CarGurus (CARG) 10-K 14 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 06, 2020	Jun. 30, 2019
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Registrant Name	CarGurus, Inc.
Trading Symbol	CARG
Entity Central Index Key	0001494259
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 2,464,065,369
Entity File Number	001-38233
Title of 12(b) Security	Class A Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3843478
Entity Address, Address Line One	2 Canal Park
Entity Address, Address Line Two	4th Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	617
Local Phone Number	354-0068
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive Proxy Statement for its 2020 Annual Meeting of Stockholders are incorporated by reference in Part III of this Annual Report on Form 10-K. Such Proxy Statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.
Class A Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		91,983,435
Class B Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		20,314,644

Consolidated Balance Sheets

Consolidated Balance Sheets $ in Thousands	Dec. 31, 2019USD ($)
Current assets:
Cash and cash equivalents	$ 59,920
Investments	111,692
Accounts receivable, net of allowance for doubtful accounts of $240 and $479, respectively	22,124
Prepaid expenses and prepaid income taxes	10,452
Deferred contract costs	9,544
Other current assets	4,972
Restricted cash	250
Total current assets	218,954
Property and equipment, net	27,950
Intangible assets	3,920
Goodwill	15,207
Operating lease right-of-use assets	59,986
Restricted cash	10,553
Deferred tax assets	42,713
Deferred contract costs, net of current portion	10,514
Other non-current assets	3,826
Total assets	393,623
Current liabilities:
Accounts payable	36,731
Accrued expenses, accrued income taxes and other current liabilities	18,262
Deferred revenue	9,984
Operating lease liabilities	8,781
Total current liabilities	73,758
Operating lease liabilities	60,818
Deferred tax liabilities	284
Other non–current liabilities	1,908
Total liabilities	136,768
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Additional paid–in capital	205,234
Retained earnings	51,859
Accumulated other comprehensive (loss) income	(350)
Total stockholders’ equity	256,855
Total liabilities and stockholders’ equity	393,623
Class A Common Stock
Stockholders’ equity:
Common stock	92
Class B Common Stock
Stockholders’ equity:
Common stock	$ 20

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 240	$ 479
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Class A Common Stock
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	91,819,649	89,728,223
Common stock, shares outstanding	91,819,649	89,728,223
Class B Common Stock
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	20,314,644	20,702,084
Common stock, shares outstanding	20,314,644	20,702,084

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue		$ 588,916	$ 454,086	$ 316,861
Cost of revenue	[1]	36,300	24,811	17,609
Gross profit		552,616	429,275	299,252
Operating expenses:
Sales and marketing		393,844	315,939	236,165
Product, technology, and development		69,462	47,866	22,470
General and administrative		50,434	39,475	22,688
Depreciation and amortization		4,554	2,804	2,655
Total operating expenses		518,294	406,084	283,978
Income from operations		34,322	23,191	15,274
Other income, net:
Interest income		2,984	2,283	869
Other income (expense), net		1,399	10	(306)
Total other income, net		4,383	2,293	563
Income before income taxes		38,705	25,484	15,837
(Benefit from) provision for income taxes		(3,441)	(39,686)	2,638
Net income		42,146	65,170	13,199
Reconciliation of net income to net income attributable to common stockholders:
Net income		42,146	65,170	13,199
Net income attributable to participating securities				(6,098)
Net income attributable to common stockholders — basic		42,146	65,170	7,101
Net income		42,146	65,170	13,199
Net income attributable to participating securities				(5,829)
Net income attributable to common stockholders — diluted		$ 42,146	$ 65,170	$ 7,370
Net income per share attributable to common stockholders: (Note 11)
Basic		$ 0.38	$ 0.60	$ 0.13
Diluted		$ 0.37	$ 0.57	$ 0.12
Weighted–average number of shares of common stock used in computing net income per share attributable to common stockholders:
Basic		111,450,443	108,833,028	55,835,265
Diluted		113,431,850	113,364,712	60,637,584
[1]	Includes depreciation and amortization expense for the years ended December 31, 2019, 2018, and 2017 of $3,263 $2,225, and $1,140, respectively.

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Depreciation and amortization expense	$ 3,263	$ 2,225	$ 1,140

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 42,146	$ 65,170	$ 13,199
Other comprehensive (loss) income:
Foreign currency translation adjustment	(421)	(157)	258
Comprehensive income	$ 41,725	$ 65,013	$ 13,457

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A Preferred Stock	Series B Preferred Stock	Series C Preferred Stock	Series D Preferred Stock	Series E Preferred Stock	Class A Common Stock	Class B Common Stock	Common StockClass A Common Stock	Common StockClass B Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Retained Earnings (Accumulated Deficit)
Beginning balance at Dec. 31, 2016	$ (67,972)								$ 14	$ 28	$ 3,714	$ (30)	$ (71,698)
Convertible preferred stock, Beginning balance, Shares at Dec. 31, 2016		2,824,703	2,938,486	1,550,612	1,673,105	1,107,202
Convertible preferred stock, Beginning balance at Dec. 31, 2016		$ 1,483	$ 2,295	$ 1,316	$ 67,872	$ 59,732
Beginning balance, Shares at Dec. 31, 2016									14,022,132	28,044,264
Net income	13,199												13,199
Stock–based compensation expense	5,204										5,204
Issuance of common stock upon exercise of stock options	398										398
Issuance of common stock upon exercise of stock options, Shares									92,944	181,840
Issuance of stock, net of issuance/offering costs	43,240								$ 3		43,237
Issuance of stock, net of issuance/offering costs, Shares									3,205,000
Payment of withholding taxes and option costs on net share settlement of restricted stock units and stock options, Shares							0
Conversion of preferred and common stock	132,698								$ 61		132,637
Convertible preferred stock, Conversion of preferred stock, Shares		(2,824,703)	(2,938,486)	(1,550,612)	(1,673,105)	(1,107,202)
Convertible preferred stock, Conversion of preferred stock		$ (1,483)	$ (2,295)	$ (1,316)	$ (67,872)	$ (59,732)
Conversion of preferred and common stock, shares issued									60,564,678
Foreign currency translation adjustment	258											258
Ending balance at Dec. 31, 2017	127,025								$ 78	$ 28	185,190	228	(58,499)
Ending balance, Shares at Dec. 31, 2017									77,884,754	28,226,104
Net income	65,170												65,170
Stock–based compensation expense	21,284										21,284
Issuance of common stock upon exercise of stock options	3,632								$ 3		3,629
Issuance of common stock upon exercise of stock options, Shares									3,186,489	10,690
Issuance of common stock upon vesting of restricted stock units									$ 2		(2)
Issuance of common stock upon vesting of restricted stock units, Shares									1,781,201
Payment of withholding taxes and option costs on net share settlement of restricted stock units and stock options	(25,885)										(25,885)
Payment of withholding taxes and option costs on net share settlement of restricted stock units and stock options, Shares							(658,931)		(658,931)
Cumulative adjustment from adoption of revenue recognition standard	3,042												3,042
Conversion of preferred and common stock									$ 7
Conversion of preferred and common stock, shares issued									7,534,710
Conversion of preferred and common stock, shares converted										(7,534,710)
Conversion of preferred and common stock, value										$ (7)
Foreign currency translation adjustment	(157)											(157)
Ending balance at Dec. 31, 2018	194,111								$ 90	$ 21	184,216	71	9,713
Ending balance, Shares at Dec. 31, 2018							89,728,223	20,702,084	89,728,223	20,702,084
Net income	42,146												42,146
Stock–based compensation expense	35,682										35,682
Issuance of common stock upon exercise of stock options	1,807										1,807
Issuance of common stock upon exercise of stock options, Shares									838,928
Issuance of common stock upon vesting of restricted stock units									$ 1		(1)
Issuance of common stock upon vesting of restricted stock units, Shares									1,317,736
Payment of withholding taxes and option costs on net share settlement of restricted stock units and stock options	(16,470)										(16,470)
Payment of withholding taxes and option costs on net share settlement of restricted stock units and stock options, Shares							(452,678)		(452,678)
Conversion of preferred and common stock									$ 1
Conversion of preferred and common stock, shares issued									387,440
Conversion of preferred and common stock, shares converted										(387,440)
Conversion of preferred and common stock, value										$ (1)
Foreign currency translation adjustment	(421)											(421)
Ending balance at Dec. 31, 2019	$ 256,855								$ 92	$ 20	$ 205,234	$ (350)	$ 51,859
Ending balance, Shares at Dec. 31, 2019							91,819,649	20,314,644	91,819,649	20,314,644

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 42,146	$ 65,170	$ 13,199
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,817	5,029	3,795
Currency (gain) loss on foreign denominated transactions	(690)	(190)	128
Deferred taxes	(3,734)	(39,040)	(1,117)
Provision for doubtful accounts	1,091	1,680	1,117
Stock–based compensation expense	34,301	20,794	5,028
Amortization of deferred contract costs	8,416	3,689
Changes in operating assets and liabilities:
Accounts receivable, net	(9,608)	(1,911)	(7,039)
Prepaid expenses, prepaid income taxes, and other assets	(378)	(11,753)	(2,287)
Deferred contracts costs	(15,979)	(12,987)
Accounts payable	4,268	9,345	6,244
Accrued expenses, accrued income taxes and other current liabilities	2,151	2,695	5,191
Deferred revenue	1,174	4,508	962
Deferred rent		4,289	227
Lease obligations	(1,468)
Other non–current liabilities	609	405	243
Net cash provided by operating activities	70,116	51,723	25,691
Investing Activities
Purchases of property and equipment	(11,205)	(5,956)	(5,157)
Capitalization of website development costs	(3,021)	(1,522)	(2,215)
Cash paid for acquisition	(19,139)
Investments in certificates of deposit	(177,808)	(212,800)	(50,000)
Maturities of certificates of deposit	188,916	140,000	44,774
Net cash used in investing activities	(22,257)	(80,278)	(12,598)
Financing Activities
Initial public offering proceeds			47,690
Payment of initial public offering costs		(1,142)	(3,308)
Proceeds from exercise of stock options	1,807	3,632	398
Financing cash flows from finance leases	(30)
Payment of withholding taxes and option costs on net share settlement of restricted stock units and stock options	(16,470)	(25,885)
Net cash (used in) provided by financing activities	(14,693)	(23,395)	44,780
Impact of foreign currency on cash, cash equivalents, and restricted cash	(1)	(44)	159
Net increase (decrease) in cash, cash equivalents, and restricted cash	33,165	(51,994)	58,032
Cash, cash equivalents, and restricted cash at beginning of period	37,558	89,552	31,520
Cash, cash equivalents, and restricted cash at end of period	70,723	37,558	89,552
Supplemental disclosure of cash flow information:
Cash paid for income taxes	300	2,308	4,393
Unpaid purchases of property and equipment	647	5,287	510
Unpaid initial public offering costs			1,142
Capitalized stock-based compensation expense in website development and internal-use software costs	1,381	$ 490	$ 176
Cash paid for operating lease liabilities	$ 10,906

Organization and Business Descr

Organization and Business Description	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Organization and Business Description	1. Organization and Business Description CarGurus, Inc. (the “Company”), is a global, online automotive marketplace connecting buyers and sellers of new and used cars. Using proprietary technology, search algorithms, and innovative data analytics, the Company provides information and analysis that create a differentiated automotive search experience for consumers. The Company’s marketplace empowers users worldwide with unbiased third-party validation on pricing and dealer reputation, as well as other useful information that aids them in finding “Great Deals from Top-Rated Dealers.” The Company is headquartered in Cambridge, Massachusetts and was incorporated in the State of Delaware on June 26, 2015. The Company operates principally in the United States and has also launched online marketplaces under the CarGurus brand in Canada, the United Kingdom, Germany, Italy, and Spain. The Company has subsidiaries in the United States, Canada, Ireland, and the United Kingdom. In the United Kingdom, the Company also operates the PistonHeads online marketplace as an independent brand. On October 16, 2017, the Company completed its initial public offering (“IPO”), in which the Company issued and sold 3,205,000 shares of its Class A common stock, including the full exercise by the underwriters of their option to purchase 705,000 shares of Class A common stock, at a public offering price of $16.00 per share for aggregate gross proceeds of $51.3 million. The Company received $43.2 million in net proceeds after deducting $3.6 million of underwriting discounts and commissions and $4.5 million in offering costs. In addition to shares of Class A common stock issued and sold by the Company, certain selling stockholders sold an aggregate of 7,605,000 shares of Class A common stock, including the full exercise by the underwriters of their option to purchase 705,000 shares of Class A common stock, as part of the IPO. Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 20,188,226 shares of Class A common stock and 40,376,452 shares of Class B common stock. The 40,376,452 shares of Class B common stock subsequently converted into 40,376,452 shares of Class A common stock resulting in a total conversion of all outstanding shares of convertible preferred stock into 60,564,678 shares of Class A common stock. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. The Company is subject to a number of risks and uncertainties common to companies in its and similar industries and stages of development including, but not limited to, rapid technological changes, competition from substitute products and services from larger companies, management of international activities, protection of proprietary rights, patent litigation, and dependence on key individuals.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The accompanying consolidated financial statements reflect the application of certain significant accounting policies as described below and elsewhere in these notes to the consolidated financial statements. The Company believes that a significant accounting policy is one that is both important to the portrayal of the Company’s financial condition and results, and requires management’s most difficult, subjective, or complex judgments, often as the result of the need to make estimates about the effect of matters that are inherently uncertain. Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Due to the adoption of ASC T opic 606, Revenue from Contracts with Customers (“ASC 606”) , which is discussed further in this Note 2, the consolidated balance sheets and the consolidated statements of operations, comprehensive income, c onvertible p referred s tock and s tockholders’ e quity ( d eficit) , and cash flows for the years ended December 31, 2019 and 2018 are not comparative to prior years. Due to the adoption of ASC Topic 842, Leases Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Subsequent Event Considerations The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure. Subsequent events have been evaluated as required. The Company has evaluated all subsequent events and determined that there are no material recognized or unrecognized subsequent events requiring disclosure, other than those disclosed in Note 16 of these consolidated financial statements. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. Significant estimates relied upon in preparing these consolidated financial statements include revenue recognition and sales allowances, variable consideration, the valuation of goodwill and intangible assets, the expensing and capitalization of product, technology, and development costs for website development and internal‑use software, and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Although the Company regularly assesses these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period in which they become known. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results may differ from management’s estimates if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Revenue Recognition The Company derives its revenue from two primary sources: (1) marketplace subscription revenue, which consists primarily of Listings, and Dealer Display subscriptions, and (2) advertising and other revenue, which consists primarily of display advertising revenue from auto manufacturers and other auto‑related brand advertisers as well as partnerships with financing services companies. Marketplace Subscription Revenue The Company offers multiple types of marketplace Listings packages to its dealers through its platform: Restricted Listings (formerly referred to as Basic Listings), which is free; and various levels of Listings packages, which each require a paid subscription under a monthly, quarterly, semiannual, or annual subscription basis. Contractual subscriptions for customers generally auto-renew on a monthly basis and are cancellable by dealers with 30 days’ advance notice at the end of the committed term. The Company also offers all dealers on the its platform access to a Dealer Dashboard, which includes a performance summary, Dealer Insights tool, and user review management platform. Dealers subscribing to a paid Listings package also have access to the Pricing Tool and Market Analysis tool. The Pricing Tool and Market Analysis tool are available only to paying dealers. Subscription pricing is determined based on a dealer’s inventory size, region, and the Company’s assessment of the connections and Return on Investment (“ROI”) the platform will provide them. Customers do not have the right to take possession of the Company’s software. In addition to listing inventory in the Company’s marketplace and providing access to the Dealer Dashboard, the Company offers dealers subscribing to one of its Enhanced, Featured, or Featured Priority Listings packages other subscription advertising and customer acquisition products, including Dealer Display, pursuant to which dealers can buy display advertising that appears in the Company’s marketplace, and on other sites on the internet, and for which such advertisements can be targeted by the user’s geography, search history, CarGurus website activity (including showing users relevant vehicles from a dealer’s inventory that they have not yet discovered on the Company’s marketplace), and a number of other targeting factors, allowing dealers to increase their visibility with in-market consumers and drive qualified traffic for dealers. Payment is typically due on first day of each calendar month and is recorded as accounts receivable or short-term deferred revenue when payment is received in advance of services being delivered to the customers. Advertising and Other Revenue Advertising and other revenue consists primarily of non-dealer display advertising revenue from auto manufacturers and other auto-related brand advertisers sold on a cost per thousand impressions (“CPM”) basis. An impression is an advertisement loaded on a web page. In addition to advertising sold on a CPM basis, the Company also has advertising sold on a cost per click basis. Auto manufacturers and other brand advertisers can execute advertising campaigns that are targeted across a wide variety of parameters, including demographic groups, behavioral characteristics, specific auto brands, categories such as Certified Pre-Owned, and segments such as hybrid vehicles. The Company does not provide minimum impression guarantees or other types of minimum guarantees in its contracts with customers. Pricing is primarily based on advertisement size and position on the Company’s websites and mobile applications, and fees are billed monthly in arrears. Unbilled accounts receivables relate to services rendered in the current period, but generally not invoiced until the subsequent period. The Company sells advertising directly to auto manufacturers and other auto related brand advertisers, as well as indirectly through revenue sharing arrangements with advertising exchange partners. Company-sold advertising is not subject to revenue sharing arrangements. Company-sold advertising revenue is recognized based on the gross amount charged to the advertiser. Partner-sold advertising revenue is recognized based on the net amount of revenue received from the content partners. Revenue from advertising sold directly by the Company is recorded on a gross basis because the Company is the principal in the arrangement, controls the ad placement and timing of the campaign, and establishes the selling price. The Company enters into contractual arrangements directly with advertisers and is directly responsible for the fulfillment of the contractual terms including any remedy for issues with such fulfillment. Advertising revenue subject to revenue sharing agreements between the Company and advertising exchange partners is recognized based on the net amount of revenue received from the partner. The advertising partner is responsible for fulfillment, including the acceptability of the services delivered. In partner-sold advertising arrangements, the advertising partner has a direct contractual relationship with the advertiser. There is no contractual relationship between the Company and the advertiser for partner-sold transactions. When an advertising exchange partner sells advertisements, the partner is responsible for fulfilling the advertisements, and accordingly, the Company has determined the advertising partner is the principal in the arrangement. Additionally, for auction-based partner agreements, the Company has latitude in establishing the floor price, but the final price established by the exchange server is at market rates. Customers are billed monthly in arrears and payment terms are generally thirty to sixty days from the date invoiced. Advertising and other revenue also includes revenue from partnerships with certain financing services companies pursuant to which the Company enables eligible consumers on the Company’s United States website to pre-qualify for financing on cars from dealerships that offer financing through such companies. The Company’s revenues from these financing partnerships are based on a funded-loan basis. Prior to adoption of ASC 606 The Company recognizes revenue when all of the following conditions are satisfied: (1) there is persuasive evidence of an arrangement; (2) the service has been provided to the customer; (3) the collection of fees is reasonably assured; and (4) the amount of fees to be paid by the customer is fixed or determinable. The Company recognizes marketplace subscription revenue on a monthly basis as revenue is earned and advertising and other revenue as impressions are delivered. Revenue is presented net of any taxes collected from customers. The Company assesses arrangements with multiple deliverables under ASU No. 2009‑13, Revenue Recognition (Topic 605), Multiple‑Deliverable Revenue Arrangements — a Consensus of the FASB Emerging Issues Task Force The Company establishes sales allowances at the time of revenue recognition based on its history of adjustments and credits provided to its customers. Sales allowances relate primarily to credits issued for service interruption. In assessing the adequacy of the sales allowance, the Company evaluates its history of adjustments and credits made through the date of the issuance of the financial statements. Estimated sales adjustments and credits and ultimate losses may vary from actual results which could be material to the financial statements; however, to date, actual sales allowances have been materially consistent with the Company’s estimates. Sales allowances are recorded as a reduction to revenue in the consolidated statements of operations. Following adoption of ASC 606 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue from Contracts with Customers Revenue Recognition ASC 606 outlines a comprehensive five-step revenue recognition model based on the principle that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, the Company applies the following five steps: 1 ) Identify the contract with a customer 2 ) Identify the performance obligations in the contract 3 ) Determine the transaction price 4 ) Allocate the transaction price to performance obligations in the contract 5 ) Recognize revenue when or as the Company satisfies a performance obligation Disaggregation of Revenue The following table summarizes revenue from contracts with customers by revenue source for the years ended December 31, 2019, 2018 and 2017. 2019 2018 2017 Revenue by Revenue Stream Marketplace subscription revenue $ 526,043 $ 405,780 $ 282,664 Advertising and other revenue 62,873 48,306 34,197 Total $ 588,916 $ 454,086 $ 316,861 The Company provides disaggregation of revenue based on the marketplace subscription versus advertising and other revenue classification in the table above and based on geographic region (see Note 13) as it believes these categories best depict how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. Marketplace Subscription Revenue For dealer listings, the Company provides a single similar service each day for a period of time. Each time increment (i.e. day), rather than the underlying activities, is distinct and substantially the same and therefore the performance obligation of the Company is to provide a series of daily activities over the contract term. Similar to the dealer listings, the dealer display advertising is considered a promise to provide a single similar service each day. Each time increment is distinct and substantially the same and therefore the performance obligation of the Company is to provide a series of daily activities over the contract term. Total consideration for marketplace subscription revenue is stated within the contracts. There are no contractual cash refund rights, but credits may be issued to a customer at the sole discretion of the Company. At an individual contract level, there is also no variable consideration, such as sales allowance, that needs to be included in the transaction price. However, at a portfolio level, the Company recognizes that there are times when there is a customer satisfaction issue or other circumstance that will lead to a credit. Due to the known possibility of future credits, a monthly sales allowance review is performed to defer revenue at a portfolio level for such future adjustments in the period of incurrence. The Company establishes sales allowances at the time of revenue recognition based on its history of adjustments and credits provided to its customers. In assessing the adequacy of the sales allowance, the Company evaluates its history of adjustments and credits made through the date of the issuance of the financial statements. Estimated sales adjustments, credits and losses may vary from actual results which could lead to material adjustments to the financial statements. To date, actual sales allowances have been materially consistent with the Company’s estimates. Sales allowances are recorded as a reduction to revenue in the consolidated statements of operations. Performance obligations are satisfied over time as the customer simultaneously receives and consumes the benefit of the service. Revenue is recognized ratably over the subscription period beginning on the date the Company starts providing services to the customer under the contract. Revenue is presented net of any taxes collected from customers. Advertising and Other Revenue For advertising revenue, the performance obligation is to publish the agreed upon campaign on the Company’s websites and load the related impressions. Advertising contracts state the transaction price within the agreement with payment being based on the number of clicks or impressions delivered on the Company’s websites As consideration is driven by the number of impressions delivered on the CarGurus websites, the consideration for each period is allocated to the period in which the service was rendered. Performance obligations for c ompany-sold advertising revenue and p artner-sold advertising revenue are satisfied over time as impressions are delivered . R evenue is recognized based on the total number of impressions delivered within the specified period . Revenue from advertising sold directly by the Company is recognized based on the gross amount charged to the advertiser and advertising revenue sold by partners is recognized based on the net amount of revenue received from the content partners. Revenue is presented net of any taxes collected from customers. Other revenue includes revenue from contracts for which the performance obligation is a series of distinct services with the same level of effort daily. For these contracts, the Company estimates the value of the variable consideration in determining the transaction price and allocates it to the performance obligation. Revenue is estimated and recognized on a ratable basis over the contractual term. The Company reassesses the estimate of variable consideration at each reporting period. Contracts with Multiple Performance Obligations The Company periodically enters into arrangements that include Listings and Dealer Display within marketplace subscription revenue. These contracts include multiple promises that the Company evaluates to determine if the promises are separate performance obligations. Performance obligations are identified based on services to be transferred to a customer that are distinct within the context of the contractual terms. Once the performance obligations have been identified, the Company determines the transaction price, which includes estimating the amount of variable consideration to be included in the transaction price, if any. If required, the transaction price is allocated to each performance obligation in the contract based on a relative standalone selling price (“SSP”) method as the performance obligation is being satisfied. For the Company’s arrangements that include Listings and Dealer Display, the performance obligations were satisfied over a consistent period of time and therefore the allocations did not impact the revenue recognized. Costs to Obtain a Contract Commissions paid to sales representatives and payroll taxes are considered costs to obtain a contract. Under ASC 606, the costs to obtain a contract require capitalization and amortization of those costs over the period of benefit. Although the guidance specifies the accounting for an individual contract with a customer, as a practical expedient, the Company has opted to apply the guidance to a portfolio of contracts with similar characteristics. The Company has opted to apply another practical expedient to immediately expense the incremental cost of obtaining a contract when the underlying related asset would have been amortized over one year or less. As such, the Company applied this practical expedient to advertising contracts as the term is one year or less and these contracts do not renew automatically. The practical expedient is not applicable to marketplace subscription contracts as the period of benefit including renewals is anticipated to be greater than one year as commissions paid on contract renewals are not commensurate with the commissions paid on the initial contract. The assets are periodically assessed for impairment. For marketplace subscription customers, the commissions paid on contracts with new customers, in addition to any commission amount related to incremental sales, are capitalized and amortized over the estimated benefit period of the customer relationship taking into account factors such as peer estimates of technology lives and customer lives as well as the Company's own historical data. Commissions paid that are not directly related to obtaining a new contract are expensed as incurred. Additionally, the Company allocates employer payroll tax expense to the commission expense in proportion to the overall payroll taxes paid during the respective period. As such, capitalized payroll taxes are amortized in the same manner as the underlying capitalized commissions. The assets recognized for costs to obtain a contract were $3,207, $12,505 and $20,058 as of January 1, 2018, December 31, 2018 and December 31, 2019, respectively. Amortization expense recognized during the years ended December 31, 2019 and 2018 related to costs to obtain a contract was $8,416 and $3,689, respectively. Financial Statement Impact of Adopting ASC 606 The cumulative effect of applying the new guidance to all contracts with customers that were not completed as of January 1, 2018 was recorded as an adjustment to accumulated deficit as of the adoption date. As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made on the consolidated balance sheet as of January 1, 2018. As Reported Adjustments As Adjusted December 2017 Marketplace Subscription Revenue Costs to Obtain a Contract January 1, 2018 Assets Current assets: Cash and cash equivalents $ 87,709 $ 87,709 Investments 50,000 50,000 Accounts receivable, net 12,577 813 13,390 Prepaid expenses and prepaid income taxes 5,313 5,313 Deferred contract costs — 1,424 1,424 Other current assets 1,605 1,605 Restricted cash — — Total current assets 157,204 813 1,424 159,441 Property and equipment, net 16,563 16,563 Restricted cash 1,843 1,843 Deferred tax assets 825 (190 ) (635 ) — Deferred contract costs, net of current portion — 1,783 1,783 Other long–term assets 159 159 Total assets $ 176,594 $ 623 $ 2,572 $ 179,789 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 23,908 $ 23,908 Accrued expenses, accrued income taxes and other current liabilities 13,588 13,588 Deferred revenue 4,305 4,305 Deferred tax liabilities — 153 153 Deferred rent 1,165 1,165 Total current liabilities 42,966 — 153 43,119 Deferred rent, net of current portion 5,648 5,648 Other non–current liabilities 955 955 Total liabilities 49,569 — 153 49,722 Commitments and contingencies Stockholders’ equity: Preferred stock — — Class A common stock 78 78 Class B common stock 28 28 Additional paid–in capital 185,190 185,190 Accumulated deficit (58,499 ) 623 2,419 (55,457 ) Accumulated other comprehensive income 228 228 Total stockholders’ equity 127,025 623 2,419 130,067 Total liabilities and stockholders’ equity $ 176,594 $ 623 $ 2,572 $ 179,789 Marketplace Subscription Revenue Under ASC 606, the Company’s accounting for contracts containing discounts resulted in accelerated revenue recognition. The cumulative impact of this change to the Company’s accounts receivable on January 1, 2018 was $813. Costs to Obtain a Contract As described above, under the new guidance, the capitalized commission expense is amortized over the estimated customer relationship period. The net impact of this change resulted in a $3,207 reduction to accumulated deficit for contracts that still require performance by the Company at the date of adoption. Income Taxes The adoption of ASC 606 primarily resulted in an acceleration of revenue and the reduction of expense, which in turn generated additional deferred tax liabilities that ultimately reduced the Company’s net deferred tax asset position. The cumulative impact resulted in a reduction to deferred tax assets of $978 which put the Company in a net deferred tax liability position on January 1, 2018. Impact of New Revenue Guidance on Financial Statement Line Items The following tables compare the reported consolidated balance sheet, statement of operations and cash flows, as of and for the year ended December 31, 2018, to the pro-forma amounts had the previous guidance been in effect. As of December 31, 2018 Balance Sheet As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Assets Current assets: Cash and cash equivalents $ 34,887 $ 34,887 Investments 122,800 122,800 Accounts receivable, net 13,614 939 12,675 Prepaid income taxes and prepaid income taxes 10,144 10,144 Deferred contract costs 5,253 5,253 — Other current assets 7,410 7,410 Restricted cash 750 750 Total current assets 194,858 939 5,253 188,666 Property and equipment, net 24,269 24,269 Restricted cash 1,921 1,921 Deferred tax assets 38,886 (227 ) (3,187 ) 42,300 Deferred contract costs, net of current portion 7,252 7,252 — Other long–term assets 1,104 1,104 Total assets $ 268,290 $ 712 $ 9,318 $ 258,260 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 34,345 $ 34,345 Accrued expenses, accrued income taxes and other current liabilities 18,654 18,654 Deferred revenue 8,811 8,811 Deferred rent 1,693 1,693 Total current liabilities 63,503 — — 63,503 Deferred rent, net of current portion 9,395 9,395 Other non–current liabilities 1,281 1,281 Total liabilities 74,179 — — 74,179 Commitments and contingencies Stockholders’ equity: Preferred stock — — Class A common stock 90 90 Class B common stock 21 21 Additional paid–in capital 184,216 184,216 Retained earnings (accumulated deficit) 9,713 712 9,318 (317 ) Accumulated other comprehensive income 71 71 Total stockholders’ equity 194,111 712 9,318 184,081 Total liabilities and stockholders’ equity $ 268,290 $ 712 $ 9,318 $ 258,260 Total reported assets were $10,030 greater than the pro-forma balance sheet, which assumes the previous guidance remained in effect as of December 31, 2018. This was largely due to the impact of $12,505 related to costs to obtain a contract. There were no changes to liabilities as of December 31, 2018 as a result of the adoption of ASC 606. The following summarizes the significant changes on the Company’s consolidated statement of operations for the year ended December 31, 2018 as a result of the adoption of ASC 606 on January 1, 2018 compared to the pro-forma amounts had the Company continued to recognize revenue under ASC 605. Year Ended December 31, 2018 Statement of Operations As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Revenue $ 454,086 $ 126 $ 453,960 Cost of revenue 24,811 24,811 Gross profit 429,275 126 — 429,149 Operating expenses: Sales and marketing 315,939 (9,298 ) 325,237 Product, technology, and development 47,866 47,866 General and administrative 39,475 39,475 Depreciation and amortization 2,804 2,804 Total operating expenses 406,084 — (9,298 ) 415,382 Income from operations 23,191 126 9,298 13,767 Other income, net: Interest income 2,283 2,283 Other income (expense) 10 10 Total other income, net 2,293 — — 2,293 Income before income taxes 25,484 126 9,298 16,060 Provision for (Benefit from) income taxes (39,686 ) 37 2,399 (42,122 ) Net income $ 65,170 $ 89 $ 6,899 $ 58,182 Basic $ 0.60 $ — $ 0.07 $ 0.53 Diluted $ 0.57 $ — $ 0.06 $ 0.51 The adoption of ASC 606 resulted in an increase to revenue of $126 during the year ended December 31, 2018 due to accelerated revenue recognition for contracts containing discounts. The adoption of ASC 606 also resulted in a $9,298 reduction in sales and marketing expense during the year ended December 31, 2018 as a result of capitalizing a portion of commission expense, which was previously expensed under the previous guidance. During the year ended December 31, 2018, the cumulative impact of these changes was a $9,424 increase in income from operations which resulted in a $2,436 reduction to the benefit from income taxes. Additionally, the adoption of ASC 606 resulted in the Company’s basic and diluted EPS for the year ended December 31, 2018 increasing $0.07 and $0.06, respectively. The following summarizes the significant changes on the Company’s consolidated statement of cash flows for the year ended December 31, 2018 as a result of the adoption of ASC 606 on January 1, 2018 compared to the pro-forma amounts had the Company continued to recognize revenue under ASC 605. Year Ended December 31, 2018 Statement of Cash Flows As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Operating Activities Net income $ 65,170 $ 89 $ 6,899 $ 58,182 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 5,029 5,029 Currency (gain) loss on foreign denominated transactions (190 ) (190 ) Deferred taxes (39,040 ) 37 2,399 (41,476 ) Provision for doubtful accounts 1,680 1,680 Stock–based compensation expense 20,794 20,794 Amortization of deferred contract costs 3,689 3,689 — Changes in operating assets and liabilities: Accounts receivable, net (1,911 ) (126 ) (1,785 ) Prepaid expenses, prepaid income taxes, and other assets (11,753 ) (11,753 ) Deferred contracts costs (12,987 ) (12,987 ) — Accounts payable 9,345 9,345 Accrued expenses, accrued income taxes and other current liabilities 2,695 2,695 Deferred revenue 4,508 4,508 Deferred rent 4,289 4,289 Other non–current liabilities 405 405 Net cash provided by operating activities $ 51,723 $ — $ — $ 51,723 The adoption of ASC 606 had no impact on the Company’s cash flows from operations. The aforementioned impacts resulted in offsetting shifts in cash flows between net income and various working capital balances. Contract Balances The following tables summarize the opening and closing balances of receivables and contract assets from contracts with customers as of January 1, 2018, December 31, 2018 and December 31, 2019. Accounts Receivable, net Contract Assets (current) Contract Assets (non-current) Balance at January 1, 2018 $ 13,390 $ 1,424 $ 1,782 Balance at December 31, 2018 13,614 5,253 7,252 Balance at December 31, 2019 22,124 9,544 10,514 Revenue recognized during the year ended December 31, 2019 and 2018 from amounts included in deferred revenue at the beginning of the period was approximately $8,811 and $4,305, respectively. Transaction Price Allocated to Future Performance Obligations Topic 606 requires that the Company disclose the aggregate amount of transaction price that is allocated to performance obligations that have not yet been satisfied as of December 31, 2019. For contracts with an original expected duration greater than one year, the aggregate amount of the transaction price allocated to the performance obligations that were unsatisfied as of December 31, 2019 is approximately $35.0 million, which the Company expects to recognize over the next twelve months. For contracts with an original expected duration of one year or less, the Company has applied the practical expedient available under Topic 606 to not disclose the amount of transaction price allocated to unsatisfied performance obligations as of December 31, 2019. For performance obligations not satisfied as of December 31, 2019, and to which this expedient applies, the nature of the performance obligations, the variable consideration and any consideration from contracts with customers not included in the transaction price is consistent with performance obligations satisfied as of December 31, 2019. The remaining duration is less than one year. From time to time, the Company may enter into contracts that include variable consideration, for which the Company estimates the value of the variable consideration in determining the transaction price and allocates it to the appropriate performance obligation(s). The Company reassesses any estimates of variable consideration at each reporting period. Deferred Revenue Deferred revenue primarily consists of payments received in advance of revenue recognition from the Company’s marketplace revenue and is recognized as the revenue recognition criteria are met. The Company generally invoices its customers monthly. Accordingly, the deferred revenue balances do not represent the total contract value of annual or multiyear subscription agreements. Deferred revenue that is expected to be recognized during the succeeding 12‑month period is recorded as current deferred revenue and the remaining portion is recorded as noncurrent in the consolidated balance sheets. All deferred revenue was recorded as current for all periods presented. Cost of Revenue Cost of revenue primarily consists of costs related to supporting and hosting the Company’s product offerings. These costs include salaries, benefits, incentive compensation and stock‑based compensation for the Company’s customer support team, and third‑party service provider costs such as data center and networking expenses, allocated overhead costs, depreciation and amortization expense associated with the Company’s property and equipment, and amortization of capitalized website development costs. Concentration of Credit Risk The Company has no significant off‑balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Acquisitions	3. Acquisitions On January 8, 2019, the Company, through CarGurus U.K. Limited, a company incorporated in England & Wales and a wholly owned subsidiary of CarGurus Ireland Limited, a company incorporated in Ireland and a wholly owned subsidiary of the Company (the “Purchaser”), completed its acquisition of PistonHeads, a U.K.-based automotive website (“PistonHeads”), by acquiring the entire issued share capital of Haymarket New4 Ltd., a company incorporated in England & Wales and now known as PistonHeads Holdco Limited (“NewCo”), from Haymarket Media Group Ltd., a company incorporated in England & Wales (the “Seller”), on the terms and subject to the conditions set forth in the Put and Call Option Agreement dated December 3, 2018, by and among the Purchaser, the Seller and Haymarket Group Limited, a company incorporated in England & Wales. The PistonHeads website hosts used car classifieds, articles and user forums. The Purchaser paid an aggregate of 15,000 GBP, or approximately $19,139, to acquire the business, inclusive of 1,000 GBP, or approximately $1,276, being held in escrow to secure post-closing claims, subject to the terms and conditions of an escrow agreement among the escrow agents, the Purchaser and the Seller. Upon completion of the acquisition, NewCo became a wholly owned subsidiary of the Purchaser. The business combination was intended to expand the Company’s consumer audience in the U.K. As of December 31, 2019, the Company has incurred total acquisition-related costs of $779 related to the transaction. The acquisition has been accounted for as a business combination under the acquisition method and, accordingly, the total purchase price is allocated to the intangible assets and goodwill. Acquired tangible assets and assumed liabilities are immaterial. The following table presents the purchase price allocation recorded in the Company's consolidated balance sheet as of the acquisition date, which was finalized as of December 31, 2019: Estimated Fair Value at Date of Acquisition Adjustment Adjusted Fair Value at Date of Acquisition Intangible assets (1) $ 4,466 $ — $ 4,466 Goodwill (2) 15,521 (655 ) 14,866 Deferred tax liabilities (3) (848 ) 655 (193 ) Total purchase price $ 19,139 $ — $ 19,139 (1) Identifiable definite-lived intangible assets were comprised of brand and customer relationships of $3,445 and $1,021, respectively, with estimated useful lives of 11 years and 3 years, respectively, which will be amortized on a straight-line basis over their estimated useful lives. (2) The goodwill represents the excess value of the purchase price over intangible assets acquired. The goodwill in this transaction is primarily attributable to future customer growth in the U.K. market as a result of acquiring an established platform and applying the Company’s technology to help improve the website experience on such platform; thus, helping to drive additional traffic to the PistonHeads website in the future. All goodwill is assigned to the International segment. The acquisition of PistonHeads was a stock acquisition and as a result, g (3) T Actual and pro forma results for this acquisition have not been presented as the financial impact to the Company’s consolidated financial statements is not material.

Fair Value of Financial Instrum

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments	4. Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments ASC 820, Fair Value Measurements and Disclosures ASC 820 identifies fair value as the exchange price, or exit price, representing the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants based on the highest and best use of the asset or liability. As such, fair value is a market‑based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The Company uses valuation techniques to measure fair value that maximize the use of observable inputs and minimize the use of unobservable inputs. These inputs are prioritized as follows: Level 1 — Quoted unadjusted prices for identical instruments in active markets. Level 2 — Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model‑derived valuations in which all observable inputs and significant value drivers are observable in active markets. Level 3 — Model‑derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company. The following tables present, for each of the fair value levels, the Company’s assets that are measured at fair value on a recurring basis at December 31, 2019 and 2018: December 31, 2019 Quoted Prices in Active Markets for Identical Assets (Level 1 Inputs) Significant Other Observable Inputs (Level 2 Inputs) Significant Unobservable Inputs (Level 3 Inputs) Total Cash equivalents: Money market funds $ 29,196 $ — $ — $ 29,196 Investments: Certificates of deposit — 111,692 — 111,692 Total $ 29,196 $ 111,692 $ — $ 140,888 December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1 Inputs) Significant Other Observable Inputs (Level 2 Inputs) Significant Unobservable Inputs (Level 3 Inputs) Total Cash equivalents: Money market funds $ 24 $ — $ — $ 24 Investments: Certificates of deposit — 122,800 — 122,800 Total $ 24 $ 122,800 $ — $ 122,824 The Company measures eligible assets and liabilities at fair value with changes in value recognized in earnings. There were no liabilities that were measured at fair value as of December 31, 2019 and 2018. Fair value treatment may be elected either upon initial recognition of an eligible asset or liability or, for an existing asset or liability, if an event triggers a new basis of accounting. The Company did not elect to remeasure any of its existing financial assets and did not elect the fair value option for any financial assets transacted during the year ended December 31, 2019 or the year ended December 31, 2018. The following is a summary of cash, cash equivalents, and investments as of December 31, 2019 and 2018. Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value December 31, 2019: Cash and cash equivalents due in 90 days or less $ 59,920 $ — $ — $ 59,920 Investments: Certificates of deposit due in one year or less 111,692 — — 111,692 Total cash, cash equivalents, and investments $ 171,612 $ — $ — $ 171,612 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value December 31, 2018: Cash and cash equivalents due in 90 days or less $ 34,887 $ — $ — $ 34,887 Investments: Certificates of deposit due in one year or less 122,800 — — 122,800 Total cash, cash equivalents, and investments $ 157,687 $ — $ — $ 157,687

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net consists of the following: At December 31, 2019 2018 Capitalized equipment $ 7,923 $ 4,208 Capitalized software 181 252 Capitalized website development costs 11,083 6,907 Furniture and fixtures 6,809 4,584 Leasehold improvements 19,507 10,821 Construction in progress 524 8,971 Finance lease right-of-use assets 78 - 46,105 35,743 Less accumulated depreciation and amortization (18,155 ) (11,474 ) Property and equipment, net $ 27,950 $ 24,269 Depreciation and amortization expense, excluding amortization of intangible assets, was $7,168, $5,029, and $3,795 for the years ended December 31, 2019, 2018, and 2017, respectively. The increase of $8,686 in leasehold improvements and the decrease of $8,447 in construction in progress at December 31, 2019 was primarily due to costs incurred to build out the Company’s new leased facility at 121 First Street in Cambridge, Massachusetts. The facility became occupied subsequent to December 31, 2018, at which time the assets ceased to be classified as construction in progress and became classified as leasehold improvement.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	6. Goodwill and other intangible assets Goodwill The changes in the carrying value of goodwill were as follows: Balance at December 31, 2018 $ — Initial value of PistonHeads acquisition 15,521 Foreign currency translation adjustment 341 Purchase price adjustment (1) (655 ) Balance at December 31, 2019 $ 15,207 (1) The purchase price adjustment corresponds to an adjustment for the deferred tax liability as a result of the Company’s evaluation of income tax treatment, which was recorded during the second quarter of 2019. The Company did not have a goodwill balance prior to the closing of the PistonHeads acquisition on January 8, 2019. The Company tests goodwill for impairment at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The Company evaluated goodwill for impairment on October 1, 2019 and did not recognize an impairment charge. Other Intangible Assets Intangible assets as of December 31, 2019 consist of the following: Weighted Average Remaining Useful Life (years) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Brand 10.0 $ 3,524 $ 313 $ 3,211 Customer relationships 2.0 1,045 336 709 Total $ 4,569 $ 649 $ 3,920 The Company did not have intangible assets prior to the closing of the PistonHeads acquisition on January 8, 2019. T The estimated useful life of brand and customer relationships is 11 years and 3 years, respectively. The Company evaluates the useful lives of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. Estimated amortization expense of intangible assets for future periods as of December 31, 2019, is as follows: Year Ending December 31, Amortization Expense 2020 $ 671 2021 671 2022 328 2023 320 2024 320 2025 and thereafter 1,610 Total $ 3,920

Accrued Expenses, Accrued Incom

Accrued Expenses, Accrued Income Taxes and Other Current Liabilities	12 Months Ended
	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Accrued Expenses, Accrued Income Taxes and Other Current Liabilities	7. Accrued expenses, accrued income taxes and other current liabilities Accrued expenses, accrued income taxes and other current liabilities consist of the following: At December 31, 2019 2018 Accrued bonus $ 8,637 $ 8,266 Other accrued expenses, accrued income taxes and other current liabilities 9,625 10,388 Total $ 18,262 $ 18,654

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Contractual Obligations and Commitments The Company’s operating lease obligations are discussed in Note 2. All of the Company’s property, equipment, and internal-use software have been purchased with cash with the exception of $647 of unpaid property and equipment and immaterial amounts related to obligations under one finance lease as of December 31, 2019. The Company has no material long-term purchase obligations outstanding with any vendors or third parties. Legal Matters From time to time the Company may become involved in legal proceedings or be subject to claims arising in the ordinary course of its business. The Company is not presently subject to any pending or threatened litigation that it believes, if determined adversely to the Company, individually, or taken together, would reasonably be expected to have a material adverse effect on its business or financial results. Guarantees and Indemnification Obligations In the ordinary course of business, the Company enters into agreements with its customers that include commercial provisions with respect to licensing, infringement, indemnification, and other common provisions. The Company does not, in the ordinary course, agree to indemnification obligations for the Company under its contracts with customers. Based on historical experience and information known at December 31, 2019 and 2018, the Company has not incurred any costs for guarantees or indemnities.

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Convertible Preferred Stock and Stockholders’ Equity	9. Convertible Preferred Stock and Stockholders’ Equity On June 21, 2017, the Company amended and restated its Certificate of Incorporation pursuant to the Third Amended and Restated Certificate of Incorporation. Under the Third Amended and Restated Certificate of Incorporation, the total number of shares of all classes of stock which the Company had authority to issue was (i) 120,020,700 shares of Class A common stock, par value $0.001 per share, (ii) 80,013,800 shares of Class B common stock, par value $0.001 per share, and (iii) 11,091,782 shares of Preferred Stock, par value $0.001 per share, of which 3,333,000 shares were designated Series A Preferred Stock, 3,329,497 shares were designated Series B Preferred Stock, 1,648,978 shares were designated Series C Preferred Stock, 1,673,105 shares were designated Series D Preferred Stock, and 1,107,202 shares were designated Series E Preferred Stock. The Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock, Series D Preferred Stock, and Series E Preferred Stock are referred to collectively as the Preferred Stock. Upon the effectiveness of the Third Amended and Restated Certificate of Incorporation, (i) each share of Class A common stock issued and outstanding was recapitalized, reclassified, and reconstituted into two fully paid and non‑assessable shares of outstanding Class A common stock and four fully paid and non‑assessable shares of outstanding Class B common stock, and (ii) each share of Class B common stock of the Company issued and outstanding was recapitalized, reclassified, and reconstituted into two fully paid and non‑assessable shares of outstanding Class A common stock and four fully paid and non‑assessable shares of outstanding Class B common stock. Further, upon the effectiveness of the Third Amended and Restated Certificate of Incorporation, the number of shares of common stock as to which each outstanding option to purchase common stock was exercisable for and each outstanding RSU was convertible into was adjusted such that upon exercise of outstanding stock options or vesting of outstanding RSUs, each holder would receive two fully paid and non‑assessable shares of Class A common stock and four fully paid and non‑assessable shares of Class B common stock in respect of each share of common stock previously underlying such option or RSU. The exercise price per share of common stock underlying each outstanding option was adjusted upon the effectiveness of the Third Amended and Restated Certificate of Incorporation to be one one All share and per share data shown in the accompanying consolidated financial statements and related notes have been retroactively revised to reflect the share recapitalization. On October 16, 2017, in connection with the closing of the IPO, all of the outstanding shares of Preferred Stock automatically converted into 20,188,226 shares of Class A common stock and 40,376,452 shares of Class B common stock. The 40,376,452 shares of Class B common stock subsequently converted into 40,376,452 shares of Class A common stock resulting in a total conversion of all outstanding shares of Preferred Stock into 60,564,678 shares of Class A common stock. Subsequent to the closing of the IPO, there were no shares of Preferred Stock outstanding. Immediately following such conversion, the Company’s Fourth Amended and Restated Certificate of Incorporation became effective. Pursuant to the Fourth Amended and Restated Certificate of Incorporation, the Company is authorized to issue up to 500,000,000 shares of Class A common stock, 100,000,000 shares of Class B common stock, and 10,000,000 shares of Preferred Stock, all with a par value of $0.001 per share. As of December 31, 2019, the Preferred Stock is undesignated and no Preferred Stock is outstanding. In addition, pursuant to the Fourth Amended and Restated Certificate of Incorporation, all shares of Class B common stock will automatically convert into shares of Class A common stock, on a share for share basis, upon the date falling after the first to occur of (1) the death of Langley Steinert, the Company’s Chief Executive Officer and Chairman, (2) his voluntary termination of all employment with the Company and service on the Company’s board of directors, or (3) the sum of the number of shares of capital stock held by Langley Steinert, by any Family Member of Langley Steinert, and by any Permitted Entity of Langley Steinert (as such terms are defined in the Fourth Amended and Restated Certificate of Incorporation), assuming the exercise and settlement in full of all outstanding options and convertible securities and calculated on an as-converted to Class A common stock basis, being less than 9,091,484 . Shares of Class B common stock will not automatically convert into shares of Class A common stock upon the termination of Mr. Steinert's status as an officer and director, unless such termination is either made voluntarily by Mr. Steinert or due to Mr. Steinert's death. Once converted into Class A common stock, the converted shares of Class B common stock will not be reissued. In addition, if all shares of Class B common stock are converted into Class A common stock, then any outstanding options or convertible securities with the right to purchase or acquire shares of Class B common stock shall become a right to purchase or acquire shares of Class A common stock. Common Stock Each share of Class A common stock entitles the holder to one vote for each share on all matters submitted to a vote of the Company’s stockholders at all meetings of stockholders and written actions in lieu of meetings. Each share of Class B common stock entitles the holder to ten votes for each share on all matters submitted to a vote of the Company’s stockholders at all meetings of stockholders and written actions in lieu of meetings. Holders of common stock are entitled to receive dividends, when and if declared by the Board. At December 31, 2019, each share of Class B common stock was convertible into one share of Class A common stock at the option of the holder at any time. Automatic conversion of each share of Class B common stock will occur upon the occurrence of certain events, as described in the Fourth Amended and Restated Certificate of Incorporation. Upon the effectiveness of the Company’s Fourth Amended and Restated Certificate of Incorporation, additional terms of conversion and transfer were implemented as discussed above. Preferred Stock Prior to the Company’s IPO, at which time all shares of Preferred Stock were converted into shares of common stock, the Company’s Preferred Stock consisted of the following: Original Issue Price Per Share Shares Authorized Outstanding Liquidation Amount Carrying Value Series A Preferred Stock $ 0.525053 3,333,000 2,824,703 $ 1,483 $ 1,483 Series B Preferred Stock $ 0.780899 3,329,497 2,938,486 2,295 2,295 Series C Preferred Stock $ 0.849012 1,648,978 1,550,612 1,316 1,316 Series D Preferred Stock $ 40.642989 1,673,105 1,673,105 68,000 67,872 Series E Preferred Stock $ 54.190650 1,107,202 1,107,202 60,000 59,732 11,091,782 10,094,108 $ 133,094 $ 132,698 The holders of the Company’s Preferred Stock had certain voting and dividend rights, as well as liquidation preferences and conversion privileges. All rights, preferences, and privileges associated with the Preferred Stock were terminated at the time of the Company’s IPO in conjunction with the conversion of all outstanding shares of Preferred Stock into shares of common stock.

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	10. Stock‑based Compensation Equity Incentive Plans The Company’s Amended and Restated 2006 Equity Incentive Plan (the “2006 Plan”) provided for the issuance of non-qualified stock options, restricted stock and stock awards to the Company’s employees, officers, directors and consultants. The 2006 Plan authorized up to an aggregate of 3,444,668 shares of the Company's Class B common stock for such issuances. In conjunction with the effectiveness of the Company’s 2015 Equity Incentive Plan (the “2015 Plan”), the Board voted that no further stock options or other equity-based awards may be granted under the 2006 Plan. In 2015, the Board first adopted the 2015 Plan, which became effective on June 26, 2015. The 2015 Plan provided for the issuance of incentive stock options, non-qualified stock options, restricted stock, stock awards and restricted stock units (“RSUs”) to employees, consultants and non-employee directors. As of the effective date of the 2015 Plan, up to 603,436 shares of common stock were authorized for issuance under the 2015 Plan. The 2015 Plan was amended and restated effective August 6, 2015 to permit the granting of RSUs under the 2015 Plan, remove Class B common stock from the pool of shares available for issuance under the 2015 Plan and make certain other desired changes. The 2015 Plan was further amended and restated at October 15, 2015 to add a ten-year term and to make certain other desired changes. The 2015 Plan was further amended and restated effective August 22, 2016 to merge the 2006 Plan into the 2015 Plan, to increase the number of shares of Class A common stock that may be issued under the 2015 Plan, and to lengthen the term of the 2015 Plan to expire on August 21, 2026. In addition, pursuant to this amendment and restatement of the 2015 Plan, prior to giving effect to the recapitalization that occurred on June 21, 2017, there were (i) 618,691 shares of Class A common stock, plus (ii) 802,562 shares of Class B common stock authorized under the 2015 Plan; provided, however, that (1) the number of shares of Class A common stock was increased, on a share for share basis, by the number of shares of Class B common stock that were (a) subject to outstanding options granted under the 2006 Plan that expired, terminated, or were cancelled for any reason without having been exercised, (b) surrendered in payment of the exercise price of outstanding options granted under the 2006 Plan or (c) withheld in satisfaction of tax withholding upon exercise of outstanding options granted under the 2006 Plan, and the number of shares of Class B common stock reserved under the amended and restated 2015 Plan was decreased, on a corresponding share for share basis, (2) no new awards of Class B common stock could be granted under the amended and restated 2015 Plan, and (3) except with respect to outstanding options granted under the 2006 Plan that were exercised on or after the date of the amendment and restatement, no Class B common stock could be issued under the 2015 Plan. In connection with the recapitalization that occurred on June 21, 2017, the 2015 Plan was further amended and restated to account for each outstanding common stock option being adjusted such that each share of common stock underlying such option became two shares of Class A common stock and four shares of Class B common stock underlying such option, and each outstanding RSU being adjusted such that each share of common stock issuable upon settlement of such RSU became two shares of Class A common stock and four shares of Class B common stock issuable upon settlement of such RSU. Pursuant to the 2015 Plan as further amended in connection with the recapitalization, there were (i) 3,181,740 shares of Class A common stock and (ii) 5,161,644 shares of Class B common stock authorized for issuance under the 2015 Plan. In connection with the IPO, in October 2017, the Board adopted, and the Company’s stockholders approved, the Omnibus Equity Compensation Plan (the “2017 Plan”) for the purpose of granting incentive stock options, non-qualified stock options, stock awards, stock units, other share-based awards and cash awards to employees, advisors and consultants to the Company and its subsidiaries and non-employee members of the Company’s board of directors. The 2017 Plan is the successor to the 2015 Plan. The 2017 Plan authorizes the issuance or transfer of the sum of: (i) 7,800,000 shares of the Company’s Class A common stock, plus (ii) the number of shares of our Class A common stock (up to 4,500,000 shares) equal to the sum of (x) the number of shares of Class A common stock and Class B common stock of the Company subject to outstanding awards under the 2015 Plan as of October 10, 2017 that terminate, expire or are cancelled, forfeited, exchanged, or surrendered on or after October 10, 2017 without having been exercised, vested, or paid prior to October 10, 2017, including shares tendered or withheld to satisfy tax withholding obligations with respect to outstanding grants under the Prior 2015 Plan, plus (y) the number of shares of Class A common stock reserved for issuance under the 2015 Plan that remain available for grant under the 2015 Plan as of the October 10, 2017. The aggregate number of shares of Class A common stock that may be issued or transferred under the 2017 Plan pursuant to incentive stock options will not exceed 12,300,000 shares of Class A common stock. Unless determined otherwise by the Compensation Committee of the Board, as of the first trading day of January of each calendar year during the term of the 2017 Plan (excluding any extensions), eligible beginning with calendar year 2019, an additional number of shares of Class A common stock will be added to the number of shares of the Company’s Class A common stock authorized to be issued or transferred under the 2017 Plan and the number of shares authorized to be issued or transferred pursuant to incentive stock options, equal to 4% of the total number of shares of our Class A common stock outstanding on the last trading day in December of the immediately preceding calendar year, or 6,000,000 shares, whichever is less, or such lesser amount as determined by the Board (the “Evergreen Increase”). The Compensation Committee of the Board determined to not effectuate the Evergreen Increase that was otherwise scheduled to have occurred on each of January 2, 2019 and January 2, 2020. In conjunction with the adoption of the 2017 Plan, options and RSUs outstanding under the 2015 Plan will remain outstanding but no additional grants will be made from the 2015 Plan. At December 31, 2019, 5,889,929 shares of Class A common stock were available for issuance under the 2017 Plan. Stock Options The following is a summary of the stock option activity for all stock‑based compensation plans during the year ended December 31, 2019: Common Stock Weighted- Average Exercise Price for Equity Weighted- Average Remaining Contractual Life (In Years) Aggregate Intrinsic Value (1) Outstanding, December 31, 2018 1,807,515 $ 2.35 5.9 $ 56,716 Granted — — Exercised (838,928 ) 2.16 28,902 Forfeited and cancelled (25,702 ) 5.09 Outstanding, December 31, 2019 942,885 $ 2.45 5.0 $ 30,859 Options exercisable at December 31, 2019 913,197 $ 2.31 5.0 $ 30,016 (1) The aggregate intrinsic value as of December 31, 2019 and 2018 was calculated based on the positive difference, if any, between the estimated fair value of our common stock on December 31, 2019 and 2018, respectively, or the date of exercise, as appropriate, and the exercise price of the underlying options. There were no options granted in the years ended December 31, 2019, 2018 and 2017. The aggregate intrinsic value for options exercised during the years ended December 31, 2018 and 2017 was $111,227 and $2,238, respectively. As of December 31, 2019, there was $16 of unrecognized stock‑based compensation expense related to unvested stock options, which is expected to be recognized over a weighted‑average period of 0.3 years. Restricted Stock Units The following is a summary of the RSU activity during the year ended December 31, 2019: Number of Shares Weighted- Average Grant Date Fair Value Aggregate Intrinsic Value Unvested outstanding, December 31, 2018 2,973,002 $ 26.06 $ 100,279 Granted 1,811,208 39.07 Vested (1,317,736 ) 23.93 Forfeited (383,173 ) 31.70 Unvested outstanding, December 31, 2019 3,083,301 $ 33.89 $ 108,471 The weighted-average grant-date fair value of RSUs granted was $35.79 and $16.99 per share in 2018 and 2017, respectively. RSUs that vested and settled during the year ended December 31, 2018 totaled 1,781,201, which included 1,087,279 and 693,922 RSUs that vested in 2018 and 2017, respectively. RSUs that vested prior to April 10, 2018 did not settle until the expiration of shareholder lock-up agreements on such date. The total fair value of RSUs vested was $31,533, $15,994, and $2,505 in the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, there was $92,700 of unrecognized stock‑based compensation expense related to unvested RSUs that is expected to be recognized over a weighted‑average period of 2.8 years. Stock-based Compensation Expense For the years ended December 31, 2019, 2018, and 2017, total stock‑based compensation expense was $34,301, $20,794, and $5,028, respectively. The following two tables show stock compensation expense by award type and where the stock compensation expense is recorded in the Company’s consolidated statements of operations Year Ended December 31, 2019 2018 2017 Options $ 155 $ 247 $ 281 RSUs 34,146 20,547 4,747 Total stock-based compensation expense $ 34,301 $ 20,794 $ 5,028 Year Ended December 31, 2019 2018 2017 Cost of revenue $ 354 $ 354 $ 151 Sales and marketing expense 9,989 5,111 1,911 Product, technology, and development expense 15,159 9,865 1,637 General and administrative expense 8,799 5,464 1,329 Total stock-based compensation expense $ 34,301 $ 20,794 $ 5,028 Excluded from stock-based compensation expense is $1,381, $490, and $176 of capitalized software development costs and internal-use software costs in 2019, 2018 and 2017, respectively. The income tax benefit from stock-based compensation expense was $2,953, $1,945, and $1,301 in the years ended December 31, 2019, 2018, and 2017, respectively. During the years ended December 31, 2019 and 2018, the Company withheld 452,678, and 658,931 shares of Class A common stock, respectively, to satisfy employee tax withholding requirements and option costs due to net share settlements. No shares were withheld during the year ended December 31, 2017. The shares withheld return to the authorized, but unissued, pool under the 2017 Plan and can be reissued by the Company. Total payments for the employees’ tax obligations to the taxing authorities and for option costs due to net share settlements were $16,470 and $25,885 for the years ended December 31, 2019 and 2018, respectively, and are reflected as a financing activity within the consolidated statements of cash flows. Common Stock Reserved for Future Issuance At December 31, 2019, the Company had reserved the following shares of voting common stock for future issuance: Common stock options outstanding 942,885 Restricted stock units outstanding 3,083,301 Shares available for issuance under the 2017 Plan 5,889,929 Total shares of authorized common stock reserved for future issuance 9,916,115

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	11. Earnings Per Share Net income per share for the years ended December 31, 2019 and 2018 was computed by dividing net income by the weighted-average number of common shares outstanding during the reporting period. The Company computes the weighted-average number of common shares outstanding during the reporting period using the total number of shares of Class A common stock and Class B common stock outstanding as of the last day of the previous year end reporting period plus the weighted-average of any additional shares issued and outstanding during the reporting period. Net income per share for the year ended December 31, 2017 was computed using the two-class method, which includes the weighted‑average number of shares of common stock outstanding during the period and other securities that participate in dividends (a participating security). For periods during the year ended December 31, 2017, the Company had convertible Preferred Stock outstanding. The Company considered the convertible Preferred Stock to be participating securities because they included rights to participate in dividends with the common stock. On October 16, 2017, in connection with the closing of the IPO, all of the outstanding shares of convertible P referred S tock automatically converted into 20,188,226 shares of Class A common stock and 40,376,452 shares of Class B common stock , the latter of which subsequently converted in full into shares of Class A common stock. As a result, there were no shares of P referred S tock outstanding at the closing of the IPO and the Company has not issued any new shares of P referred S tock since such closing. Under the two‑class method, basic net income per share attributable to common stockholders is computed by dividing the net income attributable to common stockholders by the weighted‑average number of shares of common stock outstanding during the period. Diluted net income per share attributable to common stockholders is computed using the more dilutive of (1) the two‑class method or (2) the if‑converted method. The Company allocated net income first to preferred stockholders based on dividend rights under the Company’s certificate of incorporation that was in effect prior to the closing of the IPO and then to preferred and common stockholders based on ownership interests. Net losses are not allocated to preferred stockholders as they do not have an obligation to share in the Company’s net losses. The Company has two classes of common stock authorized: Class A common stock and Class B common stock. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Each share of Class B common stock is convertible into one share of Class A common stock at the option of the holder at any time or automatically upon certain events described in the Company’s amended and restated certificate of incorporation, including on either the death or voluntary termination of the Company’s Chief Executive Officer. one‑to‑one During the years ended December 31, 2019 and 2018, holders of Class B common stock converted 387,440 shares and 7,534,710 shares, respectively, of Class B common stock to Class A common stock. Diluted net income per share gives effect to all potentially dilutive securities. Potential diluted securities for the years ended December 31, 2019, 2018 and 2017 consist of shares of common stock issuable upon the exercise of stock options and shares of common stock issuable upon the vesting of RSUs. Potential dilutive securities for the year ended December 31, 2017 also included shares of common stock issuable upon the conversion of the outstanding Preferred Stock. The dilutive effect of these common stock equivalents is reflected in diluted earnings per share by application of the treasury stock method. For the years ended December 31, 2019 and 2018, dilutive net income per share was calculated by dividing net income by the weighted-average number of shares of common stock outstanding during the period plus the dilutive impact of stock options and shares of common stock issuable upon the vesting of RSUs. For the year ended December 31, 2017, the two‑class method was used in the computation of diluted net income per share, which was equally as dilutive as the if-converted method. The following table presents a reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share: Year Ended December 31, 2019 2018 2017 Numerator: Net income $ 42,146 $ 65,170 $ 13,199 Net income attributable to participating securities — — (6,098 ) Net income attributable to common stockholders — basic $ 42,146 $ 65,170 $ 7,101 Net income $ 42,146 $ 65,170 $ 13,199 Net income attributable to participating securities — — (5,829 ) Net income attributable to common stockholders — diluted $ 42,146 $ 65,170 $ 7,370 Denominator: Weighted–average number of shares of common stock used in computing net income per share attributable to common stockholders — basic 111,450,443 108,833,028 55,835,265 Dilutive effect of share equivalents resulting from stock options 1,155,906 3,009,748 4,290,362 Dilutive effect of share equivalents resulting from unvested restricted stock units 825,501 1,521,936 511,957 Weighted–average number of shares of common stock used in computing net income per share — diluted 113,431,850 113,364,712 60,637,584 Net income per share attributable to common stockholders: Basic $ 0.38 $ 0.60 $ 0.13 Diluted $ 0.37 $ 0.57 $ 0.12 The following potentially dilutive common stock equivalents have been excluded from the calculation of diluted weighted‑average shares outstanding for the years ended December 31, 2019, 2018, and 2017, as their effect would have been anti‑dilutive for the periods presented: Year Ended December 31, 2019 2018 2017 Restricted stock units outstanding 1,144,287 126,816 829

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The domestic and foreign components of income before income taxes are as follows: Year Ended December 31, 2019 2018 2017 United States $ 37,476 $ 24,426 $ 15,543 Foreign 1,229 1,058 294 Income before income taxes $ 38,705 $ 25,484 $ 15,837 The (benefit from) provision for income taxes contained the following components: Year Ended December 31, 2019 2018 2017 Current (benefit) provision: Federal $ — $ (860 ) $ 3,262 State (220 ) 92 431 Foreign 513 122 62 293 (646 ) 3,755 Deferred (benefit) provision: Federal (2,377 ) (27,675 ) (755 ) State (1,306 ) (11,499 ) (343 ) Foreign (51 ) 134 (19 ) (3,734 ) (39,040 ) (1,117 ) Income tax (benefit) provision $ (3,441 ) $ (39,686 ) $ 2,638 The Company's effective tax rates for the years ending December 31, 2019 and 2018 are less than the U.S. federal statutory rate due to excess tax deductions related to stock-based compensation awards and federal and state research and development credits. The Company’s effective tax rate for the year ending December 31, 2017 is less than the U.S. federal statutory rate primarily due to federal and state research and development credits, excess tax deductions related to stock-based compensation awards, and tax deductions for fees incurred during the IPO process. Year Ended December 31, 2019 2018 2017 U.S. federal taxes at statutory rate 21.0 % 21.0 % 35.0 % State taxes, net of federal benefit 0.2 (25.6 ) 3.1 Nondeductible expenses 2.9 4.1 1.2 Tax deductible IPO costs — — (9.3 ) Stock compensation (22.0 ) (127.2 ) (4.4 ) Foreign rate differential (0.3 ) (0.4 ) (0.4 ) Credits (10.3 ) (28.4 ) (9.0 ) Other (0.2 ) 0.7 0.5 Total (8.7 )% (155.8 )% 16.7 % The approximate income tax effect of each type of temporary difference and carryforward as of December 31, 2019 and 2018 is as follows: As of December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 35,977 $ 34,450 Credit carryforwards 10,472 6,562 Stock-based compensation 2,953 1,945 Landlord allowance on leasehold improvements — 1,908 Lease liability 17,965 — Intangible Assets 62 — Deferred rent — 873 Accruals and reserves 1,185 1,074 68,614 46,812 Valuation Allowance (62 ) — 68,552 46,812 Deferred tax liabilities: Prepaid expenses (1,523 ) (931 ) Deferred commissions (5,100 ) (3,187 ) Right of use assets (15,270 ) — Unbilled revenue — (227 ) Fixed assets (4,230 ) (3,581 ) (26,123 ) (7,926 ) Net deferred tax assets $ 42,429 $ 38,886 The Company uses the asset and liability method to account for income taxes in accordance with ASC 740, Income Taxes. Under this method, deferred income taxes are recognized for the future tax consequences of differences between the tax and financial accounting bases of assets and liabilities at each reporting period. Deferred income taxes are based on enacted tax laws and statutory tax rates applicable to the period in which these differences are expected to affect taxable income. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company has provided an immaterial valuation allowance against its net deferred tax assets at December 31, 2019, but did not provided a valuation allowance against its net deferred tax assets at December 31, 2018. Based upon the level of historical U.S. earnings and future projections over the period in which the net deferred tax assets are deductible, at this time, management believes it is more likely than not that the Company will realize the benefits of these deductible differences, with the exception of the deferred tax asset related to intangible assets in Ireland. The change in the valuation allowance for the year ended December 31, 2019 was $62. As of December 31, 2019, the Company has federal and state net operating loss carryforwards of $136,771 and $114,459, respectively. The federal net operating losses carryforward indefinitely, subject to an annual limitation of 80% of taxable income. The state net operating losses, excluding Florida and Georgia which carryforward indefinitely, expire at various dates beginning in 2028. As of December 31, 2019, the Company has federal and state tax credit carryforwards of $6,507 and $5,018, respectively, available to reduce future tax liabilities that expire at various dates through 2039. Utilization of the net operating losses and tax credit carryforwards, respectively, may be subject to an annual limitation due to ownership change limitations that have occurred previously or that could occur in the future, as provided by Section 382 of the Code, or Section 382, as well as similar state provisions. Ownership changes may limit the amount of net operating losses or tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. In general, an ownership change, as defined by Section 382, results from transactions that increase the ownership of five percent stockholders in the stock of a corporation by more than 50% in the aggregate over a three-year At December 31, 2019 and 2018, the Company had no recorded liabilities for uncertain tax positions and had no accrued interest or penalties related to uncertain tax positions. The Company permanently reinvests the earnings, if any, of its foreign subsidiaries and, therefore, does not provide for U.S. income taxes that could result from the distribution of those earnings to the U.S . parent. As of December 31, 2019, the amount of unrecognized deferred U.S. taxes on these earnings would be immaterial . The Company and its subsidiaries are subject to various U.S. federal, state, and foreign income taxes. The Company is currently not subject to examination under the statute of limitations by the Internal Revenue Service and state jurisdictions for the tax years of 2015 and prior. The Company is currently open to examination in its foreign jurisdictions for tax years 2017 and after. In 2018, the Internal Revenue Service commenced a federal income tax audit with respect to the Company’s 2016 tax year, which was concluded in October 2019 for an immaterial amount. In 2019, the Internal Revenue Service commenced a federal employment tax audit with respect to the 2018, 2017 and 2016 calendar years, which is still open.

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment and Geographic Information	13. Segment and Geographic Information The Company has two reportable segments, United States and International. Segment information is presented in the same manner as the Company’s chief operating decision maker, or CODM, reviews the Company’s operating results in assessing performance and allocating resources. The CODM reviews revenue and operating income (loss) for each reportable segment as a proxy for the operating performance of the Company’s United States and International operations. The Company’s Chief Executive Officer is the CODM on behalf of both reportable segments. The United States segment derives revenues from marketplace subscriptions, advertising services, and other revenues from customers within the United States. The International segment derives revenues from marketplace subscriptions, advertising services, and other revenues from customers outside of the United States. A majority of the Company’s operational overhead expenses, including technology and personnel costs, and other general and administrative costs associated with running the Company’s business, are incurred in the United States and not allocated to the International segment. Assets and costs discretely incurred by reportable segments, including depreciation and amortization, are included in the calculation of reportable segment income (loss) from operations. Segment operating income (loss) does not reflect the transfer pricing adjustments related to the Company’s foreign subsidiaries, which are recorded for statutory reporting purposes. Asset information is assessed and reviewed on a global basis. Information regarding the Company’s operations by segment and geographical area is presented as follows: Year Ended December 31, 2019 2018 2017 Segment revenue: United States $ 555,007 $ 437,166 $ 307,472 International 33,909 16,920 9,389 Total revenue $ 588,916 $ 454,086 $ 316,861 Year Ended December 31, 2019 2018 2017 Segment income (loss) from operations: United States $ 73,872 $ 58,387 $ 41,586 International (39,550 ) (35,196 ) (26,312 ) Total income from operations $ 34,322 $ 23,191 $ 15,274 As of December 31, 2019 , total assets held outside of the United States were $32,528, primarily attributable to $15,207 of goodwill and $3,920 of intangible assets. As of December 31, 2018, total assets held outside the United States were not material.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	14. Employee Benefit Plans The Company maintains a defined contribution savings plan for all eligible U.S. employees under Section 401(k) of the Code. Effective July 1, 2017, the Company implemented a matching policy, under which the Company matches 50% of an employee’s annual contributions to the 401(k) plan, up to a maximum of the lesser of (i) 6% of the employee’s base salary, bonus and commissions paid during the year or (ii) $5,000. Matching contributions are subject to vesting based on the employee’s start date and length of service. Employees can designate the investment of their 401(k) accounts into several mutual funds. The Company does not allow investment in its common stock through the 401(k) plan. During the year ended December 31, 2017, the Company began matching employee 401(k) contributions up to a set limit. Total employer contributions were $2,708, $1,953, and $724 during the years ended December 31, 2019, 2018 and 2017, respectively.

Quarterly Financial Results (Un

Quarterly Financial Results (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Quarterly Financial Results (unaudited)	15. Quarterly Financial Results (unaudited) The following table presents certain unaudited quarterly financial information for the eight quarters in the period ended December 31, 2019. This information has been prepared on the same basis as the audited financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein. Fourth Quarter Third Quarter Second Quarter First Quarter Year ended December 31, 2019 Revenue $ 158,153 $ 150,462 $ 145,031 $ 135,270 Cost of revenue 10,560 9,392 8,628 7,720 Gross profit 147,593 141,070 136,403 127,550 Income from operations 13,635 9,704 3,548 7,435 Net income 13,171 10,384 6,007 12,584 Basic net income per share (1) $ 0.12 $ 0.09 $ 0.05 $ 0.11 Diluted net income per share (1) $ 0.12 $ 0.09 $ 0.05 $ 0.11 Year Ended December 31, 2018 Revenue $ 126,090 $ 119,125 $ 110,296 $ 98,575 Cost of revenue 6,871 6,412 5,959 5,569 Gross profit 119,219 112,713 104,337 93,006 Income from operations 6,902 5,877 3,953 6,459 Net income 12,450 13,882 33,343 5,495 Basic net income per share (1) $ 0.11 $ 0.13 $ 0.31 $ 0.05 Diluted net income per share (1) $ 0.11 $ 0.12 $ 0.29 $ 0.05 (1) The amounts were computed independently for each quarter, and the sum of the quarters may not total the annual amounts.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events On January 16, 2020, the Company acquired Autolist, an automotive shopping platform based in San Francisco, California, pursuant to an Agreement and Plan of Merger by and among the Company, Alpine Merger Sub, Inc., a Delaware corporation and wholly-owned subsidiary of the Company (“Merger Sub”), Auto List, Inc., a Delaware corporation (“Target”), and the stockholder representative(s) named therein, pursuant to which, among other things, the Company acquired Target through the merger of Merger Sub with and into Target (the “Merger”), with Target surviving as a wholly owned subsidiary of the Company. The Company paid an aggregate of approximately $22.0 million to consummate the Merger, inclusive of $2.2 million that is held in escrow to secure post-closing claims. The Merger is intended to both expand the Company’s consumer audience in the United States and enhance its value proposition for subscribing dealers. During the year ended December 31, 2019, the Company incurred total acquisition-related costs of $0.4 million related to the transaction. As the transaction occurred subsequent to period-end, the Company is still evaluating the purchase price allocation of the transaction but expects the primary assets acquired to be intangible assets and goodwill. Acquired tangible assets and assumed liabilities are expected to be immaterial. The allocation is expected to be finalized during the first half of 2020.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Due to the adoption of ASC T opic 606, Revenue from Contracts with Customers (“ASC 606”) , which is discussed further in this Note 2, the consolidated balance sheets and the consolidated statements of operations, comprehensive income, c onvertible p referred s tock and s tockholders’ e quity ( d eficit) , and cash flows for the years ended December 31, 2019 and 2018 are not comparative to prior years. Due to the adoption of ASC Topic 842, Leases
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Subsequent Event Considerations	Subsequent Event Considerations The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure. Subsequent events have been evaluated as required. The Company has evaluated all subsequent events and determined that there are no material recognized or unrecognized subsequent events requiring disclosure, other than those disclosed in Note 16 of these consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. Significant estimates relied upon in preparing these consolidated financial statements include revenue recognition and sales allowances, variable consideration, the valuation of goodwill and intangible assets, the expensing and capitalization of product, technology, and development costs for website development and internal‑use software, and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Although the Company regularly assesses these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period in which they become known. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results may differ from management’s estimates if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made.
Revenue Recognition	Revenue Recognition The Company derives its revenue from two primary sources: (1) marketplace subscription revenue, which consists primarily of Listings, and Dealer Display subscriptions, and (2) advertising and other revenue, which consists primarily of display advertising revenue from auto manufacturers and other auto‑related brand advertisers as well as partnerships with financing services companies. Marketplace Subscription Revenue The Company offers multiple types of marketplace Listings packages to its dealers through its platform: Restricted Listings (formerly referred to as Basic Listings), which is free; and various levels of Listings packages, which each require a paid subscription under a monthly, quarterly, semiannual, or annual subscription basis. Contractual subscriptions for customers generally auto-renew on a monthly basis and are cancellable by dealers with 30 days’ advance notice at the end of the committed term. The Company also offers all dealers on the its platform access to a Dealer Dashboard, which includes a performance summary, Dealer Insights tool, and user review management platform. Dealers subscribing to a paid Listings package also have access to the Pricing Tool and Market Analysis tool. The Pricing Tool and Market Analysis tool are available only to paying dealers. Subscription pricing is determined based on a dealer’s inventory size, region, and the Company’s assessment of the connections and Return on Investment (“ROI”) the platform will provide them. Customers do not have the right to take possession of the Company’s software. In addition to listing inventory in the Company’s marketplace and providing access to the Dealer Dashboard, the Company offers dealers subscribing to one of its Enhanced, Featured, or Featured Priority Listings packages other subscription advertising and customer acquisition products, including Dealer Display, pursuant to which dealers can buy display advertising that appears in the Company’s marketplace, and on other sites on the internet, and for which such advertisements can be targeted by the user’s geography, search history, CarGurus website activity (including showing users relevant vehicles from a dealer’s inventory that they have not yet discovered on the Company’s marketplace), and a number of other targeting factors, allowing dealers to increase their visibility with in-market consumers and drive qualified traffic for dealers. Payment is typically due on first day of each calendar month and is recorded as accounts receivable or short-term deferred revenue when payment is received in advance of services being delivered to the customers. Advertising and Other Revenue Advertising and other revenue consists primarily of non-dealer display advertising revenue from auto manufacturers and other auto-related brand advertisers sold on a cost per thousand impressions (“CPM”) basis. An impression is an advertisement loaded on a web page. In addition to advertising sold on a CPM basis, the Company also has advertising sold on a cost per click basis. Auto manufacturers and other brand advertisers can execute advertising campaigns that are targeted across a wide variety of parameters, including demographic groups, behavioral characteristics, specific auto brands, categories such as Certified Pre-Owned, and segments such as hybrid vehicles. The Company does not provide minimum impression guarantees or other types of minimum guarantees in its contracts with customers. Pricing is primarily based on advertisement size and position on the Company’s websites and mobile applications, and fees are billed monthly in arrears. Unbilled accounts receivables relate to services rendered in the current period, but generally not invoiced until the subsequent period. The Company sells advertising directly to auto manufacturers and other auto related brand advertisers, as well as indirectly through revenue sharing arrangements with advertising exchange partners. Company-sold advertising is not subject to revenue sharing arrangements. Company-sold advertising revenue is recognized based on the gross amount charged to the advertiser. Partner-sold advertising revenue is recognized based on the net amount of revenue received from the content partners. Revenue from advertising sold directly by the Company is recorded on a gross basis because the Company is the principal in the arrangement, controls the ad placement and timing of the campaign, and establishes the selling price. The Company enters into contractual arrangements directly with advertisers and is directly responsible for the fulfillment of the contractual terms including any remedy for issues with such fulfillment. Advertising revenue subject to revenue sharing agreements between the Company and advertising exchange partners is recognized based on the net amount of revenue received from the partner. The advertising partner is responsible for fulfillment, including the acceptability of the services delivered. In partner-sold advertising arrangements, the advertising partner has a direct contractual relationship with the advertiser. There is no contractual relationship between the Company and the advertiser for partner-sold transactions. When an advertising exchange partner sells advertisements, the partner is responsible for fulfilling the advertisements, and accordingly, the Company has determined the advertising partner is the principal in the arrangement. Additionally, for auction-based partner agreements, the Company has latitude in establishing the floor price, but the final price established by the exchange server is at market rates. Customers are billed monthly in arrears and payment terms are generally thirty to sixty days from the date invoiced. Advertising and other revenue also includes revenue from partnerships with certain financing services companies pursuant to which the Company enables eligible consumers on the Company’s United States website to pre-qualify for financing on cars from dealerships that offer financing through such companies. The Company’s revenues from these financing partnerships are based on a funded-loan basis. Prior to adoption of ASC 606 The Company recognizes revenue when all of the following conditions are satisfied: (1) there is persuasive evidence of an arrangement; (2) the service has been provided to the customer; (3) the collection of fees is reasonably assured; and (4) the amount of fees to be paid by the customer is fixed or determinable. The Company recognizes marketplace subscription revenue on a monthly basis as revenue is earned and advertising and other revenue as impressions are delivered. Revenue is presented net of any taxes collected from customers. The Company assesses arrangements with multiple deliverables under ASU No. 2009‑13, Revenue Recognition (Topic 605), Multiple‑Deliverable Revenue Arrangements — a Consensus of the FASB Emerging Issues Task Force The Company establishes sales allowances at the time of revenue recognition based on its history of adjustments and credits provided to its customers. Sales allowances relate primarily to credits issued for service interruption. In assessing the adequacy of the sales allowance, the Company evaluates its history of adjustments and credits made through the date of the issuance of the financial statements. Estimated sales adjustments and credits and ultimate losses may vary from actual results which could be material to the financial statements; however, to date, actual sales allowances have been materially consistent with the Company’s estimates. Sales allowances are recorded as a reduction to revenue in the consolidated statements of operations. Following adoption of ASC 606 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue from Contracts with Customers Revenue Recognition ASC 606 outlines a comprehensive five-step revenue recognition model based on the principle that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, the Company applies the following five steps: 1 ) Identify the contract with a customer 2 ) Identify the performance obligations in the contract 3 ) Determine the transaction price 4 ) Allocate the transaction price to performance obligations in the contract 5 ) Recognize revenue when or as the Company satisfies a performance obligation Disaggregation of Revenue The following table summarizes revenue from contracts with customers by revenue source for the years ended December 31, 2019, 2018 and 2017. 2019 2018 2017 Revenue by Revenue Stream Marketplace subscription revenue $ 526,043 $ 405,780 $ 282,664 Advertising and other revenue 62,873 48,306 34,197 Total $ 588,916 $ 454,086 $ 316,861 The Company provides disaggregation of revenue based on the marketplace subscription versus advertising and other revenue classification in the table above and based on geographic region (see Note 13) as it believes these categories best depict how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. Marketplace Subscription Revenue For dealer listings, the Company provides a single similar service each day for a period of time. Each time increment (i.e. day), rather than the underlying activities, is distinct and substantially the same and therefore the performance obligation of the Company is to provide a series of daily activities over the contract term. Similar to the dealer listings, the dealer display advertising is considered a promise to provide a single similar service each day. Each time increment is distinct and substantially the same and therefore the performance obligation of the Company is to provide a series of daily activities over the contract term. Total consideration for marketplace subscription revenue is stated within the contracts. There are no contractual cash refund rights, but credits may be issued to a customer at the sole discretion of the Company. At an individual contract level, there is also no variable consideration, such as sales allowance, that needs to be included in the transaction price. However, at a portfolio level, the Company recognizes that there are times when there is a customer satisfaction issue or other circumstance that will lead to a credit. Due to the known possibility of future credits, a monthly sales allowance review is performed to defer revenue at a portfolio level for such future adjustments in the period of incurrence. The Company establishes sales allowances at the time of revenue recognition based on its history of adjustments and credits provided to its customers. In assessing the adequacy of the sales allowance, the Company evaluates its history of adjustments and credits made through the date of the issuance of the financial statements. Estimated sales adjustments, credits and losses may vary from actual results which could lead to material adjustments to the financial statements. To date, actual sales allowances have been materially consistent with the Company’s estimates. Sales allowances are recorded as a reduction to revenue in the consolidated statements of operations. Performance obligations are satisfied over time as the customer simultaneously receives and consumes the benefit of the service. Revenue is recognized ratably over the subscription period beginning on the date the Company starts providing services to the customer under the contract. Revenue is presented net of any taxes collected from customers. Advertising and Other Revenue For advertising revenue, the performance obligation is to publish the agreed upon campaign on the Company’s websites and load the related impressions. Advertising contracts state the transaction price within the agreement with payment being based on the number of clicks or impressions delivered on the Company’s websites As consideration is driven by the number of impressions delivered on the CarGurus websites, the consideration for each period is allocated to the period in which the service was rendered. Performance obligations for c ompany-sold advertising revenue and p artner-sold advertising revenue are satisfied over time as impressions are delivered . R evenue is recognized based on the total number of impressions delivered within the specified period . Revenue from advertising sold directly by the Company is recognized based on the gross amount charged to the advertiser and advertising revenue sold by partners is recognized based on the net amount of revenue received from the content partners. Revenue is presented net of any taxes collected from customers. Other revenue includes revenue from contracts for which the performance obligation is a series of distinct services with the same level of effort daily. For these contracts, the Company estimates the value of the variable consideration in determining the transaction price and allocates it to the performance obligation. Revenue is estimated and recognized on a ratable basis over the contractual term. The Company reassesses the estimate of variable consideration at each reporting period. Contracts with Multiple Performance Obligations The Company periodically enters into arrangements that include Listings and Dealer Display within marketplace subscription revenue. These contracts include multiple promises that the Company evaluates to determine if the promises are separate performance obligations. Performance obligations are identified based on services to be transferred to a customer that are distinct within the context of the contractual terms. Once the performance obligations have been identified, the Company determines the transaction price, which includes estimating the amount of variable consideration to be included in the transaction price, if any. If required, the transaction price is allocated to each performance obligation in the contract based on a relative standalone selling price (“SSP”) method as the performance obligation is being satisfied. For the Company’s arrangements that include Listings and Dealer Display, the performance obligations were satisfied over a consistent period of time and therefore the allocations did not impact the revenue recognized. Costs to Obtain a Contract Commissions paid to sales representatives and payroll taxes are considered costs to obtain a contract. Under ASC 606, the costs to obtain a contract require capitalization and amortization of those costs over the period of benefit. Although the guidance specifies the accounting for an individual contract with a customer, as a practical expedient, the Company has opted to apply the guidance to a portfolio of contracts with similar characteristics. The Company has opted to apply another practical expedient to immediately expense the incremental cost of obtaining a contract when the underlying related asset would have been amortized over one year or less. As such, the Company applied this practical expedient to advertising contracts as the term is one year or less and these contracts do not renew automatically. The practical expedient is not applicable to marketplace subscription contracts as the period of benefit including renewals is anticipated to be greater than one year as commissions paid on contract renewals are not commensurate with the commissions paid on the initial contract. The assets are periodically assessed for impairment. For marketplace subscription customers, the commissions paid on contracts with new customers, in addition to any commission amount related to incremental sales, are capitalized and amortized over the estimated benefit period of the customer relationship taking into account factors such as peer estimates of technology lives and customer lives as well as the Company's own historical data. Commissions paid that are not directly related to obtaining a new contract are expensed as incurred. Additionally, the Company allocates employer payroll tax expense to the commission expense in proportion to the overall payroll taxes paid during the respective period. As such, capitalized payroll taxes are amortized in the same manner as the underlying capitalized commissions. The assets recognized for costs to obtain a contract were $3,207, $12,505 and $20,058 as of January 1, 2018, December 31, 2018 and December 31, 2019, respectively. Amortization expense recognized during the years ended December 31, 2019 and 2018 related to costs to obtain a contract was $8,416 and $3,689, respectively. Financial Statement Impact of Adopting ASC 606 The cumulative effect of applying the new guidance to all contracts with customers that were not completed as of January 1, 2018 was recorded as an adjustment to accumulated deficit as of the adoption date. As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made on the consolidated balance sheet as of January 1, 2018. As Reported Adjustments As Adjusted December 2017 Marketplace Subscription Revenue Costs to Obtain a Contract January 1, 2018 Assets Current assets: Cash and cash equivalents $ 87,709 $ 87,709 Investments 50,000 50,000 Accounts receivable, net 12,577 813 13,390 Prepaid expenses and prepaid income taxes 5,313 5,313 Deferred contract costs — 1,424 1,424 Other current assets 1,605 1,605 Restricted cash — — Total current assets 157,204 813 1,424 159,441 Property and equipment, net 16,563 16,563 Restricted cash 1,843 1,843 Deferred tax assets 825 (190 ) (635 ) — Deferred contract costs, net of current portion — 1,783 1,783 Other long–term assets 159 159 Total assets $ 176,594 $ 623 $ 2,572 $ 179,789 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 23,908 $ 23,908 Accrued expenses, accrued income taxes and other current liabilities 13,588 13,588 Deferred revenue 4,305 4,305 Deferred tax liabilities — 153 153 Deferred rent 1,165 1,165 Total current liabilities 42,966 — 153 43,119 Deferred rent, net of current portion 5,648 5,648 Other non–current liabilities 955 955 Total liabilities 49,569 — 153 49,722 Commitments and contingencies Stockholders’ equity: Preferred stock — — Class A common stock 78 78 Class B common stock 28 28 Additional paid–in capital 185,190 185,190 Accumulated deficit (58,499 ) 623 2,419 (55,457 ) Accumulated other comprehensive income 228 228 Total stockholders’ equity 127,025 623 2,419 130,067 Total liabilities and stockholders’ equity $ 176,594 $ 623 $ 2,572 $ 179,789 Marketplace Subscription Revenue Under ASC 606, the Company’s accounting for contracts containing discounts resulted in accelerated revenue recognition. The cumulative impact of this change to the Company’s accounts receivable on January 1, 2018 was $813. Costs to Obtain a Contract As described above, under the new guidance, the capitalized commission expense is amortized over the estimated customer relationship period. The net impact of this change resulted in a $3,207 reduction to accumulated deficit for contracts that still require performance by the Company at the date of adoption. Income Taxes The adoption of ASC 606 primarily resulted in an acceleration of revenue and the reduction of expense, which in turn generated additional deferred tax liabilities that ultimately reduced the Company’s net deferred tax asset position. The cumulative impact resulted in a reduction to deferred tax assets of $978 which put the Company in a net deferred tax liability position on January 1, 2018. Impact of New Revenue Guidance on Financial Statement Line Items The following tables compare the reported consolidated balance sheet, statement of operations and cash flows, as of and for the year ended December 31, 2018, to the pro-forma amounts had the previous guidance been in effect. As of December 31, 2018 Balance Sheet As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Assets Current assets: Cash and cash equivalents $ 34,887 $ 34,887 Investments 122,800 122,800 Accounts receivable, net 13,614 939 12,675 Prepaid income taxes and prepaid income taxes 10,144 10,144 Deferred contract costs 5,253 5,253 — Other current assets 7,410 7,410 Restricted cash 750 750 Total current assets 194,858 939 5,253 188,666 Property and equipment, net 24,269 24,269 Restricted cash 1,921 1,921 Deferred tax assets 38,886 (227 ) (3,187 ) 42,300 Deferred contract costs, net of current portion 7,252 7,252 — Other long–term assets 1,104 1,104 Total assets $ 268,290 $ 712 $ 9,318 $ 258,260 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 34,345 $ 34,345 Accrued expenses, accrued income taxes and other current liabilities 18,654 18,654 Deferred revenue 8,811 8,811 Deferred rent 1,693 1,693 Total current liabilities 63,503 — — 63,503 Deferred rent, net of current portion 9,395 9,395 Other non–current liabilities 1,281 1,281 Total liabilities 74,179 — — 74,179 Commitments and contingencies Stockholders’ equity: Preferred stock — — Class A common stock 90 90 Class B common stock 21 21 Additional paid–in capital 184,216 184,216 Retained earnings (accumulated deficit) 9,713 712 9,318 (317 ) Accumulated other comprehensive income 71 71 Total stockholders’ equity 194,111 712 9,318 184,081 Total liabilities and stockholders’ equity $ 268,290 $ 712 $ 9,318 $ 258,260 Total reported assets were $10,030 greater than the pro-forma balance sheet, which assumes the previous guidance remained in effect as of December 31, 2018. This was largely due to the impact of $12,505 related to costs to obtain a contract. There were no changes to liabilities as of December 31, 2018 as a result of the adoption of ASC 606. The following summarizes the significant changes on the Company’s consolidated statement of operations for the year ended December 31, 2018 as a result of the adoption of ASC 606 on January 1, 2018 compared to the pro-forma amounts had the Company continued to recognize revenue under ASC 605. Year Ended December 31, 2018 Statement of Operations As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Revenue $ 454,086 $ 126 $ 453,960 Cost of revenue 24,811 24,811 Gross profit 429,275 126 — 429,149 Operating expenses: Sales and marketing 315,939 (9,298 ) 325,237 Product, technology, and development 47,866 47,866 General and administrative 39,475 39,475 Depreciation and amortization 2,804 2,804 Total operating expenses 406,084 — (9,298 ) 415,382 Income from operations 23,191 126 9,298 13,767 Other income, net: Interest income 2,283 2,283 Other income (expense) 10 10 Total other income, net 2,293 — — 2,293 Income before income taxes 25,484 126 9,298 16,060 Provision for (Benefit from) income taxes (39,686 ) 37 2,399 (42,122 ) Net income $ 65,170 $ 89 $ 6,899 $ 58,182 Basic $ 0.60 $ — $ 0.07 $ 0.53 Diluted $ 0.57 $ — $ 0.06 $ 0.51 The adoption of ASC 606 resulted in an increase to revenue of $126 during the year ended December 31, 2018 due to accelerated revenue recognition for contracts containing discounts. The adoption of ASC 606 also resulted in a $9,298 reduction in sales and marketing expense during the year ended December 31, 2018 as a result of capitalizing a portion of commission expense, which was previously expensed under the previous guidance. During the year ended December 31, 2018, the cumulative impact of these changes was a $9,424 increase in income from operations which resulted in a $2,436 reduction to the benefit from income taxes. Additionally, the adoption of ASC 606 resulted in the Company’s basic and diluted EPS for the year ended December 31, 2018 increasing $0.07 and $0.06, respectively. The following summarizes the significant changes on the Company’s consolidated statement of cash flows for the year ended December 31, 2018 as a result of the adoption of ASC 606 on January 1, 2018 compared to the pro-forma amounts had the Company continued to recognize revenue under ASC 605. Year Ended December 31, 2018 Statement of Cash Flows As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Operating Activities Net income $ 65,170 $ 89 $ 6,899 $ 58,182 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 5,029 5,029 Currency (gain) loss on foreign denominated transactions (190 ) (190 ) Deferred taxes (39,040 ) 37 2,399 (41,476 ) Provision for doubtful accounts 1,680 1,680 Stock–based compensation expense 20,794 20,794 Amortization of deferred contract costs 3,689 3,689 — Changes in operating assets and liabilities: Accounts receivable, net (1,911 ) (126 ) (1,785 ) Prepaid expenses, prepaid income taxes, and other assets (11,753 ) (11,753 ) Deferred contracts costs (12,987 ) (12,987 ) — Accounts payable 9,345 9,345 Accrued expenses, accrued income taxes and other current liabilities 2,695 2,695 Deferred revenue 4,508 4,508 Deferred rent 4,289 4,289 Other non–current liabilities 405 405 Net cash provided by operating activities $ 51,723 $ — $ — $ 51,723 The adoption of ASC 606 had no impact on the Company’s cash flows from operations. The aforementioned impacts resulted in offsetting shifts in cash flows between net income and various working capital balances. Contract Balances The following tables summarize the opening and closing balances of receivables and contract assets from contracts with customers as of January 1, 2018, December 31, 2018 and December 31, 2019. Accounts Receivable, net Contract Assets (current) Contract Assets (non-current) Balance at January 1, 2018 $ 13,390 $ 1,424 $ 1,782 Balance at December 31, 2018 13,614 5,253 7,252 Balance at December 31, 2019 22,124 9,544 10,514 Revenue recognized during the year ended December 31, 2019 and 2018 from amounts included in deferred revenue at the beginning of the period was approximately $8,811 and $4,305, respectively. Transaction Price Allocated to Future Performance Obligations Topic 606 requires that the Company disclose the aggregate amount of transaction price that is allocated to performance obligations that have not yet been satisfied as of December 31, 2019. For contracts with an original expected duration greater than one year, the aggregate amount of the transaction price allocated to the performance obligations that were unsatisfied as of December 31, 2019 is approximately $35.0 million, which the Company expects to recognize over the next twelve months. For contracts with an original expected duration of one year or less, the Company has applied the practical expedient available under Topic 606 to not disclose the amount of transaction price allocated to unsatisfied performance obligations as of December 31, 2019. For performance obligations not satisfied as of December 31, 2019, and to which this expedient applies, the nature of the performance obligations, the variable consideration and any consideration from contracts with customers not included in the transaction price is consistent with performance obligations satisfied as of December 31, 2019. The remaining duration is less than one year. From time to time, the Company may enter into contracts that include variable consideration, for which the Company estimates the value of the variable consideration in determining the transaction price and allocates it to the appropriate performance obligation(s). The Company reassesses any estimates of variable consideration at each reporting period.
Deferred Revenue	Deferred Revenue Deferred revenue primarily consists of payments received in advance of revenue recognition from the Company’s marketplace revenue and is recognized as the revenue recognition criteria are met. The Company generally invoices its customers monthly. Accordingly, the deferred revenue balances do not represent the total contract value of annual or multiyear subscription agreements. Deferred revenue that is expected to be recognized during the succeeding 12‑month period is recorded as current deferred revenue and the remaining portion is recorded as noncurrent in the consolidated balance sheets. All deferred revenue was recorded as current for all periods presented.
Cost of Revenue	Cost of Revenue Cost of revenue primarily consists of costs related to supporting and hosting the Company’s product offerings. These costs include salaries, benefits, incentive compensation and stock‑based compensation for the Company’s customer support team, and third‑party service provider costs such as data center and networking expenses, allocated overhead costs, depreciation and amortization expense associated with the Company’s property and equipment, and amortization of capitalized website development costs.
Concentration of Credit Risk	Concentration of Credit Risk The Company has no significant off‑balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents, investments, and trade accounts receivable. The Company maintains its cash, cash equivalents, and investments principally with accredited financial institutions of high credit standing. Although the Company deposits its cash and investments with multiple financial institutions, its deposits, at times, may exceed governmental insured limits. Credit risk with respect to accounts receivable is dispersed due to the large number of customers. The Company routinely assesses the creditworthiness of its customers. The Company generally has not experienced any material losses related to receivables from individual customers, or groups of customers. The Company does not require collateral. Due to these factors, no additional credit risk beyond amounts provided for collection losses is believed by management to be probable in the Company’s accounts receivable. For the years ended December 31, 2019, 2018 and 2017, no individual customer accounted for more than 10% of total revenue. As of December 31, 2019, one customer accounted for 18% of net accounts receivable. As of December 31, 2018, two customers accounted for 21% and 14% of net accounts receivable, respectively. No other individual customer accounted for more than 10% of net accounts receivable at December 31, 2019 or 2018. Included in net accounts receivable at December 31, 2019 and 2018, is $8,880 and $5,814 of unbilled accounts receivables related to advertising customers billed within a quarter subsequent to services rendered.
Cash, Cash Equivalents, and Investments	Cash, Cash Equivalents, and Investments The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Investments not classified as cash equivalents with maturities less than one year from the balance sheet date are classified as short‑term investments, while investments with maturities in excess of one year from the balance sheet date are classified as long‑term investments. Management determines the appropriate classification of investments at the time of purchase, and re‑evaluates such determination at each balance sheet date. Cash and cash equivalents primarily consist of cash on deposit with banks, and amounts held in interest‑bearing money market accounts. Cash equivalents are carried at cost, which approximates their fair market value. The Company’s investment policy, which was approved by the Audit Committee of the Company’s board of directors (the “Board”), permits investments in fixed income securities, including U.S. government and agency securities, non‑U.S. government securities, money market instruments, commercial paper, certificates of deposit, corporate bonds, and asset‑backed securities. As of December 31, 2019 and 2018, investments consisted of U.S. certificates of deposit (“CDs”) with remaining maturities of less than twelve months. The Company classifies CDs with readily determinable market values as held‑to‑maturity, because it is the Company’s intention to hold such investments until they mature. As such, investments were recorded at amortized cost at December 31, 2019 and 2018. The Company adjusts the cost of investments for amortization of premiums and accretion of discounts to maturity, if any. For the years ended December 31, 2019, 2018 and 2017, the Company did not have any premiums or discounts. Realized gains and losses from sales of the Company’s investments are included in other income (expense), net. There were no realized gains or losses on investments for the years ended December 31, 2019, 2018 or 2017. The Company reviews investments for other‑than‑temporary impairment whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. Other‑than‑temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the investment, or if it is more likely than not that the Company will be required to sell the investment before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and duration of the impairment, and changes in value subsequent to the end of the period. As of December 31, 2019 and 2018, the Company determined that no other‑than‑temporary impairments were required to be recognized in the consolidated statements of operations.
Restricted Cash	Restricted Cash At December 31, 2019 and 2018, restricted cash was $10,803 and $2,671, respectively, and primarily related to cash held at a financial institution in an interest‑bearing cash account as collateral for four letters of credit in 2019 and three letters of credit in 2018 related to the contractual provisions for the Company’s building leases.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded based on the amount due from the customer and do not generally bear interest. The Company offsets gross trade accounts receivable with an allowance for doubtful accounts. The allowance for doubtful accounts is the Company’s best estimate of the amount of probable credit losses in the Company’s existing accounts receivable and is based upon historical loss patterns, the number of days that billings are past due, and an evaluation of the potential risk of loss associated with specific accounts. Account balances are charged against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. The Company does not have any off‑balance sheet credit exposure related to its customers. Provisions for allowances for doubtful accounts are recorded in general and administrative expense. Unbilled accounts receivables are recorded for services rendered in the current period, but generally not invoiced until the subsequent period. The Company considers current economic trends when evaluating the adequacy of the allowance for doubtful accounts. If circumstances relating to specific customers change, or unanticipated changes occur in the general business environment, particularly as it affects auto dealers, the Company’s estimates of the recoverability of receivables could be further adjusted. Below is a summary of the changes in the Company’s allowance for doubtful accounts for the years ended December 31, 2019, 2018, and 2017: Balance at Beginning of Period Provision Write – net of recoveries Balance at End of Period Year ended December 31, 2019 $ 479 $ 1,091 $ (1,330 ) $ 240 Year ended December 31, 2018 494 1,680 (1,695 ) 479 Year ended December 31, 2017 164 1,117 (787 ) 494
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization using the straight‑line method over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. The estimated useful lives of the Company’s property and equipment are as follows: Estimated Useful Life (In Years) Capitalized equipment 3 Capitalized software 3 Capitalized website development 3 Furniture and fixtures 5 Leasehold improvements Lesser of asset life or lease term Expenditures for repairs and maintenance are charged to expense as incurred, whereas major betterments are capitalized as additions to property and equipment.
Impairment of Long-Lived Assets	Impairment of Long‑Lived Assets The Company evaluates the recoverability of long‑lived assets, such as property and equipment and intangible assets, for impairment at least annually and whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. During this review, the Company re‑evaluates the significant assumptions used in determining the original cost and estimated lives of long‑lived assets. Although the assumptions may vary from asset to asset, they generally include operating results, changes in the use of the asset, cash flows, and other indicators of value. Management then determines whether the remaining useful life continues to be appropriate, or whether there has been an impairment of long‑lived assets based primarily upon whether expected future undiscounted cash flows are sufficient to support the assets’ recovery. Recoverability of these assets is measured by comparison of the carrying amount of the asset to the future undiscounted cash flows the asset is expected to generate. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. For the years ended December 31, 2019, 2018, and 2017, the Company did not identify any impairment of its long‑lived assets.
Business Combinations	Business Combinations Valuation of Acquired Assets and Liabilities The Company measures all consideration transferred in a business combination at its acquisition-date fair value. Consideration transferred is determined by the acquisition-date fair value of assets transferred, liabilities assumed, including contingent consideration obligations, as applicable. The Company measures goodwill as the excess of the consideration transferred over the net of the acquisition-date amounts of assets acquired less liabilities assumed. The Company makes significant assumptions and estimates in determining the fair value of the acquired assets and liabilities as of the acquisition date, especially the valuation of intangible assets and certain tax positions. The Company records estimates as of the acquisition date and reassess the estimates at each reporting period up to one year after the acquisition date. Changes in estimates made prior to finalization of purchase accounting are recorded to goodwill.
Intangible Assets	Intangible Assets Intangible assets are recorded at their estimated fair value at the date of acquisition. The Company amortizes intangible assets over their estimated useful lives on a straight-line basis. Amortization is recorded over the relevant estimated useful lives ranging from three to eleven years. The Company evaluates the useful lives of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. If the estimate of an intangible asset’s remaining useful life is changed, the Company amortizes the remaining carrying value of the intangible asset prospectively over the revised remaining useful life.
Goodwill	Goodwill Goodwill is recorded when consideration paid in a purchase acquisition exceeds the fair value of the net assets acquired. Goodwill is not amortized, but rather is tested for impairment annually or more frequently if facts and circumstances warrant a review. Conditions that could trigger a more frequent impairment assessment include, but are not limited to, a significant adverse change in certain agreements, significant underperformance relative to historical or projected future operating results, an economic downturn affecting automotive marketplaces, increased competition, a significant reduction in our stock price for a sustained period or a reduction of our market capitalization relative to net book value. The Company has determined that it had two reporting units, United States and International, as of and for the year ended December 31, 2019. The Company evaluates impairment annually on October 1 by comparing the estimated fair value of each reporting unit to its carrying value. The Company estimates fair value using a discounted cash flow model based on our most recent forecast at the time of its annual impairment test.
Capitalized Website Development and Internal-Use Software Costs	Capitalized Website Development and Internal-Use Software Costs The Company capitalizes certain costs associated with the development of its websites and internal‑use software products after the preliminary project stage is complete and until the software is ready for its intended use. Research and development costs incurred during the preliminary project stage or costs incurred for data conversion activities, training, maintenance, and general and administrative or overhead costs are expensed as incurred. Capitalization begins when the preliminary project stage is complete, management authorizes and commits to the funding of the software project with the required authority, it is probable the project will be completed, the software will be used to perform the functions intended and certain functional and quality standards have been met. Qualified costs incurred during the operating stage of our software applications relating to upgrades and enhancements are capitalized to the extent it is probable that they will result in added functionality, while costs that cannot be separated between maintenance of, and minor upgrades and enhancements to, internal‑use software are expensed as incurred. Capitalized website and software development costs are amortized on a straight‑line basis over their estimated useful life of three years beginning with the time when it is ready for intended use. Capitalized internal-use software costs are amortized on a straight‑line basis over their estimated useful life of the term of the hosting arrangement, taking into consideration several other factors such as, but not limited to, options to extend the hosting arrangement or options to terminate the hosting arrangement, beginning with the time when it is ready for intended use. Amounts amortized are presented through operating expense, rather than depreciation or amortization. Management evaluates the useful lives of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. During the years ended December 31, 2019 and 2018, the Company capitalized $4,176 and $2,012 of website development costs, respectively. The Company recorded amortization expense associated with its capitalized website development costs of $1,643, $1,508 and $812 for the years ended December 31, 2019, 2018, and 2017, respectively. During the year ended December 31, 2019, the Company capitalized $2,615 and $616 of internal-use software in other non-current assets and in prepaid expenses and prepaid income taxes, respectively. The Company recorded amortization expense associated with its internal-use software of $132 for the year ended December 31, 2019.
Foreign Currency Translation	Foreign Currency Translation The reporting currency of the Company is the U.S. dollar. The functional currency of the Company’s foreign subsidiaries is the local currency of each subsidiary. All assets and liabilities in the balance sheets of entities whose functional currency is a currency other than the U.S. dollar are translated into U.S. dollar equivalents at exchange rates as follows: (1) asset and liability accounts at period‑end rates; (2) income statement accounts at weighted‑average exchange rates for the period; and (3) stockholders’ equity accounts at historical exchange rates. The resulting translation adjustments are excluded from net income and reflected as a separate component of stockholders’ equity (deficit). Foreign currency transaction gains and losses are included in net income for the period. The Company may periodically have certain intercompany foreign currency transactions that are deemed to be of a long‑term investment nature; exchange adjustments related to those transactions are made directly to a separate component of stockholders’ equity (deficit).
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with the asset and liability method. Under this method, deferred tax assets and liabilities are recognized based on temporary differences between the financial reporting and income tax bases of assets and liabilities using statutory rates. In addition, this method requires a valuation allowance against net deferred tax assets if, based upon the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions recognized in the consolidated financial statements by prescribing a more‑likely‑than‑not threshold for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Interest and penalties, if applicable, related to uncertain tax positions would be recognized as a component of income tax expense. The Company has no recorded liabilities for uncertain tax positions as of December 31, 2019 and 2018. The Tax Cuts and Jobs Act subjects a U.S. shareholder to tax on global intangible low-taxed income (“GILTI”) earned by certain foreign subsidiaries. An entity can make an accounting policy election, per the FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, either to recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. The Company has elected to account for GILTI as a period cost in the year the tax is incurred. The Company uses the asset and liability method to account for income taxes in accordance with ASC 740, Income Taxes. Under this method, deferred income taxes are recognized for the future tax consequences of differences between the tax and financial accounting bases of assets and liabilities at each reporting period. Deferred income taxes are based on enacted tax laws and statutory tax rates applicable to the period in which these differences are expected to affect taxable income. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized.
Disclosure of Fair Value of Financial Instruments	Disclosure of Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, which include cash and cash equivalents, investments, accounts receivable, accounts payable, and accrued expenses, approximated their fair values at December 31, 2019 and 2018 due to the short‑term nature of these instruments. The Company has evaluated the estimated fair value of financial instruments using available market information. The use of different market assumptions, estimation methodologies, or both, could have a significant effect on the estimated fair value amounts. See Note 4 for further discussion. ASC 820, Fair Value Measurements and Disclosures ASC 820 identifies fair value as the exchange price, or exit price, representing the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants based on the highest and best use of the asset or liability. As such, fair value is a market‑based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The Company uses valuation techniques to measure fair value that maximize the use of observable inputs and minimize the use of unobservable inputs. These inputs are prioritized as follows: Level 1 — Quoted unadjusted prices for identical instruments in active markets. Level 2 — Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model‑derived valuations in which all observable inputs and significant value drivers are observable in active markets. Level 3 — Model‑derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company. The Company measures eligible assets and liabilities at fair value with changes in value recognized in earnings. There were no liabilities that were measured at fair value as of December 31, 2019 and 2018. Fair value treatment may be elected either upon initial recognition of an eligible asset or liability or, for an existing asset or liability, if an event triggers a new basis of accounting. The Company did not elect to remeasure any of its existing financial assets and did not elect the fair value option for any financial assets transacted during the year ended December 31, 2019 or the year ended December 31, 2018.
Stock-Based Compensation	Stock‑Based Compensation For stock‑based awards issued under the Company’s stock‑based compensation plans, which are more fully described in Note 10, the fair value of each award is determined on the date of grant. The Company recognizes compensation expense for service-based awards on a straight-line basis over the requisite service period for each separate vesting portion of the award, with the amount of compensation expense recognized at any date at least equaling the portion of the grant-date fair value of the award that is vested at that date. Certain awards granted by the Company prior to the IPO were subject to service‑based vesting conditions and a performance‑based vesting condition achieved upon a liquidity event, defined as either a change of control or an initial public offering. The Securities and Exchange Commission’s declaration of effectiveness of the Company’s registration statement on Form S-1 on October 11, 2017 satisfied the liquidity event performance condition. Upon the achievement of the liquidity event, the Company recorded previously unrecognized cumulative stock-based compensation expense of $ 2.5 million related to these awards. Although the performance - based vesting condition was satisfied, under the terms of the awards, the settlement of such vested RSUs and the issuance of common stock with respect to such vested RSUs occurred on Apr il 10, 2018, one hundred eighty- one days after the satisfaction of the performance condition. Given the absence of an active market for the Company’s common stock prior to the IPO, the Board was required to estimate the fair value of the Company’s common stock at the time of each grant of a stock‑based award. The Company believes that the members of its Board at all relevant times had sufficient business, finance or venture capital experience to make such estimates. The Company and the Board utilized various valuation methodologies in accordance with the framework of the American Institute of Certified Public Accountants’ Technical Practice Aid, Valuation of Privately‑Held Company Equity Securities Issued as Compensation The Company believes this methodology was reasonable based upon the Company’s internal peer company analyses, and further supported by arm’s‑length transactions involving the Company’s convertible preferred stock. As the Company’s common stock was not actively traded, the determination of fair value involved assumptions, judgments, and estimates. If different assumptions had been made, stock‑based compensation expense, consolidated net income, and consolidated net income per share could have been significantly different. For RSUs issued under the Company’s stock‑based compensation plans prior to the IPO, the fair value of each grant was calculated based on the estimated fair value of the Company’s common stock on the date of grant. The Company estimated the fair value of most stock option awards on the date of grant using the Black‑Scholes option‑pricing model. For RSUs granted subsequent to the IPO, the fair value is determined based on the closing price of the Company’s Class A common stock as reported on the Nasdaq Global Select Market on the date of grant. The Company issues shares for stock option exercises and RSUs out of its shares available for issuance. No options were granted during the years ended December 31, 2019, 2018, and 2017. The Company accounts for forfeitures when they occur. The tax effect of differences between tax deductions related to stock compensation and the corresponding financial statement expense compensation are recorded to tax expense. Excess tax benefits recognized on stock‑based compensation expense are classified as an operating activity in the consolidated statements of cash flows. During 2019, 2018 and 2017, the Company recorded tax benefits of $11,115, $40,765 and $681, respectively, related to differences between tax deductions related to stock compensation and the corresponding financial statement expense compensation. See Note 10 for a summary of the stock option and RSU activity for the year ended December 31, 2019. Stock-Based Compensation In June 2018, the FASB issued ASU 2018-07 , Compensation—Stock Compensation (Topic 718) Compensation—Stock Compensation a contract accounted for under Topic 606. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. For all other entities, the amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. The Company has assessed the impact of this guidance on its consolidated financial statements and does not deem it to be material. The Company adopted the guidance on January 1, 2019 prospectively .
Advertising Costs	Advertising Costs Advertising costs are expensed as incurred. Advertising expense, which is included within sales and marketing expense in the consolidated statements of operations, was $287,107, $238,640, and $173,186 for the years ended December 31, 2019, 2018, and 2017, respectively.
Comprehensive Income	Comprehensive Income Comprehensive income is defined as the change in stockholders’ equity (deficit) of a business enterprise during a period from transactions and other events and circumstances from non‑owner sources. Comprehensive income consists of net income and other comprehensive (loss) income, which includes certain changes in equity that are excluded from net income. Specifically, cumulative foreign currency translation adjustments are included in accumulated other comprehensive (loss) income. As of December 31, 2019 and 2018 accumulated other comprehensive (loss) income is presented separately on the consolidated balance sheets and consists entirely of cumulative foreign currency translation adjustments.
Contingent Liabilities	Contingent Liabilities The Company has certain contingent liabilities that arise in the ordinary course of business activities. The Company accrues for loss contingencies when losses become probable and are reasonably estimable. If the reasonable estimate of the loss is a range and no amount within the range is a better estimate, the minimum amount of the range is recorded as a liability. The Company does not accrue for contingent losses that, in its judgment, are considered to be reasonably possible, but not probable; however, it discloses the range of such reasonably possible losses.
Recent Adopted Accounting Pronouncements	Recent Adopted Accounting Pronouncements Lease Accounting In February 2016, the FASB issued ASC 842, which requires a lessee to recognize most leases on the consolidated balance sheet but recognize expenses on the consolidated income statement in a manner similar to current practice. The update states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying assets for the lease term. The Company adopted ASC 842 as of January 1, 2019, using the additional transition method offered through ASU No. 2018-11. This approach provides a method for recording existing leases at the adoption date and recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Lease Overview The Company’s operating lease obligations consist of various leases for office space in: Boston, Massachusetts; Cambridge, Massachusetts; Detroit, Michigan; Los Angeles, California; Dublin, Ireland; and London, United Kingdom. The Detroit, Los Angeles and London leases are immaterial to the Company. The Company also has an operating lease obligation for data center space in Needham, Massachusetts. On December 19, 2019, the Company entered into an operating lease for the lease of 273,595 square feet of office space in Boston, Massachusetts at 1001 Boylston Street. The lease provides for leasehold improvement incentives and provides for annual rent increases through the term of the lease. The “Commencement Date” of the lease term is the earlier to occur of (i) the date that is twelve months following the Delivery Date (as defined in the lease) and (ii) the date that the Company first occupies the premises for the normal conduct of business for the Permitted Use (as defined in the lease). The initial term will commence on the Commencement Date and expire on the date that is one hundred and eighty full calendar months after the Commencement Date (plus the partial month, if any, immediately following the Commencement Date). On August 30, 2019, the Company amended its operating lease agreement in Cambridge, Massachusetts at 55 Cambridge Parkway, which was originally entered into on March 11, 2016 and subsequently amended on July 30, 2016, for the lease of 51,923 square feet of office space. The 2019 amendment granted the Company an additional 36,689 square feet of office space and extended the non-cancellable lease term through 2025 for the office space currently occupied. The Company accounted for the additional 36,689 square feet of office space as a new lease as it provides an additional right-of-use asset that is not included in the original lease and the additional lease payments were determined to be commensurate with the standalone price of the additional space. The non-cancellable lease term of the additional space ends in 2025, with a portion ending in 2023. The term extension of the existing 51,923 square feet of office space was recorded as a lease modification within the consolidated balance sheet as of December 31, 2019. The lease, as amended, provides for (i) an option to extend the lease term with respect to a portion of the office space for an additional period of five years, (ii) leasehold improvement incentives and (iii) annual rent increases through the term of the lease. On May 1, 2019, the Company entered into an operating lease in Needham, Massachusetts for the lease of data center space with a non-cancellable term through 2022 with automatic renewal for one year thereafter if not terminated. The lease provides for annual rent increases through the term of the lease. On June 19, 2018, the Company entered into an operating lease in Cambridge, Massachusetts at 121 First Street for the lease of 48,393 square feet of office space with a non-cancellable lease term through 2033 with an option to extend the lease term for two additional periods of five years each. The lease provided for leasehold improvement incentives and provides for annual rent increases through the term of the lease. The Company subleases the fifth floor and records the sublease income in other income (expense), net within the consolidated income statement. The sublease income is immaterial as of December 31, 2019. On September 26, 2017, the Company assumed an operating lease, which was entered into by the original lessee on August 12, 2013, for the lease of 13,345 square feet of office space in Dublin, Ireland at Styne House, Upper Hatch Street with a non-cancellable term through 2023. The lease provided for a rent increase at the end of year five of the original lease term. On October 8, 2014, the Company entered into an operating lease in Cambridge, Massachusetts at 2 Canal Park for the lease of 48,059 square feet of office space with a non-cancellable lease term through 2022 with an option to extend the lease term for one additional period of five years. The lease provided for leasehold improvement incentives and provides for annual rent increases through the term of the lease. The Company’s financing lease obligations consist of a lease for office equipment and are immaterial. The leases in Boston Massachusetts and Cambridge, Massachusetts have associated letters of credit, which are recorded as restricted cash within the consolidated balance sheet. At December 31, 2019 and 2018, restricted cash was $10,803 and $2,671, respectively, and primarily related to cash held at a financial institution in an interest-bearing cash account as collateral for the letters of credit related to the contractual provisions for the Company’s building leases. At December 31, 2019 and 2018, portions of restricted cash were classified as a short-term asset and long-term asset. Additionally, the 121 First Street lease agreement has an associated security deposit, which is recorded in other non-current assets, net within the consolidated balance sheet. Prior to adoption of ASC 842 Prior to the adoption of ASC 842, the Company categorized leases at their inception as either operating or capital leases. On certain lease arrangements, the Company may have received rent holidays or other incentives. The Company recognized lease costs on a straight‑line basis once it achieved control of the space, without regard to deferred payment terms, such as rent holidays, that deferred the commencement date of required payments or escalating payment amounts. The Company recorded the difference between required lease payments and rent expense as deferred rent. Additionally, incentives received were treated as a reduction of costs over the term of the agreement, as they were considered an inseparable part of the lease agreement. As of December 31, 2018, the Company had deferred rent and rent incentives of $11,088, of which $1,693 and $9,395, respectively, are classified as a short‑term liability and a long‑term liability in the corresponding consolidated balance sheet. Rent expense related to the operating leases for the years ended December 31, 2018 and 2017 was $7,711 and $5,994, respectively. Following adoption of ASC 842 Upon adoption of ASC 842, the Company elected the transition relief package, permitted within the standard, pursuant to which the Company did not reassess the classification of existing leases, whether any expired or existing contracts contain a lease, and whether existing leases have any initial direct costs. The Company also elected the practical expedient of not separating lease components from non-lease components for all leases. There was no cumulative-effective adjustment to the opening balance of retained earnings. The Company reviews all material contracts for embedded leases to determine if they have a right-of-use asset. The Company recognizes rent expense on a straight-line basis over the lease period. The depreciable life of assets and leasehold improvement are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Variable lease payments that depend on an index or a rate are included in the lease payments and are measured using the prevailing index or rate at the measurement date. Variable lease payments not based on an index or a rate are excluded from lease payments and are expensed as incurred. The Company also made an accounting policy election to not recognize a lease liability or right-of-use asset on its consolidated balance sheet for leases with an initial term of twelve months or less, and instead to recognize lease payments on the consolidated income statement on a straight-line basis over the lease term and variable lease payments that do not depend on an index or rate as expense in the period in which the achievement of the specified target that triggers the variable lease payments becomes probable. Adoption of the new standard resulted in the recording of net lease assets and lease liabilities of $52,334 and $63,280, respectively, as of January 1, 2019. The standard did not materially impact the consolidated statement of cash flows and had no impact on the consolidated income statement. During the years ended December 31, 2019 and 2018, the Company recognized $10,260 and $7,711, respectively, of lease costs for leases that have commenced. The Company allocates lease costs across all departments based on headcount in the respective location. For leases commenced, as of December 31, 2019, the weighted average remaining lease term was 8.8 years and the weighted average discount rate was 5.2%. As most of the Company’s leases do not provide an implicit rate, the Company uses an estimated incremental borrowing rate based on the information available at lease commencement in determining the present value of lease payments. The Company estimated the incremental borrowing rate based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. The Company has no historical debt transactions and a collateralized rate is estimated based on a group of peer companies. The Company used the incremental borrowing rate on January 1, 2019 for leases that commenced prior to that date. Future minimum lease payments as of December 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2020 $ 12,201 2021 13,088 2022 13,016 2023 9,858 2024 8,835 Thereafter 34,423 Total lease payments 91,421 Less imputed interest (21,822 ) Total $ 69,599 The chart above does not include options to extend lease terms that are not reasonably certain of being exercised or leases signed but not yet commenced as of December 31, 2019. Total estimated future minimum lease payments for leases signed but not yet commenced as of December 31, 2019, which includes 1001 Boylston Street and portions of 55 Cambridge Parkway, are estimated to be $317,837 and have expected commencement dates ranging from February 2020 to January 2022. Stock-Based Compensation In June 2018, the FASB issued ASU 2018-07 , Compensation—Stock Compensation (Topic 718) Compensation—Stock Compensation a contract accounted for under Topic 606. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. For all other entities, the amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. The Company has assessed the impact of this guidance on its consolidated financial statements and does not deem it to be material. The Company adopted the guidance on January 1, 2019 prospectively . Internal-Use Software In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40) Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. Recent Accounting Pronouncements Not Yet Adopted From time to time, new accounting pronouncements are issued by the FASB or other standard-setting bodies and adopted by the Company on or prior to the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption. In December 2019, the FASB issued ASU 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments
Lease Accounting	Recent Adopted Accounting Pronouncements Lease Accounting In February 2016, the FASB issued ASC 842, which requires a lessee to recognize most leases on the consolidated balance sheet but recognize expenses on the consolidated income statement in a manner similar to current practice. The update states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-of-use asset for the right to use the underlying assets for the lease term. The Company adopted ASC 842 as of January 1, 2019, using the additional transition method offered through ASU No. 2018-11. This approach provides a method for recording existing leases at the adoption date and recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Lease Overview The Company’s operating lease obligations consist of various leases for office space in: Boston, Massachusetts; Cambridge, Massachusetts; Detroit, Michigan; Los Angeles, California; Dublin, Ireland; and London, United Kingdom. The Detroit, Los Angeles and London leases are immaterial to the Company. The Company also has an operating lease obligation for data center space in Needham, Massachusetts. On December 19, 2019, the Company entered into an operating lease for the lease of 273,595 square feet of office space in Boston, Massachusetts at 1001 Boylston Street. The lease provides for leasehold improvement incentives and provides for annual rent increases through the term of the lease. The “Commencement Date” of the lease term is the earlier to occur of (i) the date that is twelve months following the Delivery Date (as defined in the lease) and (ii) the date that the Company first occupies the premises for the normal conduct of business for the Permitted Use (as defined in the lease). The initial term will commence on the Commencement Date and expire on the date that is one hundred and eighty full calendar months after the Commencement Date (plus the partial month, if any, immediately following the Commencement Date). On August 30, 2019, the Company amended its operating lease agreement in Cambridge, Massachusetts at 55 Cambridge Parkway, which was originally entered into on March 11, 2016 and subsequently amended on July 30, 2016, for the lease of 51,923 square feet of office space. The 2019 amendment granted the Company an additional 36,689 square feet of office space and extended the non-cancellable lease term through 2025 for the office space currently occupied. The Company accounted for the additional 36,689 square feet of office space as a new lease as it provides an additional right-of-use asset that is not included in the original lease and the additional lease payments were determined to be commensurate with the standalone price of the additional space. The non-cancellable lease term of the additional space ends in 2025, with a portion ending in 2023. The term extension of the existing 51,923 square feet of office space was recorded as a lease modification within the consolidated balance sheet as of December 31, 2019. The lease, as amended, provides for (i) an option to extend the lease term with respect to a portion of the office space for an additional period of five years, (ii) leasehold improvement incentives and (iii) annual rent increases through the term of the lease. On May 1, 2019, the Company entered into an operating lease in Needham, Massachusetts for the lease of data center space with a non-cancellable term through 2022 with automatic renewal for one year thereafter if not terminated. The lease provides for annual rent increases through the term of the lease. On June 19, 2018, the Company entered into an operating lease in Cambridge, Massachusetts at 121 First Street for the lease of 48,393 square feet of office space with a non-cancellable lease term through 2033 with an option to extend the lease term for two additional periods of five years each. The lease provided for leasehold improvement incentives and provides for annual rent increases through the term of the lease. The Company subleases the fifth floor and records the sublease income in other income (expense), net within the consolidated income statement. The sublease income is immaterial as of December 31, 2019. On September 26, 2017, the Company assumed an operating lease, which was entered into by the original lessee on August 12, 2013, for the lease of 13,345 square feet of office space in Dublin, Ireland at Styne House, Upper Hatch Street with a non-cancellable term through 2023. The lease provided for a rent increase at the end of year five of the original lease term. On October 8, 2014, the Company entered into an operating lease in Cambridge, Massachusetts at 2 Canal Park for the lease of 48,059 square feet of office space with a non-cancellable lease term through 2022 with an option to extend the lease term for one additional period of five years. The lease provided for leasehold improvement incentives and provides for annual rent increases through the term of the lease. The Company’s financing lease obligations consist of a lease for office equipment and are immaterial. The leases in Boston Massachusetts and Cambridge, Massachusetts have associated letters of credit, which are recorded as restricted cash within the consolidated balance sheet. At December 31, 2019 and 2018, restricted cash was $10,803 and $2,671, respectively, and primarily related to cash held at a financial institution in an interest-bearing cash account as collateral for the letters of credit related to the contractual provisions for the Company’s building leases. At December 31, 2019 and 2018, portions of restricted cash were classified as a short-term asset and long-term asset. Additionally, the 121 First Street lease agreement has an associated security deposit, which is recorded in other non-current assets, net within the consolidated balance sheet. Prior to adoption of ASC 842 Prior to the adoption of ASC 842, the Company categorized leases at their inception as either operating or capital leases. On certain lease arrangements, the Company may have received rent holidays or other incentives. The Company recognized lease costs on a straight‑line basis once it achieved control of the space, without regard to deferred payment terms, such as rent holidays, that deferred the commencement date of required payments or escalating payment amounts. The Company recorded the difference between required lease payments and rent expense as deferred rent. Additionally, incentives received were treated as a reduction of costs over the term of the agreement, as they were considered an inseparable part of the lease agreement. As of December 31, 2018, the Company had deferred rent and rent incentives of $11,088, of which $1,693 and $9,395, respectively, are classified as a short‑term liability and a long‑term liability in the corresponding consolidated balance sheet. Rent expense related to the operating leases for the years ended December 31, 2018 and 2017 was $7,711 and $5,994, respectively. Following adoption of ASC 842 Upon adoption of ASC 842, the Company elected the transition relief package, permitted within the standard, pursuant to which the Company did not reassess the classification of existing leases, whether any expired or existing contracts contain a lease, and whether existing leases have any initial direct costs. The Company also elected the practical expedient of not separating lease components from non-lease components for all leases. There was no cumulative-effective adjustment to the opening balance of retained earnings. The Company reviews all material contracts for embedded leases to determine if they have a right-of-use asset. The Company recognizes rent expense on a straight-line basis over the lease period. The depreciable life of assets and leasehold improvement are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Variable lease payments that depend on an index or a rate are included in the lease payments and are measured using the prevailing index or rate at the measurement date. Variable lease payments not based on an index or a rate are excluded from lease payments and are expensed as incurred. The Company also made an accounting policy election to not recognize a lease liability or right-of-use asset on its consolidated balance sheet for leases with an initial term of twelve months or less, and instead to recognize lease payments on the consolidated income statement on a straight-line basis over the lease term and variable lease payments that do not depend on an index or rate as expense in the period in which the achievement of the specified target that triggers the variable lease payments becomes probable. Adoption of the new standard resulted in the recording of net lease assets and lease liabilities of $52,334 and $63,280, respectively, as of January 1, 2019. The standard did not materially impact the consolidated statement of cash flows and had no impact on the consolidated income statement. During the years ended December 31, 2019 and 2018, the Company recognized $10,260 and $7,711, respectively, of lease costs for leases that have commenced. The Company allocates lease costs across all departments based on headcount in the respective location. For leases commenced, as of December 31, 2019, the weighted average remaining lease term was 8.8 years and the weighted average discount rate was 5.2%. As most of the Company’s leases do not provide an implicit rate, the Company uses an estimated incremental borrowing rate based on the information available at lease commencement in determining the present value of lease payments. The Company estimated the incremental borrowing rate based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. The Company has no historical debt transactions and a collateralized rate is estimated based on a group of peer companies. The Company used the incremental borrowing rate on January 1, 2019 for leases that commenced prior to that date. Future minimum lease payments as of December 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2020 $ 12,201 2021 13,088 2022 13,016 2023 9,858 2024 8,835 Thereafter 34,423 Total lease payments 91,421 Less imputed interest (21,822 ) Total $ 69,599 The chart above does not include options to extend lease terms that are not reasonably certain of being exercised or leases signed but not yet commenced as of December 31, 2019. Total estimated future minimum lease payments for leases signed but not yet commenced as of December 31, 2019, which includes 1001 Boylston Street and portions of 55 Cambridge Parkway, are estimated to be $317,837 and have expected commencement dates ranging from February 2020 to January 2022.
Internal-Use Software	Internal-Use Software In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40) Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract.
Goodwill and Other Intangible Assets	The Company tests goodwill for impairment at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The Company evaluated goodwill for impairment on October 1, 2019 and did not recognize an impairment charge.
Earnings Per Share	Net income per share for the years ended December 31, 2019 and 2018 was computed by dividing net income by the weighted-average number of common shares outstanding during the reporting period. The Company computes the weighted-average number of common shares outstanding during the reporting period using the total number of shares of Class A common stock and Class B common stock outstanding as of the last day of the previous year end reporting period plus the weighted-average of any additional shares issued and outstanding during the reporting period. Net income per share for the year ended December 31, 2017 was computed using the two-class method, which includes the weighted‑average number of shares of common stock outstanding during the period and other securities that participate in dividends (a participating security). For periods during the year ended December 31, 2017, the Company had convertible Preferred Stock outstanding. The Company considered the convertible Preferred Stock to be participating securities because they included rights to participate in dividends with the common stock. On October 16, 2017, in connection with the closing of the IPO, all of the outstanding shares of convertible P referred S tock automatically converted into 20,188,226 shares of Class A common stock and 40,376,452 shares of Class B common stock , the latter of which subsequently converted in full into shares of Class A common stock. As a result, there were no shares of P referred S tock outstanding at the closing of the IPO and the Company has not issued any new shares of P referred S tock since such closing. Under the two‑class method, basic net income per share attributable to common stockholders is computed by dividing the net income attributable to common stockholders by the weighted‑average number of shares of common stock outstanding during the period. Diluted net income per share attributable to common stockholders is computed using the more dilutive of (1) the two‑class method or (2) the if‑converted method. The Company allocated net income first to preferred stockholders based on dividend rights under the Company’s certificate of incorporation that was in effect prior to the closing of the IPO and then to preferred and common stockholders based on ownership interests. Net losses are not allocated to preferred stockholders as they do not have an obligation to share in the Company’s net losses. The Company has two classes of common stock authorized: Class A common stock and Class B common stock. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Each share of Class B common stock is convertible into one share of Class A common stock at the option of the holder at any time or automatically upon certain events described in the Company’s amended and restated certificate of incorporation, including on either the death or voluntary termination of the Company’s Chief Executive Officer. one‑to‑one

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Summary of Revenue from Contracts with Customers by Revenue	The following table summarizes revenue from contracts with customers by revenue source for the years ended December 31, 2019, 2018 and 2017. 2019 2018 2017 Revenue by Revenue Stream Marketplace subscription revenue $ 526,043 $ 405,780 $ 282,664 Advertising and other revenue 62,873 48,306 34,197 Total $ 588,916 $ 454,086 $ 316,861
Summary of Opening and Closing Balances of Receivables and Contract Assets From Contracts with Customers	The following tables summarize the opening and closing balances of receivables and contract assets from contracts with customers as of January 1, 2018, December 31, 2018 and December 31, 2019. Accounts Receivable, net Contract Assets (current) Contract Assets (non-current) Balance at January 1, 2018 $ 13,390 $ 1,424 $ 1,782 Balance at December 31, 2018 13,614 5,253 7,252 Balance at December 31, 2019 22,124 9,544 10,514
Summary of Changes in Allowance for Doubtful Accounts	Below is a summary of the changes in the Company’s allowance for doubtful accounts for the years ended December 31, 2019, 2018, and 2017: Balance at Beginning of Period Provision Write – net of recoveries Balance at End of Period Year ended December 31, 2019 $ 479 $ 1,091 $ (1,330 ) $ 240 Year ended December 31, 2018 494 1,680 (1,695 ) 479 Year ended December 31, 2017 164 1,117 (787 ) 494
Schedule of Estimated Useful Lives of Property and Equipment	The estimated useful lives of the Company’s property and equipment are as follows: Estimated Useful Life (In Years) Capitalized equipment 3 Capitalized software 3 Capitalized website development 3 Furniture and fixtures 5 Leasehold improvements Lesser of asset life or lease term
Summary of Future Minimum Lease Payments	Future minimum lease payments as of December 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2020 $ 12,201 2021 13,088 2022 13,016 2023 9,858 2024 8,835 Thereafter 34,423 Total lease payments 91,421 Less imputed interest (21,822 ) Total $ 69,599
ASC 606
Summary of Impact of New Revenue Guidance on Financial Statement	As a result of applying the modified retrospective method to adopt the new revenue guidance, the following adjustments were made on the consolidated balance sheet as of January 1, 2018. As Reported Adjustments As Adjusted December 2017 Marketplace Subscription Revenue Costs to Obtain a Contract January 1, 2018 Assets Current assets: Cash and cash equivalents $ 87,709 $ 87,709 Investments 50,000 50,000 Accounts receivable, net 12,577 813 13,390 Prepaid expenses and prepaid income taxes 5,313 5,313 Deferred contract costs — 1,424 1,424 Other current assets 1,605 1,605 Restricted cash — — Total current assets 157,204 813 1,424 159,441 Property and equipment, net 16,563 16,563 Restricted cash 1,843 1,843 Deferred tax assets 825 (190 ) (635 ) — Deferred contract costs, net of current portion — 1,783 1,783 Other long–term assets 159 159 Total assets $ 176,594 $ 623 $ 2,572 $ 179,789 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 23,908 $ 23,908 Accrued expenses, accrued income taxes and other current liabilities 13,588 13,588 Deferred revenue 4,305 4,305 Deferred tax liabilities — 153 153 Deferred rent 1,165 1,165 Total current liabilities 42,966 — 153 43,119 Deferred rent, net of current portion 5,648 5,648 Other non–current liabilities 955 955 Total liabilities 49,569 — 153 49,722 Commitments and contingencies Stockholders’ equity: Preferred stock — — Class A common stock 78 78 Class B common stock 28 28 Additional paid–in capital 185,190 185,190 Accumulated deficit (58,499 ) 623 2,419 (55,457 ) Accumulated other comprehensive income 228 228 Total stockholders’ equity 127,025 623 2,419 130,067 Total liabilities and stockholders’ equity $ 176,594 $ 623 $ 2,572 $ 179,789 The following tables compare the reported consolidated balance sheet, statement of operations and cash flows, as of and for the year ended December 31, 2018, to the pro-forma amounts had the previous guidance been in effect. As of December 31, 2018 Balance Sheet As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Assets Current assets: Cash and cash equivalents $ 34,887 $ 34,887 Investments 122,800 122,800 Accounts receivable, net 13,614 939 12,675 Prepaid income taxes and prepaid income taxes 10,144 10,144 Deferred contract costs 5,253 5,253 — Other current assets 7,410 7,410 Restricted cash 750 750 Total current assets 194,858 939 5,253 188,666 Property and equipment, net 24,269 24,269 Restricted cash 1,921 1,921 Deferred tax assets 38,886 (227 ) (3,187 ) 42,300 Deferred contract costs, net of current portion 7,252 7,252 — Other long–term assets 1,104 1,104 Total assets $ 268,290 $ 712 $ 9,318 $ 258,260 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 34,345 $ 34,345 Accrued expenses, accrued income taxes and other current liabilities 18,654 18,654 Deferred revenue 8,811 8,811 Deferred rent 1,693 1,693 Total current liabilities 63,503 — — 63,503 Deferred rent, net of current portion 9,395 9,395 Other non–current liabilities 1,281 1,281 Total liabilities 74,179 — — 74,179 Commitments and contingencies Stockholders’ equity: Preferred stock — — Class A common stock 90 90 Class B common stock 21 21 Additional paid–in capital 184,216 184,216 Retained earnings (accumulated deficit) 9,713 712 9,318 (317 ) Accumulated other comprehensive income 71 71 Total stockholders’ equity 194,111 712 9,318 184,081 Total liabilities and stockholders’ equity $ 268,290 $ 712 $ 9,318 $ 258,260 The following summarizes the significant changes on the Company’s consolidated statement of operations for the year ended December 31, 2018 as a result of the adoption of ASC 606 on January 1, 2018 compared to the pro-forma amounts had the Company continued to recognize revenue under ASC 605. Year Ended December 31, 2018 Statement of Operations As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Revenue $ 454,086 $ 126 $ 453,960 Cost of revenue 24,811 24,811 Gross profit 429,275 126 — 429,149 Operating expenses: Sales and marketing 315,939 (9,298 ) 325,237 Product, technology, and development 47,866 47,866 General and administrative 39,475 39,475 Depreciation and amortization 2,804 2,804 Total operating expenses 406,084 — (9,298 ) 415,382 Income from operations 23,191 126 9,298 13,767 Other income, net: Interest income 2,283 2,283 Other income (expense) 10 10 Total other income, net 2,293 — — 2,293 Income before income taxes 25,484 126 9,298 16,060 Provision for (Benefit from) income taxes (39,686 ) 37 2,399 (42,122 ) Net income $ 65,170 $ 89 $ 6,899 $ 58,182 Basic $ 0.60 $ — $ 0.07 $ 0.53 Diluted $ 0.57 $ — $ 0.06 $ 0.51 The following summarizes the significant changes on the Company’s consolidated statement of cash flows for the year ended December 31, 2018 as a result of the adoption of ASC 606 on January 1, 2018 compared to the pro-forma amounts had the Company continued to recognize revenue under ASC 605. Year Ended December 31, 2018 Statement of Cash Flows As Reported Marketplace Subscription Revenue Costs to Obtain a Contract Pro forma as if the previous accounting guidance was in effect Operating Activities Net income $ 65,170 $ 89 $ 6,899 $ 58,182 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 5,029 5,029 Currency (gain) loss on foreign denominated transactions (190 ) (190 ) Deferred taxes (39,040 ) 37 2,399 (41,476 ) Provision for doubtful accounts 1,680 1,680 Stock–based compensation expense 20,794 20,794 Amortization of deferred contract costs 3,689 3,689 — Changes in operating assets and liabilities: Accounts receivable, net (1,911 ) (126 ) (1,785 ) Prepaid expenses, prepaid income taxes, and other assets (11,753 ) (11,753 ) Deferred contracts costs (12,987 ) (12,987 ) — Accounts payable 9,345 9,345 Accrued expenses, accrued income taxes and other current liabilities 2,695 2,695 Deferred revenue 4,508 4,508 Deferred rent 4,289 4,289 Other non–current liabilities 405 405 Net cash provided by operating activities $ 51,723 $ — $ — $ 51,723

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Summary of Purchase Price Allocation	The following table presents the purchase price allocation recorded in the Company's consolidated balance sheet as of the acquisition date, which was finalized as of December 31, 2019: Estimated Fair Value at Date of Acquisition Adjustment Adjusted Fair Value at Date of Acquisition Intangible assets (1) $ 4,466 $ — $ 4,466 Goodwill (2) 15,521 (655 ) 14,866 Deferred tax liabilities (3) (848 ) 655 (193 ) Total purchase price $ 19,139 $ — $ 19,139 (1) Identifiable definite-lived intangible assets were comprised of brand and customer relationships of $3,445 and $1,021, respectively, with estimated useful lives of 11 years and 3 years, respectively, which will be amortized on a straight-line basis over their estimated useful lives. (2) The goodwill represents the excess value of the purchase price over intangible assets acquired. The goodwill in this transaction is primarily attributable to future customer growth in the U.K. market as a result of acquiring an established platform and applying the Company’s technology to help improve the website experience on such platform; thus, helping to drive additional traffic to the PistonHeads website in the future. All goodwill is assigned to the International segment. The acquisition of PistonHeads was a stock acquisition and as a result, g (3) T

Fair Value of Financial Instr_2

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value Levels, Assets Measured at Fair Value on Recurring Basis	The following tables present, for each of the fair value levels, the Company’s assets that are measured at fair value on a recurring basis at December 31, 2019 and 2018: December 31, 2019 Quoted Prices in Active Markets for Identical Assets (Level 1 Inputs) Significant Other Observable Inputs (Level 2 Inputs) Significant Unobservable Inputs (Level 3 Inputs) Total Cash equivalents: Money market funds $ 29,196 $ — $ — $ 29,196 Investments: Certificates of deposit — 111,692 — 111,692 Total $ 29,196 $ 111,692 $ — $ 140,888 December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1 Inputs) Significant Other Observable Inputs (Level 2 Inputs) Significant Unobservable Inputs (Level 3 Inputs) Total Cash equivalents: Money market funds $ 24 $ — $ — $ 24 Investments: Certificates of deposit — 122,800 — 122,800 Total $ 24 $ 122,800 $ — $ 122,824
Schedule of Cash, Cash Equivalents, and Investments	The following is a summary of cash, cash equivalents, and investments as of December 31, 2019 and 2018. Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value December 31, 2019: Cash and cash equivalents due in 90 days or less $ 59,920 $ — $ — $ 59,920 Investments: Certificates of deposit due in one year or less 111,692 — — 111,692 Total cash, cash equivalents, and investments $ 171,612 $ — $ — $ 171,612 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value December 31, 2018: Cash and cash equivalents due in 90 days or less $ 34,887 $ — $ — $ 34,887 Investments: Certificates of deposit due in one year or less 122,800 — — 122,800 Total cash, cash equivalents, and investments $ 157,687 $ — $ — $ 157,687

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following: At December 31, 2019 2018 Capitalized equipment $ 7,923 $ 4,208 Capitalized software 181 252 Capitalized website development costs 11,083 6,907 Furniture and fixtures 6,809 4,584 Leasehold improvements 19,507 10,821 Construction in progress 524 8,971 Finance lease right-of-use assets 78 - 46,105 35,743 Less accumulated depreciation and amortization (18,155 ) (11,474 ) Property and equipment, net $ 27,950 $ 24,269

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Changes in Carrying Value of Goodwill	The changes in the carrying value of goodwill were as follows: Balance at December 31, 2018 $ — Initial value of PistonHeads acquisition 15,521 Foreign currency translation adjustment 341 Purchase price adjustment (1) (655 ) Balance at December 31, 2019 $ 15,207 (1) The purchase price adjustment corresponds to an adjustment for the deferred tax liability as a result of the Company’s evaluation of income tax treatment, which was recorded during the second quarter of 2019.
Summary of Other Intangible Assets	Intangible assets as of December 31, 2019 consist of the following: Weighted Average Remaining Useful Life (years) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Brand 10.0 $ 3,524 $ 313 $ 3,211 Customer relationships 2.0 1,045 336 709 Total $ 4,569 $ 649 $ 3,920
Summary of Estimated Amortization Expense of Intangible Assets	Estimated amortization expense of intangible assets for future periods as of December 31, 2019, is as follows: Year Ending December 31, Amortization Expense 2020 $ 671 2021 671 2022 328 2023 320 2024 320 2025 and thereafter 1,610 Total $ 3,920

Accrued Expenses, Accrued Inc_2

Accrued Expenses, Accrued Income Taxes and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Schedule of Accrued Expenses, Accrued Income Taxes and Other Current Liabilities	Accrued expenses, accrued income taxes and other current liabilities consist of the following: At December 31, 2019 2018 Accrued bonus $ 8,637 $ 8,266 Other accrued expenses, accrued income taxes and other current liabilities 9,625 10,388 Total $ 18,262 $ 18,654

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Preferred Stock	Prior to the Company’s IPO, at which time all shares of Preferred Stock were converted into shares of common stock, the Company’s Preferred Stock consisted of the following: Original Issue Price Per Share Shares Authorized Outstanding Liquidation Amount Carrying Value Series A Preferred Stock $ 0.525053 3,333,000 2,824,703 $ 1,483 $ 1,483 Series B Preferred Stock $ 0.780899 3,329,497 2,938,486 2,295 2,295 Series C Preferred Stock $ 0.849012 1,648,978 1,550,612 1,316 1,316 Series D Preferred Stock $ 40.642989 1,673,105 1,673,105 68,000 67,872 Series E Preferred Stock $ 54.190650 1,107,202 1,107,202 60,000 59,732 11,091,782 10,094,108 $ 133,094 $ 132,698

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	The following is a summary of the stock option activity for all stock‑based compensation plans during the year ended December 31, 2019: Common Stock Weighted- Average Exercise Price for Equity Weighted- Average Remaining Contractual Life (In Years) Aggregate Intrinsic Value (1) Outstanding, December 31, 2018 1,807,515 $ 2.35 5.9 $ 56,716 Granted — — Exercised (838,928 ) 2.16 28,902 Forfeited and cancelled (25,702 ) 5.09 Outstanding, December 31, 2019 942,885 $ 2.45 5.0 $ 30,859 Options exercisable at December 31, 2019 913,197 $ 2.31 5.0 $ 30,016 (1) The aggregate intrinsic value as of December 31, 2019 and 2018 was calculated based on the positive difference, if any, between the estimated fair value of our common stock on December 31, 2019 and 2018, respectively, or the date of exercise, as appropriate, and the exercise price of the underlying options.
Summary of Restricted Stock Unit Activity	The following is a summary of the RSU activity during the year ended December 31, 2019: Number of Shares Weighted- Average Grant Date Fair Value Aggregate Intrinsic Value Unvested outstanding, December 31, 2018 2,973,002 $ 26.06 $ 100,279 Granted 1,811,208 39.07 Vested (1,317,736 ) 23.93 Forfeited (383,173 ) 31.70 Unvested outstanding, December 31, 2019 3,083,301 $ 33.89 $ 108,471
Summary of Stock-based Compensation Expense by Award Type	Year Ended December 31, 2019 2018 2017 Options $ 155 $ 247 $ 281 RSUs 34,146 20,547 4,747 Total stock-based compensation expense $ 34,301 $ 20,794 $ 5,028
Summary of Allocation of Stock-based Compensation Expense	Year Ended December 31, 2019 2018 2017 Cost of revenue $ 354 $ 354 $ 151 Sales and marketing expense 9,989 5,111 1,911 Product, technology, and development expense 15,159 9,865 1,637 General and administrative expense 8,799 5,464 1,329 Total stock-based compensation expense $ 34,301 $ 20,794 $ 5,028
Summary of Shares of Common Stock Reserved for Future Issuance	At December 31, 2019, the Company had reserved the following shares of voting common stock for future issuance: Common stock options outstanding 942,885 Restricted stock units outstanding 3,083,301 Shares available for issuance under the 2017 Plan 5,889,929 Total shares of authorized common stock reserved for future issuance 9,916,115

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Income Per Share	The following table presents a reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share: Year Ended December 31, 2019 2018 2017 Numerator: Net income $ 42,146 $ 65,170 $ 13,199 Net income attributable to participating securities — — (6,098 ) Net income attributable to common stockholders — basic $ 42,146 $ 65,170 $ 7,101 Net income $ 42,146 $ 65,170 $ 13,199 Net income attributable to participating securities — — (5,829 ) Net income attributable to common stockholders — diluted $ 42,146 $ 65,170 $ 7,370 Denominator: Weighted–average number of shares of common stock used in computing net income per share attributable to common stockholders — basic 111,450,443 108,833,028 55,835,265 Dilutive effect of share equivalents resulting from stock options 1,155,906 3,009,748 4,290,362 Dilutive effect of share equivalents resulting from unvested restricted stock units 825,501 1,521,936 511,957 Weighted–average number of shares of common stock used in computing net income per share — diluted 113,431,850 113,364,712 60,637,584 Net income per share attributable to common stockholders: Basic $ 0.38 $ 0.60 $ 0.13 Diluted $ 0.37 $ 0.57 $ 0.12
Schedule of Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Weighted-average Shares Outstanding	The following potentially dilutive common stock equivalents have been excluded from the calculation of diluted weighted‑average shares outstanding for the years ended December 31, 2019, 2018, and 2017, as their effect would have been anti‑dilutive for the periods presented: Year Ended December 31, 2019 2018 2017 Restricted stock units outstanding 1,144,287 126,816 829

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Domestic and Foreign Components of Income Before Income Taxes	The domestic and foreign components of income before income taxes are as follows: Year Ended December 31, 2019 2018 2017 United States $ 37,476 $ 24,426 $ 15,543 Foreign 1,229 1,058 294 Income before income taxes $ 38,705 $ 25,484 $ 15,837
Schedule of (Benefit From) Provision for Income Taxes	The (benefit from) provision for income taxes contained the following components: Year Ended December 31, 2019 2018 2017 Current (benefit) provision: Federal $ — $ (860 ) $ 3,262 State (220 ) 92 431 Foreign 513 122 62 293 (646 ) 3,755 Deferred (benefit) provision: Federal (2,377 ) (27,675 ) (755 ) State (1,306 ) (11,499 ) (343 ) Foreign (51 ) 134 (19 ) (3,734 ) (39,040 ) (1,117 ) Income tax (benefit) provision $ (3,441 ) $ (39,686 ) $ 2,638
Schedule of Effective Tax Rates Less than US Federal Statutory Rate Primarily Due to Excess Tax Deductions	The Company's effective tax rates for the years ending December 31, 2019 and 2018 are less than the U.S. federal statutory rate due to excess tax deductions related to stock-based compensation awards and federal and state research and development credits. The Company’s effective tax rate for the year ending December 31, 2017 is less than the U.S. federal statutory rate primarily due to federal and state research and development credits, excess tax deductions related to stock-based compensation awards, and tax deductions for fees incurred during the IPO process. Year Ended December 31, 2019 2018 2017 U.S. federal taxes at statutory rate 21.0 % 21.0 % 35.0 % State taxes, net of federal benefit 0.2 (25.6 ) 3.1 Nondeductible expenses 2.9 4.1 1.2 Tax deductible IPO costs — — (9.3 ) Stock compensation (22.0 ) (127.2 ) (4.4 ) Foreign rate differential (0.3 ) (0.4 ) (0.4 ) Credits (10.3 ) (28.4 ) (9.0 ) Other (0.2 ) 0.7 0.5 Total (8.7 )% (155.8 )% 16.7 %
Schedule of Income Tax Effect of Each Type of Temporary Difference and Carryforward	The approximate income tax effect of each type of temporary difference and carryforward as of December 31, 2019 and 2018 is as follows: As of December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 35,977 $ 34,450 Credit carryforwards 10,472 6,562 Stock-based compensation 2,953 1,945 Landlord allowance on leasehold improvements — 1,908 Lease liability 17,965 — Intangible Assets 62 — Deferred rent — 873 Accruals and reserves 1,185 1,074 68,614 46,812 Valuation Allowance (62 ) — 68,552 46,812 Deferred tax liabilities: Prepaid expenses (1,523 ) (931 ) Deferred commissions (5,100 ) (3,187 ) Right of use assets (15,270 ) — Unbilled revenue — (227 ) Fixed assets (4,230 ) (3,581 ) (26,123 ) (7,926 ) Net deferred tax assets $ 42,429 $ 38,886

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Summary of Operations by Segment and Geographical Area	Information regarding the Company’s operations by segment and geographical area is presented as follows: Year Ended December 31, 2019 2018 2017 Segment revenue: United States $ 555,007 $ 437,166 $ 307,472 International 33,909 16,920 9,389 Total revenue $ 588,916 $ 454,086 $ 316,861 Year Ended December 31, 2019 2018 2017 Segment income (loss) from operations: United States $ 73,872 $ 58,387 $ 41,586 International (39,550 ) (35,196 ) (26,312 ) Total income from operations $ 34,322 $ 23,191 $ 15,274

Quarterly Financial Results (_2

Quarterly Financial Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Schedule of Unaudited Quarterly Financial Information	The following table presents certain unaudited quarterly financial information for the eight quarters in the period ended December 31, 2019. This information has been prepared on the same basis as the audited financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein. Fourth Quarter Third Quarter Second Quarter First Quarter Year ended December 31, 2019 Revenue $ 158,153 $ 150,462 $ 145,031 $ 135,270 Cost of revenue 10,560 9,392 8,628 7,720 Gross profit 147,593 141,070 136,403 127,550 Income from operations 13,635 9,704 3,548 7,435 Net income 13,171 10,384 6,007 12,584 Basic net income per share (1) $ 0.12 $ 0.09 $ 0.05 $ 0.11 Diluted net income per share (1) $ 0.12 $ 0.09 $ 0.05 $ 0.11 Year Ended December 31, 2018 Revenue $ 126,090 $ 119,125 $ 110,296 $ 98,575 Cost of revenue 6,871 6,412 5,959 5,569 Gross profit 119,219 112,713 104,337 93,006 Income from operations 6,902 5,877 3,953 6,459 Net income 12,450 13,882 33,343 5,495 Basic net income per share (1) $ 0.11 $ 0.13 $ 0.31 $ 0.05 Diluted net income per share (1) $ 0.11 $ 0.12 $ 0.29 $ 0.05 (1) The amounts were computed independently for each quarter, and the sum of the quarters may not total the annual amounts.

Organization and Business Des_2

Organization and Business Description - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 16, 2017	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2018
Organization And Business Description [Line Items]
State of incorporation		DE
Date of incorporation		Jun. 26, 2015
Issuance of stock, net of issuance/offering costs			$ 43,240
Net proceeds received after deducting underwriting discounts and commissions and offering costs			$ 47,690
Conversion of convertible securities into shares of common stock	9,091,484
Preferred stock, shares outstanding	0	0		0
Class A Common Stock
Organization And Business Description [Line Items]
Conversion of convertible securities into shares of common stock	60,564,678
Class A Common Stock | Selling Shareholders
Organization And Business Description [Line Items]
Issuance of stock, net of issuance/offering costs, Shares	7,605,000
Class A Common Stock | Subsequent Conversion
Organization And Business Description [Line Items]
Conversion of convertible securities into shares of common stock	40,376,452
Class B Common Stock
Organization And Business Description [Line Items]
Conversion of convertible securities into shares of common stock	40,376,452
IPO
Organization And Business Description [Line Items]
Preferred stock, shares outstanding	0
IPO | Class A Common Stock
Organization And Business Description [Line Items]
Issuance of stock, net of issuance/offering costs, Shares	3,205,000
Number of shares issued for services	705,000
Offering price per share	$ 16
Issuance of stock, net of issuance/offering costs	$ 51,300
Net proceeds received after deducting underwriting discounts and commissions and offering costs	43,200
Underwriting discounts and commissions	3,600
Stock issuance costs	$ 4,500
Conversion of convertible securities into shares of common stock	20,188,226
IPO | Convertible Preferred Stock
Organization And Business Description [Line Items]
Preferred stock, shares outstanding	0

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	Dec. 19, 2019ft²	May 01, 2019	Aug. 12, 2013ft²	Dec. 31, 2019USD ($)$ / shares		Sep. 30, 2019USD ($)$ / shares		Jun. 30, 2019USD ($)$ / shares		Mar. 31, 2019USD ($)$ / shares		Dec. 31, 2018USD ($)$ / shares		Sep. 30, 2018USD ($)$ / shares		Jun. 30, 2018USD ($)$ / shares		Mar. 31, 2018USD ($)$ / shares		Dec. 31, 2019USD ($)CustomerReportingUnit$ / sharesshares	Dec. 31, 2018USD ($)Customer$ / sharesshares	Dec. 31, 2017USD ($)Customer$ / sharesshares	Aug. 30, 2019ft²	Jan. 01, 2019USD ($)	Jun. 19, 2018ft²	Jan. 01, 2018USD ($)	Oct. 11, 2017USD ($)	Jul. 30, 2016ft²	Oct. 08, 2014ft²
Summary Of Significant Accounting Policies [Line Items]
Payment of revenue, performance obligation, description of payment terms																				thirty to sixty
Costs to obtain a contract				$ 20,058,000								$ 12,505,000								$ 20,058,000	$ 12,505,000					$ 3,207,000
Amortization of deferred contract costs																				8,416,000	3,689,000
Accounts receivable, net				22,124,000								13,614,000								22,124,000	13,614,000	$ 12,577,000				13,390,000
Reduction to accumulated deficit				(51,859,000)								(9,713,000)								(51,859,000)	(9,713,000)	58,499,000
Assets				393,623,000								268,290,000								393,623,000	268,290,000	176,594,000
Liabilities				136,768,000								74,179,000								136,768,000	74,179,000	49,569,000
Revenue				$ 158,153,000		$ 150,462,000		$ 145,031,000		$ 135,270,000		$ 126,090,000		$ 119,125,000		$ 110,296,000		$ 98,575,000		588,916,000	454,086,000	316,861,000
Sales and marketing																				393,844,000	315,939,000	236,165,000
Income before income taxes																				38,705,000	25,484,000	15,837,000
(Benefit from) provision for income taxes																				$ (3,441,000)	$ (39,686,000)	$ 2,638,000
Basic net income per share | $ / shares				$ 0.12	[1]	$ 0.09	[1]	$ 0.05	[1]	$ 0.11	[1]	$ 0.11	[1]	$ 0.13	[1]	$ 0.31	[1]	$ 0.05	[1]	$ 0.38	$ 0.60	$ 0.13
Diluted net income per share | $ / shares				$ 0.12	[1]	$ 0.09	[1]	$ 0.05	[1]	$ 0.11	[1]	$ 0.11	[1]	$ 0.12	[1]	$ 0.29	[1]	$ 0.05	[1]	$ 0.37	$ 0.57	$ 0.12
Revenue recognized																				$ 8,811,000	$ 4,305,000
Performance obligation unsatisfied				$ 35,000,000																$ 35,000,000
Description of significant off-balance sheet risk																				The Company has no significant off‑balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.
Amortization (accretion) of premiums or discounts																				$ 0	0
Realized gains or losses on investments																				0	0	$ 0
Other than temporary impairments recognized in statements of operations																				0	0
Restricted cash				10,803,000								$ 2,671,000								10,803,000	2,671,000
Impairment of long lived assets																				$ 0	0	$ 0
Number of reporting units | ReportingUnit																				2
Liabilities for uncertain tax positions				0								0								$ 0	$ 0
Unrecognized stock-based compensation expense related to stock-based awards																											$ 2,500,000
Options granted during period | shares																				0	0	0
Advertising expense																				$ 287,107,000	$ 238,640,000	$ 173,186,000
Deferred rent and rent incentives, current												1,693,000									1,693,000	1,165,000
Deferred rent and rent incentives, noncurrent												9,395,000									9,395,000	5,648,000
Rent expense																					7,711,000	5,994,000
Cumulative adjustment from adoption of revenue recognition standard																					3,042,000
Net lease assets				59,986,000																59,986,000
Lease liabilities				$ 69,599,000																69,599,000
Lease costs																				$ 10,260,000	7,711,000
Weighted average remaining lease term				8 years 9 months 18 days																8 years 9 months 18 days
Weighted average discount rate				5.20%																5.20%
Future minimum lease payments for leases signed but not yet commenced				$ 317,837,000																$ 317,837,000
Boston, Massachusetts at 1001 Boylston Street
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²	273,595
Lessee, operating lease, existence of option to terminate	true
Lessee, operating lease, option to terminate																				The “Commencement Date” of the lease term is the earlier to occur of (i) the date that is twelve months following the Delivery Date (as defined in the lease) and (ii) the date that the Company first occupies the premises for the normal conduct of business for the Permitted Use (as defined in the lease). The initial term will commence on the Commencement Date and expire on the date that is one hundred and eighty full calendar months after the Commencement Date (plus the partial month, if any, immediately following the Commencement Date). The lease provides for the option to terminate early under certain circumstances including if there is a material delay in construction (subject to the terms and conditions of the lease), and contains two Company options to extend the lease term (including for a portion of the office space thereunder) for an additional period of five years.
Operating lease, option to extend																				contains two Company options to extend the lease term (including for a portion of the office space thereunder) for an additional period of five years
Cambridge, Massachusetts at 55 Cambridge Parkway
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²																							36,689					51,923
Operating lease, option to extend																				option to extend the lease term with respect to a portion of the office space for an additional period of five years
Needham, Massachusetts
Summary Of Significant Accounting Policies [Line Items]
Lessee, operating lease, existence of option to terminate		true
Lessee, operating lease, renewal term		1 year
Cambridge, Massachusetts at 121 First Street
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²																									48,393
Operating lease, option to extend																				option to extend the lease term for two additional periods of five years each.
Dublin, Ireland
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²			13,345
Operating lease, rent increasing year			5 years
Cambridge, Massachusetts at 2 Canal Park
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²																													48,059
Operating lease, option to extend																				option to extend the lease term for one additional period of five years.
Website and Software Development Costs
Summary Of Significant Accounting Policies [Line Items]
Software and website development costs capitalized				4,176,000								2,012,000								$ 4,176,000	2,012,000
Amortization expense																				$ 1,643,000	$ 1,508,000	$ 812,000
Estimated useful life																				3 years
Internal Use Software
Summary Of Significant Accounting Policies [Line Items]
Amortization expense																				$ 132,000
Estimated useful life																				3 years
Internal Use Software | Other Non-Current Assets
Summary Of Significant Accounting Policies [Line Items]
Software and website development costs capitalized				2,615,000																$ 2,615,000
Internal Use Software | Prepaid Expenses and Prepaid Income Taxes
Summary Of Significant Accounting Policies [Line Items]
Software and website development costs capitalized				616,000																$ 616,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives																				3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Maturity of certificates of deposit, description																				As of December 31, 2019 and 2018, investments consisted of U.S. certificates of deposit (“CDs”) with remaining maturities of less than twelve months.
Maturity period of certificates of deposit																				12 months	12 months
Business acquisition valuation period																				1 year
Estimated useful lives																				11 years
Sales Revenue, Net | Concentration of Credit Risk
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk, percentage																				10.00%	10.00%	10.00%
Number of major customers | Customer																				0	0	0
Net Accounts Receivable | Advertising Customers
Summary Of Significant Accounting Policies [Line Items]
Unbilled accounts receivables				$ 8,880,000								5,814,000								$ 8,880,000	$ 5,814,000
Net Accounts Receivable | Concentration of Credit Risk
Summary Of Significant Accounting Policies [Line Items]
Number of major customers | Customer																				1	2
Net Accounts Receivable | Concentration of Credit Risk | Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk, percentage																				18.00%	21.00%
Net Accounts Receivable | Concentration of Credit Risk | Customer Two
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk, percentage																					14.00%
Commission Contract | Restatement Adjustment
Summary Of Significant Accounting Policies [Line Items]
Reduction to accumulated deficit																										3,207,000
Marketplace Subscription Revenue
Summary Of Significant Accounting Policies [Line Items]
Revenue																				$ 526,043,000	$ 405,780,000	$ 282,664,000
ASC 606
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable, net																										13,390,000
Reduction to accumulated deficit																										55,457,000
Assets																										179,789,000
Liabilities																										49,722,000
Deferred rent and rent incentives, current																										1,165,000
Deferred rent and rent incentives, noncurrent																										5,648,000
ASC 606 | Adjustments
Summary Of Significant Accounting Policies [Line Items]
Costs to obtain a contract												12,505,000									12,505,000
Reduction to deferred tax assets																										978,000
Assets												10,030,000									10,030,000
Liabilities												0									0
Revenue																					126,000
Sales and marketing																					(9,298,000)
Income before income taxes																					9,424,000
(Benefit from) provision for income taxes																					$ 2,436,000
Basic net income per share | $ / shares																					$ 0.07
Diluted net income per share | $ / shares																					$ 0.06
ASC 606 | Marketplace Subscription Revenue | Adjustments
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable, net												939,000									$ 939,000					813,000
Reduction to accumulated deficit												(712,000)									(712,000)					(623,000)
Assets												712,000									712,000					$ 623,000
Revenue																					126,000
Income before income taxes																					126,000
(Benefit from) provision for income taxes																					37,000
Accounting Standards Update 2016-09
Summary Of Significant Accounting Policies [Line Items]
(Benefit from) provision for income taxes																				(11,115,000)	(40,765,000)	$ (681,000)
ASC 842
Summary Of Significant Accounting Policies [Line Items]
Deferred rent and rent incentives												11,088,000									11,088,000
Deferred rent and rent incentives, current												1,693,000									1,693,000
Deferred rent and rent incentives, noncurrent												$ 9,395,000									$ 9,395,000
Cumulative adjustment from adoption of revenue recognition standard																				$ 0
Net lease assets																								$ 52,334,000
Lease liabilities																								$ 63,280,000
[1]	The amounts were computed independently for each quarter, and the sum of the quarters may not total the annual amounts.

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Revenue from Contracts with Customers by Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue by Revenue Stream [Abstract]
Revenue	$ 158,153	$ 150,462	$ 145,031	$ 135,270	$ 126,090	$ 119,125	$ 110,296	$ 98,575	$ 588,916	$ 454,086	$ 316,861
Marketplace Subscription Revenue
Revenue by Revenue Stream [Abstract]
Revenue									526,043	405,780	282,664
Advertising and Other Revenue
Revenue by Revenue Stream [Abstract]
Revenue									$ 62,873	$ 48,306	$ 34,197

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Adjustments in Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 59,920	$ 34,887		$ 87,709
Investments	111,692	122,800		50,000
Accounts receivable, net	22,124	13,614	$ 13,390	12,577
Prepaid expenses and prepaid income taxes	10,452	10,144		5,313
Deferred contract costs	9,544	5,253	1,424
Other current assets	4,972	7,410		1,605
Restricted cash	250	750
Total current assets	218,954	194,858		157,204
Property and equipment, net	27,950	24,269		16,563
Restricted cash	10,553	1,921		1,843
Deferred tax assets	42,713	38,886		825
Deferred contract costs, net of current portion	10,514	7,252	1,782
Other non-current assets	3,826	1,104		159
Total assets	393,623	268,290		176,594
Current liabilities:
Accounts payable	36,731	34,345		23,908
Accrued expenses, accrued income taxes and other current liabilities	18,262	18,654		13,588
Deferred revenue	9,984	8,811		4,305
Deferred rent		1,693		1,165
Total current liabilities	73,758	63,503		42,966
Deferred rent		9,395		5,648
Other non–current liabilities	1,908	1,281		955
Total liabilities	136,768	74,179		49,569
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock
Additional paid–in capital	205,234	184,216		185,190
Retained earnings	51,859	9,713		(58,499)
Accumulated other comprehensive (loss) income	(350)	71		228
Total stockholders’ equity	256,855	194,111		127,025	$ (67,972)
Total liabilities and stockholders’ equity	393,623	268,290		176,594
ASC 606
Current assets:
Cash and cash equivalents			87,709
Investments			50,000
Accounts receivable, net			13,390
Prepaid expenses and prepaid income taxes			5,313
Deferred contract costs			1,424
Other current assets			1,605
Total current assets			159,441
Property and equipment, net			16,563
Restricted cash			1,843
Deferred contract costs, net of current portion			1,783
Other non-current assets			159
Total assets			179,789
Current liabilities:
Accounts payable			23,908
Accrued expenses, accrued income taxes and other current liabilities			13,588
Deferred revenue			4,305
Deferred tax liabilities			153
Deferred rent			1,165
Total current liabilities			43,119
Deferred rent			5,648
Other non–current liabilities			955
Total liabilities			49,722
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock
Additional paid–in capital			185,190
Retained earnings			(55,457)
Accumulated other comprehensive (loss) income			228
Total stockholders’ equity			130,067
Total liabilities and stockholders’ equity			179,789
Adjustments | ASC 606
Current assets:
Total assets		10,030
Current liabilities:
Total liabilities		0
Adjustments | ASC 606 | Marketplace Subscription Revenue
Current assets:
Accounts receivable, net		939	813
Total current assets		939	813
Deferred tax assets		(227)	(190)
Total assets		712	623
Current liabilities:
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock
Retained earnings		712	623
Total stockholders’ equity		712	623
Total liabilities and stockholders’ equity		712	623
Adjustments | ASC 606 | Costs To Obtain a Contract
Current assets:
Deferred contract costs		5,253	1,424
Total current assets		5,253	1,424
Deferred tax assets		(3,187)	(635)
Deferred contract costs, net of current portion		7,252	1,783
Total assets		9,318	2,572
Current liabilities:
Deferred tax liabilities			153
Total current liabilities			153
Total liabilities			153
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock
Retained earnings		9,318	2,419
Total stockholders’ equity		9,318	2,419
Total liabilities and stockholders’ equity		9,318	2,572
Class A Common Stock
Stockholders’ equity:
Common stock	92	90		78
Class A Common Stock | ASC 606
Stockholders’ equity:
Common stock			78
Class B Common Stock
Stockholders’ equity:
Common stock	$ 20	$ 21		$ 28
Class B Common Stock | ASC 606
Stockholders’ equity:
Common stock			$ 28

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Summary of Compare the Reported Consolidated Balance Sheet to Pro-forma Amounts had Previous Guidance Been in Effect (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 59,920	$ 34,887		$ 87,709
Investments	111,692	122,800		50,000
Accounts receivable, net	22,124	13,614	$ 13,390	12,577
Prepaid expenses and prepaid income taxes	10,452	10,144		5,313
Deferred contract costs	9,544	5,253	1,424
Other current assets	4,972	7,410		1,605
Restricted cash	250	750
Total current assets	218,954	194,858		157,204
Property and equipment, net	27,950	24,269		16,563
Restricted cash	10,553	1,921		1,843
Deferred tax assets	42,713	38,886		825
Deferred contract costs, net of current portion	10,514	7,252	1,782
Other non-current assets	3,826	1,104		159
Total assets	393,623	268,290		176,594
Current liabilities:
Accounts payable	36,731	34,345		23,908
Accrued expenses, accrued income taxes and other current liabilities	18,262	18,654		13,588
Deferred revenue	9,984	8,811		4,305
Deferred rent		1,693		1,165
Total current liabilities	73,758	63,503		42,966
Deferred rent		9,395		5,648
Other non–current liabilities	1,908	1,281		955
Total liabilities	136,768	74,179		49,569
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Additional paid–in capital	205,234	184,216		185,190
Retained earnings	51,859	9,713		(58,499)
Accumulated other comprehensive (loss) income	(350)	71		228
Total stockholders’ equity	256,855	194,111		127,025	$ (67,972)
Total liabilities and stockholders’ equity	393,623	268,290		176,594
ASC 606
Current assets:
Cash and cash equivalents			87,709
Investments			50,000
Accounts receivable, net			13,390
Prepaid expenses and prepaid income taxes			5,313
Deferred contract costs			1,424
Other current assets			1,605
Total current assets			159,441
Property and equipment, net			16,563
Restricted cash			1,843
Deferred contract costs, net of current portion			1,783
Other non-current assets			159
Total assets			179,789
Current liabilities:
Accounts payable			23,908
Accrued expenses, accrued income taxes and other current liabilities			13,588
Deferred revenue			4,305
Deferred rent			1,165
Total current liabilities			43,119
Deferred rent			5,648
Other non–current liabilities			955
Total liabilities			49,722
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Additional paid–in capital			185,190
Retained earnings			(55,457)
Accumulated other comprehensive (loss) income			228
Total stockholders’ equity			130,067
Total liabilities and stockholders’ equity			179,789
Adjustments | ASC 606
Current assets:
Total assets		10,030
Current liabilities:
Total liabilities		0
Adjustments | ASC 606 | Marketplace Subscription Revenue
Current assets:
Accounts receivable, net		939	813
Total current assets		939	813
Deferred tax assets		(227)	(190)
Total assets		712	623
Current liabilities:
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Retained earnings		712	623
Total stockholders’ equity		712	623
Total liabilities and stockholders’ equity		712	623
Adjustments | ASC 606 | Costs To Obtain a Contract
Current assets:
Deferred contract costs		5,253	1,424
Total current assets		5,253	1,424
Deferred tax assets		(3,187)	(635)
Deferred contract costs, net of current portion		7,252	1,783
Total assets		9,318	2,572
Current liabilities:
Total current liabilities			153
Total liabilities			153
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Retained earnings		9,318	2,419
Total stockholders’ equity		9,318	2,419
Total liabilities and stockholders’ equity		9,318	2,572
Pro Forma as if the Previous Accounting Guidance was in Effect | ASC 606
Current assets:
Cash and cash equivalents		34,887
Investments		122,800
Accounts receivable, net		12,675
Prepaid expenses and prepaid income taxes		10,144
Other current assets		7,410
Restricted cash		750
Total current assets		188,666
Property and equipment, net		24,269
Restricted cash		1,921
Deferred tax assets		42,300
Other non-current assets		1,104
Total assets		258,260
Current liabilities:
Accounts payable		34,345
Accrued expenses, accrued income taxes and other current liabilities		18,654
Deferred revenue		8,811
Deferred rent		1,693
Total current liabilities		63,503
Deferred rent		9,395
Other non–current liabilities		1,281
Total liabilities		74,179
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Additional paid–in capital		184,216
Retained earnings		(317)
Accumulated other comprehensive (loss) income		71
Total stockholders’ equity		184,081
Total liabilities and stockholders’ equity		258,260
Class A Common Stock
Stockholders’ equity:
Common stock	92	90		78
Class A Common Stock | ASC 606
Stockholders’ equity:
Common stock			78
Class A Common Stock | Pro Forma as if the Previous Accounting Guidance was in Effect | ASC 606
Stockholders’ equity:
Common stock		90
Class B Common Stock
Stockholders’ equity:
Common stock	$ 20	21		$ 28
Class B Common Stock | ASC 606
Stockholders’ equity:
Common stock			$ 28
Class B Common Stock | Pro Forma as if the Previous Accounting Guidance was in Effect | ASC 606
Stockholders’ equity:
Common stock		$ 21

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Summary of Changes on Consolidated Statement of Operations as a Result of Adoption of ASC 606 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Revenue	$ 158,153		$ 150,462		$ 145,031		$ 135,270		$ 126,090		$ 119,125		$ 110,296		$ 98,575		$ 588,916		$ 454,086		$ 316,861
Cost of revenue	10,560		9,392		8,628		7,720		6,871		6,412		5,959		5,569		36,300	[1]	24,811	[1]	17,609	[1]
Gross profit	147,593		141,070		136,403		127,550		119,219		112,713		104,337		93,006		552,616		429,275		299,252
Operating expenses:
Sales and marketing																	393,844		315,939		236,165
Product, technology, and development																	69,462		47,866		22,470
General and administrative																	50,434		39,475		22,688
Depreciation and amortization																	4,554		2,804		2,655
Total operating expenses																	518,294		406,084		283,978
Income from operations	13,635		9,704		3,548		7,435		6,902		5,877		3,953		6,459		34,322		23,191		15,274
Other income, net:
Interest income																	2,984		2,283		869
Other income (expense), net																	1,399		10		(306)
Total other income, net																	4,383		2,293		563
Income before income taxes																	38,705		25,484		15,837
(Benefit from) provision for income taxes																	(3,441)		(39,686)		2,638
Net income	$ 13,171		$ 10,384		$ 6,007		$ 12,584		$ 12,450		$ 13,882		$ 33,343		$ 5,495		$ 42,146		$ 65,170		$ 13,199
Basic	$ 0.12	[2]	$ 0.09	[2]	$ 0.05	[2]	$ 0.11	[2]	$ 0.11	[2]	$ 0.13	[2]	$ 0.31	[2]	$ 0.05	[2]	$ 0.38		$ 0.60		$ 0.13
Diluted	$ 0.12	[2]	$ 0.09	[2]	$ 0.05	[2]	$ 0.11	[2]	$ 0.11	[2]	$ 0.12	[2]	$ 0.29	[2]	$ 0.05	[2]	$ 0.37		$ 0.57		$ 0.12
Marketplace Subscription Revenue
Summary Of Significant Accounting Policies [Line Items]
Revenue																	$ 526,043		$ 405,780		$ 282,664
Adjustments | ASC 606
Summary Of Significant Accounting Policies [Line Items]
Revenue																			126
Operating expenses:
Sales and marketing																			(9,298)
Other income, net:
Income before income taxes																			9,424
(Benefit from) provision for income taxes																			$ 2,436
Basic																			$ 0.07
Diluted																			$ 0.06
Adjustments | ASC 606 | Costs To Obtain a Contract
Operating expenses:
Sales and marketing																			$ (9,298)
Total operating expenses																			(9,298)
Income from operations																			9,298
Other income, net:
Income before income taxes																			9,298
(Benefit from) provision for income taxes																			2,399
Net income																			$ 6,899
Basic																			$ 0.07
Diluted																			$ 0.06
Adjustments | ASC 606 | Marketplace Subscription Revenue
Summary Of Significant Accounting Policies [Line Items]
Revenue																			$ 126
Gross profit																			126
Operating expenses:
Income from operations																			126
Other income, net:
Income before income taxes																			126
(Benefit from) provision for income taxes																			37
Net income																			89
Pro Forma as if the Previous Accounting Guidance was in Effect | ASC 606
Summary Of Significant Accounting Policies [Line Items]
Revenue																			453,960
Cost of revenue																			24,811
Gross profit																			429,149
Operating expenses:
Sales and marketing																			325,237
Product, technology, and development																			47,866
General and administrative																			39,475
Depreciation and amortization																			2,804
Total operating expenses																			415,382
Income from operations																			13,767
Other income, net:
Interest income																			2,283
Other income (expense), net																			10
Total other income, net																			2,293
Income before income taxes																			16,060
(Benefit from) provision for income taxes																			(42,122)
Net income																			$ 58,182
Basic																			$ 0.53
Diluted																			$ 0.51
[1]	Includes depreciation and amortization expense for the years ended December 31, 2019, 2018, and 2017 of $3,263 $2,225, and $1,140, respectively.
[2]	The amounts were computed independently for each quarter, and the sum of the quarters may not total the annual amounts.

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Summary of Changes on Consolidated Statement of Cash Flows as a Result of Adoption of ASC 606 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 42,146	$ 65,170	$ 13,199
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,817	5,029	3,795
Currency (gain) loss on foreign denominated transactions	(690)	(190)	128
Deferred taxes	(3,734)	(39,040)	(1,117)
Provision for doubtful accounts	1,091	1,680	1,117
Stock–based compensation expense	34,301	20,794	5,028
Amortization of deferred contract costs	8,416	3,689
Changes in operating assets and liabilities:
Accounts receivable, net	(9,608)	(1,911)	(7,039)
Prepaid expenses, prepaid income taxes, and other assets	(378)	(11,753)	(2,287)
Deferred contracts costs	(15,979)	(12,987)
Accounts payable	4,268	9,345	6,244
Accrued expenses, accrued income taxes and other current liabilities	2,151	2,695	5,191
Deferred revenue	1,174	4,508	962
Deferred rent		4,289	227
Other non–current liabilities	609	405	243
Net cash provided by operating activities	$ 70,116	51,723	$ 25,691
Adjustments | ASC 606 | Costs To Obtain a Contract
Operating Activities
Net income		6,899
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred taxes		2,399
Amortization of deferred contract costs		3,689
Changes in operating assets and liabilities:
Deferred contracts costs		(12,987)
Adjustments | ASC 606 | Marketplace Subscription Revenue
Operating Activities
Net income		89
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred taxes		37
Changes in operating assets and liabilities:
Accounts receivable, net		(126)
Pro Forma as if the Previous Accounting Guidance was in Effect | ASC 606
Operating Activities
Net income		58,182
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		5,029
Currency (gain) loss on foreign denominated transactions		(190)
Deferred taxes		(41,476)
Provision for doubtful accounts		1,680
Stock–based compensation expense		20,794
Changes in operating assets and liabilities:
Accounts receivable, net		(1,785)
Prepaid expenses, prepaid income taxes, and other assets		(11,753)
Accounts payable		9,345
Accrued expenses, accrued income taxes and other current liabilities		2,695
Deferred revenue		4,508
Deferred rent		4,289
Other non–current liabilities		405
Net cash provided by operating activities		$ 51,723

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Summary of Opening and Closing Balances of Receivables and Contract Assets From Contracts with Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts Receivable, net	$ 22,124	$ 13,614	$ 13,390	$ 12,577
Contract Assets(current)	9,544	5,253	1,424
Contract Assets(non-current)	$ 10,514	$ 7,252	$ 1,782

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Summary of Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Balance at Beginning of Period	$ 479	$ 494	$ 164
Provision for doubtful accounts	1,091	1,680	1,117
Write–offs, net of recoveries	(1,330)	(1,695)	(787)
Balance at End of Period	$ 240	$ 479	$ 494

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Capitalized Equipment
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Capitalized Software
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Capitalized Website Development Costs
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Estimated Useful Life	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated Useful Life	Lesser of asset life or lease term

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Summary of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Operating Lease Commitments
2020	$ 12,201
2021	13,088
2022	13,016
2023	9,858
2024	8,835
Thereafter	34,423
Total lease payments	91,421
Less imputed interest	(21,822)
Total	$ 69,599

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) £ in Thousands, $ in Thousands	Jan. 08, 2019USD ($)	Jan. 08, 2019GBP (£)	Dec. 31, 2019USD ($)
Business Acquisition [Line Items]
Payments to acquire business			$ 19,139
PistonHeads Holdco Limited | United Kingdom | Put and Call Option Agreement
Business Acquisition [Line Items]
Payments to acquire business	$ 19,139	£ 15,000
Acquisition-related costs incurred			$ 779
Business acquisition completed date	Jan. 8, 2019	Jan. 8, 2019
PistonHeads Holdco Limited | United Kingdom | Escrow Agreement
Business Acquisition [Line Items]
Payments to acquire business	$ 1,276	£ 1,000

Acquisitions - Summary of Purch

Acquisitions - Summary of Purchase Price Allocation (Details) - USD ($) $ in Thousands		Jan. 08, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill			$ 15,207
Goodwill, Adjustment	[1]		$ 655
PistonHeads Holdco Limited
Business Acquisition [Line Items]
Intangible assets, Estimated fair value	[2]	$ 4,466
Goodwill	[3]	15,521
Deferred tax liabilities, Estimated Fair Value	[4]	(848)
Total purchase price, Estimated fair value		19,139
Goodwill, Adjustment	[3]	(655)
Deferred tax liabilities, Adjustment	[4]	655
Intangible assets, Adjusted fair value	[2]	4,466
Goodwill, Adjusted fair value	[3]	14,866
Deferred tax liabilities, Adjusted fair value	[4]	(193)
Total purchase price , Adjusted fair value		$ 19,139
[1]	The purchase price adjustment corresponds to an adjustment for the deferred tax liability as a result of the Company’s evaluation of income tax treatment, which was recorded during the second quarter of 2019.
[2]	Identifiable definite-lived intangible assets were comprised of brand and customer relationships of $3,445 and $1,021, respectively, with estimated useful lives of 11 years and 3 years, respectively, which will be amortized on a straight-line basis over their estimated useful lives.
[3]	The goodwill represents the excess value of the purchase price over intangible assets acquired. The goodwill in this transaction is primarily attributable to future customer growth in the U.K. market as a result of acquiring an established platform and applying the Company’s technology to help improve the website experience on such platform; thus, helping to drive additional traffic to the PistonHeads website in the future. All goodwill is assigned to the International segment. The acquisition of PistonHeads was a stock acquisition and as a result, g
[4]	T

Acquisitions - Summary of Pur_2

Acquisitions - Summary of Purchase Price Allocation (Parenthetical) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Jan. 08, 2019
PistonHeads Holdco Limited
Business Acquisition [Line Items]
Intangible assets	[1]		$ 4,466
Brand
Business Acquisition [Line Items]
Estimated useful lives		11 years
Brand | PistonHeads Holdco Limited
Business Acquisition [Line Items]
Intangible assets			3,445
Estimated useful lives		11 years
Customer Relationships
Business Acquisition [Line Items]
Estimated useful lives		3 years
Customer Relationships | PistonHeads Holdco Limited
Business Acquisition [Line Items]
Intangible assets			$ 1,021
Estimated useful lives		3 years
[1]	Identifiable definite-lived intangible assets were comprised of brand and customer relationships of $3,445 and $1,021, respectively, with estimated useful lives of 11 years and 3 years, respectively, which will be amortized on a straight-line basis over their estimated useful lives.

Fair Value of Financial Instr_3

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments - Schedule of Fair Value Levels, Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	$ 59,920	$ 34,887
Investments:	111,692	122,800	$ 50,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments:	$ 111,692	$ 122,800
Debt Securities, Held-to-maturity, Type [Extensible List]	us-gaap:CertificatesOfDepositMember	us-gaap:CertificatesOfDepositMember
Total	$ 140,888	$ 122,824
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1 Inputs)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	29,196	24
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2 Inputs)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments:	$ 111,692	$ 122,800
Debt Securities, Held-to-maturity, Type [Extensible List]	us-gaap:CertificatesOfDepositMember	us-gaap:CertificatesOfDepositMember
Total	$ 111,692	$ 122,800
Fair Value, Measurements, Recurring | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	29,196	24
Fair Value, Measurements, Recurring | Money Market Funds | Quoted Prices in Active Markets for Identical Assets (Level 1 Inputs)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	$ 29,196	$ 24

Fair Value of Financial Instr_4

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments - Additional Information (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Liabilities, fair value	$ 0	$ 0

Fair Value of Financial Instr_5

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments - Schedule of Cash, Cash Equivalents, and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Cash and cash equivalents due in 90 days or less, Amortized Cost	$ 59,920	$ 34,887	$ 87,709
Certificates of deposit due in one year or less, Amortized Cost	111,692	122,800
Total cash, cash equivalents, and investments, Amortized Cost	171,612	157,687
Cash and cash equivalents due in 90 days or less, Estimated Fair Value	59,920	34,887
Certificates of deposit due in one year or less, Estimated Fair Value	111,692	122,800
Total cash, cash equivalents, and investments, Estimated Fair Value	$ 171,612	$ 157,687

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 46,105	$ 35,743
Less accumulated depreciation and amortization	(18,155)	(11,474)
Property and equipment, net	27,950	24,269	$ 16,563
Capitalized Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	7,923	4,208
Capitalized Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	181	252
Capitalized Website Development Costs
Property Plant And Equipment [Line Items]
Property and equipment, gross	11,083	6,907
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,809	4,584
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	19,507	10,821
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	524	$ 8,971
Finance Lease Right-of-use Assets
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 78

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Depreciation	$ 7,168	$ 5,029	$ 3,795
Leasehold Improvements
Property Plant And Equipment [Line Items]
Increase (decrease) in property and equipment	8,686
Construction in Progress
Property Plant And Equipment [Line Items]
Increase (decrease) in property and equipment	$ (8,447)

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Summary of Changes in Carrying Value of Goodwill (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Initial value of PistonHeads acquisition	$ 15,521
Foreign currency translation adjustment	341
Purchase price adjustment	(655)	[1]
Balance at December 31, 2019	$ 15,207
[1]	The purchase price adjustment corresponds to an adjustment for the deferred tax liability as a result of the Company’s evaluation of income tax treatment, which was recorded during the second quarter of 2019.

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Summary of Other Intangible Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,569
Accumulated Amortization	649
Net Carrying Amount	$ 3,920
Brand
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (years)	10 years
Gross Carrying Amount	$ 3,524
Accumulated Amortization	313
Net Carrying Amount	$ 3,211
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (years)	2 years
Gross Carrying Amount	$ 1,045
Accumulated Amortization	336
Net Carrying Amount	$ 709

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019
Goodwill [Line Items]
Amortization expense of intangible assets		$ 649,000
Goodwill impairment	$ 0
Brand
Goodwill [Line Items]
Estimated useful life		11 years
Customer Relationships
Goodwill [Line Items]
Estimated useful life		3 years

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Summary of Estimated Amortization Expense of Intangible Assets (Details) $ in Thousands	Dec. 31, 2019USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
2020	$ 671
2021	671
2022	328
2023	320
2024	320
2025 and thereafter	1,610
Net Carrying Amount	$ 3,920

Accrued Expenses, Accrued Inc_3

Accrued Expenses, Accrued Income Taxes and Other Current Liabilities - Schedule of Accrued Expenses, Accrued Income Taxes and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
Accrued bonus	$ 8,637	$ 8,266
Other accrued expenses, accrued income taxes and other current liabilities	9,625	10,388
Total	$ 18,262	$ 18,654	$ 13,588

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Unpaid property and equipment	$ 647	$ 5,287	$ 510

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details) - $ / shares	Oct. 16, 2017	Jun. 21, 2017	Dec. 31, 2019	Dec. 31, 2018	Oct. 11, 2017
Class Of Stock [Line Items]
Preferred stock, shares authorized	10,000,000	11,091,782			11,091,782
Preferred stock, par value	$ 0.001	$ 0.001
Percentage of common stock exercise price adjusted		0.167%
Percentage of common stock fair value adjusted prior to recapitalization		0.167%
Common stock exercise feature			the number of shares of common stock as to which each outstanding option to purchase common stock was exercisable for and each outstanding RSU was convertible into was adjusted such that upon exercise of outstanding stock options or vesting of outstanding RSUs, each holder would receive two fully paid and non‑assessable shares of Class A common stock and four fully paid and non‑assessable shares of Class B common stock in respect of each share of common stock previously underlying such option or RSU
Conversion of convertible securities into shares of common stock	9,091,484
Preferred stock, shares outstanding	0		0	0
IPO
Class Of Stock [Line Items]
Preferred stock, shares outstanding	0
Class A Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	500,000,000	120,020,700	500,000,000	500,000,000
Common stock, par value	$ 0.001	$ 0.001	$ 0.001	$ 0.001
Common stock conversion terms			each share of Class A common stock issued and outstanding was recapitalized, reclassified, and reconstituted into two fully paid and non‑assessable shares of outstanding Class A common stock and four fully paid and non‑assessable shares of outstanding Class B common stock
Number of shares issued upon exercise of outstanding stock options or vesting of outstanding RSUs		2
Conversion of convertible securities into shares of common stock	60,564,678
Class A Common Stock | IPO
Class Of Stock [Line Items]
Conversion of convertible securities into shares of common stock	20,188,226
Class A Common Stock | Class A Common Stock Recapitalized, Reclassified And Reconstituted [Member]
Class Of Stock [Line Items]
Common stock issued in conversion		2
Class A Common Stock | Class B Common Stock Recapitalized, Reclassified And Reconstituted [Member]
Class Of Stock [Line Items]
Common stock issued in conversion		2
Class A Common Stock | Subsequent Conversion
Class Of Stock [Line Items]
Conversion of convertible securities into shares of common stock	40,376,452
Class B Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	100,000,000	80,013,800	100,000,000	100,000,000
Common stock, par value	$ 0.001	$ 0.001	$ 0.001	$ 0.001
Common stock conversion terms			each share of Class B common stock of the Company issued and outstanding was recapitalized, reclassified, and reconstituted into two fully paid and non‑assessable shares of outstanding Class A common stock and four fully paid and non‑assessable shares of outstanding Class B common stock
Number of shares issued upon exercise of outstanding stock options or vesting of outstanding RSUs		4
Conversion of convertible securities into shares of common stock	40,376,452
Class B Common Stock | Class A Common Stock Recapitalized, Reclassified And Reconstituted [Member]
Class Of Stock [Line Items]
Common stock issued in conversion		4
Class B Common Stock | Class B Common Stock Recapitalized, Reclassified And Reconstituted [Member]
Class Of Stock [Line Items]
Common stock issued in conversion		4
Series A Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized		3,333,000			3,333,000
Series B Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized		3,329,497			3,329,497
Series D Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized		1,673,105			1,673,105
Series C Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized		1,648,978			1,648,978
Series E Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized		1,107,202			1,107,202

Convertible Preferred Stock a_4

Convertible Preferred Stock and Stockholders' Equity - Common Stock - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019Voteshares	Dec. 31, 2018shares
Class Of Stock [Line Items]
Common stock conversion feature	Each share of Class B common stock entitles the holder to ten votes for each share on all matters submitted to a vote of the Company’s stockholders at all meetings of stockholders and written actions in lieu of meetings.
Class A Common Stock
Class Of Stock [Line Items]
Number of votes entitled to stockholders per share | Vote	1
Conversion of stock | shares	387,440	7,534,710
Class B Common Stock
Class Of Stock [Line Items]
Number of votes entitled to stockholders per share | Vote	10
Class of share converted to another class	one share of Class A common stock
Conversion of stock | shares	1

Convertible Preferred Stock a_5

Convertible Preferred Stock and Stockholders' Equity - Summary of Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 16, 2017	Oct. 11, 2017	Jun. 21, 2017	Dec. 31, 2016
Temporary Equity [Line Items]
Shares Authorized	10,000,000	11,091,782	11,091,782
Outstanding		10,094,108
Liquidation Amount		$ 133,094
Carrying Value		$ 132,698
Series A Preferred Stock
Temporary Equity [Line Items]
Original Issue Price Per Share		$ 0.525053
Shares Authorized		3,333,000	3,333,000
Outstanding		2,824,703		2,824,703
Liquidation Amount		$ 1,483
Carrying Value		$ 1,483		$ 1,483
Series B Preferred Stock
Temporary Equity [Line Items]
Original Issue Price Per Share		$ 0.780899
Shares Authorized		3,329,497	3,329,497
Outstanding		2,938,486		2,938,486
Liquidation Amount		$ 2,295
Carrying Value		$ 2,295		$ 2,295
Series C Preferred Stock
Temporary Equity [Line Items]
Original Issue Price Per Share		$ 0.849012
Shares Authorized		1,648,978	1,648,978
Outstanding		1,550,612		1,550,612
Liquidation Amount		$ 1,316
Carrying Value		$ 1,316		$ 1,316
Series D Preferred Stock
Temporary Equity [Line Items]
Original Issue Price Per Share		$ 40.642989
Shares Authorized		1,673,105	1,673,105
Outstanding		1,673,105		1,673,105
Liquidation Amount		$ 68,000
Carrying Value		$ 67,872		$ 67,872
Series E Preferred Stock
Temporary Equity [Line Items]
Original Issue Price Per Share		$ 54.190650
Shares Authorized		1,107,202	1,107,202
Outstanding		1,107,202		1,107,202
Liquidation Amount		$ 60,000
Carrying Value		$ 59,732		$ 59,732

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 22, 2016	Aug. 15, 2015	Jun. 26, 2015	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017	Oct. 16, 2017	Oct. 11, 2017	Jun. 21, 2017	Dec. 31, 2006
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of options granted in period				0		0	0
Unrecognized stock-based compensation expense related to RSUs									$ 2,500
Total stock-based compensation expense				$ 34,301		$ 20,794	$ 5,028
Capitalized software development costs and internal-use software costs excluded from stock-based compensation expense				1,381		490	176
Income tax benefit from stock-based compensation expense				2,953		1,945	$ 1,301
Total payments for employees' tax obligations to taxing authorities due to net share settlements				$ 16,470		$ 25,885
Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of options granted in period				0		0	0
Aggregate intrinsic value for options exercised				$ 28,902	[1]	$ 111,227	$ 2,238
Unrecognized stock-based compensation expense related to stock options				$ 16
Unrecognized stock-based compensation expense, expected period for recognition				3 months 18 days
Total stock-based compensation expense				$ 155		$ 247	$ 281
RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of RSUs granted in period				1,811,208
Unrecognized stock-based compensation expense, expected period for recognition				2 years 9 months 18 days
Weighted average grant date fair value of RSUs granted				$ 39.07		$ 35.79	$ 16.99
Number of RSUs vested and settled during period						1,781,201
Number of RSUs vested in period				1,317,736		1,087,279	693,922
Total fair value of RSUs vested				$ 31,533		$ 15,994	$ 2,505
Unrecognized stock-based compensation expense related to RSUs				92,700
Total stock-based compensation expense				$ 34,146		$ 20,547	$ 4,747
Class A Common Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Employee tax withholding requirements and option costs due to net share settlement				452,678		658,931	0
2006 Plan
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock options, granted			0
Number of RSUs granted in period			0
2006 Plan | Class B Common Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance											3,444,668
2015 Plan
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance			603,436
Term of authorized shares		10 years
Award expiration date	Aug. 21, 2026
Equity Incentive Plan, plan modification, description and terms				(1) the number of shares of Class A common stock was increased, on a share for share basis, by the number of shares of Class B common stock that were (a) subject to outstanding options granted under the 2006 Plan that expired, terminated, or were cancelled for any reason without having been exercised, (b) surrendered in payment of the exercise price of outstanding options granted under the 2006 Plan or (c) withheld in satisfaction of tax withholding upon exercise of outstanding options granted under the 2006 Plan, and the number of shares of Class B common stock reserved under the amended and restated 2015 Plan was decreased, on a corresponding share for share basis, (2) no new awards of Class B common stock could be granted under the amended and restated 2015 Plan, and (3) except with respect to outstanding options granted under the 2006 Plan that were exercised on or after the date of the amendment and restatement, no Class B common stock could be issued under the 2015 Plan.
2015 Plan | Class B Common Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance										5,161,644
Number of additional shares authorized	802,562
2015 Plan | Class B Common Stock | Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares called by each instrument										4
2015 Plan | Class B Common Stock | RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares called by each instrument										4
2015 Plan | Class A Common Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance										3,181,740
Number of additional shares authorized	618,691
2015 Plan | Class A Common Stock | Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares called by each instrument										2
2015 Plan | Class A Common Stock | RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares called by each instrument										2
2017 Plan
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of additional shares authorized				6,000,000
Equity incentive plan, issuance of additional shares, description and terms				Unless determined otherwise by the Compensation Committee of the Board, as of the first trading day of January of each calendar year during the term of the 2017 Plan (excluding any extensions), eligible beginning with calendar year 2019, an additional number of shares of Class A common stock will be added to the number of shares of the Company’s Class A common stock authorized to be issued or transferred under the 2017 Plan and the number of shares authorized to be issued or transferred pursuant to incentive stock options, equal to 4% of the total number of shares of our Class A common stock outstanding on the last trading day in December of the immediately preceding calendar year, or 6,000,000 shares, whichever is less, or such lesser amount as determined by the Board (the “Evergreen Increase”). The Compensation Committee of the Board determined to not effectuate the Evergreen Increase that was otherwise scheduled to have occurred on each of January 2, 2019 and January 2, 2020.
2017 Plan | Class A Common Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Equity incentive plan, additional shares authorized percentage				4.00%
Number of shares available for issuance during period				5,889,929
2017 Plan | Class A Common Stock | Maximum
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance								12,300,000
2017 Plan | Class A Common Stock | Awarded Under 2017 Plan
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance								7,800,000
2017 Plan | Class A Common Stock | Awarded Under 2015 Plan
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Number of shares authorized for issuance								4,500,000
[1]	The aggregate intrinsic value as of December 31, 2019 and 2018 was calculated based on the positive difference, if any, between the estimated fair value of our common stock on December 31, 2019 and 2018, respectively, or the date of exercise, as appropriate, and the exercise price of the underlying options

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Common Stock
Options granted during period		0		0	0
Stock Options
Common Stock
Outstanding, Beginning balance		1,807,515
Options granted during period		0		0	0
Exercised		(838,928)
Forfeited and cancelled		(25,702)
Outstanding, Ending balance		942,885		1,807,515
Options exercisable		913,197
Weighted-Average Exercise Price for Equity
Outstanding, Beginning balance		$ 2.35
Exercised		2.16
Forfeited and cancelled		5.09
Outstanding, Ending balance		2.45		$ 2.35
Options exercisable		$ 2.31
Weighted-Average Remaining Contractual Life (In Years)
Outstanding		5 years		5 years 10 months 24 days
Options exercisable		5 years
Aggregate Intrinsic Value
Outstanding, Beginning balance	[1]	$ 56,716
Exercised		28,902	[1]	$ 111,227	$ 2,238
Outstanding, Ending balance	[1]	30,859		$ 56,716
Options exercisable	[1]	$ 30,016
[1]	The aggregate intrinsic value as of December 31, 2019 and 2018 was calculated based on the positive difference, if any, between the estimated fair value of our common stock on December 31, 2019 and 2018, respectively, or the date of exercise, as appropriate, and the exercise price of the underlying options

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Restricted Stock Unit Activity (Details) - RSUs - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Unvested outstanding, beginning balance	2,973,002
Granted	1,811,208
Vested	(1,317,736)	(1,087,279)	(693,922)
Forfeited	(383,173)
Unvested outstanding, ending balance	3,083,301	2,973,002
Weighted-Average Grant Date Fair Value
Unvested outstanding, beginning balance	$ 26.06
Granted	39.07	$ 35.79	$ 16.99
Vested	23.93
Forfeited	31.70
Unvested outstanding, ending balance	$ 33.89	$ 26.06
Aggregate Intrinsic Value
Unvested outstanding, beginning balance	$ 100,279
Unvested outstanding, ending balance	$ 108,471	$ 100,279

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Stock-based Compensation Expense by Award Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 34,301	$ 20,794	$ 5,028
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	155	247	281
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 34,146	$ 20,547	$ 4,747

Stock-based Compensation - Su_4

Stock-based Compensation - Summary of Allocation of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 34,301	$ 20,794	$ 5,028
Cost of Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	354	354	151
Sales and Marketing Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	9,989	5,111	1,911
Product, Technology, and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	15,159	9,865	1,637
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 8,799	$ 5,464	$ 1,329

Stock-based Compensation - Su_5

Stock-based Compensation - Summary of Shares of Common Stock Reserved for Future Issuance (Details)	Dec. 31, 2019shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares of authorized common stock reserved for future issuance	9,916,115
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares of authorized common stock reserved for future issuance	942,885
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares of authorized common stock reserved for future issuance	3,083,301
2017 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares of authorized common stock reserved for future issuance	5,889,929

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Details)	Oct. 16, 2017shares	Dec. 31, 2019Voteshares	Dec. 31, 2018shares
Earnings Per Share Basic [Line Items]
Convertible preferred stock, terms of conversion		On October 16, 2017, in connection with the closing
Conversion of preferred stock	9,091,484
Preferred stock, shares outstanding	0	0	0
Conversion of stock, description		Each share of Class B common stock is convertible into one share of Class A common stock at the option of the holder at any time or automatically upon certain events described in the Company’s amended and restated certificate of incorporation, including on either the death or voluntary termination of the Company’s Chief Executive Officer.
Undistributed earnings ratio used to calculate allocation to class of stock		100.00%
IPO
Earnings Per Share Basic [Line Items]
Preferred stock, shares outstanding	0
Class A Common Stock
Earnings Per Share Basic [Line Items]
Conversion of preferred stock	60,564,678
Right to voting		one vote per share
Number of votes entitled to stockholders per share | Vote		1
Conversion of stock		387,440	7,534,710
Class A Common Stock | IPO
Earnings Per Share Basic [Line Items]
Conversion of preferred stock	20,188,226
Class B Common Stock
Earnings Per Share Basic [Line Items]
Conversion of preferred stock	40,376,452
Right to voting		ten votes per share
Number of votes entitled to stockholders per share | Vote		10
Class of share converted to another class		one share of Class A common stock
Conversion of stock		1

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 13,171		$ 10,384		$ 6,007		$ 12,584		$ 12,450		$ 13,882		$ 33,343		$ 5,495		$ 42,146	$ 65,170	$ 13,199
Net income attributable to participating securities																			(6,098)
Net income attributable to common stockholders — basic																	42,146	65,170	7,101
Net income attributable to participating securities																			(5,829)
Net income attributable to common stockholders — diluted																	$ 42,146	$ 65,170	$ 7,370
Denominator:
Weighted–average number of shares of common stock used in computing net income per share attributable to common stockholders — basic																	111,450,443	108,833,028	55,835,265
Dilutive effect of share equivalents resulting from stock options																	1,155,906	3,009,748	4,290,362
Dilutive effect of share equivalents resulting from unvested restricted stock units																	825,501	1,521,936	511,957
Weighted–average number of shares of common stock used in computing net income per share — diluted																	113,431,850	113,364,712	60,637,584
Net income per share attributable to common stockholders:
Basic	$ 0.12	[1]	$ 0.09	[1]	$ 0.05	[1]	$ 0.11	[1]	$ 0.11	[1]	$ 0.13	[1]	$ 0.31	[1]	$ 0.05	[1]	$ 0.38	$ 0.60	$ 0.13
Diluted	$ 0.12	[1]	$ 0.09	[1]	$ 0.05	[1]	$ 0.11	[1]	$ 0.11	[1]	$ 0.12	[1]	$ 0.29	[1]	$ 0.05	[1]	$ 0.37	$ 0.57	$ 0.12
[1]	The amounts were computed independently for each quarter, and the sum of the quarters may not total the annual amounts.

Earnings Per Share - Schedule_2

Earnings Per Share - Schedule of Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Weighted-average Shares Outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock Units Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive common stock equivalents excluded from calculation of diluted weighted-average shares outstanding	1,144,287	126,816	829

Income Taxes - Schedule of Dome

Income Taxes - Schedule of Domestic and Foreign Components of Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments [Abstract]
United States	$ 37,476	$ 24,426	$ 15,543
Foreign	1,229	1,058	294
Income before income taxes	$ 38,705	$ 25,484	$ 15,837

Income Taxes - Schedule of (Ben

Income Taxes - Schedule of (Benefit From) Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current (benefit) provision:
Federal		$ (860)	$ 3,262
State	$ (220)	92	431
Foreign	513	122	62
Current (benefit) provision	293	(646)	3,755
Deferred (benefit) provision:
Federal	(2,377)	(27,675)	(755)
State	(1,306)	(11,499)	(343)
Foreign	(51)	134	(19)
Deferred (benefit) provision	(3,734)	(39,040)	(1,117)
Income tax (benefit) provision	$ (3,441)	$ (39,686)	$ 2,638

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Tax Rates Less than US Federal Statutory Rate Primarily Due to Excess Tax Deductions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
U.S. federal taxes at statutory rate	21.00%	21.00%	35.00%
State taxes, net of federal benefit	0.20%	(25.60%)	3.10%
Nondeductible expenses	2.90%	4.10%	1.20%
Tax deductible IPO costs			(9.30%)
Stock compensation	(22.00%)	(127.20%)	(4.40%)
Foreign rate differential	(0.30%)	(0.40%)	(0.40%)
Credits	(10.30%)	(28.40%)	(9.00%)
Other	(0.20%)	0.70%	0.50%
Total	(8.70%)	(155.80%)	16.70%

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Effect of Each Type of Temporary Difference and Carryforward (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 35,977	$ 34,450
Credit carryforwards	10,472	6,562
Stock-based compensation	2,953	1,945
Landlord allowance on leasehold improvements		1,908
Lease liability	17,965
Intangible Assets	62
Deferred rent		873
Accruals and reserves	1,185	1,074
Deferred tax assets	68,614	46,812
Valuation Allowance	(62)
Valuation Allowance, net	68,552	46,812
Deferred tax liabilities:
Prepaid expenses	(1,523)	(931)
Deferred commissions	(5,100)	(3,187)
Right of use assets	(15,270)
Unbilled revenue		(227)
Fixed assets	(4,230)	(3,581)
Deferred tax liability	(26,123)	(7,926)
Net deferred tax assets	$ 42,429	$ 38,886

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Line Items]
Change in valuation allowance	$ 62,000
Deferred tax assets, federal net operating loss carryforwards	136,771,000
Deferred tax assets, state net operating loss carryforwards	$ 114,459,000
Percentage of annual limitation of taxable income	80.00%
State net operating loss carryforward, expiration year	2028
Tax credit carryforward, expiration year	2039
Liabilities for uncertain tax positions	$ 0	$ 0
Accrued interest or penalties related to uncertain tax positions	0	$ 0
Federal
Income Tax Disclosure [Line Items]
Tax credit carryforwards	6,507,000
State
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 5,018,000
Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Tax credit carryforward limitations on use, cumulative ownership change, period	3 years
Tax credit carryforward, limitations on use	an ownership change, as defined by Section 382, results from transactions that increase the ownership of five percent stockholders in the stock of a corporation by more than 50% in the aggregate over a three-year period.
Internal Revenue Service (IRS) | Minimum
Income Tax Disclosure [Line Items]
Tax credit carryforward limitations on use, cumulative ownership change percentage	5.00%
Internal Revenue Service (IRS) | Maximum
Income Tax Disclosure [Line Items]
Tax credit carryforward limitations on use, cumulative ownership change percentage	50.00%
Internal Revenue Service (IRS) | Federal
Income Tax Disclosure [Line Items]
Income tax examination year under examination	2017
Closed tax year	2015
Internal Revenue Service (IRS) | State
Income Tax Disclosure [Line Items]
Closed tax year	2015
UK Revenue Agency | Foreign
Income Tax Disclosure [Line Items]
Open tax year	2016
Canada Revenue Agency | Foreign
Income Tax Disclosure [Line Items]
Open tax year	2016
Revenue Commissioners, Ireland | Foreign
Income Tax Disclosure [Line Items]
Open tax year	2016

Segment and Geographic Inform_3

Segment and Geographic Information - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)Segment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	2
Assets	$ 393,623	$ 268,290	$ 176,594
Goodwill	15,207
Intangible assets	3,920
International
Segment Reporting Information [Line Items]
Assets	32,528
Goodwill	15,207
Intangible assets	$ 3,920

Segment and Geographic Inform_4

Segment and Geographic Information - Summary of Operations by Segment and Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment revenue:
Revenue	$ 158,153	$ 150,462	$ 145,031	$ 135,270	$ 126,090	$ 119,125	$ 110,296	$ 98,575	$ 588,916	$ 454,086	$ 316,861
Segment income (loss) from operations:
Total income from operations	$ 13,635	$ 9,704	$ 3,548	$ 7,435	$ 6,902	$ 5,877	$ 3,953	$ 6,459	34,322	23,191	15,274
United States
Segment revenue:
Revenue									555,007	437,166	307,472
Segment income (loss) from operations:
Total income from operations									73,872	58,387	41,586
International
Segment revenue:
Revenue									33,909	16,920	9,389
Segment income (loss) from operations:
Total income from operations									$ (39,550)	$ (35,196)	$ (26,312)

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Employer matching contribution, percent of match	50.00%
Defined contribution plan, maximum annual contributions per employee, percent	6.00%
Annual maximum amount of employee contributions	$ 5,000,000
Defined contribution plan, employer contribution	$ 2,708,000	$ 1,953,000	$ 724,000

Quarterly Financial Results (_3

Quarterly Financial Results (Unaudited) - Schedule of Unaudited Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Quarterly Financial Data [Abstract]
Revenue	$ 158,153		$ 150,462		$ 145,031		$ 135,270		$ 126,090		$ 119,125		$ 110,296		$ 98,575		$ 588,916		$ 454,086		$ 316,861
Cost of revenue	10,560		9,392		8,628		7,720		6,871		6,412		5,959		5,569		36,300	[1]	24,811	[1]	17,609	[1]
Gross profit	147,593		141,070		136,403		127,550		119,219		112,713		104,337		93,006		552,616		429,275		299,252
Income from operations	13,635		9,704		3,548		7,435		6,902		5,877		3,953		6,459		34,322		23,191		15,274
Net income	$ 13,171		$ 10,384		$ 6,007		$ 12,584		$ 12,450		$ 13,882		$ 33,343		$ 5,495		$ 42,146		$ 65,170		$ 13,199
Basic net income per share	$ 0.12	[2]	$ 0.09	[2]	$ 0.05	[2]	$ 0.11	[2]	$ 0.11	[2]	$ 0.13	[2]	$ 0.31	[2]	$ 0.05	[2]	$ 0.38		$ 0.60		$ 0.13
Diluted net income per share	$ 0.12	[2]	$ 0.09	[2]	$ 0.05	[2]	$ 0.11	[2]	$ 0.11	[2]	$ 0.12	[2]	$ 0.29	[2]	$ 0.05	[2]	$ 0.37		$ 0.57		$ 0.12
[1]	Includes depreciation and amortization expense for the years ended December 31, 2019, 2018, and 2017 of $3,263 $2,225, and $1,140, respectively.
[2]	The amounts were computed independently for each quarter, and the sum of the quarters may not total the annual amounts.

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands	Jan. 16, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Payments to acquire business		$ 19,139
Auto List, Inc | San Francisco, California
Subsequent Event [Line Items]
Acquisition-related costs incurred		$ 400
Auto List, Inc | Subsequent Event | San Francisco, California
Subsequent Event [Line Items]
Business acquisition date	Jan. 16, 2020
Payments to acquire business	$ 22,000
Amount held in escrow	$ 2,200