CarGurus (CARG) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 03, 2019
Document And Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Registrant Name	CarGurus, Inc.
Trading Symbol	CARG
Entity Central Index Key	0001494259
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Class A Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		90,537,641
Class B Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		20,702,084

Unaudited Condensed Consolidate

Unaudited Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 29,939	$ 34,887
Investments	108,500	122,800
Accounts receivable, net of allowance for doubtful accounts of $223 and $479, respectively	15,111	13,614
Prepaid expenses and prepaid income taxes	9,680	10,144
Deferred contract costs	6,591	5,253
Other current assets	8,835	7,410
Restricted cash	750	750
Total current assets	179,406	194,858
Property and equipment, net	26,550	24,269
Intangible assets	4,407
Goodwill	15,852
Operating lease right-of-use assets	50,742
Restricted cash	1,918	1,921
Deferred tax assets	42,714	38,886
Deferred contract costs, net of current portion	8,446	7,252
Other long–term assets	1,892	1,104
Total assets	331,927	268,290
Current liabilities
Accounts payable	35,253	34,345
Accrued expenses, accrued income taxes and other current liabilities	13,793	18,654
Deferred revenue	8,942	8,811
Operating lease liabilities	7,486	1,693
Total current liabilities	65,474	63,503
Operating lease liability non-current	52,956	9,395
Deferred tax liabilities	1,002
Other non–current liabilities	1,486	1,281
Total liabilities	120,918	74,179
Commitments and contingencies (Note 8)
Stockholders’ equity:
Additional paid-in capital	188,954	184,216
Retained earnings	22,297	9,713
Accumulated other comprehensive (loss) income	(353)	71
Total stockholders’ equity	211,009	194,111
Total liabilities and stockholders’ equity	331,927	268,290
Class A Common Stock
Stockholders’ equity:
Common stock	90	90
Class B Common Stock
Stockholders’ equity:
Common stock	$ 21	$ 21

Unaudited Condensed Consolida_2

Unaudited Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 223	$ 479
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	90,370,773	89,728,223
Common stock, shares outstanding	90,370,773	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	20,702,084	20,702,084
Common stock, shares outstanding	20,702,084	20,702,084

Unaudited Condensed Consolida_3

Unaudited Condensed Consolidated Income Statements - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue		$ 135,270	$ 98,575
Cost of revenue	[1]	7,720	5,569
Gross profit		127,550	93,006
Operating expenses:
Sales and marketing		91,316	68,845
Product, technology, and development		15,972	9,098
General and administrative		11,760	7,871
Depreciation and amortization		1,067	733
Total operating expenses		120,115	86,547
Income from operations		7,435	6,459
Other income, net:
Interest income		744	291
Other income (expense)		902	(9)
Total other income, net		1,646	282
Income before income taxes		9,081	6,741
(Benefit from) provision for income taxes		(3,503)	1,246
Net income		$ 12,584	$ 5,495
Net income per share attributable to common stockholders: (Note 10)
Basic		$ 0.11	$ 0.05
Diluted		$ 0.11	$ 0.05
Weighted-average number of shares of common stock used in computing net income per share attributable to common stockholders:
Basic		110,800,037	106,942,799
Diluted		113,406,320	113,341,308
[1]	Includes depreciation and amortization expense for the three months ended March 31, 2019 and 2018 of $560 and $504, respectively.

Unaudited Condensed Consolida_4

Unaudited Condensed Consolidated Income Statements (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Depreciation and amortization expense	$ 560	$ 504

Unaudited Condensed Consolida_5

Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 12,584	$ 5,495
Other comprehensive income:
Foreign currency translation adjustment	(424)	72
Comprehensive income	$ 12,160	$ 5,567

Unaudited Condensed Consolida_6

Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	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 Income (Loss)	Retained Earnings (Accumulated Deficit)
Beginning balance at Dec. 31, 2017	$ 127,025			$ 78	$ 28	$ 185,190	$ 228	$ (58,499)
Beginning balance, Shares at Dec. 31, 2017				77,884,754	28,226,104
Net income	5,495							5,495
Stock–based compensation expense	3,967					3,967
Issuance of common stock upon exercise of stock options	80					80
Issuance of common stock upon exercise of stock options, Shares				6,574	10,690
Cumulative adjustment from adoption of revenue recognition model	3,042							3,042
Conversion of common stock				$ 7
Conversion of common stock, shares issued				7,534,710
Conversion of common stock, shares converted					(7,534,710)
Conversion of common stock, value					$ (7)
Foreign currency translation adjustment	72						72
Ending balance at Mar. 31, 2018	139,681			$ 85	$ 21	189,237	300	(49,962)
Ending balance, Shares at Mar. 31, 2018				85,426,038	20,702,084
Beginning balance at Dec. 31, 2018	194,111			$ 90	$ 21	184,216	71	9,713
Beginning balance, Shares at Dec. 31, 2018		89,728,223	20,702,084	89,728,223	20,702,084
Net income	12,584							12,584
Stock–based compensation expense	7,995					7,995
Issuance of common stock upon exercise of stock options	697					697
Issuance of common stock upon exercise of stock options, Shares				447,210
Issuance of common stock upon vesting of restricted stock units, Shares				297,374
Payment of withholding taxes on net share settlements of equity awards	(3,954)					(3,954)
Payment of withholding taxes on net share settlements of equity awards, Shares		(102,034)		(102,034)
Foreign currency translation adjustment	(424)						(424)
Ending balance at Mar. 31, 2019	$ 211,009			$ 90	$ 21	$ 188,954	$ (353)	$ 22,297
Ending balance, Shares at Mar. 31, 2019		90,370,773	20,702,084	90,370,773	20,702,084

Unaudited Condensed Consolida_7

Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Operating Activities
Net income	$ 12,584	$ 5,495
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,627	1,237
Unrealized currency (gain) loss on foreign denominated transactions	(833)	53
Deferred taxes	(3,692)	(1,317)
Provision for doubtful accounts	15	377
Stock-based compensation expense	7,686	3,818
Amortization of deferred contract costs	1,830	513
Changes in operating assets and liabilities:
Accounts receivable	(1,519)	133
Prepaid expenses, prepaid income taxes, and other assets	(1,760)	(507)
Deferred contract costs	(4,376)	(3,176)
Accounts payable	3,225	649
Accrued expenses, accrued income taxes, and other current liabilities	(4,009)	(3,651)
Deferred revenue	132	2,811
Lease obligations	(1,380)	(215)
Other non-current liabilities	155	154
Net cash provided by operating activities	9,685	6,374
Investing Activities
Purchases of property and equipment	(5,700)	(434)
Capitalization of website development costs	(811)	(581)
Cash paid for acquisition	(19,139)
Investments in certificates of deposit	(25,700)	(60,000)
Maturities of certificates of deposit	40,000	30,000
Net cash used in investing activities	(11,350)	(31,015)
Financing Activities
Proceeds from exercise of stock options	697	80
Financing cash flows from finance leases	(6)
Payment of initial public offering costs		(1,142)
Payment of withholding taxes on net share settlements of equity awards	(3,954)
Net cash used in financing activities	(3,263)	(1,062)
Impact of foreign currency on cash, cash equivalents, and restricted cash	(23)	24
Net decrease in cash, cash equivalents, and restricted cash	(4,951)	(25,679)
Cash, cash equivalents, and restricted cash at beginning of period	37,558	89,552	$ 89,552
Cash, cash equivalents, and restricted cash at end of period	32,607	63,873	$ 37,558
Supplemental disclosure of cash flow information:
Cash paid for income taxes	14	5
Cash paid for interest	1	5
Unpaid purchases of property and equipment	2,112	188
Capitalized stock-based compensation expense in website development costs	309	$ 149
Cash paid for operating lease liabilities	$ 3,005

Organization and Business Descr

Organization and Business Description	3 Months Ended
	Mar. 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 in Canada, the United Kingdom, Germany, Italy, and Spain. The Company has subsidiaries in the United States, Canada, Ireland, and the United Kingdom. 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	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying interim condensed consolidated financial statements (the “Unaudited Condensed Consolidated Financial Statements”) are unaudited. These Unaudited Condensed Consolidated Financial Statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2018 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the on February 28, 2019 (the “2018 Annual Report”). The Unaudited Condensed Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. The Unaudited Condensed Consolidated Financial Statements reflect all adjustments, consisting of only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2019 and December 31, 2018, results of operations, comprehensive income, changes in shareholders’ equity and cash flows for the three months ended March 31, 2019 and 2018. In the results of operations for the three months ended March 31, 2019 and 2018, the Company has separately presented interest income from other income, net due to the increase in amount during the three months ended March 31, 2019 as compared to the three months ended March 31, 2018. Additionally, the results of operations and statement of cash flows for the three months ended March 31, 2018, were adjusted due to the impact of the adoption of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers The accompanying Unaudited Condensed Consolidated Financial Statements reflect the application of certain significant accounting policies as described below and elsewhere in these notes to the Unaudited Condensed Consolidated Financial Statements there have been no material changes in the Company's significant accounting policies from those that were disclosed in the 2018 Annual Report, other than those resulting from the adoption of ASC 842, which is described below. Principles of Consolidation The accompanying Unaudited Condensed Consolidated Financial Statements include the accounts of CarGurus, Inc. and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company prepares its Unaudited Condensed Consolidated Financial Statements and related disclosures in conformity with GAAP. 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 . 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 Unaudited Condensed Consolidated Financial Statements 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. 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 federally 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 three months ended March 31, 2019 and the year ended December 31, 2018, no individual customer accounted for more than 10% of total revenue. As of March 31, 2019 , one customer accounted for 13% 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 March 31, 2019 or December 31, 2018. Included in net accounts receivable at March 31, 2019 and December 31, 2018, is $7,329 and $5,815, respectively, of unbilled accounts receivable related to advertising customers billed within a quarter subsequent to services rendered. Revenue Recognition The following table summarizes revenue from contracts with customers by revenue source for the three months ended March 31, 2019 and 2018. Three Months Ended March 31, 2019 2018 Revenue by Revenue Stream Marketplace subscription revenue $ 120,843 $ 89,159 Advertising and other revenue 14,427 9,416 Total $ 135,270 $ 98,575 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 12) as it believes these categories best depict how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. 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 the relevant quarter end. However, the Company has applied the practical expedient available under Topic 606 to not disclose the amount of transaction price allocated to unsatisfied performance obligations when any such performance obligation was part of a contract having an original expected duration of one year or less. The Company does not have future obligations associated with marketplace revenue subscriptions or advertising and other services that extend beyond one year. For performance obligations not satisfied as of March 31, 2019, 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 March 31, 2019. The remaining duration is less than one year. Revenue recognized during the three months ended March 31, 2019 from amounts included in deferred revenue at the beginning of the period was approximately $8,792. Recent Accounting Pronouncements Adopted Lease Accounting In February 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (as amended, “ASC 842”). ASC 842 requires a lessee to recognize most leases on the Unaudited Condensed Consolidated Balance Sheet but recognize expenses on the Unaudited Condensed 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-to-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: 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. On June 19, 2018, the Company entered into an operating lease in Cambridge, Massachusetts at 121 First St. 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 Company subleases the fifth floor and records the sublease income in other income, net within the Unaudited Condensed Consolidated Income Statement. The sublease income is immaterial. On March 11, 2016, the Company entered into an operating lease in Cambridge, Massachusetts at 55 Cambridge Parkway for the lease of 51,923 square feet of office space with a non-cancellable lease term through 2024 with an option to extend the lease term for one additional period of five years. 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. Each of the three leases described above provides for leasehold improvement incentives and annual rent increases through the term of the lease. Each of the three leases above also has an associated letter of credit, which is recorded as restricted cash within the Unaudited Condensed Consolidated Balance Sheet. At March 31, 2019 and December 31, 2018, restricted cash was $2,668 and $2,671, Additionally, 121 First St. has an associated security deposit, which was recorded in other assets, net within the Unaudited Condensed Consolidated Balance Sheet. On August 12, 2013, the Company entered into an operating lease in Dublin, Ireland at Styne House, Upper Hatch St. for the lease of 13,345 square feet of office space with a non-cancellable term through 2023. The lease provided for a rent increase at the end of year five. The Company’s financing lease obligations consists of a lease for office equipment and is immaterial. Prior to 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. Post adoption of ASC 842 Upon adoption, 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 on not separating lease components from non-lease components for all leases. The Company reviews all material contacts 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. The Company also made an accounting policy election to not recognize a lease liability or right-of-use asset on its Unaudited Condensed Consolidated Balance Sheet for leases with an initial term of twelve months or less, and instead recognize lease payments on the Unaudited Condensed 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 approximately $52,334 and $63,280, respectively, as of January 1, 2019. The standard did not materially impact the Unaudited Condensed Consolidated Statement of Cash Flows and had no impact on the Unaudited Condensed Consolidated Income Statement. During the three months ended March 31, 2019 and 2018, the Company recognized $2,448 and $1,672, respectively, of rent expense. The Company allocates lease costs across all departments based on headcount in the respective location. As of March 31, 2019, the weighted average remaining lease term was 9.9 years and the weighted average discount rate was 5.9%. 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 uses the incremental borrowing rate on January 1, 2019 for leases that commenced prior to that date. Future minimum lease payments as of March 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2019 (excluding the three months ended March 31, 2019) $ 7,351 2020 11,020 2021 11,169 2022 10,862 2023 5,672 Thereafter 37,645 Total lease payments 83,719 Less imputed interest (23,277 ) Total $ 60,442 Options to extend lease terms are not included in the chart above as they are not reasonably certain of being exercised. Stock-Based Compensation In June 2018, the FASB issued ASU No. 2018-07 , Compensation—Stock Compensation (Topic 718) Compensation—Stock Compensation 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. launched an initiative designed to evaluate and enhance its enterprise applications. Recent Accounting Pronouncements Not Yet Adopted From time to time, new accounting pronouncements are issued by the FASB In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Acquisitions	3. Acquisitions On January 8, 2019, the Company, through CarGurus UK 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 UK-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 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 between the Purchaser and the Seller. Upon completion of the acquisition, NewCo became a wholly owned subsidiary of the Purchaser. The business combination is intended to expand the Company’s consumer audience in the UK. As of March 31, 2019, the Company has incurred total acquisition-related costs of $649 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 preliminary purchase price allocation recorded in the Company's Unaudited Condensed Consolidated Balance Sheet as of the acquisition date: Estimated Fair Value at Date of Acquisition Intangible assets (1) $ 4,466 Goodwill (2) 15,521 Deferred tax liabilities (3) (848 ) Total purchase price $ 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 UK 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 g (3) The deferred tax liability corresponds to the acquired intangible assets which do not have tax basis. As a result of the deferred tax liability, an adjustment was recorded to goodwill to account for the tax effect of the deferred tax liability. Actual and pro forma results for these acquisitions have not been presented as the financial impact to the Company’s Unaudited Condensed Consolidated Financial Statements is not material.

Fair Value of Financial Instrum

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments	3 Months Ended
	Mar. 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 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 March 31, 2019 and at December 31, 2018: At March 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 Assets: Money market funds $ 19 $ — $ — $ 19 Investments: Certificates of deposit — 108,500 — 108,500 Total $ 19 $ 108,500 $ — $ 108,519 At 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 Assets: Money market funds $ 24 $ — $ — $ 24 Investments: Certificates of deposit — 122,800 — 122,800 Total $ 24 $ 122,800 $ — $ 122,824 Certificates of deposit at March 31, 2019 and December 31, 2018 had maturity dates of one year or less. 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 for the three months ended March 31, 2019. 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 or liabilities, and did not elect the fair value option for any financial assets and liabilities transacted in the three months ended March 31, 2019 or the year ended December 31, 2018. The Company considers all highly liquid investments with an original maturity of 90 days or less at the date of purchase to be cash equivalents. Investments not classified as cash equivalents with maturities one year or less 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 following is a summary of cash, cash equivalents, and investments as of March 31, 2019 At March 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents due in 90 days or less $ 29,939 $ — $ — $ 29,939 Investments: Certificates of deposit due in one year or less 108,500 — — 108,500 Total cash, cash equivalents, and investments $ 138,439 $ — $ — $ 138,439 At December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value 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	3 Months Ended
	Mar. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment consists of the following: At March 31, 2019 At December 31, 2018 Computer equipment $ 4,917 $ 4,208 Capitalized software 252 252 Website development costs 8,027 6,907 Furniture and fixtures 6,539 4,584 Leasehold improvements 19,642 10,821 Construction in progress — 8,971 Finance lease right-of-use assets 107 — 39,484 35,743 Less accumulated depreciation (12,934 ) (11,474 ) Property and equipment, net $ 26,550 $ 24,269 Depreciation and amortization expense, which includes amortization expense associated with capitalized website was $1,472 and $5,029 for the three months ended and , respectively. The increase of $8,821 in leasehold improvements and the decrease of $8,971 in construction in progress at March 31, 2019 is primarily due to costs incurred to build out the Company’s new leased facility. 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	3 Months Ended
	Mar. 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 $ — PistonHeads acquisition 15,521 Foreign currency translation adjustment 331 Balance at March 31, 2019 $ 15,852 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. Other Intangible Assets Intangible assets as of March 31, 2019 consist of the following: Weighted Average Remaining Useful Life (years) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Brand 10.8 $ 3,518 $ 74 $ 3,444 Customer relationships 2.8 1,044 81 963 Total $ 4,562 $ 155 $ 4,407 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 March 31, 2019, is as follows: Year Ending December 31, Amortization Expense Remainder of 2019 $ 502 2020 667 2021 667 2022 326 2023 320 2024 and thereafter 1,925 Total $ 4,407

Accrued Expenses, Accrued Incom

Accrued Expenses, Accrued Income Taxes and Other Current Liabilities	3 Months Ended
	Mar. 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 March 31, 2019 At December 31, 2018 Accrued bonus $ 3,000 $ 8,266 Accrued commissions 3,530 2,878 Other accrued expenses, accrued income taxes and other current liabilities 7,263 7,510 $ 13,793 $ 18,654

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Operating Leases As of March 31, 2019 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 March 31, 2019 and December 31, 2018,

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	9. Stock-based Compensation For the three months ended March 31, 2019 and 2018, total stock-based compensation expense was $7,686 and $3,818, respectively. The following two tables show stock compensation expense by award type and where the stock compensation expense is recorded in the Company’s : Three Months Ended March 31, 2019 2018 Options $ 51 $ 65 RSUs 7,635 3,753 Total stock-based compensation expense $ 7,686 $ 3,818 Three Months Ended March 31, 2019 2018 Cost of revenue $ 81 $ 89 Sales and marketing expense 2,312 1,010 Product, technology, and development expense 3,183 1,661 General and administrative expense 2,110 1,058 Total $ 7,686 $ 3,818 Excluded from stock-based compensation expense is $309 and $149 of capitalized website development costs in the three months ended March 31, 2019 and 2018, respectively. During the three months ended March 31, 2019, the Company withheld 102,034 shares of Class A common stock to satisfy employee tax withholding requirements due to net share settlement. The shares withheld remain in the authorized, but unissued pool under the Company’s Omnibus Equity Compensation Plan and can be reissued by the Company. Total payments of $3,954 for the employees’ tax obligations to the taxing authorities due to net share settlements are reflected as a financing activity within the Unaudited Condensed Consolidated Statements of Cash Flows

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	10. Earnings Per Share Net income per share for the three months ended March 31, 2019 and 2018 is 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. 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 , including on either the death or voluntary termination of the Company’s Chief Executive Officer. The Company allocates undistributed earnings attributable to common stock between the common stock classes on a one‑to‑one basis when computing net income per share. As a result, basic and diluted net income per share of Class A common stock and per share of Class B common stock are equivalent. During the three months ended March 31, 2019, no holders of Class B common stock converted shares of Class B common stock to Class A common stock. During , holders of Class B common stock converted 7,534,710 shares of Class B common stock to Class A common stock. Diluted net income per share gives effect to all potentially dilutive securities. Potential dilutive securities for the three months ended March 31, 2019 and 2018 consist of shares of common stock issuable upon the exercise of stock options and shares of common stock issuable upon the vesting of restricted stock units (“RSUs”). The dilutive effect of these common stock equivalents is reflected in diluted earnings per share by application of the treasury stock method. For the three months ended March 31, 2019 and 2018, diluted 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. The following table presents a reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share: Three Months Ended March 31, 2019 2018 Numerator: Net income $ 12,584 $ 5,495 Denominator: Weighted-average number of shares of common stock used in computing net income per share attributable to common stockholders — basic 110,800,037 106,942,799 Dilutive effect of share equivalents resulting from stock options 1,450,076 4,772,154 Dilutive effect of share equivalents resulting from unvested restricted stock units 1,156,207 1,626,355 Weighted-average number of shares of common stock used in computing net income per share — diluted 113,406,320 113,341,308 Net income per share attributable to common stockholders: Basic $ 0.11 $ 0.05 Diluted $ 0.11 $ 0.05 There were no anti-dilutive securities for the three months ended March 31, 2018. The following potentially dilutive common stock equivalents have been excluded from the calculation of diluted weighted-average shares outstanding for the three months ended March 31, 2019, as their effect would have been anti-dilutive for the period presented: Three Months Ended March 31, 2019 Restricted stock units outstanding 858,417

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes During the three months ended March 31, 2019, the Company recorded an income tax benefit of $3,503, representing an effective tax rate of (38.6)%. The effective tax rate for the three months ended March 31, 2019 was lower than the statutory tax rate of 21% principally due to excess stock deductions from the taxable compensation of share-based awards and federal and state research and development tax credits, partially offset by state and local income taxes. During the three months ended March 31, 2018, the Company recorded income tax expense of $1,246, representing an effective tax rate of 18.5%. The effective tax rate for the three months ended March 31, 2018 was lower than the statutory tax rate of 21% principally due to federal and state research and development tax credits and excess stock deductions from the taxable compensation of share-based awards, partially offset by state and local income taxes. In 2018, the Internal Revenue Service commenced a federal income tax audit with respect to the Company’s 2016 tax year. In 2019, the Internal Revenue Service commenced a federal employment tax audit with respect to the 2016 calendar year.

Segment and Geographic Informat

Segment and Geographic Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment and Geographic Information	12. 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 (the “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: Three Months Ended March 31, 2019 2018 Segment revenue: United States $ 128,403 $ 95,060 International 6,867 3,515 Total revenue $ 135,270 $ 98,575 Three Months Ended March 31, 2019 2018 Segment income (loss) from operations: United States $ 17,381 $ 13,933 International (9,946 ) (7,474 ) Total income from operations $ 7,435 $ 6,459 As of March 31, 2019

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements (the “Unaudited Condensed Consolidated Financial Statements”) are unaudited. These Unaudited Condensed Consolidated Financial Statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2018 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the on February 28, 2019 (the “2018 Annual Report”). The Unaudited Condensed Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. The Unaudited Condensed Consolidated Financial Statements reflect all adjustments, consisting of only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2019 and December 31, 2018, results of operations, comprehensive income, changes in shareholders’ equity and cash flows for the three months ended March 31, 2019 and 2018. In the results of operations for the three months ended March 31, 2019 and 2018, the Company has separately presented interest income from other income, net due to the increase in amount during the three months ended March 31, 2019 as compared to the three months ended March 31, 2018. Additionally, the results of operations and statement of cash flows for the three months ended March 31, 2018, were adjusted due to the impact of the adoption of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers The accompanying Unaudited Condensed Consolidated Financial Statements reflect the application of certain significant accounting policies as described below and elsewhere in these notes to the Unaudited Condensed Consolidated Financial Statements there have been no material changes in the Company's significant accounting policies from those that were disclosed in the 2018 Annual Report, other than those resulting from the adoption of ASC 842, which is described below.
Principles of Consolidation	Principles of Consolidation The accompanying Unaudited Condensed Consolidated Financial Statements include the accounts of CarGurus, Inc. and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company prepares its Unaudited Condensed Consolidated Financial Statements and related disclosures in conformity with GAAP.
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 .
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 Unaudited Condensed Consolidated Financial Statements 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.
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 federally 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 three months ended March 31, 2019 and the year ended December 31, 2018, no individual customer accounted for more than 10% of total revenue. As of March 31, 2019 , one customer accounted for 13% 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 March 31, 2019 or December 31, 2018. Included in net accounts receivable at March 31, 2019 and December 31, 2018, is $7,329 and $5,815, respectively, of unbilled accounts receivable related to advertising customers billed within a quarter subsequent to services rendered.
Revenue Recognition	Revenue Recognition The following table summarizes revenue from contracts with customers by revenue source for the three months ended March 31, 2019 and 2018. Three Months Ended March 31, 2019 2018 Revenue by Revenue Stream Marketplace subscription revenue $ 120,843 $ 89,159 Advertising and other revenue 14,427 9,416 Total $ 135,270 $ 98,575 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 12) as it believes these categories best depict how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. 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 the relevant quarter end. However, the Company has applied the practical expedient available under Topic 606 to not disclose the amount of transaction price allocated to unsatisfied performance obligations when any such performance obligation was part of a contract having an original expected duration of one year or less. The Company does not have future obligations associated with marketplace revenue subscriptions or advertising and other services that extend beyond one year. For performance obligations not satisfied as of March 31, 2019, 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 March 31, 2019. The remaining duration is less than one year. Revenue recognized during the three months ended March 31, 2019 from amounts included in deferred revenue at the beginning of the period was approximately $8,792.
Recent Accounting Pronouncements Adopted	Recent Accounting Pronouncements Adopted Lease Accounting In February 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (as amended, “ASC 842”). ASC 842 requires a lessee to recognize most leases on the Unaudited Condensed Consolidated Balance Sheet but recognize expenses on the Unaudited Condensed 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-to-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: 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. On June 19, 2018, the Company entered into an operating lease in Cambridge, Massachusetts at 121 First St. 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 Company subleases the fifth floor and records the sublease income in other income, net within the Unaudited Condensed Consolidated Income Statement. The sublease income is immaterial. On March 11, 2016, the Company entered into an operating lease in Cambridge, Massachusetts at 55 Cambridge Parkway for the lease of 51,923 square feet of office space with a non-cancellable lease term through 2024 with an option to extend the lease term for one additional period of five years. 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. Each of the three leases described above provides for leasehold improvement incentives and annual rent increases through the term of the lease. Each of the three leases above also has an associated letter of credit, which is recorded as restricted cash within the Unaudited Condensed Consolidated Balance Sheet. At March 31, 2019 and December 31, 2018, restricted cash was $2,668 and $2,671, Additionally, 121 First St. has an associated security deposit, which was recorded in other assets, net within the Unaudited Condensed Consolidated Balance Sheet. On August 12, 2013, the Company entered into an operating lease in Dublin, Ireland at Styne House, Upper Hatch St. for the lease of 13,345 square feet of office space with a non-cancellable term through 2023. The lease provided for a rent increase at the end of year five. The Company’s financing lease obligations consists of a lease for office equipment and is immaterial. Prior to 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. Post adoption of ASC 842 Upon adoption, 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 on not separating lease components from non-lease components for all leases. The Company reviews all material contacts 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. The Company also made an accounting policy election to not recognize a lease liability or right-of-use asset on its Unaudited Condensed Consolidated Balance Sheet for leases with an initial term of twelve months or less, and instead recognize lease payments on the Unaudited Condensed 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 approximately $52,334 and $63,280, respectively, as of January 1, 2019. The standard did not materially impact the Unaudited Condensed Consolidated Statement of Cash Flows and had no impact on the Unaudited Condensed Consolidated Income Statement. During the three months ended March 31, 2019 and 2018, the Company recognized $2,448 and $1,672, respectively, of rent expense. The Company allocates lease costs across all departments based on headcount in the respective location. As of March 31, 2019, the weighted average remaining lease term was 9.9 years and the weighted average discount rate was 5.9%. 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 uses the incremental borrowing rate on January 1, 2019 for leases that commenced prior to that date. Future minimum lease payments as of March 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2019 (excluding the three months ended March 31, 2019) $ 7,351 2020 11,020 2021 11,169 2022 10,862 2023 5,672 Thereafter 37,645 Total lease payments 83,719 Less imputed interest (23,277 ) Total $ 60,442 Options to extend lease terms are not included in the chart above as they are not reasonably certain of being exercised. Stock-Based Compensation In June 2018, the FASB issued ASU No. 2018-07 , Compensation—Stock Compensation (Topic 718) Compensation—Stock Compensation 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. launched an initiative designed to evaluate and enhance its enterprise applications.
Lease Accounting	Lease Accounting In February 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (as amended, “ASC 842”). ASC 842 requires a lessee to recognize most leases on the Unaudited Condensed Consolidated Balance Sheet but recognize expenses on the Unaudited Condensed 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-to-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: 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. On June 19, 2018, the Company entered into an operating lease in Cambridge, Massachusetts at 121 First St. 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 Company subleases the fifth floor and records the sublease income in other income, net within the Unaudited Condensed Consolidated Income Statement. The sublease income is immaterial. On March 11, 2016, the Company entered into an operating lease in Cambridge, Massachusetts at 55 Cambridge Parkway for the lease of 51,923 square feet of office space with a non-cancellable lease term through 2024 with an option to extend the lease term for one additional period of five years. 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. Each of the three leases described above provides for leasehold improvement incentives and annual rent increases through the term of the lease. Each of the three leases above also has an associated letter of credit, which is recorded as restricted cash within the Unaudited Condensed Consolidated Balance Sheet. At March 31, 2019 and December 31, 2018, restricted cash was $2,668 and $2,671, Additionally, 121 First St. has an associated security deposit, which was recorded in other assets, net within the Unaudited Condensed Consolidated Balance Sheet. On August 12, 2013, the Company entered into an operating lease in Dublin, Ireland at Styne House, Upper Hatch St. for the lease of 13,345 square feet of office space with a non-cancellable term through 2023. The lease provided for a rent increase at the end of year five. The Company’s financing lease obligations consists of a lease for office equipment and is immaterial. Prior to 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. Post adoption of ASC 842 Upon adoption, 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 on not separating lease components from non-lease components for all leases. The Company reviews all material contacts 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. The Company also made an accounting policy election to not recognize a lease liability or right-of-use asset on its Unaudited Condensed Consolidated Balance Sheet for leases with an initial term of twelve months or less, and instead recognize lease payments on the Unaudited Condensed 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 approximately $52,334 and $63,280, respectively, as of January 1, 2019. The standard did not materially impact the Unaudited Condensed Consolidated Statement of Cash Flows and had no impact on the Unaudited Condensed Consolidated Income Statement. During the three months ended March 31, 2019 and 2018, the Company recognized $2,448 and $1,672, respectively, of rent expense. The Company allocates lease costs across all departments based on headcount in the respective location. As of March 31, 2019, the weighted average remaining lease term was 9.9 years and the weighted average discount rate was 5.9%. 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 uses the incremental borrowing rate on January 1, 2019 for leases that commenced prior to that date. Future minimum lease payments as of March 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2019 (excluding the three months ended March 31, 2019) $ 7,351 2020 11,020 2021 11,169 2022 10,862 2023 5,672 Thereafter 37,645 Total lease payments 83,719 Less imputed interest (23,277 ) Total $ 60,442 Options to extend lease terms are not included in the chart above as they are not reasonably certain of being exercised.
Stock-Based Compensation	Stock-Based Compensation In June 2018, the FASB issued ASU No. 2018-07 , Compensation—Stock Compensation (Topic 718) Compensation—Stock Compensation
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. launched an initiative designed to evaluate and enhance its enterprise applications.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted From time to time, new accounting pronouncements are issued by the FASB In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.
Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments	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 for the three months ended March 31, 2019. 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 or liabilities, and did not elect the fair value option for any financial assets and liabilities transacted in the three months ended March 31, 2019 or the year ended December 31, 2018. The Company considers all highly liquid investments with an original maturity of 90 days or less at the date of purchase to be cash equivalents. Investments not classified as cash equivalents with maturities one year or less 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.
Earnings Per Share	Net income per share for the three months ended March 31, 2019 and 2018 is 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. 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 , including on either the death or voluntary termination of the Company’s Chief Executive Officer. The Company allocates undistributed earnings attributable to common stock between the common stock classes on a one‑to‑one basis when computing net income per share. As a result, basic and diluted net income per share of Class A common stock and per share of Class B common stock are equivalent.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Revenue from Contracts with Customers by Revenue	The following table summarizes revenue from contracts with customers by revenue source for the three months ended March 31, 2019 and 2018. Three Months Ended March 31, 2019 2018 Revenue by Revenue Stream Marketplace subscription revenue $ 120,843 $ 89,159 Advertising and other revenue 14,427 9,416 Total $ 135,270 $ 98,575
Summary of Future Minimum Lease Payments	Future minimum lease payments as of March 31, 2019 are as follows: Year Ending December 31, Operating Lease Commitments 2019 (excluding the three months ended March 31, 2019) $ 7,351 2020 11,020 2021 11,169 2022 10,862 2023 5,672 Thereafter 37,645 Total lease payments 83,719 Less imputed interest (23,277 ) Total $ 60,442

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Summary of Preliminary Purchase Price Allocation	. The following table presents the preliminary purchase price allocation recorded in the Company's Unaudited Condensed Consolidated Balance Sheet as of the acquisition date: Estimated Fair Value at Date of Acquisition Intangible assets (1) $ 4,466 Goodwill (2) 15,521 Deferred tax liabilities (3) (848 ) Total purchase price $ 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 UK 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 g (3) The deferred tax liability corresponds to the acquired intangible assets which do not have tax basis. As a result of the deferred tax liability, an adjustment was recorded to goodwill to account for the tax effect of the deferred tax liability.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments (Tables)	3 Months Ended
	Mar. 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 March 31, 2019 and at December 31, 2018: At March 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 Assets: Money market funds $ 19 $ — $ — $ 19 Investments: Certificates of deposit — 108,500 — 108,500 Total $ 19 $ 108,500 $ — $ 108,519 At 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 Assets: 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 March 31, 2019 At March 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents due in 90 days or less $ 29,939 $ — $ — $ 29,939 Investments: Certificates of deposit due in one year or less 108,500 — — 108,500 Total cash, cash equivalents, and investments $ 138,439 $ — $ — $ 138,439 At December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value 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)	3 Months Ended
	Mar. 31, 2019
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consists of the following: At March 31, 2019 At December 31, 2018 Computer equipment $ 4,917 $ 4,208 Capitalized software 252 252 Website development costs 8,027 6,907 Furniture and fixtures 6,539 4,584 Leasehold improvements 19,642 10,821 Construction in progress — 8,971 Finance lease right-of-use assets 107 — 39,484 35,743 Less accumulated depreciation (12,934 ) (11,474 ) Property and equipment, net $ 26,550 $ 24,269

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 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 $ — PistonHeads acquisition 15,521 Foreign currency translation adjustment 331 Balance at March 31, 2019 $ 15,852
Summary of Other Intangible Assets	Intangible assets as of March 31, 2019 consist of the following: Weighted Average Remaining Useful Life (years) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Brand 10.8 $ 3,518 $ 74 $ 3,444 Customer relationships 2.8 1,044 81 963 Total $ 4,562 $ 155 $ 4,407
Summary of Estimated Amortization Expense of Intangible Assets	Estimated amortization expense of intangible assets for future periods as of March 31, 2019, is as follows: Year Ending December 31, Amortization Expense Remainder of 2019 $ 502 2020 667 2021 667 2022 326 2023 320 2024 and thereafter 1,925 Total $ 4,407

Accrued Expenses, Accrued Inc_2

Accrued Expenses, Accrued Income Taxes and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 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 March 31, 2019 At December 31, 2018 Accrued bonus $ 3,000 $ 8,266 Accrued commissions 3,530 2,878 Other accrued expenses, accrued income taxes and other current liabilities 7,263 7,510 $ 13,793 $ 18,654

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-based Compensation Expense by Award Type	Three Months Ended March 31, 2019 2018 Options $ 51 $ 65 RSUs 7,635 3,753 Total stock-based compensation expense $ 7,686 $ 3,818
Summary of Allocation of Stock-based Compensation Expense	Three Months Ended March 31, 2019 2018 Cost of revenue $ 81 $ 89 Sales and marketing expense 2,312 1,010 Product, technology, and development expense 3,183 1,661 General and administrative expense 2,110 1,058 Total $ 7,686 $ 3,818

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 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: Three Months Ended March 31, 2019 2018 Numerator: Net income $ 12,584 $ 5,495 Denominator: Weighted-average number of shares of common stock used in computing net income per share attributable to common stockholders — basic 110,800,037 106,942,799 Dilutive effect of share equivalents resulting from stock options 1,450,076 4,772,154 Dilutive effect of share equivalents resulting from unvested restricted stock units 1,156,207 1,626,355 Weighted-average number of shares of common stock used in computing net income per share — diluted 113,406,320 113,341,308 Net income per share attributable to common stockholders: Basic $ 0.11 $ 0.05 Diluted $ 0.11 $ 0.05
Schedule of Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Weighted-average Shares Outstanding	There were no anti-dilutive securities for the three months ended March 31, 2018. The following potentially dilutive common stock equivalents have been excluded from the calculation of diluted weighted-average shares outstanding for the three months ended March 31, 2019, as their effect would have been anti-dilutive for the period presented: Three Months Ended March 31, 2019 Restricted stock units outstanding 858,417

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	3 Months Ended
	Mar. 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: Three Months Ended March 31, 2019 2018 Segment revenue: United States $ 128,403 $ 95,060 International 6,867 3,515 Total revenue $ 135,270 $ 98,575 Three Months Ended March 31, 2019 2018 Segment income (loss) from operations: United States $ 17,381 $ 13,933 International (9,946 ) (7,474 ) Total income from operations $ 7,435 $ 6,459

Organization and Business Des_2

Organization and Business Description - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
State of incorporation	Delaware
Date of incorporation	Jun. 26, 2015

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	Aug. 12, 2013ft²	Mar. 31, 2019USD ($)Customer	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)Customer	Jan. 01, 2019USD ($)	Jun. 19, 2018ft²	Mar. 11, 2016ft²	Oct. 08, 2014ft²
Summary Of Significant Accounting Policies [Line Items]
Description of significant off-balance sheet risk		The Company has no significant offbalance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.
Revenue recognized		$ 8,792
Restricted cash		2,668		$ 2,671
Net lease assets		50,742
Lease liabilities		60,442
Rent expense		$ 2,448	$ 1,672
Weighted average remaining lease term		9 years 10 months 24 days
Weighted average discount rate		5.90%
Implementation costs associated with service contracts		$ 876
ASC 842
Summary Of Significant Accounting Policies [Line Items]
Net lease assets					$ 52,334
Lease liabilities					$ 63,280
Cambridge, Massachusetts at 121 First St.
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
Cambridge, Massachusetts at 55 Cambridge Parkway
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²							51,923
Operating lease, option to extend		option to extend the lease term for one additional period of five 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
Dublin, Ireland
Summary Of Significant Accounting Policies [Line Items]
Operating lease of office space | ft²	13,345
Operating lease, rent increasing year	5 years
Sales Revenue, Net | Concentration of Credit Risk
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk, percentage		10.00%		10.00%
Number of major customers | Customer		0		0
Net Accounts Receivable | Advertising Customers
Summary Of Significant Accounting Policies [Line Items]
Unbilled accounts receivable		$ 7,329		$ 5,815
Net Accounts Receivable | Concentration of Credit Risk
Summary Of Significant Accounting Policies [Line Items]
Number of major customers | Customer		0		0
Net Accounts Receivable | Concentration of Credit Risk | Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk, percentage		13.00%		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%

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
	Mar. 31, 2019	Mar. 31, 2018
Revenue by Revenue Stream [Abstract]
Revenue	$ 135,270	$ 98,575
Marketplace Subscription Revenue
Revenue by Revenue Stream [Abstract]
Revenue	120,843	89,159
Advertising and Other Revenue
Revenue by Revenue Stream [Abstract]
Revenue	$ 14,427	$ 9,416

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Future Minimum Lease Payments (Details) $ in Thousands	Mar. 31, 2019USD ($)
Operating Lease Commitments
2019 (excluding the three months ended March 31, 2019)	$ 7,351
2020	11,020
2021	11,169
2022	10,862
2023	5,672
Thereafter	37,645
Total lease payments	83,719
Less imputed interest	(23,277)
Total	$ 60,442

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) £ in Thousands, $ in Thousands	Jan. 08, 2019USD ($)	Jan. 08, 2019GBP (£)	Mar. 31, 2019USD ($)
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			$ 649
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 Preli

Acquisitions - Summary of Preliminary Purchase Price Allocation (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Jan. 08, 2019
Business Acquisition [Line Items]
Goodwill		$ 15,852
PistonHeads Holdco Limited
Business Acquisition [Line Items]
Intangible assets	[1]		$ 4,466
Goodwill	[2]		15,521
Deferred tax liabilities	[3]		(848)
Total purchase price			$ 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 UK 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 goodwill is not deductible for tax purposes. The deferred tax liability corresponds to the acquired intangible assets which do not have tax basis. As a result of the deferred tax liability, an adjustment was recorded to goodwill to account for the tax effect of the deferred tax liability.
[3]	The deferred tax liability corresponds to the acquired intangible assets which do not have tax basis. As a result of the deferred tax liability, an adjustment was recorded to goodwill to account for the tax effect of the deferred tax liability.

Acquisitions - Summary of Pre_2

Acquisitions - Summary of Preliminary Purchase Price Allocation (Parenthetical) (Details) - USD ($) $ in Thousands		Jan. 08, 2019	Mar. 31, 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	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	$ 29,939	$ 34,887
Investments:	108,500	122,800
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments:	$ 108,500	$ 122,800
Debt Securities, Held-to-maturity, Type [Extensible List]	us-gaap:CertificatesOfDepositMember	us-gaap:CertificatesOfDepositMember
Total	$ 108,519	$ 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	19	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:	$ 108,500	$ 122,800
Debt Securities, Held-to-maturity, Type [Extensible List]	us-gaap:CertificatesOfDepositMember	us-gaap:CertificatesOfDepositMember
Total	$ 108,500	$ 122,800
Fair Value, Measurements, Recurring | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	19	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:	$ 19	$ 24

Fair Value of Financial Instr_4

Fair Value of Financial Instruments Including Cash, Cash Equivalents and Investments - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Maturity period of certificates of deposit	1 year	1 year
Maturity of certificates of deposit, description	Certificates of deposit at March 31, 2019 and December 31, 2018 had maturity dates of one year or less.
Liabilities, fair value	$ 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	Mar. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Cash and cash equivalents due in 90 days or less, Amortized Cost	$ 29,939	$ 34,887
Certificates of deposit due in one year or less, Amortized Cost	108,500	122,800
Total cash, cash equivalents, and investments, Amortized Cost	138,439	157,687
Cash and cash equivalents due in 90 days or less, Estimated Fair Value	29,939	34,887
Certificates of deposit due in one year or less, Estimated Fair Value	108,500	122,800
Total cash, cash equivalents, and investments, Estimated Fair Value	$ 138,439	$ 157,687

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 39,484	$ 35,743
Less accumulated depreciation	(12,934)	(11,474)
Property and equipment, net	26,550	24,269
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,917	4,208
Capitalized Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	252	252
Website Development Costs
Property Plant And Equipment [Line Items]
Property and equipment, gross	8,027	6,907
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,539	4,584
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	19,642	10,821
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 8,971
Finance Lease Right-of-use Assets
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 107

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Depreciation and amortization	$ 1,627	$ 1,237
Capitalized Website Development Costs
Property Plant And Equipment [Line Items]
Depreciation and amortization	1,472		$ 5,029
Leasehold Improvements
Property Plant And Equipment [Line Items]
Increase (decrease) in property and equipment	8,821
Construction in Progress
Property Plant And Equipment [Line Items]
Increase (decrease) in property and equipment	$ (8,971)

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Summary of Changes in Carrying Value of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
PistonHeads acquisition	$ 15,521
Foreign currency translation adjustment	331
Balance at March 31, 2019	$ 15,852

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Summary of Other Intangible Assets (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,562
Accumulated Amortization	155
Net Carrying Amount	$ 4,407
Brand
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (years)	10 years 9 months 18 days
Gross Carrying Amount	$ 3,518
Accumulated Amortization	74
Net Carrying Amount	$ 3,444
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (years)	2 years 9 months 18 days
Gross Carrying Amount	$ 1,044
Accumulated Amortization	81
Net Carrying Amount	$ 963

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Goodwill [Line Items]
Amortization expense of intangible assets	$ 155
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	Mar. 31, 2019USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Remainder of 2019	$ 502
2020	667
2021	667
2022	326
2023	320
2024 and thereafter	1,925
Net Carrying Amount	$ 4,407

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	Mar. 31, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Accrued bonus	$ 3,000	$ 8,266
Accrued commissions	3,530	2,878
Other accrued expenses, accrued income taxes and other current liabilities	7,263	7,510
Accrued expenses, accrued income taxes and other current liabilities, Total	$ 13,793	$ 18,654

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Unpaid property and equipment costs	$ 2,112	$ 188
Finance lease obligations	$ 101

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 7,686	$ 3,818
Capitalized website development costs excluded from stock-based compensation expense	309	$ 149
Total payments for employees’ tax obligations to taxing authorities due to net share settlements	$ 3,954
Class A Common Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Employee tax withholding requirements due to net share settlement	102,034

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock-based Compensation Expense by Award Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,686	$ 3,818
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	51	65
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,635	$ 3,753

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Allocation of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 7,686	$ 3,818
Cost of Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	81	89
Sales and Marketing Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,312	1,010
Product, Technology, and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,183	1,661
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,110	$ 1,058

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019Voteshares	Mar. 31, 2018shares
Earnings Per Share Basic [Line Items]
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%
Antidilutive securities		0
Class A Common Stock
Earnings Per Share Basic [Line Items]
Right to voting	one vote per share
Number of votes entitled to stockholders per share | Vote	1
Conversion of stock	0	7,534,710
Class B Common Stock
Earnings Per Share Basic [Line Items]
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
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income	$ 12,584	$ 5,495
Denominator:
Weighted-average number of shares of common stock used in computing net income per share attributable to common stockholders — basic	110,800,037	106,942,799
Dilutive effect of share equivalents resulting from stock options	1,450,076	4,772,154
Dilutive effect of share equivalents resulting from unvested restricted stock units	1,156,207	1,626,355
Weighted-average number of shares of common stock used in computing net income per share — diluted	113,406,320	113,341,308
Net income per share attributable to common stockholders:
Basic	$ 0.11	$ 0.05
Diluted	$ 0.11	$ 0.05

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	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
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		0
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	858,417

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ (3,503)	$ 1,246
Effective income tax rate	(38.60%)	18.50%
Internal Revenue Service (IRS) | Federal
Income Tax Disclosure [Line Items]
Income tax examination year under examination			2016

Segment and Geographic Inform_3

Segment and Geographic Information - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019Segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment and Geographic Inform_4

Segment and Geographic Information - Summary of Operations by Segment and Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment revenue:
Revenue	$ 135,270	$ 98,575
Segment income (loss) from operations:
Total income from operations	7,435	6,459
United States
Segment revenue:
Revenue	128,403	95,060
Segment income (loss) from operations:
Total income from operations	17,381	13,933
International
Segment revenue:
Revenue	6,867	3,515
Segment income (loss) from operations:
Total income from operations	$ (9,946)	$ (7,474)