets	$ 14,840
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired intangible assets	$ 14,130
Estimated useful lives of acquired intangible assets	5 years
Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired intangible assets	$ 690
Estimated useful lives of acquired intangible assets	2 years
Trademark & trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired intangible assets	$ 20
Estimated useful lives of acquired intangible assets	1 year 6 months

Business Combinations Pro forma information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
nToggle
Business Acquisition [Line Items]
Pro forma revenues	$ 156,480	$ 278,995
Pro forma net income (loss)	$ (158,443)	$ (25,116)
Pro forma net income (loss) per share, basic (usd per share)	$ (3.24)	$ (0.54)
Pro forma net income(loss) per share, diluted (usd per share)	$ (3.24)	$ (0.54)
Chango
Business Acquisition [Line Items]
Pro forma revenues			$ 265,134
Pro forma net income (loss)			$ 673
Pro forma net income (loss) per share, basic (usd per share)			$ 0.02
Pro forma net income(loss) per share, diluted (usd per share)			$ 0.01

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Nets assets carrying value prior to impairment		$ 274,400,000
Impairment of goodwill	$ 0	90,251,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251,000	$ 0	$ 0
Amortization expense of intangible assets									4,800,000	$ 20,500,000	15,700,000
Decrease in diluted earnings per share due to increase in amortization expense (usd per share)										$ 0.09
Asset impairment charges	$ 4,585,000	$ 0	$ 0	$ 0	$ 23,473,000	$ 0	$ 0	$ 0	4,585,000	$ 23,473,000	0
Impairment of intangible assets and internal use software									$ 4,585,000	23,473,000	0
Nonrecurring
Goodwill [Line Items]
Asset impairment charges										23,500,000.0	$ 0
Technology-based intangible asset and customer relationships
Goodwill [Line Items]
Increase in amortization expense										$ 4,200,000
Decrease in basic earnings per share due to increase in amortization expense (usd per share)										$ 0.09

Goodwill and Intangible Assets - Activity in Goodwill (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Beginning balance				$ 65,705,000				$ 65,705,000	$ 65,705,000	$ 65,705,000
Additions from the acquisition of nToggle (See Note 7)									24,546,000	0
Impairment of goodwill	$ 0	$ (90,251,000)	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	(90,251,000)	0	$ 0
Ending balance	$ 0				$ 65,705,000				$ 0	$ 65,705,000	$ 65,705,000

Goodwill and Intangible Assets - Intangible Assets, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	$ 17,588	$ 21,738
Total accumulated amortization—intangible assets	(4,229)	(14,934)
Total	13,359	6,804
Developed technology
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	16,878	13,418
Total accumulated amortization—intangible assets	(4,062)	(7,652)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	0	3,330
Total accumulated amortization—intangible assets	0	(2,837)
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	690	4,990
Total accumulated amortization—intangible assets	(161)	(4,445)
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	20	0
Total accumulated amortization—intangible assets	$ (6)	$ 0

Goodwill and Intangible Assets - Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
2018	$ 3,185
2019	3,010
2020	2,826
2021	2,826
2022	1,512
Total	$ 13,359	$ 6,804

Fair Value Measurements - Financial Instruments (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 1,807	$ 15,776
Money Market Funds [Member] \| 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	210	7,781
Money Market Funds [Member] \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	1,597	7,995
Money Market Funds [Member] \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	25,098	17,314
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	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	17,314
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	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	29,901	23,236
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	29,901	23,236
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 ($)	3 Months Ended								12 Months Ended
Fair Value Measurements - Narrative (Details) - USD ($)	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Change in fair value of contingent consideration									$ 0	$ 0	$ 306,000
EBITDA multiple used for fair value									2.0
Impairment of goodwill	$ 0	$ 90,251,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 90,251,000	0	0
Goodwill	0				65,705,000				0	65,705,000	65,705,000
Asset impairment charges	4,585,000	$ 0	$ 0	$ 0	23,473,000	$ 0	$ 0	$ 0	4,585,000	23,473,000	0
Intangible Assets, Net (Including Goodwill)	0				$ 0				$ 0	0
Nonrecurring
Class of Stock [Line Items]
Asset impairment charges										23,500,000.0	0
Nonrecurring \| Finite-Lived Intangible Assets
Class of Stock [Line Items]
Asset impairment charges	3,500,000.0
Nonrecurring \| Software development
Class of Stock [Line Items]
Asset impairment charges	$ 1,100,000									$ 0	0
Significant Unobservable Inputs (Level 3) \| Recurring
Class of Stock [Line Items]
Change in fair value of contingent consideration											$ 300,000
Income Approach Valuation Technique [Member]
Class of Stock [Line Items]
Fair Value Inputs, Discount Rate									16.20%
Market Approach Valuation Technique [Member]
Class of Stock [Line Items]
Fair Value Inputs, Control Premium									15.00%

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable—seller	$ 203,694	$ 197,261
Accounts payable—trade	3,764	7,930
Accrued employee-related payables	6,645	9,712
Accounts payable and accrued expenses	$ 214,103	$ 214,903

Debt - Narrative (Details) - Silicon Valley Bank - Line of Credit - Revolving Credit Facility - 2011 Loan Agreement	12 Months Ended
	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 40,000,000.0
Debt instrument, minimum net cash balance before increase in variable rate	$ 1
Line of credit facility, unused capacity, commitment fee percentage	0.15%
Debt instrument, covenant, fixed charge coverage ratio, minimum allowed	1.1
Debt instrument, covenant, fixed charge coverage ratio, calculation period	12 months
Line of credit	$ 0
Debt instrument, covenant, minimum remaining borrowing capacity threshold, percent	20.00%
Debt Instrument, Maturity Date	Sep. 27, 2018
Prime Rate \| Net Cash Balance Exceeding One Dollar, Maintained
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.00%
Prime Rate \| Net Cash Balance Exceeding One Dollar, Not Maintained
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.50%
London Interbank Offered Rate (LIBOR) \| Net Cash Balance Exceeding One Dollar, Maintained
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%

Accumulated Other Comprehensive Income (Loss) - Schedule of Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 299,513	$ 278,101	$ 128,752
Other comprehensive income (loss)	314	(258)	(7)
Ending Balance	164,611	299,513	278,101
Unrealized Gain (Loss) on Investments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(1)	(68)
Other comprehensive income (loss)	(28)	67
Ending Balance	(29)	(1)	(68)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(272)	53
Other comprehensive income (loss)	342	(325)
Ending Balance	70	(272)	53
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(273)	(15)	(8)
Ending Balance	$ 41	$ (273)	$ (15)

Stock-Based Compensation (Details) - USD ($) $ in Thousands		12 Months Ended
Stock-Based Compensation (Details) - USD ($) $ in Thousands	Jan. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Vesting Period		4 years
Number of shares reserved		15,881,965
Number of Shares
Net deferred tax assets related to net operating losses for income tax benefits	$ 7,500
2014 Equity Incentive Plan
Number of Shares
Evergreen provision, automatic annual increase in share reserve (as a percent)		5.00%
Number of Shares Available for Grant		6,073,370
Additional Paid-In Capital \| Accounting Standards Update 2016-09 [Member] \| New Accounting Pronouncement, Early Adoption, Effect [Member]
Number of Shares
Cumulative-effect adjustment	$ 700		$ 658
Stock Option
Number of Shares
Award Vesting Rights, Percentage		25.00%

Stock-Based Compensation - Stock Options Outstanding (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares) \| shares	3,861
Granted (in shares) \| shares	1,424
Exercised (in shares) \| shares	(106)
Expired (in shares) \| shares	(506)
Forfeited (in shares) \| shares	(310)
Ending balance (in shares) \| shares	4,363
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (in dollars per share) \| $ / shares	$ 11.16
Granted (in dollars per share) \| $ / shares	4.20
Exercised (in dollars per share) \| $ / shares	3.71
Expired (in dollars per share) \| $ / shares	12.07
Forfeited (in dollars per share) \| $ / shares	14.26
Ending balance (in dollars per share) \| $ / shares	$ 8.75
Outstanding	5 years 8 months 23 days
Outstanding, aggregate intrinsic value \| $	$ 600
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercisable (in shares) \| shares	2,785
Exercisable (in dollars per share) \| $ / shares	$ 10.44
Exercisable	3 years 11 months 1 day
Exercisable, aggregate intrinsic value \| $	$ 99

Stock-Based Compensation - Stock Options Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 400	$ 18,500	$ 28,300
Unrecognized employee stock-based compensation	$ 5,400
Weighted average grant date fair value	$ 3.55	$ 6.29	$ 9.25
Options outstanding (in shares)	4,363	3,861
Beginning balance (in dollars per share)	$ 11.16
Vesting Period	4 years
Stock-based compensation expense	$ 20,504	$ 28,694	$ 30,584
Stock Option
Number of Shares
Unrecognized employee stock-based compensation, period for recognition	2 years 9 months 12 days

Stock-Based Compensation - Valuation Assumptions (Details) - Stock Option	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Expected term (in years)	5 years 9 months	5 years 10 months 30 days	4 years 5 months 30 days
Risk-free interest rate	2.03%	1.47%	1.30%
Expected volatility	57.00%	49.00%	47.00%
Dividend yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock Awards shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Number of Shares
Beginning balance \| shares	1,113
Granted \| shares	77
Canceled \| shares	(267)
Vested \| shares	(365)
Ending balance \| shares	558
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) \| $ / shares	$ 14.07
Granted (in dollars per share) \| $ / shares	5.07
Canceled (in dollars per share) \| $ / shares	13.27
Vested (in dollars per share) \| $ / shares	15.01
Ending balance (in dollars per share) \| $ / shares	$ 12.60

Stock-Based Compensation - Restricted Stock Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Feb. 29, 2016	May 31, 2015	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Vesting Period				4 years
Stock-based compensation expense				$ 20,504	$ 28,694	$ 30,584
Unvested restricted stock awards
Number of Shares
Granted				77,000
Granted (in dollars per share)				$ 5.07
Unvested restricted stock awards \| Vesting, Requisite Service Conditions
Number of Shares
Unrecognized employee stock-based compensation				$ 2,600
Unrecognized employee stock-based compensation, period for recognition				1 year 8 months 12 days
Granted (in dollars per share)				$ 5.07	$ 13.26	$ 16.75
Fair value of awards				$ 1,700	$ 5,700	$ 9,800
Unvested restricted stock awards \| Vesting, Market Conditions
Number of Shares
Granted			280,000
Unrecognized employee stock-based compensation				$ 100
Unrecognized employee stock-based compensation, period for recognition				3 years 5 months
Granted (in dollars per share)			$ 13.15
Weighted average period			1 year 8 months 12 days
Unvested restricted stock awards \| Vesting, Stock Price Performance
Number of Shares
Unrecognized employee stock-based compensation				$ 600
Unrecognized employee stock-based compensation, period for recognition				7 months 17 days
Granted (in dollars per share)	$ 11.07	$ 13.81

Stock-Based Compensation - Restricted Stock Units Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Number of Shares
Granted (in dollars per share)	$ 4.20
Restricted Stock Units (RSUs)
Number of Shares
Beginning balance \| shares	2,903
Granted \| shares	3,149
Canceled \| shares	(1,170)
Vested \| shares	(1,273)
Ending balance \| shares	3,609
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 13.63
Granted (in dollars per share)	5.61
Canceled (in dollars per share)	12.11
Vested (in dollars per share)	12.43
Ending balance (in dollars per share)	$ 7.55

Stock-Based Compensation - Restricted Stock Units Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unvested restricted stock awards
Number of Shares
Grant date fair value	$ 5.07
Restricted Stock Units (RSUs)
Number of Shares
Unrecognized employee stock-based compensation	$ 23.9
Unrecognized employee stock-based compensation, period for recognition	2 years 9 months 15 days
Grant date fair value	$ 5.61
Fair value of awards	$ 5.1	$ 11.5	$ 3.6
Intrinsic value of nonvested unit	$ 6.7
Restricted Stock Units (RSUs) \| Weighted Average Grant Date Value Per Share
Number of Shares
Grant date fair value	$ 5.61	$ 12.66	$ 16.45

Stock-Based Compensation - Employee Stock Purchase Plan Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Number of shares reserved	15,881,965
Stock-based compensation expense	$ 20,504	$ 28,694	$ 30,584
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 reserved	1,279,464
Increase in shares authorized, percent of outstanding stock	1.00%

Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 20,504	$ 28,694	$ 30,584
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	404	344	240
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,582	8,520	7,415
Technology and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,034	5,788	4,963
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	9,924	14,042	17,966
Restructuring and other exit costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,560	$ 0	$ 0

Restructuring and Other Exit Costs - Schedule of Restructuring and Other Exit Costs (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Accrued restructuring and other exit costs at December 31, 2016				$ 801				$ 0	$ 801	$ 0
Restructuring and other exit costs	$ 0	$ 0	$ 1,621	4,338	$ 3,316	$ 0	$ 0	0	5,959	3,316	$ 0
Cash paid for restructuring and other exit costs									(5,059)	(2,515)
Non-cash stock-based compensation for restructuring and other exit costs									(1,560)
Accrued restructuring and other exit costs at December 31, 2017	141				801				141	801	0
Restructuring and other exit costs
Employee termination costs									5,753	3,270
Facility closing costs									206	46
Total restructuring and other exit costs	$ 0	$ 0	$ 1,621	$ 4,338	$ 3,316	$ 0	$ 0	$ 0	$ 5,959	$ 3,316	$ 0

Income Taxes - Income before Income Tax, Domestic and Foreign (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ (104,750)	$ 25,704	$ 15,723
International	(51,795)	(48,617)	(19,862)
Loss before income taxes	$ (156,545)	$ (22,913)	$ (4,139)

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal									$ (140)	$ 441	$ 196
State									78	713	90
Foreign									(250)	613	367
Total current provision									(312)	1,767	653
Deferred:
Federal									(1,877)	0	0
State									288	(289)	1
Foreign									139	(6,338)	(5,215)
Total deferred benefit									(1,450)	(6,627)	(5,214)
Total provision (benefit) for income taxes	$ (252)	$ (2,031)	$ 146	$ 375	$ 121	$ (5,557)	$ 4,904	$ (4,328)	$ (1,762)	$ (4,860)	$ (4,561)

Income Taxes - Narrative (Details) - USD ($)		3 Months Ended								12 Months Ended
Income Taxes - Narrative (Details) - USD ($)	Jan. 01, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Benefit for income taxes		$ (252,000)	$ (2,031,000)	$ 146,000	$ 375,000	$ 121,000	$ (5,557,000)	$ 4,904,000	$ (4,328,000)	$ (1,762,000)	$ (4,860,000)	$ (4,561,000)
Tax benefit related to worthless stock deduction		(145,800,000)
Income tax benefit, net of valuation allowance related to worthless stock deduction		0
Provisional Transition Tax which reduced U.S. net deferred tax assets										600,000
Decrease to U.S. net deferred tax assets										31,600,000
Write-off recorded due to new Tax Act										$ 12,400,000
U.S. federal statutory income tax rate										34.00%	34.00%	34.00%
Operating Loss Carryforwards [Line Items]
Net deferred tax assets related to net operating losses for income tax benefits	$ 7,500,000
Change in valuation allowance										$ 42,300,000	$ 10,200,000	$ 3,200,000
Unremitted earnings of the subsidiaries outside of the United States		5,100,000								5,100,000
Provisional transition tax related to unremitted earnings of subsidiaries outside United States										600,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		23,800,000								23,800,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		238,700,000								238,700,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		139,800,000								139,800,000
Research Tax Credit Carryforward \| Foreign Tax Authority
Tax Credit Carryforward [Line Items]
Tax credit carryforwards		700,000								700,000
Research Tax Credit Carryforward \| Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Tax credit carryforwards		10,200,000								10,200,000
Research Tax Credit Carryforward \| State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Tax credit carryforwards		$ 8,000,000								$ 8,000,000

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	34.00%	34.00%	34.00%
State income taxes, net of federal benefit	0.00%	(2.10%)	(1.40%)
Foreign income at other than U.S. rates	0.20%	(14.40%)	(31.00%)
Stock-based compensation expense	(3.80%)	2.10%	(31.50%)
Meals and entertainment	(0.10%)	(1.50%)	(14.20%)
Acquisition and related items	0.00%	0.00%	(8.60%)
Goodwill impairment	(19.00%)	0.00%	0.00%
Non-deductible gifts	0.00%	(0.10%)	(0.80%)
Research and development tax credits	0.80%	7.20%	42.30%
Tax effect of intercompany financing	(0.00%)	4.90%	11.20%
Worthless stock	31.70%	0.00%	0.00%
Other permanent items	(0.50%)	0.00%	(0.50%)
Provision (benefit) to return adjustments	0.00%	0.60%	(9.40%)
Change in valuation allowance	(22.00%)	(9.50%)	120.10%
Tax rate change; U.S. tax reform	(20.20%)	0.00%	0.00%
Effective income tax rate	1.10%	21.20%	110.20%

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Accrued liabilities	$ 2,648	$ 1,287
Stock-based compensation	3,685	7,381
Net operating loss carryovers	65,648	21,375
Research tax credit carryovers	13,494	10,915
Other	1,502	2,360
Total deferred tax assets	86,977	43,318
Less valuation allowance	(81,767)	(39,491)
Deferred tax assets, net of valuation allowance	5,210	3,827
Deferred Tax Liabilities:
Fixed assets	(3,864)	(3,764)
Intangible assets	(955)	468
Other	0	0
Total deferred tax liabilities	(4,819)	(3,296)
Net deferred tax assets (liability)	$ 391	$ 531

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Benefit for income taxes	$ (252)	$ (2,031)	$ 146	$ 375	$ 121	$ (5,557)	$ 4,904	$ (4,328)	$ (1,762)	$ (4,860)	$ (4,561)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance				$ 5,027				$ 4,325	5,027	4,325	2,131
Increases related to current year tax positions									550	702	2,194
Increases related to prior year tax positions									69
Decreases related to prior year tax positions									0	0	0
Ending Balance	$ 5,646				$ 5,027				$ 5,646	$ 5,027	$ 4,325

Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Geographic Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 31,397	$ 35,211	$ 42,922	$ 46,015	$ 72,667	$ 65,811	$ 70,511	$ 69,232	$ 155,545	$ 278,221	$ 248,484
Property and equipment, net	47,393				36,246				47,393	36,246	25,403
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									95,567	182,777	172,188
Property and equipment, net	37,566				29,032				37,566	29,032	21,782
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									11,140	20,778	20,355
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									48,838	74,666	55,941
Property and equipment, net	$ 9,827				$ 7,214				$ 9,827	$ 7,214	$ 3,621

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Commitments [Line Items]
Rental expense	$ 12.7	$ 11.5	$ 9.5
Rent expense for sublease rentals	4.0	3.0	1.7
Data centers for cloud-based services
Other Commitments [Line Items]
Rental expense	4.9	5.8	$ 3.8
Office Lease \| Financial Standby Letter of Credit
Other Commitments [Line Items]
New letters of credit entered into during period		0.5
Letters of credit outstanding, amount	$ 2.9	$ 2.9

- Operating Leases, Future Minimum Payments Due (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Operating lease obligations
2018	$ 9,419
2019	7,198
2020	3,650
2021	1,251
2022	438
Thereafter	280
Total	22,236
Operating sublease income
2018	(766)
2019	(286)
2020	(196)
2021	(196)
2022	(196)
Thereafter	(147)
Total	(1,787)
Total lease obligations and sublease income
2018	8,653
2019	6,912
2020	3,454
2021	1,055
2022	242
Thereafter	133
Total	$ 20,449

Related Party Transactions (Details) $ in Millions	12 Months Ended
Related Party Transactions (Details) $ in Millions	Dec. 31, 2015 USD ($)
Related Party Transactions [Abstract]
Revenue from related parties	$ 3.3

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 31,397,000	$ 35,211,000	$ 42,922,000	$ 46,015,000	$ 72,667,000	$ 65,811,000	$ 70,511,000	$ 69,232,000	$ 155,545,000	$ 278,221,000	$ 248,484,000
Cost of revenue	15,465,000	12,985,000	13,698,000	14,688,000	21,126,000	17,798,000	17,540,000	16,783,000	56,836,000	73,247,000	58,495,000
Sales and marketing	12,134,000	12,503,000	12,529,000	14,628,000	18,449,000	21,635,000	21,966,000	21,278,000	51,794,000	83,328,000	83,333,000
Technology and development	11,123,000	11,580,000	12,044,000	12,753,000	12,934,000	12,513,000	13,294,000	12,443,000	47,500,000	51,184,000	42,055,000
General and administrative	12,517,000	13,644,000	14,355,000	15,080,000	15,337,000	16,238,000	16,390,000	20,605,000	55,596,000	68,570,000	70,199,000
Restructuring and other exit costs	0	0	1,621,000	4,338,000	3,316,000	0	0	0	5,959,000	3,316,000	0
Impairment of intangible assets and internal use software	4,585,000	0	0	0	23,473,000	0	0	0	4,585,000	23,473,000	0
Impairment of goodwill	0	90,251,000	0	0	0	0	0	0	90,251,000	0	0
Total expenses	55,824,000	140,963,000	54,247,000	61,487,000	94,635,000	68,184,000	69,190,000	71,109,000	312,521,000	303,118,000	254,082,000
Loss from operations	(24,427,000)	(105,752,000)	(11,325,000)	(15,472,000)	(21,968,000)	(2,373,000)	1,321,000	(1,877,000)	(156,976,000)	(24,897,000)	(5,598,000)
Other (income) expense, net	(358,000)	(150,000)	84,000	(7,000)	(899,000)	(346,000)	(906,000)	167,000	(431,000)	(1,984,000)	(1,459,000)
Loss before income taxes	(24,069,000)	(105,602,000)	(11,409,000)	(15,465,000)	(21,069,000)	(2,027,000)	2,227,000	(2,044,000)	(156,545,000)	(22,913,000)	(4,139,000)
Provision (benefit) for income taxes	(252,000)	(2,031,000)	146,000	375,000	121,000	(5,557,000)	4,904,000	(4,328,000)	(1,762,000)	(4,860,000)	(4,561,000)
Net income (loss)	$ (23,817,000)	$ (103,571,000)	$ (11,555,000)	$ (15,840,000)	$ (21,190,000)	$ 3,530,000	$ (2,677,000)	$ 2,284,000	$ (154,783,000)	$ (18,053,000)	$ 422,000
Net income (loss) per share:
Basic (usd per share)	$ (0.48)	$ (2.11)	$ (0.24)	$ (0.33)	$ (0.44)	$ 0.07	$ (0.06)	$ 0.05	$ (3.17)	$ (0.39)	$ 0.01
Diluted (usd per share)	$ (0.48)	$ (2.11)	$ (0.24)	$ (0.33)	$ (0.44)	$ 0.07	$ (0.06)	$ 0.05	$ (3.17)	$ (0.39)	$ 0.01
Weighted-average shares used to compute net income (loss) per share:
Basic (in shares)	49,293	49,055	48,783	48,332	48,051	47,538	46,341	44,663	48,869	46,655	39,663
Diluted (in shares)	49,293	49,055	48,783	48,332	48,051	48,683	46,341	48,676	48,869	46,655	44,495

Subsequent Events (Details) $ in Thousands		3 Months Ended	12 Months Ended
Subsequent Events (Details) $ in Thousands	Mar. 14, 2018 employee	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) employee	Dec. 31, 2016 USD ($)
Subsequent Event [Line Items]
Headcount, number of employees \| employee				514
Severance costs				$ 5,753	$ 3,270
Forecast
Subsequent Event [Line Items]
Severance costs		$ 3,000
Forecast \| Reduced Employee Expenses
Subsequent Event [Line Items]
Net offset to operating expenses			$ (15,000)
Expected offset to future cash expenses annually			$ (24,000)
Subsequent Event
Subsequent Event [Line Items]
Number of employees in headcount reduction (approximately) \| employee	100
Number of employees in headcount reduction, percentage	19.00%
Headcount, number of employees	415