Etsy (ETSY) 10-K 1 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 26, 2016	Jun. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	ETSY INC
Entity Central Index Key	1,370,637
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		112,699,756
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1,018,474,398

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 271,244	$ 69,659
Short-term investments	21,620	19,184
Accounts receivable, net of allowance for doubtful accounts of $1,841 and $2,071 as of December 31, 2014 and December 31, 2015, respectively	20,275	15,404
Prepaid and other current assets	9,521	12,241
Deferred tax charge—current	17,132	0
Funds receivable and seller accounts	19,262	10,573
Total current assets	359,054	127,061
Restricted cash	5,341	5,341
Property and equipment, net	105,021	75,538
Goodwill	27,752	30,831
Intangible assets, net	2,871	5,410
Deferred tax charge—net of current portion	51,396	0
Other assets	1,626	2,022
Total assets	553,061	246,203
Current liabilities:
Accounts payable	14,382	8,231
Accrued expenses	31,253	12,852
Capital lease obligations—current	5,610	1,755
Funds payable and amounts due to sellers	19,262	10,573
Deferred revenue	4,712	3,452
Other current liabilities	4,903	4,590
Total current liabilities	80,122	41,453
Capital lease obligations—net of current portion	7,571	3,148
Warrant liability	0	1,920
Deferred tax liabilities	61,420	149
Facility financing obligation	51,804	50,320
Other liabilities	21,646	1,913
Total liabilities	$ 222,563	$ 98,903
Commitments and contingencies
Convertible preferred stock:
Carrying Values	$ 0	$ 80,212
Stockholders’ equity:
Common stock ($0.001 par value, 120,000,000 and 1,400,000,000 shares authorized as of December 31, 2014 and December 31, 2015; 44,180,939 and 112,563,354 shares issued and outstanding as of December 31, 2014, and December 31, 2015, respectively)	113	44
Preferred Stock ($0.001 par value, 25,000,000 shares authorized as of December 31, 2015)	0	0
Additional paid-in capital	406,020	103,355
Accumulated deficit	(86,440)	(32,377)
Accumulated other comprehensive (loss) income	10,805	(3,934)
Total stockholders’ equity	330,498	67,088
Total liabilities, convertible preferred stock and stockholders’ equity	553,061	246,203
Series A and A-1 preferred stock
Convertible preferred stock:
Carrying Values	0	808
Series B preferred stock
Convertible preferred stock:
Carrying Values	0	865
Series C preferred stock
Current liabilities:
Warrant liability		579
Convertible preferred stock:
Carrying Values	0	3,361
Series D and D-1 preferred stock
Current liabilities:
Warrant liability		1,156
Convertible preferred stock:
Carrying Values	0	27,870
Series E preferred stock
Current liabilities:
Warrant liability		185
Convertible preferred stock:
Carrying Values	0	6,201
Series 1 preferred stock
Convertible preferred stock:
Carrying Values	0	1,322
Series F preferred stock
Convertible preferred stock:
Carrying Values	$ 0	$ 39,785

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts	$ 2,071	$ 1,841
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	1,400,000,000	120,000,000
Common stock, shares issued	112,563,354	44,180,939
Common stock, shares outstanding	112,563,354	44,180,939
Preferred stock, par value	$ 0.001
Preferred stock, shares authorized	25,000,000
Convertible preferred stock
Shares Authorized		21,165,473
Shares Outstanding	0	21,124,432
Series A and A-1 preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		2,363,786
Temporary equity, shares issued	0	2,363,786
Shares Outstanding	0	2,363,786
Temporary equity, aggregate liquidation preference		$ 808
Series B preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		1,128,431
Temporary equity, shares issued	0	1,128,425
Shares Outstanding	0	1,128,425
Temporary equity, aggregate liquidation preference		$ 903
Series C preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		1,234,084
Temporary equity, shares issued	0	1,222,282
Shares Outstanding	0	1,222,282
Temporary equity, aggregate liquidation preference		$ 3,263
Series D and D-1 preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		4,240,120
Temporary equity, shares issued	0	4,215,610
Shares Outstanding	0	4,215,610
Temporary equity, aggregate liquidation preference		$ 27,949
Series E preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		401,450
Temporary equity, shares issued	0	396,727
Shares Outstanding	0	396,727
Temporary equity, aggregate liquidation preference		$ 6,300
Series 1 preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		203,399
Temporary equity, shares issued	0	203,399
Shares Outstanding	0	203,399
Temporary equity, aggregate liquidation preference		$ 1,312
Series F preferred stock
Temporary equity, par value		$ 0.001
Shares Authorized		11,594,203
Temporary equity, shares issued	0	11,594,203
Shares Outstanding	0	11,594,203
Temporary equity, aggregate liquidation preference		$ 40,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenue	$ 273,499	$ 195,591	$ 125,022
Cost of revenue	96,979	73,633	47,779
Gross profit	176,520	121,958	77,243
Operating expenses:
Marketing	66,771	39,655	17,850
Product development	42,694	36,634	27,548
General and administrative	68,939	51,920	31,112
Total operating expenses	178,404	128,209	76,510
Income (loss) from operations	(1,884)	(6,251)	733
Other income (expense):
Interest expense and amortization of deferred financing costs	(1,526)	(590)	(302)
Interest and other income	324	41	46
Net unrealized loss on warrant and other liabilities	(3,133)	(411)	(419)
Foreign exchange loss	(21,775)	(3,049)	0
Total other expense	(26,110)	(4,009)	(675)
Income (loss) before income taxes	(27,994)	(10,260)	58
Provision for income taxes	(26,069)	(4,983)	(854)
Net loss	$ (54,063)	$ (15,243)	$ (796)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollars per share)	$ (0.59)	$ (0.38)	$ (0.02)
Weighted average common shares outstanding:
Basic and diluted (shares)	91,122,291	40,246,663	32,667,242

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (54,063)	$ (15,243)	$ (796)
Other comprehensive income (loss):
Cumulative translation adjustment	14,746	(4,091)	221
Unrealized gains on marketable securities, net of tax	(7)	(3)	(9)
Other comprehensive income (loss)	14,739	(4,094)	212
Comprehensive loss	$ (39,324)	$ (19,337)	$ (584)

Consolidated Statements of Chan

Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible preferred stock	Series A and A-1 preferred stock	Series B preferred stock	Series C preferred stock	Series D and D-1 preferred stock	Series E preferred stock	Series 1 preferred stock	Series F preferred stock	Preferred StockSeries A and A-1 preferred stock	Preferred StockSeries B preferred stock	Preferred StockSeries C preferred stock	Preferred StockSeries D and D-1 preferred stock	Preferred StockSeries E preferred stock	Preferred StockSeries 1 preferred stock	Preferred StockSeries F preferred stock	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income
Convertible preferred stock, beginning balance at Dec. 31, 2012										$ 808	$ 865	$ 3,361	$ 27,870	$ 6,201	$ 1,322	$ 39,785
Convertible preferred stock, beginning balance (in shares) at Dec. 31, 2012										2,363,786	1,128,425	1,222,282	4,215,610	396,727	203,399	11,594,203
Convertible preferred stock, ending balance at Dec. 31, 2013										$ 808	$ 865	$ 3,361	$ 27,870	$ 6,201	$ 1,322	$ 39,785
Convertible preferred stock, ending balance (in shares) at Dec. 31, 2013										2,363,786	1,128,425	1,222,282	4,215,610	396,727	203,399	11,594,203
Beginning balance at Dec. 31, 2012	$ (652)																$ 33	$ (1)	$ 15,706	$ (16,338)	$ (52)
Beginning balance (in shares) at Dec. 31, 2012																	32,730,683	648,795
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	4,077																		4,077
Exercise of vested options	$ 1,328																$ 1		1,327
Exercise of vested options (in shares)	1,024,560																1,024,560
Repurchase of shares	$ (188)																		(188)
Repurchase of shares (in shares)																		(23,500)
Retirement of repurchased shares (in shares)																	(672,295)	(672,295)
Retirement of repurchased shares																	$ (1)	$ 1
Excess tax benefit from the exercise of stock options	22																		22
Other comprehensive income (loss)	212																				212
Net loss	(796)																			(796)
Ending balance at Dec. 31, 2013	4,003																$ 33		20,944	(17,134)	160
Ending balance (in shares) at Dec. 31, 2013																	(33,082,948)
Convertible preferred stock, ending balance at Dec. 31, 2014	80,212	$ 80,212	$ 808	$ 865	$ 3,361	$ 27,870	$ 6,201	$ 1,322	$ 39,785	$ 808	$ 865	$ 3,361	$ 27,870	$ 6,201	$ 1,322	$ 39,785
Convertible preferred stock, ending balance (in shares) at Dec. 31, 2014		21,124,432	2,363,786	1,128,425	1,222,282	4,215,610	396,727	203,399	11,594,203	2,363,786	1,128,425	1,222,282	4,215,610	396,727	203,399	11,594,203
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	6,110																		6,110
Exercise of vested options	$ 7,956																$ 4		7,952
Exercise of vested options (in shares)	4,215,628																4,215,628
Issuance of stock at acquisition date (in shares)																	3,580,476
Issuance of stock at acquisition date	$ 27,723																$ 4		27,719
Stock expense-acquisitions	756																		756
Common stock issued through public offering	35,000																$ 3		34,997
Common stock issued through public offering (in shares)																	3,301,887
Excess tax benefit from the exercise of stock options	4,877																		4,877
Other comprehensive income (loss)	(4,094)																				(4,094)
Net loss	(15,243)																			(15,243)
Ending balance at Dec. 31, 2014	67,088																$ 44		103,355	(32,377)	(3,934)
Ending balance (in shares) at Dec. 31, 2014																	(44,180,939)
Increase (Decrease) in Temporary Equity [Roll Forward]
Convertible preferred stock, conversion of preferred stock upon public offering										$ (808)	$ (865)	$ (3,361)	$ (27,870)	$ (6,201)	$ (1,322)	$ (39,785)
Convertible preferred stock, conversion of preferred stock upon public offering (in shares)										(2,363,786)	(1,128,425)	(1,222,282)	(4,215,610)	(396,727)	(203,399)	(11,594,203)
Convertible preferred stock, ending balance at Dec. 31, 2015	0		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Convertible preferred stock, ending balance (in shares) at Dec. 31, 2015		0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	9,444																		9,444
Exercise of vested options	$ 3,626																$ 2		3,624
Exercise of vested options (in shares)	1,315,735																1,315,735
Stock expense-acquisitions	$ 1,122																		1,122
Exercise of warrants	110																$ 1		109
Exercise of warrants (in shares)																	105,099
Shares withheld in net exercise of warrants	(110)																$ (1)		(109)
Shares witheld in net exercise of warrants (in shares)																	(8,230)
Common stock issued through public offering	194,361																$ 14		194,347
Common stock issued through public offering (in shares)																	13,333,333
Contribution to Etsy.org	3,200																		3,200
Contribution to Etsy.org, (in shares)																	188,235
Conversion of liability-classified vested restricted shares	1,755																		1,755
Conversion of preferred stock upon public offering	80,212																$ 53		80,159
Conversion of preferred stock upon public offering (in shares)																	53,448,243
Conversion of liability-classified warrants upon public offering	5,070																		5,070
Excess tax benefit from the exercise of stock options	3,944																		3,944
Other comprehensive income (loss)	14,739																				14,739
Net loss	(54,063)																			(54,063)
Ending balance at Dec. 31, 2015	$ 330,498																$ 113		$ 406,020	$ (86,440)	$ 10,805
Ending balance (in shares) at Dec. 31, 2015																	(112,563,354)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net loss	$ (54,063)	$ (15,243)	$ (796)
Adjustments to reconcile net loss to net cash provided by operating activities:
Stock-based compensation expense	8,981	5,920	3,834
Stock-based compensation expense-acquisitions	1,860	4,130	0
Contribution of stock to Etsy.org	3,200	0	0
Depreciation and amortization expense	18,550	17,223	12,380
Bad debt expense	1,780	1,881	1,002
Foreign exchange loss	21,775	3,049	0
Amortization of debt issuance costs	167	68	8
Net unrealized loss on warrant and other liabilities	3,133	411	419
Loss on disposal of assets	1,319	79	677
Amortization of deferred tax charges	17,132	0	0
Excess tax benefit from exercise of stock options	(3,944)	(4,877)	(22)
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(6,739)	(6,197)	(4,832)
Funds receivable and seller accounts	(9,025)	(3,975)	(2,907)
Prepaid expenses and other current assets	(266)	(5,820)	(1,667)
Other assets	225	(1,446)	(295)
Accounts payable	6,728	1,046	1,712
Accrued expenses	12,395	11,463	1,960
Funds payable and amounts due to sellers	9,025	3,880	2,993
Deferred revenue	1,279	693	794
Other liabilities	(4,301)	(198)	1,282
Net cash provided by operating activities	29,211	12,087	16,542
Cash flows from investing activities
Acquisition of businesses, net of cash acquired	0	(4,688)	(675)
Purchases of property and equipment	(11,116)	(1,304)	(7,762)
Development of internal-use software	(9,719)	(8,280)	(9,310)
Purchase of U.S. Government and agency bills	(26,040)	(21,698)	(39)
Sale of marketable securities	23,592	20,588	2,761
Net increase in restricted cash	0	(5,341)	0
Net cash used in investing activities	(23,283)	(20,723)	(15,025)
Cash flows from financing activities
Proceeds from public offering	199,467	0	0
Proceeds from the issuance of common stock	0	35,000	0
Repurchase of stock			(188)
Proceeds from exercise of stock options	3,626	7,956	1,328
Excess tax benefit from the exercise of stock options	3,944	4,877	22
Payments on capitalized lease obligations	(3,377)	(1,480)	(1,265)
Deferred payments on acquisition of business	0	(75)	0
Payments relating to public offering	(4,052)	(1,041)	0
Net cash (used in) provided by financing activities	199,608	45,237	(103)
Effect of exchange rate changes on cash	(3,951)	(3,737)	446
Net increase in cash and cash equivalents	201,585	32,864	1,860
Cash and cash equivalents at beginning of period	69,659	36,795	34,935
Cash and cash equivalents at end of period	271,244	69,659	36,795
Supplemental cash flow disclosures:
Cash paid for interest		342	233
Cash paid for income taxes	7,604	217	206
Supplemental non-cash disclosures
Equipment acquired under capital lease obligations	11,657	5,564	0
Stock-based compensation capitalized in development of capitalized software	463	190	243
Non-cash additions to development of internal-use software and property and equipment	12,721	2,510	398
Non-cash additions to facility financing obligation related to build-to-suit lease	1,484	50,320	0
Non-cash addition to capitalized public offering costs	13	1,413	0
Fair value of common stock issued in acquisition	$ 0	$ 27,723	$ 0

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Description of Business Etsy, Inc. (the “Company” or “Etsy”) was incorporated in Delaware in February 2006. Etsy operates a marketplace where people around the world connect, both online and offline, to make, sell and buy unique goods. The Company generates revenue primarily from transaction and listing fees, Promoted Listings, Direct Checkout fees, and Shipping Label sales. Initial Public Offering On April 21, 2015, the Company completed an initial public offering (the "IPO") in which it issued and sold 13,333,333 shares of common stock at a public offering price of $16.00 per share. The Company received net proceeds of $194.4 million after deducting underwriting discounts of $13.9 million and other offering expenses of approximately $5.1 million . These expenses were recorded against the proceeds received from the IPO. Certain selling stockholders sold an additional 5,833,332 shares of common stock in the IPO. The Company did not receive any proceeds from the sale of shares sold by the selling stockholders. Upon the closing of the IPO, all outstanding shares of preferred stock of the Company converted into 53,448,243 shares of common stock. In addition, all outstanding warrants for preferred stock converted into warrants for 203,030 shares of common stock. The Company effected a 1-for-2 reverse split of its common stock on March 25, 2015. The reverse split combined each two shares of the Company’s issued and outstanding common stock into one share of common stock and correspondingly adjusted the conversion prices of its convertible preferred stock. No fractional shares were issued in connection with the reverse split, and any fractional shares resulting from the reverse split were rounded down to the nearest whole share. All share, per share and related information presented in the consolidated financial statements and accompanying notes have been retroactively adjusted, where applicable, to reflect the reverse stock split. Basis of Consolidation The consolidated financial statements include the accounts of Etsy and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Reclassifications Certain items in the prior years’ consolidated financial statements have been reclassified to conform to the current year presentation reflected in the financial statements. Specifically, the Company reclassified $4.6 million previously included in accrued expenses and other current liabilities to other current liabilities on the consolidated balance sheets for 2014, to conform to the current year presentation. Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The accounting estimates that require management’s most difficult and subjective judgments include revenue recognition, income taxes, website development costs and internal-use software, purchase price allocations for business combinations, valuation of goodwill and intangible assets, leases and stock-based compensation. The Company evaluates its estimates and judgments on an ongoing basis and revises them when necessary. Actual results may differ from the original or revised estimates. Revenue Recognition The Company operates a platform for third-party sellers. Its business model is based on shared success: the Company makes money when Etsy sellers make money, and the Company offers services to help Etsy sellers be more successful. The Company does not compete with Etsy sellers, hold inventory or sell goods. The Company’s revenue is diversified, generated from a mix of marketplace activities and the services the Company provides Etsy sellers to help them create and grow their businesses. The Company’s revenue consists of Marketplace revenue, Seller Services revenue and Other revenue. The Company’s revenue is recorded net of actual and expected refunds. Marketplace revenue includes the fee an Etsy seller pays for each completed transaction and the listing fee an Etsy seller pays for each item she lists. Seller Services revenue includes fees an Etsy seller pays for services such as prominent placement in search results via Promoted Listings, payment processing via Direct Checkout and purchases of shipping labels through the Company’s platform via Shipping Labels. The Company deducts its cost of shipping labels and estimated refunds from gross shipping fees to determine net shipping fees. Other revenue includes the fees the Company receives from a third-party payment processor and derecognized funds the Company receives from a third-party for unused Etsy Gift Cards. The Company recognizes revenue when all of the following conditions are satisfied: (1) there is persuasive evidence of an arrangement; (2) the service has been provided to the Etsy seller; (3) the collection of fees is reasonably assured; and (4) the amount of fees to be paid by the Etsy seller is fixed or determinable. The Company evaluates whether it is appropriate to recognize revenue on a gross or net basis based upon its evaluation of whether it is the primary obligor in a transaction, has inventory risk and has latitude in establishing pricing and selecting suppliers. Based on its evaluation of these factors, revenue is recorded net of merchandise values associated with the transaction. Marketplace revenue . Marketplace revenue consists of the 3.5% fee that an Etsy seller pays for each completed transaction on the Company’s platform, exclusive of shipping fees charged. Marketplace revenue also consists of a listing fee of $0.20 per item that she lists in its marketplace. Revenue from completed Wholesale transactions is also included in Marketplace revenue. Transaction fees are recognized when the corresponding transaction is made. Listing fees are recognized ratably over a four -month listing period, unless the item is sold or the seller relists it, at which time any remaining listing fee is recognized. Seller Services revenue . Seller Services revenue consists of fees an Etsy seller pays the Company for the Seller Services she uses, including Promoted Listings, Direct Checkout and Shipping Labels. • Revenue from Promoted Listings consists of cost-per-click based fees an Etsy seller pays the Company for prominent placement of her listings in search results generated by Etsy buyers in its marketplace. Revenue is recognized when the Promoted Listing is clicked. • Revenue from Direct Checkout consists of fees an Etsy seller pays the Company to process credit, debit and Etsy Gift Card payments. Direct Checkout fees vary between 3 - 4% of the item’s total sale price plus a flat fee per order, depending on the country in which her bank account is located. Direct Checkout fees are based on the item’s total sale price, including shipping. Revenue from Direct Checkout is recognized when the corresponding transaction is made. • Revenue from Shipping Labels consists of fees an Etsy seller pays the Company when she purchases shipping labels directly through its platform, net of the cost it incurs in purchasing those shipping labels. The Company provides its sellers shipping labels from the United States Postal Service and Canada Post at a discounted price due to the volume of purchases through its platform. The Company recognizes Shipping Label revenue when an Etsy seller purchases a shipping label. The Company recognizes Shipping Label revenue on a net basis as it is not the primary obligor in the delivery of these services. Other revenue . Other revenue includes the fees the Company receives from a third-party payment processor, which is recognized as the transactions are processed by the third-party payment processor, and derecognized funds the Company receives from a third-party for unused Etsy Gift Cards, which are recognized when the third-party approves the release of these funds. The following table summarizes revenue by type of service (in thousands): Year Ended 2013 2014 2015 Marketplace $ 78,544 $ 108,732 $ 132,648 Seller Services 42,817 82,502 136,608 Other 3,661 4,357 4,243 Revenue $ 125,022 $ 195,591 $ 273,499 Cost of Revenue Cost of revenue consists primarily of expenses associated with the operation and maintenance of the Company’s platform and data centers, including depreciation and amortization, employee-related costs, including stock-based compensation expense, and hosting and bandwidth costs. Cost of revenue also includes the cost of interchange and other fees for credit card processing services, credit card verification service fees and credit card chargebacks to support Direct Checkout revenue and costs of refunds made to Etsy buyers that the Company is not able to collect from Etsy sellers. Accounts Receivable and Allowance for Doubtful Accounts The Company’s trade accounts receivable are recorded at amounts billed to Etsy sellers and are presented on the consolidated balance sheet net of the allowance for doubtful accounts. The allowance is determined by a number of factors, including age of the receivable, current economic conditions, historical losses and management’s assessment of the financial condition of Etsy sellers. Receivables are written off once they are deemed uncollectible, which may arise when Etsy sellers file for bankruptcy or are otherwise deemed unable to repay the amounts owed to the Company. Estimates of uncollectible accounts receivable are recorded to general and administrative expense. The following table summarizes the allowance activity during the periods indicated (in thousands): Year Ended 2013 2014 2015 Balance as of the beginning of period $ 1,357 $ 1,279 $ 1,841 Bad debt expense 1,002 1,881 1,780 Write-offs, net of recoveries and other adjustments (1,080 ) (1,319 ) (1,550 ) Balance as of the end of period $ 1,279 $ 1,841 $ 2,071 Funds Receivable and Seller Accounts and Funds Payable and Amounts due to Sellers The Company records funds receivable and seller accounts and funds payable and amounts due to sellers as current assets and liabilities, respectively, on the consolidated balance sheet. Funds receivable and seller accounts represent amounts received or expected to be received from Etsy buyers via third-party credit card processors, which flow through an Etsy bank account for payment to Etsy sellers. This cash and related receivable represent the total amount due to sellers, and as such a liability for the same amount is recorded to funds payable and amounts due to Etsy sellers. Property and Equipment Property and equipment, consisting principally of construction in process, computer equipment and leasehold improvements, are recorded at cost. The Company capitalizes construction in progress for build-to-suit lease agreements where we are the owner, for accounting purposes only, during the construction period. Depreciation and amortization begin at the time the asset is placed into service and are recognized using the straight-line method in amounts sufficient to relate the cost of depreciable and amortizable assets to operations over their estimated useful lives. Repairs and maintenance are charged to operations as incurred. Upon sale or retirement of assets, the cost and related accumulated depreciation or amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations. When events or changes in circumstances require, the Company assesses the likelihood of recovering the cost of tangible long-lived assets based on its expectations of future profitability, undiscounted cash flows and management’s plans with respect to operations to determine if the asset is impaired and subject to write-off. Measurement of any impairment loss is based on the excess of the carrying value of the asset over the fair value. Internal-use Software and Website Development Costs Costs incurred to develop software for internal use and the Company’s website are capitalized and amortized over the estimated useful life of the software, generally three years. The Company also capitalizes costs related to upgrades and enhancements when it is probable the expenditures will result in additional functionality or will extend the useful life of existing functionality. Costs related to the design or maintenance of internal-use software and website development are expensed as incurred. The Company periodically reviews internal-use software and website development costs to determine whether the projects will be completed, placed in service, removed from service, or replaced by other internally developed or third-party software. If the asset is not expected to provide any future benefit, the asset is retired and any unamortized cost is expensed. Leases The Company leases office space and certain computer equipment in multiple locations under non-cancelable lease agreements. The leases are reviewed for classification as operating, capital or build-to-suit leases. For operating leases, rent is recognized on a straight-line basis over the lease period. For capital leases, the Company records the leased asset with a corresponding liability. Payments are recorded as reductions to the liability with an appropriate interest charge recorded based on the then-outstanding remaining liability. The Company considers the nature of the renovations and the Company’s involvement during the construction period of newly leased office space to determine if it is considered, for accounting purposes only, to be the owner of the construction project during the construction period. If the Company determines that it is the owner of the construction project, it is required to capitalize the fair value of the building as well as the construction costs incurred on its consolidated balance sheet along with a corresponding financing liability (“build-to-suit accounting”). Upon occupancy for build-to-suit leases, the Company assesses whether the circumstances qualify for sales recognition under the sale-leaseback accounting guidance. If the lease meets the sale-leaseback criteria, the Company will remove the asset and related financial obligation from the balance sheet and treat the building lease as an operating lease. If upon completion of construction, the project does not meet the sale-leaseback criteria, the leased property will be treated as a capital lease for financial reporting purposes. Income Taxes Income tax benefit (provision) is based on (loss) income before income taxes and is accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income or expense in the period that includes the enactment date. Management assesses the need for a valuation allowance on a quarterly basis to reduce deferred tax assets to the amounts expected to be realized. The Company accounts for uncertainty in income taxes using a recognition threshold and a measurement attribute for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by the taxing authorities. The amount recognized is measured as the largest amount of benefit that has a greater than 50% likelihood of being realized upon ultimate audit settlement. The Company has an unrecognized tax benefit of $0.4 million and $22.2 million at December 31, 2014 and 2015 , respectively. The Company recognizes interest and penalties, if any, associated with income tax matters as part of the income tax provision and includes accrued interest and penalties with the related income tax liability in the consolidated balance sheet. Business Combinations The Company has completed a number of acquisitions of other businesses in the past and may acquire additional businesses or technologies in the future. The results of businesses acquired in a business combination are included in the Company’s consolidated financial statements from the date of acquisition. The Company allocates the purchase price, which is the sum of the consideration provided and may consist of cash, equity or a combination of the two, in a business combination to the identifiable assets and liabilities of the acquired business at their acquisition date fair values. The excess of the purchase price over the amount allocated to the identifiable assets and liabilities, if any, is recorded as goodwill. Determining the fair value of assets acquired and liabilities assumed requires management to use significant judgment and estimates, including the selection of valuation methodologies, estimates of future revenue and cash flows, discount rates and selection of comparable companies. When the Company issues stock-based or cash awards to an acquired company’s stockholders, the Company evaluates whether the awards are contingent consideration or compensation for post-acquisition services. The evaluation includes, among other things, whether the vesting of the awards is contingent on the continued employment of the acquired company’s stockholder beyond the acquisition date. If continued employment is required for vesting, the awards are treated as compensation for post-acquisition services and recognized as expense over the requisite service period. The Company carries intangible assets at cost, and it amortizes them on a straight-line basis over their estimated useful lives, typically three years. When circumstances indicate that the carrying value of these assets may not be recoverable, the Company reviews its identifiable amortizable intangible assets for impairment. To date, the assets acquired and liabilities assumed in the Company’s business combinations have primarily consisted of goodwill and finite-lived intangible assets, consisting primarily of developed technologies, customer relationships and trademarks. The estimated fair values and useful lives of identifiable intangible assets are based on many factors, including estimates and assumptions of future operating performance and cash flows of the acquired business, the nature of the business acquired, and the specific characteristics of the identified intangible assets. The estimates and assumptions used to determine the fair values and useful lives of identified intangible assets could change due to numerous factors, including market conditions, technological developments, economic conditions and competition. In connection with determination of fair values, the Company may engage independent appraisal firms to assist with the valuation of intangible and certain tangible assets acquired and certain assumed obligations. Acquisition-related transaction costs incurred by the Company are not included as a component of consideration transferred, but are accounted for as an expense in the period in which the costs are incurred. Goodwill Goodwill represents the excess of the aggregate fair value of the consideration transferred in a business combination over the fair value of the assets acquired, net of liabilities assumed. Goodwill is not amortized, but is subject to an annual impairment test. Management has determined that the Company has a single reporting unit and performs its annual goodwill impairment test during the fourth quarter or more frequently if events or changes in circumstances indicate that the goodwill may be impaired. Events or changes in circumstances which could trigger an impairment review include significant changes in the manner of the Company’s use of the acquired assets or the strategy for the Company’s overall business, significant negative industry or economic trends, significant underperformance relative to historical or projected future results of operations, a significant adverse change in the business climate, an adverse action or assessment by a regulator, unanticipated competition or a loss of key personnel. The Company has the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, an entity determines it is not more likely than not that the fair value of the reporting unit is less than its carrying amount, then additional impairment testing is not required. However, if an entity concludes otherwise, then it is required to perform the first of a two-step impairment test. The first step involves comparing the estimated fair value of the reporting unit with its respective book value, including goodwill. If the estimated fair value exceeds book value, goodwill is considered not to be impaired and no additional steps are necessary. If, however, the fair value of the reporting unit is less than book value, then a second step is required that compares the carrying amount of the goodwill with its implied fair value. The estimate of implied fair value of goodwill may require valuations of certain internally-generated and unrecognized intangible and tangible net assets. If the carrying amount of goodwill exceeds the implied fair value of the goodwill, an impairment loss is recognized in an amount equal to the excess. The Company completed a Step Zero analysis during the fourth quarter of 2015 . No impairment of goodwill was recorded at December 31, 2014 or 2015 . Intangible Assets Intangible assets are amortized over the estimated useful life of the acquired technology, customer relationships and trademarks, generally three years. Stock-Based Compensation For employee stock-based awards, the Company calculates the fair value of the award on the date of grant using the Black-Scholes option-pricing model and the expense is recognized over the service period for awards expected to vest. Prior to the IPO, the Company utilized equity valuations based on comparable publicly-traded companies, discounted free cash flows, an analysis of the Company's enterprise value and any other factors deemed relevant in estimating the fair value of its common stock. Subsequent to the IPO, the Company has used the closing price of its common stock on Nasdaq as the fair value of its common stock. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. Expected volatilities are based on implied volatilities from market comparisons of certain publicly traded companies and other factors. The expected term of stock options granted has been determined using the simplified method, which uses the midpoint between the vesting date and the contractual term. The requisite service period is generally four years from the date of grant. The fair value of RSUs is determined based on the closing price of the Company's common stock on Nasdaq on the grant date. We account for stock-based compensation arrangements in restricted shares, subject to a put option that allows the holder of the shares to put the shares back to the Company for cash, as liability-classified stock awards. These awards are re-measured at each reporting period, with changes in fair value being charged to the statement of operations. Compensation expense is recognized using a graded vesting methodology for each separately vesting tranche as though the award were, in substance, multiple awards. Unless the put option is exercised, the restricted shares will be reclassified from a liability to an equity classified award upon the termination of the put option at the vesting of each separate tranche. For the years ended December 31, 2013, 2014 and 2015 , the Company recognized expenses of approximately $3.6 million , $5.9 million and $8.9 million for employee stock options, respectively, and $0.2 million , $0.1 million and $0.1 million for non-employee stock options, respectively. Additionally, the Company recorded $4.1 million and $1.86 million in acquisition-related stock-based compensation expense for the years ended December 31, 2014 and 2015, respectively, of which $3.4 million and $0.7 million relates to liability-classified awards, respectively. Cash and Cash Equivalents The Company considers all investments with an original maturity of three months or less at time of purchase to be cash equivalents. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash and cash equivalents. The Company reduces credit risk by placing its cash and cash equivalents with major financial institutions with high credit ratings. At times, such amounts may exceed federally insured limits. Fair Value of Financial Instruments Management believes that the fair value of financial instruments, consisting of cash and cash equivalents, accounts receivable and accounts payable, approximates carrying value due to the immediate or short-term maturity associated with its cash and cash equivalents, accounts receivable and accounts payable. Marketing Marketing expenses consist primarily of targeted online marketing costs, such as product listing ads, search engine marketing, affiliate marketing and, to a much lesser extent, offline marketing expenses. Marketing expenses also include employee-related costs, including stock-based compensation expense, for our employees involved in digital marketing, seller development and growth, public relations and communications, brand marketing and design, product marketing and marketing research activities. Marketing expenses are primarily driven by investments to grow and retain members on our platform. Net (Loss) Income Per Share Prior to the IPO, the Company followed the two-class method when computing net (loss) income per share as the Company had issued shares that met the definition of participating securities. The two-class method determined net (loss) income per share for each class of common stock and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method required income available to common stockholders for the period to be allocated between common stock and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s convertible preferred stock contractually entitled the holders of such shares to participate in dividends, but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, the two-class method did not apply for periods in which the Company reports a net loss or a net loss attributable to common stockholders resulting from dividends, accretion or modifications to its convertible preferred stock. Upon the closing of the IPO on April 21, 2015, all outstanding shares of convertible preferred stock were converted into shares of common stock. For current and future periods, the two-class method is not applicable to the computation of net (loss) income per share until shares of authorized preferred stock become issued and outstanding. Basic net (loss) income per share attributable to common stockholders is computed by dividing the net (loss) income attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net (loss) income attributable to common stockholders is computed by adjusting net (loss) income attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities, including outstanding common stock options, convertible preferred stock and warrants to purchase common stock and convertible preferred stock. For periods in which the Company has reported net losses, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, because dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Segment Data The Company identifies operating segments as components of an entity for which discrete financial information is available and is regularly reviewed by the chief operating decision maker, or decision-making group, in making decisions regarding resource allocation and performance assessment. The Company defines the term “chief operating decision maker” to be its chief executive officer. The Company has determined it operates in one operating segment and one reportable segment, as its chief operating decision maker reviews financial information presented on only a consolidated basis for purposes of allocating resources and evaluating financial performance. Foreign Currency The Company has determined that the functional currency for each of its foreign operations is the local currency in which the operation is located. All assets and liabilities are translated into U.S. dollars using exchange rates in effect at the balance sheet date. Revenue and expenses are translated using average exchange rates during the period. Foreign currency translation adjustments are reflected in stockholders’ equity as a component of other comprehensive (loss) income. Transaction gains and losses including intercompany transactions denominated in a currency other than the functional currency of the entity involved are included in foreign exchange loss within other (expense) income in the statement of operations. Excess Tax Benefits from Exercise of Stock Options The Company uses the “with and without” approach in determining the order in which tax attributes are utilized. As a result, the Company recognizes a tax benefit from stock-based awards in additional paid-in capital only if an incremental tax benefit is realized after all other tax attributes currently available to the Company have been utilized. When tax deductions from stock-based awards are less than the cumulative book compensation expense, the tax effect of the resulting difference (“shortfall”) is charged first to additional paid-in capital, to the extent of the Company’s pool of windfall tax benefits, with any remainder recognized in income tax expense. The Company determined that it had a sufficient windfall pool available through December 31, 2015 to absorb any shortfalls. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued an accounting standards update that replaces existing revenue recognition guidance. The new guidance is effective for the annual and interim periods beginning after December 15, 2017. Among other things, the updated guidance requires companies to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company is currently evaluating the effect the guidance will have on its consolidated financial statements. In August 2014, the FASB issued an accounting standard update under which management will be required to assess an entity’s ability to continue as a going concern and provide related disclosures in certain circumstances. The new guidance is effective for annual and interim periods beginning after December 15, 2016. The adoption of this guidance is not expected to have an impact on the Company’s consolidated financial statements or disclosures. In April 2015, the FASB issued an accounting standard under which customers will apply the same criteria as vendors to determine whether a cloud computing arrangement contains a software license or is solely a service contract. The new standard is effective for annual and interim periods beginning after December 15, 2015. The Company has evaluated the effect this guidance will have on the consolidated financial statements and do not believe the impact to be

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Business Combinations	Business Combinations In January 2013, the Company acquired the assets of The Lascaux Company, Inc., owners of the “Mixel” iOS mobile application, for a purchase price of $750,000 , which consisted of $675,000 paid on the closing date and $75,000 due on the first anniversary of the closing date, subject to indemnification provisions. In connection with the acquisition, the Company granted options to purchase 181,160 shares of common stock to certain key employees of the acquired company. Acquired assets consisted of the Mixel iOS mobile application and related source code and domain name registration. The purchase price was allocated between acquired technology intangible assets and goodwill in the Company’s consolidated financial statements. This acquisition did not have any measureable impact on consolidated revenue or (loss) income from operations. On April 29, 2014, the Company completed the acquisition of Jarvis Labs, Inc., owners of the “Grand St.” online technology marketplace. Total consideration for the acquisition was approximately $3.2 million , consisting of $1.0 million in cash and 212,552 shares of the Company’s common stock with a fair value of $2.2 million on the acquisition date. Additionally, the Company issued 328,580 shares of common stock, with a fair value of $3.4 million on the acquisition date, which are tied to continuous service with the Company as an employee or consultant and are being accounted for as post-acquisition stock-based compensation expense over the 3 -year vesting period. Because the Company was not publicly traded at the time of the acquisition, the Company utilized equity valuations based on comparable publicly-traded companies, discounted cash flows, an analysis of the Company’s enterprise value and any other factors deemed relevant in estimating the fair value of its common stock for purposes of calculating the fair value of the purchase price. The following table summarizes the components of the Grand St. purchase price and the allocation of the purchase price at fair value (in thousands): Cash paid $ 1,040 Common shares 2,202 Total purchase consideration $ 3,242 Working capital $ 85 Developed technology 2,000 Customer relationships 600 Trademarks 200 Goodwill 991 Deferred tax liability (634 ) Net assets acquired $ 3,242 Included in working capital is approximately $0.1 million of cash acquired. The amounts allocated to developed technology, customer relationships and trademark (the acquired intangible assets) total $2.8 million . The fair value assigned to developed technology was determined primarily using the cost approach, which estimates the cost to reproduce the asset, adjusted for loss due to functional and economic obsolescence. The fair value of the Company’s customer relationships was determined primarily using the income approach, which discounts expected future cash flows to present value using estimates and assumptions determined by management. The fair value assigned to trademark was determined using the relief from royalty method, where the owner of the asset realizes a benefit from owning the intangible asset rather than paying a rental or royalty rate for use of the asset. The acquired identifiable intangible assets are being amortized on a straight-line basis over three years, which approximates the pattern in which the assets are utilized. None of the goodwill recorded in the acquisition is deductible for tax purposes. On June 18, 2014, the Company completed the acquisition of Incubart SAS, a societe par actions simplifiee organized under the laws of France, which operates the online marketplace A Little Market (“ALM”). Total consideration for the acquisition was $30.8 million , consisting of $5.3 million in cash, of which $4.2 million was paid on the closing date, $0.3 million was paid on March 31, 2015 and $0.8 million was paid on February 18, 2016, and 2,439,847 shares of the Company’s common stock with a fair value of $25.5 million on the acquisition date. Because the Company was not publicly traded at the time of the acquisition, the Company utilized equity valuations based on comparable publicly-traded companies, discounted cash flows, an analysis of the Company’s enterprise value and any other factors deemed relevant in estimating the fair value of its common stock for purposes of calculating the fair value of the purchase price. The terms of the purchase agreement provide for the sale of put options to certain of the former shareholders of ALM. The put options enable the holders of the options to sell up to all of their shares back to the Company, subject to certain vesting and restrictions, at fair value, but not to exceed $8.26 per share and not less than $4.00 per share. The put right terminates with respect to a share on the earlier of one year from when such share is vested or the liquidation date, as defined in the agreement containing the put option. The holders of the options paid an aggregate of $0.1 million cash to the Company at the date of acquisition and the Company recorded a $0.1 million liability for the fair value of the put options at that time. Additionally, the Company issued 599,497 shares of common stock, with a fair value of $6.3 million on the acquisition date, which are tied to continuous service with the Company as an employee or consultant and are being accounted for as post-acquisition stock-based compensation expense over the three-year vesting period. Since the put options relate in part to these shares, these restricted shares will be recorded as liability-classified stock awards as earned. The following table summarizes the components of the purchase price at fair value and the allocation of the purchase price at fair value (in thousands): Cash paid $ 5,290 Common shares 25,521 Total purchase consideration $ 30,811 Working capital $ 625 Property and equipment and other assets 95 Developed technology 1,636 Customer relationships 1,693 Trademarks 775 Goodwill 27,309 Deferred tax liability (757 ) Other long-term liabilities (565 ) Net assets acquired $ 30,811 Included in working capital is approximately $0.5 million of cash and cash equivalents acquired. The amount allocated to developed technology, customer relationships and trademark (the acquired intangible assets) totals $4.1 million . The fair value assigned to developed technology was determined primarily by using the cost approach, which estimates the cost to reproduce the asset, adjusted for loss due to functional and economic obsolescence. The fair value of the Company’s customer relationships was determined primarily by using the income approach, which discounts expected future cash flows to present value using estimates and assumptions determined by management. The fair value assigned to trademark was determined using the relief from royalty method, where the owner of the asset realizes a benefit from owning the intangible asset rather than paying a rental or royalty rate for use of the asset. The acquired identifiable intangible assets are being amortized on a straight-line basis over three years, which approximates the pattern in which the assets are utilized. Goodwill of $27.3 million , none of which is deductible for tax purposes, was recorded in connection with the ALM acquisition, which is primarily attributed to synergies arising from the acquisition and the value of the acquired workforce. The Company incurred approximately $2.1 million in acquisition-related costs, included in general and administrative expenses. These acquisitions increased revenue by $1.8 million and contributed $5.7 million to the Company’s consolidated net loss in the year ended December 31, 2014. The impact to net loss was primarily due to amortization of intangibles and stock-based compensation associated with the acquisitions. The following unaudited pro forma financial information presents the combined operating results of the Company, Grand St. and ALM as if each acquisition had occurred as of January 1, 2013. The unaudited pro forma financial information includes the accounting effects of the business combinations, including adjustments to the amortization of intangible assets and professional fees associated with the acquisition. The unaudited pro forma information does not necessarily reflect the actual results that would have been achieved, nor is it necessarily indicative of our future consolidated results. The unaudited pro forma financial information is presented in the table below for the years ended December 31, 2013 and 2014 (in thousands except per share amounts): Year Ended December 31, 2013 2014 Revenue $ 127,838 $ 197,395 Net loss (7,533 ) (15,403 ) Basic net loss per share (0.21 ) (0.37 ) Diluted net loss per share (0.21 ) (0.37 ) During the second quarter of 2015, the Company recognized changes to assets and liabilities impacting the associated purchase price allocations of ALM and Grand St. at their respective dates of acquisition. These adjustments resulted in a decrease to the initial purchase price allocation of goodwill for ALM and Grand St. of $0.4 million and $0.2 million , respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company has characterized its investments in marketable securities, based on the priority of the inputs used to value the investments, into a three-level fair value hierarchy. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1), and lowest priority to unobservable inputs (Level 3). If the inputs used to measure the investments fall within different levels of the hierarchy, the categorization is based on the lowest level input that is significant to the fair value measurement of the investment. Investments recorded in the accompanying consolidated balance sheet are categorized based on the inputs to valuation techniques as follows: Level 1—These are investments where values are based on unadjusted quoted prices for identical assets in an active market that the Company has the ability to access. Level 2—These are investments where values are based on quoted market prices in markets that are not active or model derived valuations in which all significant inputs are observable in active markets. Level 3—These are liabilities where values are derived from techniques in which one or more significant inputs are unobservable. The following are the major categories of assets and liabilities measured at fair value on a recurring basis as of December 31, 2014 and December 31, 2015 using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2) and significant unobservable inputs (Level 3) (in thousands): As of December 31, 2014 Level 1 Level 2 Level 3 Total Asset Cash equivalents: Money market funds $ 20,288 $ — $ — $ 20,288 U.S. Government bills 2,426 — — 2,426 22,714 — — 22,714 Short-term investments: U.S. Government and agency bills 19,184 — — 19,184 $ 41,898 $ — $ — $ 41,898 Liability Put option classified as liability $ — $ — $ 16 $ 16 Acquisition–related contingent consideration classified as liability — — 3,374 3,374 Warrants classified as liability — — 1,920 1,920 $ — $ — $ 5,310 $ 5,310 As of December 31, 2015 Level 1 Level 2 Level 3 Total Asset Cash equivalents: Money market funds $ 212,390 $ — $ — $ 212,390 U.S. Government bills 3 — — 3 212,393 — — 212,393 Short-term investments: U.S. Government and agency bills 21,620 — — 21,620 $ 234,013 $ — $ — $ 234,013 Liability Put option classified as liability $ — $ — $ — $ — Acquisition–related contingent consideration classified as liability — — 2,357 2,357 $ — $ — $ 2,357 $ 2,357 Level 1 instruments include money market funds and Corporate Certificates of Deposit and AAA-rated U.S. Government and agency securities, which are valued based on inputs including quotes from broker-dealers or recently executed transactions in the same or similar securities. In April 2015, all IPO proceeds were invested into money market fund accounts. Level 3 instruments include contingent consideration classified as liability in connection with the acquisition of ALM and convertible warrants classified as liability. The contingent consideration is classified as liability due to its affiliation with a related put option, and its fair value is determined based on the fair value of the Company's common stock at the period-end reporting date. The fair value of the warrants classified as liability is determined using the period-end fair value of the Company's common stock, the risk-free rate for periods within the contractual life of the warrant based on the U.S. Treasury yield curve in effect at the time of grant, implied volatilities from market comparisons of certain publicly traded companies and the contractual term. On the date of the IPO, the warrants converted from warrants for preferred stock to warrants for common stock and as a result are no longer classified as liability or subject to further fair value adjustments. The table below provides a reconciliation of the beginning and ending balances for the liabilities measured at fair value using significant unobservable inputs (Level 3) (in thousands): Year Ended 2014 2015 Balance at beginning of period $ 1,428 $ 5,310 Acquired 97 — Changes to liability-classified stock awards 3,374 738 Settled — — Conversion of liability-classified instruments to equity — (6,824 ) Net increase in fair value 411 3,133 Balance at end of period $ 5,310 $ 2,357

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities Short-term investments consist of marketable securities that are available-for-sale. The cost and fair value of available-for-sale securities were as follows as of the dates indicated (in thousands): Cost Gross Unrealized Holding Loss Gross Unrealized Holding Gain Fair Value December 31, 2014 U.S. Government and agency bills $ 19,188 $ (5 ) $ 1 $ 19,184 $ 19,188 $ (5 ) $ 1 $ 19,184 December 31, 2015 U.S. Government and agency bills $ 21,636 $ (16 ) $ — $ 21,620 $ 21,636 $ (16 ) $ — $ 21,620 The Company’s investments in marketable securities consist primarily of investments in Corporate Certificates of Deposit and AAA-rated U.S. Government and agency bills. When evaluating investments for other-than-temporary impairment, the Company reviews factors such as length of time and extent to which fair value has been below cost basis, the financial condition of the issuer and the Company’s ability and intent to hold the investment for a period of time, which may be sufficient for anticipated recovery in market value. The Company evaluates fair values for each individual security in the investment portfolio.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consisted of the following as of the dates indicated (in thousands): As of Estimated useful lives 2014 2015 Computer equipment 3 years $ 16,876 $ 27,054 Furniture and equipment 2 - 4 years 1,987 1,959 Software 1 - 3 years 1,146 1,427 Leasehold improvements Shorter of life of asset or lease term 3,134 8,097 Construction in progress (1) Not applicable 51,796 71,106 Website development 3 years 31,156 33,469 106,095 143,112 Less: Accumulated amortization and depreciation 30,557 38,091 $ 75,538 $ 105,021 (1) The Company capitalizes construction in progress and records a corresponding long-term liability for build-to-suit lease arrangements where it is considered the owner, for accounting purposes, during the construction period. Depreciation and amortization expense on property and equipment was $12.1 million , $15.7 million and $16.3 million for the years ended December 31, 2013, 2014 and 2015 , respectively, which includes amortization expense for equipment acquired under capital leases of $1.2 million , $1.5 million and $3.8 million for the years ended December 31, 2013, 2014 and 2015 , respectively. The gross balance of leased equipment as of December 31, 2014 and 2015 was $6.0 million and $17.2 million , respectively. The related accumulated amortization of equipment under capital leases was $1.2 million and $4.6 million at December 31, 2014 and 2015 , respectively. The following table summarizes capitalized website development and internal-use software activities during the periods indicated (in thousands): Year Ended 2014 2015 Balance as of the beginning of the period $ 23,897 $ 31,156 Additions to website development, excluding stock-based compensation 8,281 9,719 Additions to website development—stock-based compensation 190 463 Less: Retirements 1,212 7,869 31,156 33,469 Less: Accumulated amortization 18,968 19,676 $ 12,188 $ 13,793 For the years ended December 31, 2013, 2014 and 2015 , the Company recorded amortization expense relating to capitalized website development and internal-use software of $6.3 million , $8.1 million and $7.3 million , respectively. The loss on write-off for website development and internal-use software assets that were retired during the years ended December 31, 2013, 2014 and 2015 was $0.7 million , $0.1 million and $1.3 million , respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The following table summarizes the changes in the carrying amount of goodwill for the periods indicated (in thousands): Year Ended 2014 2015 Balance as of the beginning of the period $ 5,346 $ 30,831 Acquisitions 28,300 — Other adjustments(1) (2,815 ) (3,079 ) Balance as of the end of the period $ 30,831 $ 27,752 (1) Includes the effect of foreign currency translation and adjustment to purchase price allocation of $0.6 million in 2015. The Company did not recognize any goodwill impairments during the years ended December 31, 2013, 2014 and 2015 . At December 31, 2014 and 2015 , the gross book value and accumulated amortization of intangible assets were as follows (in thousands): As of December 31, 2014 As of December 31, 2015 Gross book Accumulated Net book Gross book Accumulated Net book Trademarks $ 892 $ (169 ) $ 723 $ 822 $ (427 ) $ 395 Technology 4,505 (1,547 ) 2,958 3,882 (2,341 ) 1,541 Customer relationships 2,313 (584 ) 1,729 1,959 (1,024 ) 935 Intangible assets, net $ 7,710 $ (2,300 ) $ 5,410 $ 6,663 $ (3,792 ) $ 2,871 Amortization expense for the years ended December 31, 2013, 2014 and 2015 was $0.3 million , $1.5 million and $2.2 million , respectively. Based on amounts recorded at December 31, 2015 , the Company will recognize intangible asset amortization expense in each of the years ending December 31 as follows (in thousands): 2016 $ 2,020 2017 851 Thereafter — Total amortization expense $ 2,871

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	Debt Credit Agreement In May 2014, the Company entered into a $35.0 million senior secured revolving credit facility pursuant to a Revolving Credit and Guaranty Agreement with several lenders (the “Credit Agreement”). In March 2015, the Company amended the Credit Agreement to increase the credit facility to $50.0 million. In December 2015, the Company amended the Credit Agreement to clarify certain provisions relating to permitted investments and to make other immaterial updates. As amended, the Credit Agreement will mature in May 2019. The amended Credit Agreement includes a letter of credit sublimit of $10.0 million and a swingline loan sublimit of $15.0 million. Borrowings under the Credit Agreement (other than swingline loans) bear interest, at the Company’s option, at (i) a base rate equal to the highest of (a) the prime rate, (b) the federal funds rate plus 0.50% and (c) an adjusted LIBOR rate for a one-month interest period plus 1.00% , in each case plus a margin ranging from 0.00% to 0.25% or (ii) an adjusted LIBOR rate plus a margin ranging from 1.00% to 1.25% . Swingline loans under the Credit Agreement bear interest at the same base rate (plus the margin applicable to borrowings bearing interest at the base rate). These margins are determined based on the total leverage ratio for the preceding four fiscal quarters. The Company is also obligated to pay other customary fees for a credit facility of this size and type, including an unused commitment fee and fees associated with letters of credit. As amended, the Credit Agreement also permits the Company, in certain circumstances, to request an increase in the facility by an amount of up to $50.0 million (and in minimum amounts of $10.0 million ) at the same maturity, pricing and other terms. The amended Credit Agreement contains customary representations and warranties applicable to the Company and its subsidiaries and customary affirmative and negative covenants applicable to the Company and its restricted subsidiaries. The negative covenants include restrictions on, among other things, indebtedness, liens, investments, mergers, dispositions, transactions with affiliates and dividends and other distributions. These restrictions do not prohibit any of the Company's subsidiaries from making pro rata payments to the Company or any other person that owns an equity interest in such subsidiary. The Credit Agreement contains a financial covenant that requires the Company and its subsidiaries to maintain a total leverage ratio (defined as net debt to adjusted EBITDA) not to exceed 3.50 to 1.00 . As amended, the Credit Agreement includes customary events of default, including a change in control and a cross-default on the Company’s material indebtedness. The Company’s obligations under the Credit Agreement are secured by substantially all of the Company and its subsidiaries’ assets, and its obligations under the Credit Agreement are guaranteed by certain of the Company’s subsidiaries. At December 31, 2015 , the Company did not have any borrowings under the Credit Agreement.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2015
Temporary Equity Disclosure [Abstract]
Warrants	Warrants As of December 31, 2014, the Company had outstanding warrants to purchase 11,373 shares of its Series C Preferred stock with an exercise price of $2.67 per share, 24,510 shares of its Series D Preferred stock with an exercise price of $6.63 per share, and 4,723 shares of its Series E Preferred stock with an exercise price of $15.88 per share (see Note 9). All of these warrants were originally issued in connection with previous lines of credit and were fair valued on the date of issuance, with the fair value amount recognized as debt issuance costs and amortized to interest expense over the original life of the line of credit. As these warrants were exercisable into shares of Preferred stock, which included certain redemption rights that are outside of the control of the Company, in accordance with ASC Topic 480 Distinguishing Liabilities from Equity , the warrants were accounted for as liabilities and were revalued at each balance sheet date. The warrants were fully vested at issuance. During 2015 upon the closing of the IPO, all outstanding warrants for Preferred stock were converted into warrants for 203,030 shares of common stock. The warrants were revalued at the opening stock price of $24.97 on April 21, 2015, the closing date of the IPO, and $5.1 million was reclassified from liabilities to equity on that date. In October 2015, the Company issued 96,869 shares of common stock upon the net exercise of warrants to purchase 105,099 shares of common stock with a weighted-average exercise price of $1.03 per share and a weighted-average fair market value of common stock at the date of exercise of $12.90 . The warrant holders exercised this warrant in a cashless transaction and 8,230 shares were forfeited to the Company as payment of the exercise price. As of December 31, 2015, the Company had outstanding warrants to purchase 97,931 shares of common stock, at a weighted-average exercise price of $1.62 per share. For 2013 and 2014, the Company determined the fair value of the convertible preferred stock warrants utilizing the Black-Scholes model with the following weighted-average assumptions: Series C December 31, 2013 2014 Risk-free interest rate 1.3 % 1.1 % Expected term (in years) 4 3 Estimated dividend yield — % — % Weighted-average estimated volatility 41.0 % 43.1 % Fair value (in thousands) $ 442 $ 579 Series D December 31, 2013 2014 Risk-free interest rate 0.3 % 0.5 % Expected term (in years) 1.5 0.5 Estimated dividend yield — % — % Weighted-average estimated volatility 36.0 % 38.9 % Fair value (in thousands) $ 859 $ 1,156 Series E December 31, 2013 2014 Risk-free interest rate 1.3 % 1.1 % Expected term (in years) 4 3 Estimated dividend yield — % — % Weighted-average estimated volatility 41.0 % 43.1 % Fair value (in thousands) $ 127 $ 185 For 2015, the Company determined the fair value of the convertible preferred stock warrants through April 21, 2015, the closing date of the IPO, utilizing the opening stock price of $24.97 per share. During the years ended December 31, 2013, 2014 and 2015 , the Company recorded an unrealized loss of $0.4 million , $0.5 million and $3.1 million , respectively, from the remeasurement of the warrants to fair value.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity At December 31, 2014 and 2015, the authorized capital stock of the Company included 120,000,000 and 1,400,000,000 shares of common stock, respectively. At December 31, 2014 and 2015 there were 21,165,473 shares of convertible preferred stock and 25,000,000 shares of preferred stock authorized, respectively. The convertible preferred stock, with the exclusion of Series 1 preferred stock, is referred to as “senior preferred stock.” Common Stock At December 31, 2013, 2014 and 2015 there were 33,082,948 , 44,180,939 and 112,563,354 shares of common stock issued and outstanding, respectively. Holders of common stock are entitled to one vote per share. Holders of common stock are not entitled to receive dividends unless declared by the board of directors. No dividends have been declared through December 31, 2015 . The common stock has a $0.001 par value. Convertible Preferred Stock At December 31, 2014, the Company’s outstanding convertible preferred stock consisted of the following (in thousands, except share data): Shares Authorized Shares Outstanding Carrying Values Series A and A-1 preferred stock 2,363,786 2,363,786 $ 808 Series B preferred stock 1,128,431 1,128,425 865 Series C preferred stock 1,234,084 1,222,282 3,361 Series D and D-1 preferred stock 4,240,120 4,215,610 27,870 Series E preferred stock 401,450 396,727 6,201 Series 1 preferred stock 203,399 203,399 1,322 Series F preferred stock 11,594,203 11,594,203 39,785 Total convertible preferred stock 21,165,473 21,124,432 $ 80,212 At December 31, 2014, the holders of the convertible preferred stock had certain voting rights and dividend and liquidity preferences. The liquidation preference provisions of the convertible preferred stock were considered contingent redemption provisions because there were certain elements that were not solely within the control of the Company, such as a change in control of the Company. Accordingly, the Company presented the convertible preferred stock within the mezzanine portion of the accompanying consolidated balance sheets. Each outstanding share of convertible preferred stock was convertible, at the holder’s option or automatically upon certain events as described below, into shares of common stock at a conversion rate determined by dividing the original issue price for such share by the then Conversion Price for such share. The original issue price, conversion price and liquidation preference price of each series of preferred stock were as follows: Price Per Share Original Issue Price Conversion Price Liquidation Preference Series A preferred stock $ 0.2429 $ 0.04858 $ 0.2429 Series A-1 preferred stock 0.3915 0.07830 0.3915 Series B preferred stock 0.80 0.160 0.80 Series C preferred stock 2.67 0.534 2.67 Series D preferred stock 6.63 1.326 6.63 Series D-1 preferred stock 6.63 1.326 6.63 Series E preferred stock 15.88 3.176 15.88 Series 1 preferred stock 6.45 1.290 6.45 Series F preferred stock 3.45 6.90 3.45 The conversion price was subject to adjustment in the event of certain anti-dilutive issuances of shares of common stock. The conversion price per share in the table above reflects the adjustment for the 10 -for-1 stock split of the Company’s common stock effective in May 2011 and the 1-for-2 reverse split of the Company's common stock, which was effected on March 25, 2015. Upon the closing of the IPO on April 21, 2015, all outstanding shares of convertible preferred stock were converted into 53,448,243 shares of common stock. As of December 31, 2015, there was no convertible preferred stock outstanding. Tender Offers On January 13, 2014, certain investors participated in a tender offer to purchase shares of common stock and preferred stock at a price of $10.60 per share (on an as-converted basis) from the Company’s employees and existing stockholders with the maximum aggregate offer price of up to $74.2 million . The terms of the tender offer were limited to a maximum of one-half of an employee’s fully-vested stock and options and warrants to purchase stock and a minimum of one-half of a former employee’s or non-employee’s fully-vested stock and options and warrants to purchase stock. At the close of the transaction, 3,154,219 shares were tendered for a total price of $33.4 million . Common Stock Issuances In April 2014, the Company issued 3,301,887 shares of common stock to certain investors at $10.60 per share for an aggregate value of $35.0 million . Additionally, the Company issued a total of 3,580,476 shares of common stock in connection with the acquisitions of Grand St. and ALM, of which 2,652,399 shares with an aggregate fair value of $27.7 million on the applicable acquisition dates are included in the Company’s purchase price and 928,077 shares with an aggregate fair value of $9.7 million on the applicable acquisition dates are tied to continued employment with the Company and are being accounted for as post-acquisition compensation expense. Stock Repurchases In 2013, the board of directors authorized the repurchase and retirement of 23,500 shares of outstanding common stock at a cost of $0.2 million . The repurchased shares were retired and have been removed from both the issued and outstanding number of shares in the consolidated balance sheet and consolidated statement of stockholders’ equity. Secondary Transactions In the year ended December 31, 2014, the Company recorded $0.5 million as compensation expense related to the excess of the selling price per share paid to certain of the Company’s former employees over the fair value of the shares sold to an investor by these former employees in secondary transactions.

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based Compensation	Stock-based Compensation The Company's 2015 Equity Incentive Plan (the "2015 Plan") was adopted by its board of directors and approved by stockholders in March 2015. The 2015 Plan became effective immediately upon adoption although no awards were made under it until the effective date of the IPO. The 2015 Plan replaced the 2006 Stock Plan, and no further grants were made under the 2006 Stock Plan as of the effective date of the IPO. Under the 2006 Stock Plan, incentive and nonqualified stock options or rights to purchase common stock were granted to eligible participants. Options were generally granted for a term of 10 years and generally vested 25% after the first year of service and ratably each month over the remaining 36 -month period contingent on continued employment with the Company on each vesting date. At December 31, 2014, 24,252,967 shares were authorized under the 2006 Stock Plan and 1,518,002 shares were available for future grant. The 2015 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units ("RSUs") and performance cash awards to employees, directors and consultants. Beginning in 2016, the number of shares available for issuance under the 2015 Plan may be increased annually by an amount equal to the lesser of 7,050,000 shares of common stock, 5% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year, or such other amount as determined by the Company's board of directors. The Board of Directors approved an increase of 2,814,083 shares available for issuance under the 2015 Plan as of January 4, 2016. Any awards issued under the 2015 Plan that are forfeited by the participant will become available for future grant under the 2015 Plan. The number of shares of the Company’s common stock initially reserved for issuance under the 2015 Plan equaled the sum of 14,100,000 shares plus up to 12,653,075 shares reserved for issuance or subject to outstanding awards under the 2006 Stock Plan. At December 31, 2015 , 14,735,179 shares were authorized under the 2015 Plan, and 14,362,827 shares were available for future grant. In the year ended December 31, 2015 , we granted incentive stock options, nonqualified stock options and RSUs to eligible participants. Options were generally granted for a term of 10 years and vest 25% after the first year of service and ratably each month over the remaining 36 -month period contingent on continued employment with the Company on each vesting date. RSUs generally vest 25% after the first year following the vesting commencement date, which is the first day of the fiscal quarter closest to the date of grant, and then vest ratably each quarter over the remaining 12 -quarter period contingent on continued employment with the Company on each vesting date. The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model using the inputs below. Prior to the IPO, the Company utilized equity valuations based on comparable publicly-traded companies, discounted free cash flows, an analysis of the Company's enterprise value and any other factors deemed relevant in estimating the fair value of its common stock. Subsequent to the IPO, the Company has used the closing price of its common stock on Nasdaq as the fair value of its common stock. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. Expected volatilities are based on implied volatilities from market comparisons of certain publicly traded companies and other factors. The expected term of stock options granted has been determined using the simplified method, which uses the midpoint between the vesting date and the contractual term. The requisite service period is generally four years from the date of grant. The fair value of RSUs is determined based on the closing price of the Company's common stock on Nasdaq on the grant date. The fair value of options granted in each year using the Black-Scholes pricing model has been based on the following assumptions: Year Ended 2013 2014 2015 Volatility 45.7% - 50.3% 43.0% - 49.0% 40.4% - 45.0% Risk-free interest rate 0.9% - 1.9% 1.7% - 2.1% 1.3% - 1.9% Expected term (in years) 5.48 - 6.08 5.46 - 6.08 5.5 - 6.1 Dividend rate —% —% —% The following table summarizes the activity for the Company’s options: Shares Weighted-Average Exercise Price Weighted-Average Remaining Contract Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2013 11,936,131 $ 2.36 Granted 3,076,101 5.52 Exercised (1,024,560 ) 1.30 Forfeited/Cancelled (797,252 ) 3.80 Outstanding at December 31, 2013 13,190,420 3.10 Granted 3,206,717 10.28 Exercised (4,215,628 ) 1.89 Forfeited/Cancelled (656,230 ) 6.58 Outstanding at December 31, 2014 11,525,279 5.34 Granted 1,660,170 16.19 Exercised (1,315,735 ) 2.76 Forfeited/Cancelled (800,855 ) 9.94 Outstanding at December 31, 2015 11,068,859 6.94 7.01 $ 31,932,259 Total exercisable at December 31, 2015 6,873,262 4.43 6.14 28,485,307 Total vested and expected to vest at December 31, 2015 10,574,276 6.79 6.94 31,678,517 The weighted-average grant date fair value of options granted in the years ended December 31, 2013, 2014 and 2015 was $2.60 , $4.86 and $6.89 , respectively. The total intrinsic value of options exercised in the years ended December 31, 2013, 2014 and 2015 was $4.0 million , $24.8 million and $15.1 million , respectively, and the total fair value of awards that vested in the years ended December 31, 2013, 2014 and 2015 was $3.5 million , $4.7 million and $8.3 million , respectively. The total unrecognized compensation at December 31, 2015 was $15.8 million , which will be recognized over a weighted-average period of 2.6 years . The following table summarizes the activity for the Company’s unvested RSUs: Shares Weighted-Average Grant Date Fair Value Unvested at December 31, 2014 — $ — Granted 407,368 13.78 Vested — — Forfeited/Cancelled (11,522 ) 16.76 Unvested at December 31, 2015 395,846 13.70 Total expected to vest at December 31, 2015 343,291 13.68 The total unrecognized compensation at December 31, 2015 was $4.2 million , which will be recognized over a weighted-average period of 3.11 years . Total stock-based compensation expense included in the consolidated statements of operations is as follows (in thousands): Year Ended 2013 2014 2015 Cost of revenue $ 200 $ 1,113 $ 871 Marketing 79 216 560 Product development 785 1,461 2,860 General and administrative 2,770 7,260 6,550 $ 3,834 $ 10,050 $ 10,841 The total stock-based compensation expense in the years ended December 31, 2014 and 2015 includes $4.1 million and $1.9 million in acquisition-related stock-based compensation expense, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following are the domestic and foreign components of the Company’s income (loss) before income taxes (in thousands): Year Ended 2013 2014 2015 Domestic $ (544 ) $ 6,084 $ 25,627 International 602 (16,344 ) (53,621 ) Income (loss) before income taxes $ 58 $ (10,260 ) $ (27,994 ) The income tax provision is comprised of the following (in thousands): Year Ended 2013 2014 2015 Current: Federal $ 91 $ 5,378 $ 24,524 State (614 ) 21 3,843 Foreign 95 401 579 Total current (428 ) 5,800 28,946 Deferred: Federal 871 (50 ) (2,863 ) State 411 (186 ) 108 Foreign — (581 ) (122 ) Total deferred 1,282 (817 ) (2,877 ) Total income tax provision $ 854 $ 4,983 $ 26,069 The current tax expense listed above does not reflect income tax benefits of $22,000 , $4.9 million and $3.9 million for the years ended December 31, 2013, 2014 and 2015 , respectively, related to excess tax deductions on share-based compensation because we recorded these benefits directly to additional paid-in capital. A reconciliation of the income tax provision (benefit) at the U.S. federal statutory income tax rate of 35% to the Company’s total income tax provision is as follows (in thousands): Year Ended 2013 2014 2015 Income tax provision (benefit) at federal statutory rate $ 20 $ (3,488 ) $ (9,798 ) State and local taxes net of federal benefit (135 ) (109 ) 2,575 Foreign income tax rate differential (131 ) 3,255 11,584 Non-deductible stock-based compensation 611 1,963 1,571 Net unrealized loss on warrant and other liabilities 143 140 1,097 Non-deductible items 114 152 1,314 Uncertain tax positions — 398 5,523 Return to provision adjustment 240 36 (25 ) Non-deductible acquisition costs — 582 10 Change in valuation allowance — 2,065 7,957 Research and development credit — — (7,684 ) Deferred charge on restructuring — — 12,168 Other (8 ) (11 ) (223 ) Total income tax provision $ 854 $ 4,983 $ 26,069 Deferred income taxes reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets (liabilities) are as follows (in thousands): As of December 31, 2014 2015 Deferred tax assets: Net operating loss carryforwards $ 3,274 $ 7,961 Research and development credit carryforwards — 898 Stock-based compensation expense 2,222 3,953 Accrued VAT liability 612 74 Alternative minimum tax credit 163 717 Allowance for doubtful accounts 701 650 Deferred rent 108 146 Accrued vacation 413 640 Unrealized loss on foreign currency 554 3,035 Other, net 1,041 1,143 Total deferred tax assets 9,088 19,217 Less valuation allowance 1,892 9,540 Total net deferred tax asset 7,196 9,677 Deferred tax liabilities: Depreciation and amortization (5,467 ) (4,490 ) Restructuring liability — (65,585 ) Other liabilities (1,878 ) (1,022 ) Total deferred tax liabilities (7,345 ) (71,097 ) Net deferred tax liabilities $ (149 ) $ (61,420 ) As of December 31, 2014 , the Company had approximately $6.9 million and $4.3 million of federal and preapportionment New York City NOL carryforwards, respectively, as well as immaterial amounts of NOLs in other states. As of December 31, 2015, the Company had approximately $0.2 million and $0.0 million of federal and preapportionment New York City NOL carryforwards, respectively, as well as immaterial amounts of NOLs in other states. The federal NOLs will begin to expire in 2032 if unused. The remainder of the NOL deferred tax asset balance is comprised of losses in certain foreign jurisdiction and are currently subject to a valuation allowance. The utilization of the Company’s NOL carryforwards is subject to an annual limitation under Section 382 of the Internal Revenue Code due to a change of ownership. However, the Company does not believe such annual limitation will impact its realization of the NOL carryforwards. As of December 31, 2014 and 2015 , the Company had approximately $0.2 million and $0.7 million of federal alternative minimum tax credits, which may be carried forward indefinitely. As of December 31, 2015, the Company had federal research and development tax credit carryforwards of $2.8 million , which will begin to expire in 2031 if unused. The Company assesses the likelihood of its ability to realize the benefit of its deferred tax assets in each jurisdiction by evaluating all relevant positive and negative evidence. To the extent the Company determines that some or all of its deferred tax assets are not more likely than not to be realized, it establishes a valuation allowance. For the year ended December 31, 2015 , the Company determined that the existence of a three -year cumulative loss incurred in certain foreign jurisdictions, inclusive of 2015 , constituted sufficiently strong negative evidence to warrant the establishment of a valuation allowance. As a result, a valuation allowance of $9.5 million as of December 31, 2015 has been recorded against certain of the Company’s deferred tax assets. The amount of the deferred tax assets considered realizable is $9.7 million . The following table summarizes the valuation allowance activity for the periods indicated (in thousands): Year Ended 2013 2014 2015 Balance as of the beginning of period $ — $ — $ 1,892 Additions charged to expense — 3,915 7,983 Deletions credited to expense — (1,850 ) — Currency translation — (173 ) (335 ) Balance as of the end of period $ — $ 1,892 $ 9,540 The Company has not recorded deferred income taxes with respect to undistributed earnings of foreign subsidiaries as such earnings are expected to remain reinvested indefinitely. Upon distribution as dividends or otherwise, such amounts would be subject to taxation in the U.S. However, U.S. tax liabilities would be offset, in whole or part, by allowable tax credits with respect to income taxes previously paid to foreign jurisdictions. The amount of undistributed earnings of non-U.S. subsidiaries at December 31, 2015, as well as the related deferred income tax, if any, is not material. As of December 31, 2013, the Company had no unrecognized income tax benefits. As of December 31, 2014 and 2015 the Company had unrecognized income tax benefits of $0.4 million and $22.2 million , respectively. The following table summarizes the unrecognized tax benefit activity for the periods indicated (in thousands): As of December 31, 2013 2014 2015 Balance as of the beginning of period $ — $ — $ 398 Additions based on tax positions related to the current year — 398 21,797 Additions for tax positions of prior years — — 34 Reductions for tax provisions of prior years — — — Settlements — — — Balance as of the end of period $ — $ 398 $ 22,229 The Company files tax returns in the United States, New York, and various other state and foreign jurisdictions. Generally, tax returns for the Company's tax year 2012 and later remain open to examination. To the extent tax attributes generated in earlier closed years are carried forward into years that are open to examination, they may be subject to adjustment in audit. In January 2015, the Company implemented an updated global corporate structure to more closely align with its global operations and future expansion plans outside of the United States. The new structure changed how the Company uses its intellectual property and implemented certain intercompany arrangements. The Company believes this may eventually result in a reduction in its overall effective tax rate and other operational efficiencies. The revised structure resulted in the setup of a deferred tax liability in the amount of $66.0 million on the taxable gain created in the transaction. A deferred charge was recorded for the same amount representing the future income tax which will be amortized into income tax expense over five years. During the twelve months ended December 31, 2015 , $13.2 million was recorded to income tax expense. The amount of unrecognized tax benefits, included within “other liabilities” on the consolidated balance sheets, increased $21.8 million in the year ended December 31, 2015 , from $0.4 million at December 31, 2014 to $22.2 million at December 31, 2015 . The increase was primarily in connection with the implementation of the updated global corporate structure. A deferred charge of $19.7 million related to the unrecognized tax benefit of the implementation was recorded representing the future income tax which will be amortized into income tax expense over five years. During the twelve months ended December 31, 2015 , $3.9 million was recorded to income tax expense for the implementation. The total amount of unrecognized tax benefits that, if recognized, would favorably affect the effective tax rate is $6.5 million at December 31, 2015 .

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The following table presents the calculation of basic and diluted net loss per share for periods presented (in thousands, except share and per share data): Year Ended 2013 2014 2015 Net loss $ (796 ) $ (15,243 ) $ (54,063 ) Basic and diluted shares: Weighted average common shares outstanding 32,667,242 40,246,663 91,122,291 Net loss per share attributable to common stockholders: Basic and diluted net loss per share applicable to common stockholders $ (0.02 ) $ (0.38 ) $ (0.59 ) The following potential common shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive for the periods presented: Year Ended 2013 2014 2015 Stock options 12,422,276 11,308,241 11,806,620 Restricted Stock Units — — 128,200 Warrants 203,030 203,030 182,031 Convertible preferred stock 53,448,243 53,448,243 16,254,123 Total anti-dilutive securities 66,073,549 64,959,514 28,370,974

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment and Geographic Information	Segment and Geographic Information Revenue by country is based on the billing address of the seller. The following table summarizes revenue by geographic area (in thousands): Year Ended 2013 2014 2015 United States $ 103,428 $ 153,866 $ 213,389 International 21,594 41,725 60,110 Revenue $ 125,022 $ 195,591 $ 273,499 No individual international country’s revenue exceeded 5% of total revenue. All significant long-lived assets are located in the United States.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Commitments Capital Leases The Company entered into a credit agreement with ePlus Group, Inc. (“ePlus”) on January 3, 2014, which provided the Company with a credit line of up to $8.0 million for computer equipment leases (the “ePlus Line”), which was increased to $18.0 million during 2015. The ePlus Line allows the Company to order equipment from any approved vendor. ePlus purchases the equipment on behalf of the Company and leases it back to the Company. The leases have a 36 -month term and are payable in equal monthly installments with a buy-out option of $1 or fair market value at the end of the lease term depending on the equipment. As of December 31, 2015 , the Company has leased approximately $17.2 million of computer equipment using the ePlus Line. The Company had a credit agreement with TriplePoint Capital, LLC (“TriplePoint”), which provided the Company with a credit line of up to $20.0 million for computer equipment leases (the “TriplePoint Line”). The TriplePoint Line allowed the Company to order equipment from any vendor. TriplePoint purchased the equipment on behalf of the Company and leased it back to the Company. The leases have a 36 -month term, interest rate of 8.25% , and are payable in equal monthly installments. The Company stopped buying equipment under the TriplePoint Line in June 2012 and paid off the remaining lease obligations during 2015 in accordance with the terms of the credit agreement. At December 31, 2015, the Company no longer had any leased computer equipment under the TriplePoint Line. For the years ended December 31, 2013, 2014 and 2015, the accompanying consolidated statement of operations includes charges of approximately $0.2 million , $0.4 million and $1.2 million for interest expense, respectively, related to the equipment leased using the TriplePoint Line and ePlus Lines. Operating Leases In 2014, the Company entered into a new lease for office space in Dublin, Ireland expiring in 2024 . In 2015, the Company entered into a new lease for office space in London, UK expiring in 2025, and entered into lease extensions for existing office space in San Francisco, California and Hudson, New York expiring in 2020 and 2021, respectively. Rent expense for these operating leases is recognized over the term of each respective lease on a straight-line basis. In addition, the Company leases other office facilities under shorter terms and cancellable leases. Total rent expense for the years ended December 31, 2013, 2014 and 2015 was $2.4 million , $3.6 million and $5.1 million respectively. Build-to-Suit Lease In May 2014, the Company entered into a 10 -year lease agreement for approximately 199,000 rentable square feet of office space in Brooklyn, New York for the Company’s new headquarters, which commenced in 2015 . Of the total new office space, approximately 172,000 rentable square feet is being accounted for as a build-to-suit lease and approximately 27,000 rentable square feet located in an adjacent building is being accounted for as an operating lease. In connection with the lease agreement, the Company established a $5.3 million collateral account, reflected in the restricted cash balance on the consolidated balance sheet. The following table represents the Company’s commitments under its current capital, operating, and build-to-suit lease agreements as of December 31, 2015 (in thousands): Capital Lease Obligations Operating Leases Build-to-Suit Lease Periods ending 2016 $ 7,011 $ 3,716 $ — 2017 5,946 2,912 5,883 2018 2,413 3,901 9,381 2019 — 3,951 9,451 2020 — 3,604 9,522 Thereafter — 13,801 59,188 Total minimum payments required $ 15,370 $ 31,885 $ 93,425 Amounts representing interest 2,189 Present value of net minimum payments 13,181 Current maturities 5,610 Long-term payment obligations $ 7,571 Tax Contingencies The Company had reserves of $3.5 million and $2.6 million at December 31, 2014 and 2015 , respectively, for certain non-income tax obligations, representing management’s best estimate of its potential liability. The Company could also be subject to examination in various jurisdictions related to income tax and non-income tax matters. The resolution of these types of matters, if in excess of the recorded reserve, could have an adverse impact on the Company’s business. Legal Proceedings On May 13, 2015, a purported securities class action complaint ( Altayyar v. Etsy, Inc., et al. , Docket No. 1:15-cv-02785) was filed in the United States District Court for the Eastern District of New York against the Company and certain officers. The complaint was brought on behalf of a purported class consisting of all persons or entities who purchased or otherwise acquired shares of the Company's common stock from April 16, 2015 through and including May 10, 2015. It asserted violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 based on allegedly false or misleading statements and omissions with respect to, among other things, merchandise for sale on the Company's website that may be counterfeit or constitute trademark or copyright infringement and actions taken by third-party brands against Etsy sellers for trademark or copyright infringement. On October 22, 2015, the court appointed a lead plaintiff and lead plaintiff’s counsel. On January 21, 2016, lead plaintiff filed an amended class action complaint alleging false or misleading statements or omissions with respect to substantially the same topics as the original complaint. The amended complaint adds certain outside directors and underwriters as defendants, expands the purported class period to be April 16, 2015 to August 4, 2015, inclusive, and asserts violations of Sections 11, 12(a)(2), and 15 of the Securities Act of 1933, as well as Sections 10(b) and 20(a) of the Securities Exchange Act of 1934. The amended complaint seeks certification as a class action and unspecified compensatory damages plus interest and attorneys' fees. The Company and the named officers and directors intend to defend themselves vigorously against this action. In light of, among other things, the early stage of the litigation, the Company is unable to predict the outcome of this matter and is unable to make a meaningful estimate of the amount or range of loss, if any, that could result from an unfavorable outcome. On July 21, 2015, a purported securities class action complaint ( Cervantes v. Dickerson, et.al ., Case No. CIV 534768) was filed in the Superior Court of State of California, County of San Mateo against the Company, certain officers, directors and underwriters. The complaint asserts violations of Sections 11 and 15 of the Securities Act of 1933. As in the Altayyar litigation, the complaint alleges misrepresentations in the Company’s Registration Statement on Form S-1 and Prospectus with respect to, among other things, merchandise for sale on the Company's website that may be counterfeit or constitute trademark or copyright infringement. The complaint seeks certification as a class action and unspecified compensatory damages plus interest and attorneys' fees. On December 7, 2015, the Company and the underwriter defendants moved to stay the Cervantes action on the grounds of forum non conveniens. On November 5, 2015, another purported securities class action complaint ( Weiss v. Etsy et al. , No. CIV 536123) was filed in the Superior Court of State of California, County of San Mateo. The Weiss complaint names as defendants the Company and the same officers, directors and underwriters named in the Cervantes complaint, and also asserts violations of Sections 11 and 15 of the Securities Act of 1933 based on allegedly false or misleading statements or omissions with respect to, among other things, merchandise for sale on the Company's website that may be counterfeit or constitute trademark or copyright infringement. On December 24, 2015, the court consolidated the Cervantes and Weiss actions. The Company and the named officers and directors intend to defend themselves vigorously against these consolidated actions. In light of, among other things, the early stage of the litigation, the Company is unable to predict the outcome of this matter and is unable to make a meaningful estimate of the amount or range of loss, if any, that could result from an unfavorable outcome. On February 3, 2016, the court granted the Company’s motion to stay the consolidated actions. In addition, from time to time in the normal course of business, various other claims and litigation have been asserted or commenced against the Company. Due to uncertainties inherent in litigation and other claims, the Company can give no assurance that it will prevail in any such matters, which could subject the Company to significant liability for damages. Any claims or litigation, regardless of their success, could have an adverse effect on the Company’s consolidated results of operations or cash flows in the period the claims or litigation are resolved. As of December 31, 2015 , the Company does not believe that there are any material litigation exposures relating to these other claims.

Basis of Presentation and Sum22

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Consolidation	The consolidated financial statements include the accounts of Etsy and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Certain items in the prior years’ consolidated financial statements have been reclassified to conform to the current year presentation reflected in the financial statements.
Use of Estimates	The preparation of the Company’s consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The accounting estimates that require management’s most difficult and subjective judgments include revenue recognition, income taxes, website development costs and internal-use software, purchase price allocations for business combinations, valuation of goodwill and intangible assets, leases and stock-based compensation. The Company evaluates its estimates and judgments on an ongoing basis and revises them when necessary. Actual results may differ from the original or revised estimates.
Revenue Recognition	The Company operates a platform for third-party sellers. Its business model is based on shared success: the Company makes money when Etsy sellers make money, and the Company offers services to help Etsy sellers be more successful. The Company does not compete with Etsy sellers, hold inventory or sell goods. The Company’s revenue is diversified, generated from a mix of marketplace activities and the services the Company provides Etsy sellers to help them create and grow their businesses. The Company’s revenue consists of Marketplace revenue, Seller Services revenue and Other revenue. The Company’s revenue is recorded net of actual and expected refunds. Marketplace revenue includes the fee an Etsy seller pays for each completed transaction and the listing fee an Etsy seller pays for each item she lists. Seller Services revenue includes fees an Etsy seller pays for services such as prominent placement in search results via Promoted Listings, payment processing via Direct Checkout and purchases of shipping labels through the Company’s platform via Shipping Labels. The Company deducts its cost of shipping labels and estimated refunds from gross shipping fees to determine net shipping fees. Other revenue includes the fees the Company receives from a third-party payment processor and derecognized funds the Company receives from a third-party for unused Etsy Gift Cards. The Company recognizes revenue when all of the following conditions are satisfied: (1) there is persuasive evidence of an arrangement; (2) the service has been provided to the Etsy seller; (3) the collection of fees is reasonably assured; and (4) the amount of fees to be paid by the Etsy seller is fixed or determinable. The Company evaluates whether it is appropriate to recognize revenue on a gross or net basis based upon its evaluation of whether it is the primary obligor in a transaction, has inventory risk and has latitude in establishing pricing and selecting suppliers. Based on its evaluation of these factors, revenue is recorded net of merchandise values associated with the transaction. Marketplace revenue . Marketplace revenue consists of the 3.5% fee that an Etsy seller pays for each completed transaction on the Company’s platform, exclusive of shipping fees charged. Marketplace revenue also consists of a listing fee of $0.20 per item that she lists in its marketplace. Revenue from completed Wholesale transactions is also included in Marketplace revenue. Transaction fees are recognized when the corresponding transaction is made. Listing fees are recognized ratably over a four -month listing period, unless the item is sold or the seller relists it, at which time any remaining listing fee is recognized. Seller Services revenue . Seller Services revenue consists of fees an Etsy seller pays the Company for the Seller Services she uses, including Promoted Listings, Direct Checkout and Shipping Labels. • Revenue from Promoted Listings consists of cost-per-click based fees an Etsy seller pays the Company for prominent placement of her listings in search results generated by Etsy buyers in its marketplace. Revenue is recognized when the Promoted Listing is clicked. • Revenue from Direct Checkout consists of fees an Etsy seller pays the Company to process credit, debit and Etsy Gift Card payments. Direct Checkout fees vary between 3 - 4% of the item’s total sale price plus a flat fee per order, depending on the country in which her bank account is located. Direct Checkout fees are based on the item’s total sale price, including shipping. Revenue from Direct Checkout is recognized when the corresponding transaction is made. • Revenue from Shipping Labels consists of fees an Etsy seller pays the Company when she purchases shipping labels directly through its platform, net of the cost it incurs in purchasing those shipping labels. The Company provides its sellers shipping labels from the United States Postal Service and Canada Post at a discounted price due to the volume of purchases through its platform. The Company recognizes Shipping Label revenue when an Etsy seller purchases a shipping label. The Company recognizes Shipping Label revenue on a net basis as it is not the primary obligor in the delivery of these services. Other revenue . Other revenue includes the fees the Company receives from a third-party payment processor, which is recognized as the transactions are processed by the third-party payment processor, and derecognized funds the Company receives from a third-party for unused Etsy Gift Cards, which are recognized when the third-party approves the release of these funds.
Cost of Revenue	Cost of revenue consists primarily of expenses associated with the operation and maintenance of the Company’s platform and data centers, including depreciation and amortization, employee-related costs, including stock-based compensation expense, and hosting and bandwidth costs. Cost of revenue also includes the cost of interchange and other fees for credit card processing services, credit card verification service fees and credit card chargebacks to support Direct Checkout revenue and costs of refunds made to Etsy buyers that the Company is not able to collect from Etsy sellers.
Accounts Receivable	The Company’s trade accounts receivable are recorded at amounts billed to Etsy sellers and are presented on the consolidated balance sheet net of the allowance for doubtful accounts. The allowance is determined by a number of factors, including age of the receivable, current economic conditions, historical losses and management’s assessment of the financial condition of Etsy sellers. Receivables are written off once they are deemed uncollectible, which may arise when Etsy sellers file for bankruptcy or are otherwise deemed unable to repay the amounts owed to the Company. Estimates of uncollectible accounts receivable are recorded to general and administrative expense.
Property and Equipment	Property and equipment, consisting principally of construction in process, computer equipment and leasehold improvements, are recorded at cost. The Company capitalizes construction in progress for build-to-suit lease agreements where we are the owner, for accounting purposes only, during the construction period. Depreciation and amortization begin at the time the asset is placed into service and are recognized using the straight-line method in amounts sufficient to relate the cost of depreciable and amortizable assets to operations over their estimated useful lives. Repairs and maintenance are charged to operations as incurred. Upon sale or retirement of assets, the cost and related accumulated depreciation or amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations. When events or changes in circumstances require, the Company assesses the likelihood of recovering the cost of tangible long-lived assets based on its expectations of future profitability, undiscounted cash flows and management’s plans with respect to operations to determine if the asset is impaired and subject to write-off. Measurement of any impairment loss is based on the excess of the carrying value of the asset over the fair value.
Funds Receivable and Seller Accounts and Funds Payable and Amounts Due to Sellers	The Company records funds receivable and seller accounts and funds payable and amounts due to sellers as current assets and liabilities, respectively, on the consolidated balance sheet. Funds receivable and seller accounts represent amounts received or expected to be received from Etsy buyers via third-party credit card processors, which flow through an Etsy bank account for payment to Etsy sellers. This cash and related receivable represent the total amount due to sellers, and as such a liability for the same amount is recorded to funds payable and amounts due to Etsy sellers.
Internal-use Software and Website Development Costs	Costs incurred to develop software for internal use and the Company’s website are capitalized and amortized over the estimated useful life of the software, generally three years. The Company also capitalizes costs related to upgrades and enhancements when it is probable the expenditures will result in additional functionality or will extend the useful life of existing functionality. Costs related to the design or maintenance of internal-use software and website development are expensed as incurred. The Company periodically reviews internal-use software and website development costs to determine whether the projects will be completed, placed in service, removed from service, or replaced by other internally developed or third-party software. If the asset is not expected to provide any future benefit, the asset is retired and any unamortized cost is expensed.
Leases	The Company leases office space and certain computer equipment in multiple locations under non-cancelable lease agreements. The leases are reviewed for classification as operating, capital or build-to-suit leases. For operating leases, rent is recognized on a straight-line basis over the lease period. For capital leases, the Company records the leased asset with a corresponding liability. Payments are recorded as reductions to the liability with an appropriate interest charge recorded based on the then-outstanding remaining liability. The Company considers the nature of the renovations and the Company’s involvement during the construction period of newly leased office space to determine if it is considered, for accounting purposes only, to be the owner of the construction project during the construction period. If the Company determines that it is the owner of the construction project, it is required to capitalize the fair value of the building as well as the construction costs incurred on its consolidated balance sheet along with a corresponding financing liability (“build-to-suit accounting”). Upon occupancy for build-to-suit leases, the Company assesses whether the circumstances qualify for sales recognition under the sale-leaseback accounting guidance. If the lease meets the sale-leaseback criteria, the Company will remove the asset and related financial obligation from the balance sheet and treat the building lease as an operating lease. If upon completion of construction, the project does not meet the sale-leaseback criteria, the leased property will be treated as a capital lease for financial reporting purposes.
Income Taxes	Income tax benefit (provision) is based on (loss) income before income taxes and is accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income or expense in the period that includes the enactment date. Management assesses the need for a valuation allowance on a quarterly basis to reduce deferred tax assets to the amounts expected to be realized. The Company accounts for uncertainty in income taxes using a recognition threshold and a measurement attribute for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by the taxing authorities. The amount recognized is measured as the largest amount of benefit that has a greater than 50% likelihood of being realized upon ultimate audit settlement. The Company has an unrecognized tax benefit of $0.4 million and $22.2 million at December 31, 2014 and 2015 , respectively. The Company recognizes interest and penalties, if any, associated with income tax matters as part of the income tax provision and includes accrued interest and penalties with the related income tax liability in the consolidated balance sheet.
Business Combinations	The Company has completed a number of acquisitions of other businesses in the past and may acquire additional businesses or technologies in the future. The results of businesses acquired in a business combination are included in the Company’s consolidated financial statements from the date of acquisition. The Company allocates the purchase price, which is the sum of the consideration provided and may consist of cash, equity or a combination of the two, in a business combination to the identifiable assets and liabilities of the acquired business at their acquisition date fair values. The excess of the purchase price over the amount allocated to the identifiable assets and liabilities, if any, is recorded as goodwill. Determining the fair value of assets acquired and liabilities assumed requires management to use significant judgment and estimates, including the selection of valuation methodologies, estimates of future revenue and cash flows, discount rates and selection of comparable companies. When the Company issues stock-based or cash awards to an acquired company’s stockholders, the Company evaluates whether the awards are contingent consideration or compensation for post-acquisition services. The evaluation includes, among other things, whether the vesting of the awards is contingent on the continued employment of the acquired company’s stockholder beyond the acquisition date. If continued employment is required for vesting, the awards are treated as compensation for post-acquisition services and recognized as expense over the requisite service period. The Company carries intangible assets at cost, and it amortizes them on a straight-line basis over their estimated useful lives, typically three years. When circumstances indicate that the carrying value of these assets may not be recoverable, the Company reviews its identifiable amortizable intangible assets for impairment. To date, the assets acquired and liabilities assumed in the Company’s business combinations have primarily consisted of goodwill and finite-lived intangible assets, consisting primarily of developed technologies, customer relationships and trademarks. The estimated fair values and useful lives of identifiable intangible assets are based on many factors, including estimates and assumptions of future operating performance and cash flows of the acquired business, the nature of the business acquired, and the specific characteristics of the identified intangible assets. The estimates and assumptions used to determine the fair values and useful lives of identified intangible assets could change due to numerous factors, including market conditions, technological developments, economic conditions and competition. In connection with determination of fair values, the Company may engage independent appraisal firms to assist with the valuation of intangible and certain tangible assets acquired and certain assumed obligations. Acquisition-related transaction costs incurred by the Company are not included as a component of consideration transferred, but are accounted for as an expense in the period in which the costs are incurred.
Goodwill	Goodwill represents the excess of the aggregate fair value of the consideration transferred in a business combination over the fair value of the assets acquired, net of liabilities assumed. Goodwill is not amortized, but is subject to an annual impairment test. Management has determined that the Company has a single reporting unit and performs its annual goodwill impairment test during the fourth quarter or more frequently if events or changes in circumstances indicate that the goodwill may be impaired. Events or changes in circumstances which could trigger an impairment review include significant changes in the manner of the Company’s use of the acquired assets or the strategy for the Company’s overall business, significant negative industry or economic trends, significant underperformance relative to historical or projected future results of operations, a significant adverse change in the business climate, an adverse action or assessment by a regulator, unanticipated competition or a loss of key personnel. The Company has the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, an entity determines it is not more likely than not that the fair value of the reporting unit is less than its carrying amount, then additional impairment testing is not required. However, if an entity concludes otherwise, then it is required to perform the first of a two-step impairment test. The first step involves comparing the estimated fair value of the reporting unit with its respective book value, including goodwill. If the estimated fair value exceeds book value, goodwill is considered not to be impaired and no additional steps are necessary. If, however, the fair value of the reporting unit is less than book value, then a second step is required that compares the carrying amount of the goodwill with its implied fair value. The estimate of implied fair value of goodwill may require valuations of certain internally-generated and unrecognized intangible and tangible net assets. If the carrying amount of goodwill exceeds the implied fair value of the goodwill, an impairment loss is recognized in an amount equal to the excess.
Intangible Assets	Intangible assets are amortized over the estimated useful life of the acquired technology, customer relationships and trademarks, generally three years.
Stock-Based Compensation	For employee stock-based awards, the Company calculates the fair value of the award on the date of grant using the Black-Scholes option-pricing model and the expense is recognized over the service period for awards expected to vest. Prior to the IPO, the Company utilized equity valuations based on comparable publicly-traded companies, discounted free cash flows, an analysis of the Company's enterprise value and any other factors deemed relevant in estimating the fair value of its common stock. Subsequent to the IPO, the Company has used the closing price of its common stock on Nasdaq as the fair value of its common stock. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. Expected volatilities are based on implied volatilities from market comparisons of certain publicly traded companies and other factors. The expected term of stock options granted has been determined using the simplified method, which uses the midpoint between the vesting date and the contractual term. The requisite service period is generally four years from the date of grant. The fair value of RSUs is determined based on the closing price of the Company's common stock on Nasdaq on the grant date. We account for stock-based compensation arrangements in restricted shares, subject to a put option that allows the holder of the shares to put the shares back to the Company for cash, as liability-classified stock awards. These awards are re-measured at each reporting period, with changes in fair value being charged to the statement of operations. Compensation expense is recognized using a graded vesting methodology for each separately vesting tranche as though the award were, in substance, multiple awards. Unless the put option is exercised, the restricted shares will be reclassified from a liability to an equity classified award upon the termination of the put option at the vesting of each separate tranche.
Cash and Cash Equivalents	The Company considers all investments with an original maturity of three months or less at time of purchase to be cash equivalents.
Concentration of Credit Risk	Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash and cash equivalents. The Company reduces credit risk by placing its cash and cash equivalents with major financial institutions with high credit ratings. At times, such amounts may exceed federally insured limits.
Fair Value of Financial Instruments	Management believes that the fair value of financial instruments, consisting of cash and cash equivalents, accounts receivable and accounts payable, approximates carrying value due to the immediate or short-term maturity associated with its cash and cash equivalents, accounts receivable and accounts payable.
Marketing	Marketing expenses consist primarily of targeted online marketing costs, such as product listing ads, search engine marketing, affiliate marketing and, to a much lesser extent, offline marketing expenses. Marketing expenses also include employee-related costs, including stock-based compensation expense, for our employees involved in digital marketing, seller development and growth, public relations and communications, brand marketing and design, product marketing and marketing research activities. Marketing expenses are primarily driven by investments to grow and retain members on our platform.
Net (Loss) Income Per Share	Prior to the IPO, the Company followed the two-class method when computing net (loss) income per share as the Company had issued shares that met the definition of participating securities. The two-class method determined net (loss) income per share for each class of common stock and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method required income available to common stockholders for the period to be allocated between common stock and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s convertible preferred stock contractually entitled the holders of such shares to participate in dividends, but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, the two-class method did not apply for periods in which the Company reports a net loss or a net loss attributable to common stockholders resulting from dividends, accretion or modifications to its convertible preferred stock. Upon the closing of the IPO on April 21, 2015, all outstanding shares of convertible preferred stock were converted into shares of common stock. For current and future periods, the two-class method is not applicable to the computation of net (loss) income per share until shares of authorized preferred stock become issued and outstanding. Basic net (loss) income per share attributable to common stockholders is computed by dividing the net (loss) income attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net (loss) income attributable to common stockholders is computed by adjusting net (loss) income attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities, including outstanding common stock options, convertible preferred stock and warrants to purchase common stock and convertible preferred stock. For periods in which the Company has reported net losses, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, because dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Segment Data	The Company identifies operating segments as components of an entity for which discrete financial information is available and is regularly reviewed by the chief operating decision maker, or decision-making group, in making decisions regarding resource allocation and performance assessment. The Company defines the term “chief operating decision maker” to be its chief executive officer. The Company has determined it operates in one operating segment and one reportable segment, as its chief operating decision maker reviews financial information presented on only a consolidated basis for purposes of allocating resources and evaluating financial performance.
Foreign Currency	The Company has determined that the functional currency for each of its foreign operations is the local currency in which the operation is located. All assets and liabilities are translated into U.S. dollars using exchange rates in effect at the balance sheet date. Revenue and expenses are translated using average exchange rates during the period. Foreign currency translation adjustments are reflected in stockholders’ equity as a component of other comprehensive (loss) income. Transaction gains and losses including intercompany transactions denominated in a currency other than the functional currency of the entity involved are included in foreign exchange loss within other (expense) income in the statement of operations.
Excess Tax Benefits from Exercise of Stock Options	The Company uses the “with and without” approach in determining the order in which tax attributes are utilized. As a result, the Company recognizes a tax benefit from stock-based awards in additional paid-in capital only if an incremental tax benefit is realized after all other tax attributes currently available to the Company have been utilized. When tax deductions from stock-based awards are less than the cumulative book compensation expense, the tax effect of the resulting difference (“shortfall”) is charged first to additional paid-in capital, to the extent of the Company’s pool of windfall tax benefits, with any remainder recognized in income tax expense.
Recent Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board, or FASB, issued an accounting standards update that replaces existing revenue recognition guidance. The new guidance is effective for the annual and interim periods beginning after December 15, 2017. Among other things, the updated guidance requires companies to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company is currently evaluating the effect the guidance will have on its consolidated financial statements. In August 2014, the FASB issued an accounting standard update under which management will be required to assess an entity’s ability to continue as a going concern and provide related disclosures in certain circumstances. The new guidance is effective for annual and interim periods beginning after December 15, 2016. The adoption of this guidance is not expected to have an impact on the Company’s consolidated financial statements or disclosures. In April 2015, the FASB issued an accounting standard under which customers will apply the same criteria as vendors to determine whether a cloud computing arrangement contains a software license or is solely a service contract. The new standard is effective for annual and interim periods beginning after December 15, 2015. The Company has evaluated the effect this guidance will have on the consolidated financial statements and do not believe the impact to be material. In August 2015, the FASB issued an accounting standard update to address the presentation and subsequent measurement of debt issuance costs related to line-of-credit arrangements. The guidance affirms the Company's treatment of such costs, which is to defer and present the debt issuance costs as an asset and subsequently amortize the costs over the term of the line-of-credit arrangement. The new standard is effective for annual and interim periods beginning after December 15, 2015. The adoption of this guidance is not expected to have an impact on the Company’s consolidated financial statements or disclosures. In September 2015, the FASB issued an accounting standard update that eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively. Instead, an acquirer will recognize a measurement-period adjustment during the period in which it determines the amount of the adjustment. The new guidance is effective for annual and interim periods beginning after December 15, 2015. The adoption of this guidance is not expected to have an impact on the Company’s consolidated financial statements or disclosures. In November 2015, the FASB issued an accounting standard update that requires a reporting entity to classify deferred tax assets and liabilities as noncurrent in a classified statement of financial position. Current guidance requiring the offsetting of deferred tax assets and liabilities of a tax-paying component of an entity and presentation as a single noncurrent amount is not affected. The new guidance is effective for annual and interim periods beginning after December 15, 2015, and early adoption is permitted for financial statements as of the beginning of an interim or annual reporting period. The Company made the decision to adopt this guidance early and have applied it retroactively in the current fiscal period. The adoption of this guidance has impacted the current and noncurrent deferred tax asset and liability balances for the current and prior fiscal years on the consolidated balance sheets.

Basis of Presentation and Sum23

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Revenue by Type of Service	The following table summarizes revenue by type of service (in thousands): Year Ended 2013 2014 2015 Marketplace $ 78,544 $ 108,732 $ 132,648 Seller Services 42,817 82,502 136,608 Other 3,661 4,357 4,243 Revenue $ 125,022 $ 195,591 $ 273,499
Schedule of Allowance Activity	The following table summarizes the allowance activity during the periods indicated (in thousands): Year Ended 2013 2014 2015 Balance as of the beginning of period $ 1,357 $ 1,279 $ 1,841 Bad debt expense 1,002 1,881 1,780 Write-offs, net of recoveries and other adjustments (1,080 ) (1,319 ) (1,550 ) Balance as of the end of period $ 1,279 $ 1,841 $ 2,071

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the components of the purchase price at fair value and the allocation of the purchase price at fair value (in thousands): Cash paid $ 5,290 Common shares 25,521 Total purchase consideration $ 30,811 Working capital $ 625 Property and equipment and other assets 95 Developed technology 1,636 Customer relationships 1,693 Trademarks 775 Goodwill 27,309 Deferred tax liability (757 ) Other long-term liabilities (565 ) Net assets acquired $ 30,811 The following table summarizes the components of the Grand St. purchase price and the allocation of the purchase price at fair value (in thousands): Cash paid $ 1,040 Common shares 2,202 Total purchase consideration $ 3,242 Working capital $ 85 Developed technology 2,000 Customer relationships 600 Trademarks 200 Goodwill 991 Deferred tax liability (634 ) Net assets acquired $ 3,242
Summary of Unaudited Pro Forma Financial Information	The unaudited pro forma financial information is presented in the table below for the years ended December 31, 2013 and 2014 (in thousands except per share amounts): Year Ended December 31, 2013 2014 Revenue $ 127,838 $ 197,395 Net loss (7,533 ) (15,403 ) Basic net loss per share (0.21 ) (0.37 ) Diluted net loss per share (0.21 ) (0.37 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements, Recurring	The following are the major categories of assets and liabilities measured at fair value on a recurring basis as of December 31, 2014 and December 31, 2015 using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2) and significant unobservable inputs (Level 3) (in thousands): As of December 31, 2014 Level 1 Level 2 Level 3 Total Asset Cash equivalents: Money market funds $ 20,288 $ — $ — $ 20,288 U.S. Government bills 2,426 — — 2,426 22,714 — — 22,714 Short-term investments: U.S. Government and agency bills 19,184 — — 19,184 $ 41,898 $ — $ — $ 41,898 Liability Put option classified as liability $ — $ — $ 16 $ 16 Acquisition–related contingent consideration classified as liability — — 3,374 3,374 Warrants classified as liability — — 1,920 1,920 $ — $ — $ 5,310 $ 5,310 As of December 31, 2015 Level 1 Level 2 Level 3 Total Asset Cash equivalents: Money market funds $ 212,390 $ — $ — $ 212,390 U.S. Government bills 3 — — 3 212,393 — — 212,393 Short-term investments: U.S. Government and agency bills 21,620 — — 21,620 $ 234,013 $ — $ — $ 234,013 Liability Put option classified as liability $ — $ — $ — $ — Acquisition–related contingent consideration classified as liability — — 2,357 2,357 $ — $ — $ 2,357 $ 2,357
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The table below provides a reconciliation of the beginning and ending balances for the liabilities measured at fair value using significant unobservable inputs (Level 3) (in thousands): Year Ended 2014 2015 Balance at beginning of period $ 1,428 $ 5,310 Acquired 97 — Changes to liability-classified stock awards 3,374 738 Settled — — Conversion of liability-classified instruments to equity — (6,824 ) Net increase in fair value 411 3,133 Balance at end of period $ 5,310 $ 2,357

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Summary of Cost and Fair Value of Available-For-Sale Securities	The cost and fair value of available-for-sale securities were as follows as of the dates indicated (in thousands): Cost Gross Unrealized Holding Loss Gross Unrealized Holding Gain Fair Value December 31, 2014 U.S. Government and agency bills $ 19,188 $ (5 ) $ 1 $ 19,184 $ 19,188 $ (5 ) $ 1 $ 19,184 December 31, 2015 U.S. Government and agency bills $ 21,636 $ (16 ) $ — $ 21,620 $ 21,636 $ (16 ) $ — $ 21,620

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following as of the dates indicated (in thousands): As of Estimated useful lives 2014 2015 Computer equipment 3 years $ 16,876 $ 27,054 Furniture and equipment 2 - 4 years 1,987 1,959 Software 1 - 3 years 1,146 1,427 Leasehold improvements Shorter of life of asset or lease term 3,134 8,097 Construction in progress (1) Not applicable 51,796 71,106 Website development 3 years 31,156 33,469 106,095 143,112 Less: Accumulated amortization and depreciation 30,557 38,091 $ 75,538 $ 105,021 (1) The Company capitalizes construction in progress and records a corresponding long-term liability for build-to-suit lease arrangements where it is considered the owner, for accounting purposes, during the construction period.
Summary of Capitalized Website Development and Internal-Use Software Activities	The following table summarizes capitalized website development and internal-use software activities during the periods indicated (in thousands): Year Ended 2014 2015 Balance as of the beginning of the period $ 23,897 $ 31,156 Additions to website development, excluding stock-based compensation 8,281 9,719 Additions to website development—stock-based compensation 190 463 Less: Retirements 1,212 7,869 31,156 33,469 Less: Accumulated amortization 18,968 19,676 $ 12,188 $ 13,793

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table summarizes the changes in the carrying amount of goodwill for the periods indicated (in thousands): Year Ended 2014 2015 Balance as of the beginning of the period $ 5,346 $ 30,831 Acquisitions 28,300 — Other adjustments(1) (2,815 ) (3,079 ) Balance as of the end of the period $ 30,831 $ 27,752 (1) Includes the effect of foreign currency translation and adjustment to purchase price allocation of $0.6 million in 2015.
Schedule of Indefinite-Lived Intangible Assets	At December 31, 2014 and 2015 , the gross book value and accumulated amortization of intangible assets were as follows (in thousands): As of December 31, 2014 As of December 31, 2015 Gross book Accumulated Net book Gross book Accumulated Net book Trademarks $ 892 $ (169 ) $ 723 $ 822 $ (427 ) $ 395 Technology 4,505 (1,547 ) 2,958 3,882 (2,341 ) 1,541 Customer relationships 2,313 (584 ) 1,729 1,959 (1,024 ) 935 Intangible assets, net $ 7,710 $ (2,300 ) $ 5,410 $ 6,663 $ (3,792 ) $ 2,871
Schedule of Finite-Lived Intangible Assets	At December 31, 2014 and 2015 , the gross book value and accumulated amortization of intangible assets were as follows (in thousands): As of December 31, 2014 As of December 31, 2015 Gross book Accumulated Net book Gross book Accumulated Net book Trademarks $ 892 $ (169 ) $ 723 $ 822 $ (427 ) $ 395 Technology 4,505 (1,547 ) 2,958 3,882 (2,341 ) 1,541 Customer relationships 2,313 (584 ) 1,729 1,959 (1,024 ) 935 Intangible assets, net $ 7,710 $ (2,300 ) $ 5,410 $ 6,663 $ (3,792 ) $ 2,871
Schedule of Future Amortization Expense	Based on amounts recorded at December 31, 2015 , the Company will recognize intangible asset amortization expense in each of the years ending December 31 as follows (in thousands): 2016 $ 2,020 2017 851 Thereafter — Total amortization expense $ 2,871

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2015
Temporary Equity Disclosure [Abstract]
Schedule of the Assumptions Used to Determine the Fair Value of Convertible Preferred Stock Warrants Utilizing the Black-Scholes Model	For 2013 and 2014, the Company determined the fair value of the convertible preferred stock warrants utilizing the Black-Scholes model with the following weighted-average assumptions: Series C December 31, 2013 2014 Risk-free interest rate 1.3 % 1.1 % Expected term (in years) 4 3 Estimated dividend yield — % — % Weighted-average estimated volatility 41.0 % 43.1 % Fair value (in thousands) $ 442 $ 579 Series D December 31, 2013 2014 Risk-free interest rate 0.3 % 0.5 % Expected term (in years) 1.5 0.5 Estimated dividend yield — % — % Weighted-average estimated volatility 36.0 % 38.9 % Fair value (in thousands) $ 859 $ 1,156 Series E December 31, 2013 2014 Risk-free interest rate 1.3 % 1.1 % Expected term (in years) 4 3 Estimated dividend yield — % — % Weighted-average estimated volatility 41.0 % 43.1 % Fair value (in thousands) $ 127 $ 185

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Schedule of Preferred Stock	The original issue price, conversion price and liquidation preference price of each series of preferred stock were as follows: Price Per Share Original Issue Price Conversion Price Liquidation Preference Series A preferred stock $ 0.2429 $ 0.04858 $ 0.2429 Series A-1 preferred stock 0.3915 0.07830 0.3915 Series B preferred stock 0.80 0.160 0.80 Series C preferred stock 2.67 0.534 2.67 Series D preferred stock 6.63 1.326 6.63 Series D-1 preferred stock 6.63 1.326 6.63 Series E preferred stock 15.88 3.176 15.88 Series 1 preferred stock 6.45 1.290 6.45 Series F preferred stock 3.45 6.90 3.45 At December 31, 2014, the Company’s outstanding convertible preferred stock consisted of the following (in thousands, except share data): Shares Authorized Shares Outstanding Carrying Values Series A and A-1 preferred stock 2,363,786 2,363,786 $ 808 Series B preferred stock 1,128,431 1,128,425 865 Series C preferred stock 1,234,084 1,222,282 3,361 Series D and D-1 preferred stock 4,240,120 4,215,610 27,870 Series E preferred stock 401,450 396,727 6,201 Series 1 preferred stock 203,399 203,399 1,322 Series F preferred stock 11,594,203 11,594,203 39,785 Total convertible preferred stock 21,165,473 21,124,432 $ 80,212

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of options granted in each year using the Black-Scholes pricing model has been based on the following assumptions: Year Ended 2013 2014 2015 Volatility 45.7% - 50.3% 43.0% - 49.0% 40.4% - 45.0% Risk-free interest rate 0.9% - 1.9% 1.7% - 2.1% 1.3% - 1.9% Expected term (in years) 5.48 - 6.08 5.46 - 6.08 5.5 - 6.1 Dividend rate —% —% —%
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	The following table summarizes the activity for the Company’s options: Shares Weighted-Average Exercise Price Weighted-Average Remaining Contract Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2013 11,936,131 $ 2.36 Granted 3,076,101 5.52 Exercised (1,024,560 ) 1.30 Forfeited/Cancelled (797,252 ) 3.80 Outstanding at December 31, 2013 13,190,420 3.10 Granted 3,206,717 10.28 Exercised (4,215,628 ) 1.89 Forfeited/Cancelled (656,230 ) 6.58 Outstanding at December 31, 2014 11,525,279 5.34 Granted 1,660,170 16.19 Exercised (1,315,735 ) 2.76 Forfeited/Cancelled (800,855 ) 9.94 Outstanding at December 31, 2015 11,068,859 6.94 7.01 $ 31,932,259 Total exercisable at December 31, 2015 6,873,262 4.43 6.14 28,485,307 Total vested and expected to vest at December 31, 2015 10,574,276 6.79 6.94 31,678,517
Summary of the Activity of Unvested RSUs	The following table summarizes the activity for the Company’s unvested RSUs: Shares Weighted-Average Grant Date Fair Value Unvested at December 31, 2014 — $ — Granted 407,368 13.78 Vested — — Forfeited/Cancelled (11,522 ) 16.76 Unvested at December 31, 2015 395,846 13.70 Total expected to vest at December 31, 2015 343,291 13.68
Schedule of Share-based Compensation, Allocation of Recognized Period Costs	Total stock-based compensation expense included in the consolidated statements of operations is as follows (in thousands): Year Ended 2013 2014 2015 Cost of revenue $ 200 $ 1,113 $ 871 Marketing 79 216 560 Product development 785 1,461 2,860 General and administrative 2,770 7,260 6,550 $ 3,834 $ 10,050 $ 10,841

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	The following are the domestic and foreign components of the Company’s income (loss) before income taxes (in thousands): Year Ended 2013 2014 2015 Domestic $ (544 ) $ 6,084 $ 25,627 International 602 (16,344 ) (53,621 ) Income (loss) before income taxes $ 58 $ (10,260 ) $ (27,994 )
Income Tax (Benefit) Provision	The income tax provision is comprised of the following (in thousands): Year Ended 2013 2014 2015 Current: Federal $ 91 $ 5,378 $ 24,524 State (614 ) 21 3,843 Foreign 95 401 579 Total current (428 ) 5,800 28,946 Deferred: Federal 871 (50 ) (2,863 ) State 411 (186 ) 108 Foreign — (581 ) (122 ) Total deferred 1,282 (817 ) (2,877 ) Total income tax provision $ 854 $ 4,983 $ 26,069
Reconciliation of the Income Tax (Benefit) Provision	A reconciliation of the income tax provision (benefit) at the U.S. federal statutory income tax rate of 35% to the Company’s total income tax provision is as follows (in thousands): Year Ended 2013 2014 2015 Income tax provision (benefit) at federal statutory rate $ 20 $ (3,488 ) $ (9,798 ) State and local taxes net of federal benefit (135 ) (109 ) 2,575 Foreign income tax rate differential (131 ) 3,255 11,584 Non-deductible stock-based compensation 611 1,963 1,571 Net unrealized loss on warrant and other liabilities 143 140 1,097 Non-deductible items 114 152 1,314 Uncertain tax positions — 398 5,523 Return to provision adjustment 240 36 (25 ) Non-deductible acquisition costs — 582 10 Change in valuation allowance — 2,065 7,957 Research and development credit — — (7,684 ) Deferred charge on restructuring — — 12,168 Other (8 ) (11 ) (223 ) Total income tax provision $ 854 $ 4,983 $ 26,069
Significant Components of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets (liabilities) are as follows (in thousands): As of December 31, 2014 2015 Deferred tax assets: Net operating loss carryforwards $ 3,274 $ 7,961 Research and development credit carryforwards — 898 Stock-based compensation expense 2,222 3,953 Accrued VAT liability 612 74 Alternative minimum tax credit 163 717 Allowance for doubtful accounts 701 650 Deferred rent 108 146 Accrued vacation 413 640 Unrealized loss on foreign currency 554 3,035 Other, net 1,041 1,143 Total deferred tax assets 9,088 19,217 Less valuation allowance 1,892 9,540 Total net deferred tax asset 7,196 9,677 Deferred tax liabilities: Depreciation and amortization (5,467 ) (4,490 ) Restructuring liability — (65,585 ) Other liabilities (1,878 ) (1,022 ) Total deferred tax liabilities (7,345 ) (71,097 ) Net deferred tax liabilities $ (149 ) $ (61,420 )
Summary of Valuation Allowance	The following table summarizes the valuation allowance activity for the periods indicated (in thousands): Year Ended 2013 2014 2015 Balance as of the beginning of period $ — $ — $ 1,892 Additions charged to expense — 3,915 7,983 Deletions credited to expense — (1,850 ) — Currency translation — (173 ) (335 ) Balance as of the end of period $ — $ 1,892 $ 9,540
Schedule of Unrecognized Tax Benefits Activity	The following table summarizes the unrecognized tax benefit activity for the periods indicated (in thousands): As of December 31, 2013 2014 2015 Balance as of the beginning of period $ — $ — $ 398 Additions based on tax positions related to the current year — 398 21,797 Additions for tax positions of prior years — — 34 Reductions for tax provisions of prior years — — — Settlements — — — Balance as of the end of period $ — $ 398 $ 22,229

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted net loss per share for periods presented (in thousands, except share and per share data): Year Ended 2013 2014 2015 Net loss $ (796 ) $ (15,243 ) $ (54,063 ) Basic and diluted shares: Weighted average common shares outstanding 32,667,242 40,246,663 91,122,291 Net loss per share attributable to common stockholders: Basic and diluted net loss per share applicable to common stockholders $ (0.02 ) $ (0.38 ) $ (0.59 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following potential common shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive for the periods presented: Year Ended 2013 2014 2015 Stock options 12,422,276 11,308,241 11,806,620 Restricted Stock Units — — 128,200 Warrants 203,030 203,030 182,031 Convertible preferred stock 53,448,243 53,448,243 16,254,123 Total anti-dilutive securities 66,073,549 64,959,514 28,370,974

Segment and Geographic Inform34

Segment and Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Revenue from External Customers by Geographic Areas	The following table summarizes revenue by geographic area (in thousands): Year Ended 2013 2014 2015 United States $ 103,428 $ 153,866 $ 213,389 International 21,594 41,725 60,110 Revenue $ 125,022 $ 195,591 $ 273,499

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments Under Current Capital, Operating and Build-to-Suit Lease Agreements	The following table represents the Company’s commitments under its current capital, operating, and build-to-suit lease agreements as of December 31, 2015 (in thousands): Capital Lease Obligations Operating Leases Build-to-Suit Lease Periods ending 2016 $ 7,011 $ 3,716 $ — 2017 5,946 2,912 5,883 2018 2,413 3,901 9,381 2019 — 3,951 9,451 2020 — 3,604 9,522 Thereafter — 13,801 59,188 Total minimum payments required $ 15,370 $ 31,885 $ 93,425 Amounts representing interest 2,189 Present value of net minimum payments 13,181 Current maturities 5,610 Long-term payment obligations $ 7,571

Basis of Presentation and Sum36

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)	Apr. 21, 2015USD ($)$ / sharesshares	Mar. 25, 2015	May. 31, 2011	Dec. 31, 2015USD ($)reportable_segmentoperating_segment	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Apr. 30, 2014$ / shares	Dec. 31, 2012USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price | $ / shares							$ 10.60
Proceeds from initial public offering				$ 199,467,000	$ 0	$ 0
Reverse stock split conversion ratio		0.5	10
Fee for each completed transaction, percent				3.50%
Listing fee per item				$ 0.20
Period over which listing fee is recognized				4 months
Unrecognized tax benefits				$ 22,229,000	398,000	0		$ 0
Goodwill impairment				$ 0	0
Intangible asset, useful life				3 years
Share-based compensation expense				$ 10,841,000	10,050,000	3,834,000
Stock-based compensation expense-acquisitions				$ 1,860,000	$ 4,130,000	0
Number of operating segments | operating_segment				1
Number of reportable segments | reportable_segment				1
IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued | shares	13,333,333
Share price | $ / shares	$ 16
Proceeds from initial public offering	$ 194,400,000
Underwriting discount	13,900,000
Other offering expense	$ 5,100,000
Sale of stock by stockholders | shares	5,833,332
Conversion of preferred stock warrants into common stock warrants | shares	203,030
Convertible preferred stock | IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of convertible preferred stock into common stock, shares | shares	53,448,243
Accrued Expenses and Other Current Liabilities
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Prior period reclassification adjustment				$ 4,600,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Direct checkout fees, percent				3.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Direct checkout fees, percent				4.00%
Software
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated useful lives				3 years
Software | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated useful lives				1 year	1 year
Software | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated useful lives				3 years	3 years
Put option classified as liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense-acquisitions				$ 700,000	$ 3,400,000
Employee stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				8,900,000	5,900,000	3,600,000
Non-employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				$ 100,000	100,000	$ 200,000
New Accounting Pronouncement, Early Adoption, Effect
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reclassification of deferred tax assets					$ 2,900,000

Basis of Presentation and Sum37

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Revenue by Type of Service (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Product Information [Line Items]
Revenue	$ 273,499	$ 195,591	$ 125,022
Marketplace
Product Information [Line Items]
Revenue	132,648	108,732	78,544
Seller Services
Product Information [Line Items]
Revenue	136,608	82,502	42,817
Other
Product Information [Line Items]
Revenue	$ 4,243	$ 4,357	$ 3,661

Basis of Presentation and Sum38

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Allowance Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance as of the beginning of period	$ 1,841	$ 1,279	$ 1,357
Bad debt expense	1,780	1,881	1,002
Write-offs, net of recoveries and other adjustments	(1,550)	(1,319)	(1,080)
Balance as of the end of period	$ 2,071	$ 1,841	$ 1,279

Business Combinations - Additio

Business Combinations - Additional Information (Details) - USD ($)

Feb. 18, 2016

Mar. 31, 2015

Jun. 18, 2014

Apr. 29, 2014

Jan. 31, 2014

Jan. 31, 2013

Jun. 30, 2015

Jun. 30, 2015

Dec. 31, 2015

Feb. 18, 2016

Dec. 31, 2014

Dec. 31, 2013

Business Acquisition [Line Items]

Goodwill

$ 27,752,000

$ 30,831,000

$ 5,346,000

Increase in revenue as a result of the acquisitions

1,800,000

Loss of acquirees since acquisition date

5,700,000

Lascaux Company, Inc.

Business Acquisition [Line Items]

Total purchase consideration

$ 750,000

Cash paid

$ 75,000

$ 675,000

Number of shares issued for business acquisition

181,160

Jarvis Labs, Inc

Business Acquisition [Line Items]

Total purchase consideration

$ 3,242,000

Cash paid

$ 1,040,000

Number of shares issued for business acquisition

212,552

Common shares

$ 2,202,000

Shares issued

328,580

Fair value of shares issued

$ 3,400,000

Vesting period

3 years

Cash and equivalents acquired

$ 100,000

Acquired intangible assets

2,800,000

Goodwill

$ 991,000

Purchase accounting adjustments

$ (200,000)

Incubart SAS

Business Acquisition [Line Items]

Total purchase consideration

$ 30,811,000

Cash paid

$ 300,000

$ 4,200,000

Number of shares issued for business acquisition

2,439,847

Common shares

$ 25,521,000

Shares issued

599,497

Fair value of shares issued

$ 6,300,000

Cash and equivalents acquired

500,000

Acquired intangible assets

4,100,000

Goodwill

27,309,000

Tax deductible amount of goodwill

$ 0

Purchase accounting adjustments

(400,000)

Put option classified as liability | Incubart SAS

Business Acquisition [Line Items]

Proceeds from sale of options indexed to issuers' equity

$ 100,000

Liability recorded for fair value of put options

$ 100,000

$ 100,000

Maximum | Put option classified as liability | Incubart SAS

Business Acquisition [Line Items]

Price per share (USD per share)

$ 8.26

Minimum | Put option classified as liability | Incubart SAS

Business Acquisition [Line Items]

Price per share (USD per share)

$ 4

General and administrative

Business Acquisition [Line Items]

Acquisition related costs

$ 2,100,000

Subsequent Event | Incubart SAS

Business Acquisition [Line Items]

Cash paid

$ 800,000

$ 5,290,000

Business Combinations - Compone

Business Combinations - Components of the Purchase Price Allocation (Details) - USD ($) $ in Thousands	Feb. 18, 2016	Mar. 31, 2015	Jun. 18, 2014	Apr. 29, 2014	Feb. 18, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill						$ 27,752	$ 30,831	$ 5,346
Jarvis Labs, Inc
Business Acquisition [Line Items]
Cash paid				$ 1,040
Common shares				2,202
Total purchase consideration				3,242
Working capital				85
Goodwill				991
Deferred tax liability				(634)
Net assets acquired				3,242
Incubart SAS
Business Acquisition [Line Items]
Cash paid		$ 300	$ 4,200
Common shares			25,521
Total purchase consideration			30,811
Working capital			625
Property and equipment and other assets			95
Goodwill			27,309
Deferred tax liability			(757)
Other long-term liabilities			(565)
Net assets acquired			30,811
Developed technology | Jarvis Labs, Inc
Business Acquisition [Line Items]
Finite-lived intangibles				2,000
Developed technology | Incubart SAS
Business Acquisition [Line Items]
Finite-lived intangibles			1,636
Customer relationships | Jarvis Labs, Inc
Business Acquisition [Line Items]
Finite-lived intangibles				600
Customer relationships | Incubart SAS
Business Acquisition [Line Items]
Finite-lived intangibles			1,693
Trademarks | Jarvis Labs, Inc
Business Acquisition [Line Items]
Trademarks				$ 200
Trademarks | Incubart SAS
Business Acquisition [Line Items]
Trademarks			$ 775
Subsequent Event | Incubart SAS
Business Acquisition [Line Items]
Cash paid	$ 800				$ 5,290

Business Combinations - Summary

Business Combinations - Summary of Unaudited Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Combinations [Abstract]
Revenue	$ 197,395	$ 127,838
Net loss	$ (15,403)	$ (7,533)
Basic net loss per share (in dollars per share)	$ (0.37)	$ (0.21)
Diluted net loss per share (in dollars per share)	$ (0.37)	$ (0.21)

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Major Categories of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 212,393	$ 22,714
Asset	234,013	41,898
Liability	2,357	5,310
Put option classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	0	16
Acquisition–related contingent consideration classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	2,357	3,374
Warrants classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability		1,920
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	212,390	20,288
U.S. Government bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3	2,426
U.S. Government and agency bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	21,620	19,184
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	212,393	22,714
Asset	234,013	41,898
Liability	0	0
Level 1 | Put option classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	0	0
Level 1 | Acquisition–related contingent consideration classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	0	0
Level 1 | Warrants classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability		0
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	212,390	20,288
Level 1 | U.S. Government bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3	2,426
Level 1 | U.S. Government and agency bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	21,620	19,184
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Asset	0	0
Liability	0	0
Level 2 | Put option classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	0	0
Level 2 | Acquisition–related contingent consideration classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	0	0
Level 2 | Warrants classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability		0
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 2 | U.S. Government bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 2 | U.S. Government and agency bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Asset	0	0
Liability	2,357	5,310
Level 3 | Put option classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	0	16
Level 3 | Acquisition–related contingent consideration classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability	2,357	3,374
Level 3 | Warrants classified as liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability		1,920
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 3 | U.S. Government bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 3 | U.S. Government and agency bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 0	$ 0

Fair Value Measurements - Sch43

Fair Value Measurements - Schedule of Unobservable Inputs Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 5,310	$ 1,428
Acquired	0	97
Changes to liability-classified stock awards	738	3,374
Settled	0	0
Conversion of liability-classified instruments to equity	(6,824)	0
Net increase in fair value	3,133	411
Balance at end of period	$ 2,357	$ 5,310

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 21,636	$ 19,188
Gross Unrealized Holding Loss	(16)	(5)
Gross Unrealized Holding Gain	0	1
Fair Value	21,620	19,184
U.S. Government and agency bills
Schedule of Available-for-sale Securities [Line Items]
Cost	21,636	19,188
Gross Unrealized Holding Loss	(16)	(5)
Gross Unrealized Holding Gain	0	1
Fair Value	$ 21,620	$ 19,184

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 143,112	$ 106,095
Less: Accumulated depreciation and amortization	38,091	30,557
Property and equipment, net	$ 105,021	$ 75,538
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years	3 years
Property and equipment, gross	$ 27,054	$ 16,876
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,959	$ 1,987
Furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years	2 years
Furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	4 years	4 years
Software
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Property and equipment, gross	$ 1,427	$ 1,146
Software | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	1 year	1 year
Software | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years	3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,097	$ 3,134
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 71,106	$ 51,796
Website development
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years	3 years
Property and equipment, gross	$ 33,469	$ 31,156

Property and Equipment - Summ46

Property and Equipment - Summary of Capitalized Website Development and Internal-Use Software Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Movement in Capitalized Computer Software, Net [Roll Forward]
Balance as of the beginning of the period	$ 31,156	$ 23,897
Additions to website development, excluding stock-based compensation	9,719	8,281
Additions to website development—stock-based compensation	463	190
Less: Retirements	7,869	1,212
Balance as of the end of the period	33,469	31,156
Less: Accumulated amortization	19,676	18,968
Capitalized Computer Software, Net	$ 13,793	$ 12,188

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Depreciation	$ 16,307,000	$ 15,700,000	$ 12,100,000
Amortization expense for equipment acquired under capital leases	3,787,000	1,500,000	1,200,000
Gross balance of leased equipment		17,221,000	6,000,000
Accumulated amortization of equipment under capital leases		4,575,000	1,200,000
Amortization expense related to capitalized website development and internal-use software	7,272,000	8,100,000	6,300,000
Website development and internal-use software assets
Property, Plant and Equipment [Line Items]
Loss on write-off of retired website development and internal-use software	$ 1,303,000	$ 100,000	$ 700,000

Goodwill and Intangible Asset48

Goodwill and Intangible Assets - Summary of Changes in the Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Balance as of the beginning of the period	$ 30,831	$ 5,346
Acquisitions	0	28,300
Other adjustments	(3,079)	(2,815)
Balance as of the end of the period	27,752	$ 30,831
Foreign currency translation and adjustment	$ 600

Goodwill and Intangible Asset49

Goodwill and Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross book value	$ 6,663	$ 7,710
Accumulated amortization	(3,792)	(2,300)
Total amortization expense	2,871	5,410
Amortization expense of intangible assets	2,243	1,500	$ 300
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross book value	822	892
Accumulated amortization	(427)	(169)
Total amortization expense	395	723
Technology
Finite-Lived Intangible Assets [Line Items]
Gross book value	3,882	4,505
Accumulated amortization	(2,341)	(1,547)
Total amortization expense	1,541	2,958
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross book value	1,959	2,313
Accumulated amortization	(1,024)	(584)
Total amortization expense	$ 935	$ 1,729

Goodwill and Intangible Asset50

Goodwill and Intangible Assets - Summary of Future Amortization Expense for Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
2,016	$ 2,020
2,017	851
Thereafter	0
Total amortization expense	$ 2,871	$ 5,410

Debt (Details)

Debt (Details) - Revolving Credit Facility	12 Months Ended
	Dec. 31, 2015USD ($)	Mar. 31, 2015USD ($)	May. 31, 2014USD ($)
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity		$ 50,000,000	$ 35,000,000
Line of credit, maximum available borrowing capacity	$ 50,000,000
Line of credit, maximum available borrowing capacity, minimum increment of increase	$ 10,000,000
Total leverage ratio	3.50
Outstanding borrowings	$ 0
Letter of Credit
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity			10,000,000
Bridge Loan
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity			$ 15,000,000
Federal Funds Effective Swap Rate
Debt Instrument [Line Items]
Line of credit, basis spread on variable interest rate	0.50%
One-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Line of credit, basis spread on variable interest rate	1.00%
Minimum | One-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Line of credit, basis spread on variable interest rate	1.00%
Minimum | Base Rate
Debt Instrument [Line Items]
Line of credit, basis spread on variable interest rate	0.00%
Maximum | One-Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Line of credit, basis spread on variable interest rate	1.25%
Maximum | Base Rate
Debt Instrument [Line Items]
Line of credit, basis spread on variable interest rate	0.25%

Warrants (Details)

Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Class of Stock [Line Items]
Fair value (in thousands)	$ 1,920		$ 0
Series C preferred stock
Class of Stock [Line Items]
Risk-free interest rate	1.10%	1.30%
Expected term (in years)	3 years	4 years
Estimated dividend yield	0.00%	0.00%
Weighted-average estimated volatility	43.10%	41.00%
Fair value (in thousands)	$ 579	$ 442
Series D preferred stock
Class of Stock [Line Items]
Risk-free interest rate	0.50%	0.30%
Expected term (in years)	6 months	1 year 6 months
Estimated dividend yield	0.00%	0.00%
Weighted-average estimated volatility	38.90%	36.00%
Fair value (in thousands)	$ 1,156	$ 859
Series E preferred stock
Class of Stock [Line Items]
Risk-free interest rate	1.10%	1.30%
Expected term (in years)	3 years	4 years
Estimated dividend yield	0.00%	0.00%
Weighted-average estimated volatility	43.10%	41.00%
Fair value (in thousands)	$ 185	$ 127

Warrants - Additional Informati

Warrants - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 21, 2015
Class of Stock [Line Items]
Net unrealized loss on warrant and other liabilities		$ (3,133)	$ (411)	$ (419)
Series C preferred stock
Class of Stock [Line Items]
Conversion of preferred stock warrants into common stock warrants			11,373
Exercise price of warrant			$ 2.67
Series D preferred stock
Class of Stock [Line Items]
Conversion of preferred stock warrants into common stock warrants			24,510
Exercise price of warrant			$ 6.63
Series E preferred stock
Class of Stock [Line Items]
Conversion of preferred stock warrants into common stock warrants			4,723
Exercise price of warrant			$ 15.88
Warrants
Class of Stock [Line Items]
Net unrealized loss on warrant and other liabilities		$ (3,100)	$ (500)	$ (400)
Common Stock
Class of Stock [Line Items]
Conversion of preferred stock warrants into common stock warrants		97,931
Exercise price of warrant	$ 1.03	$ 1.62
Share price	$ 12.90
Stock Issued During Period, Shares, Warrants Exercised in Period Net of Forfeitures	96,869
Warrants exercised in period	105,099	105,099
Warrants forfeited	8,230	8,230
IPO
Class of Stock [Line Items]
Conversion of preferred stock warrants into common stock warrants					203,030
Exercise price of warrant					$ 24.97
Share price					$ 24.97
Fair value adjustment of warrants					$ 5,100

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2014
Class of Stock [Line Items]
Share-based compensation expense	$ 10,841	$ 10,050	$ 3,834
Common stock, shares authorized	1,400,000,000	120,000,000
Preferred stock, shares authorized	25,000,000
Common stock, shares issued	112,563,354	44,180,939	33,082,948	3,301,887
Convertible preferred stock
Class of Stock [Line Items]
Temporary equity, shares authorized		21,165,473
Secondary Offering
Class of Stock [Line Items]
Share-based compensation expense		$ 500

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details)	12 Months Ended
	Dec. 31, 2015USD ($)vote$ / sharesshares	Dec. 31, 2014$ / sharesshares	Apr. 30, 2014shares	Dec. 31, 2013shares
Equity [Abstract]
Common stock, shares issued	112,563,354	44,180,939	3,301,887	33,082,948
Common stock, shares outstanding	112,563,354	44,180,939		33,082,948
Common stock, votes per share of stock held | vote	1
Dividends declared for common stock | $	$ 0
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001

Stockholders' Equity - Converti

Stockholders' Equity - Convertible Preferred Stock (Details) $ / shares in Units, $ in Thousands	Apr. 21, 2015shares	Mar. 25, 2015	May. 31, 2011	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)$ / sharesshares
Class of Stock [Line Items]
Carrying Values | $				$ 0	$ 80,212
Reverse stock split conversion ratio		0.5	10
Series A and A-1 preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					2,363,786
Shares Outstanding | shares				0	2,363,786
Carrying Values | $				$ 0	$ 808
Original Issue Price					$ 0.2429
Conversion Price					0.04858
Liquidation Preference					0.2429
Series A-1 preferred stock
Class of Stock [Line Items]
Original Issue Price					0.3915
Conversion Price					0.07830
Liquidation Preference					$ 0.3915
Series B preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					1,128,431
Shares Outstanding | shares				0	1,128,425
Carrying Values | $				$ 0	$ 865
Original Issue Price					$ 0.80
Conversion Price					0.160
Liquidation Preference					$ 0.80
Series C preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					1,234,084
Shares Outstanding | shares				0	1,222,282
Carrying Values | $				$ 0	$ 3,361
Original Issue Price					$ 2.67
Conversion Price					0.534
Liquidation Preference					$ 2.67
Series D and D-1 preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					4,240,120
Shares Outstanding | shares				0	4,215,610
Carrying Values | $				$ 0	$ 27,870
Original Issue Price					$ 6.63
Conversion Price					1.326
Liquidation Preference					6.63
Series D-1 preferred stock
Class of Stock [Line Items]
Original Issue Price					6.63
Conversion Price					1.326
Liquidation Preference					$ 6.63
Series E preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					401,450
Shares Outstanding | shares				0	396,727
Carrying Values | $				$ 0	$ 6,201
Original Issue Price					$ 15.88
Conversion Price					3.176
Liquidation Preference					$ 15.88
Series 1 preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					203,399
Shares Outstanding | shares				0	203,399
Carrying Values | $				$ 0	$ 1,322
Original Issue Price					$ 6.45
Conversion Price					1.29
Liquidation Preference					$ 6.45
Series F preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					11,594,203
Shares Outstanding | shares				0	11,594,203
Carrying Values | $				$ 0	$ 39,785
Original Issue Price					$ 3.45
Conversion Price					6.90
Liquidation Preference					$ 3.45
Convertible preferred stock
Class of Stock [Line Items]
Shares Authorized | shares					21,165,473
Shares Outstanding | shares				0	21,124,432
Carrying Values | $					$ 80,212
Common Stock
Class of Stock [Line Items]
Conversion of preferred stock upon public offering (in shares) | shares	53,448,243			53,448,243

Stockholders' Equity - Tender O

Stockholders' Equity - Tender Offers (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 13, 2014	Dec. 31, 2015	Dec. 31, 2014	Apr. 30, 2014
Class of Stock [Line Items]
Share price				$ 10.60
Value of stock issued		$ 194,361	$ 35,000
Employee | Common Stock and Preferred Stock | Tender Offer
Class of Stock [Line Items]
Limitation of participant in tender offer, percentage of fully-vested stock, options and warrants, maximum	50.00%
Non-Employee | Common Stock and Preferred Stock | Tender Offer
Class of Stock [Line Items]
Limitation of participant in tender offer, percentage of fully-vested stock, options and warrants, minimum	50.00%
Plan | Common Stock and Preferred Stock | Tender Offer
Class of Stock [Line Items]
Share price	$ 10.60
Plan | Maximum | Common Stock and Preferred Stock | Tender Offer
Class of Stock [Line Items]
Value of stock issued	$ 74,200
Actual | Common Stock and Preferred Stock | Tender Offer
Class of Stock [Line Items]
Shares issued	3,154,219
Value of stock issued	$ 33,400

Stockholders' Equity - Common58

Stockholders' Equity - Common Stock Issuances (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended
	Jun. 18, 2014	Dec. 31, 2015	Dec. 31, 2014	Apr. 30, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Common stock, shares issued		112,563,354	44,180,939	3,301,887	33,082,948
Share price				$ 10.60
Value of shares issued		$ 113	$ 44	$ 35,000
Jarvis Labs, Inc. and Incubart SAS
Class of Stock [Line Items]
Shares issued in connection with acquisitions	3,580,476
Number of shares issued for business acquisition	2,652,399
Common shares	$ 27,700
Shares issued	928,077
Fair value of shares issued	$ 9,700

Stockholders' Equity - Stock Re

Stockholders' Equity - Stock Repurchases (Details) $ in Millions	Dec. 31, 2013USD ($)shares
Class of Stock [Line Items]
Number of shares authorized to be repurchased	23,500
Number of shares authorized to be retired	23,500
Value of shares authorized to be repurchased | $	$ 0.2

Stock-based Compensation - Fair

Stock-based Compensation - Fair Value of Options Granted Using the Black-Scholes Pricing Model (Details) - Stock options	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility, minimum	40.40%	43.00%	45.70%
Volatility, maximum	45.00%	49.00%	50.30%
Risk-free interest rate, minimum	1.30%	1.70%	0.90%
Risk-free interest rate, maximum	1.90%	2.10%	1.90%
Dividend rate	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 6 months	5 years 5 months 16 days	5 years 5 months 23 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 29 days	6 years 29 days

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shares
Outstanding, beginning balance (in shares)	11,525,279	13,190,420	11,936,131
Granted	1,660,170	3,206,717	3,076,101
Exercised	(1,315,735)	(4,215,628)	(1,024,560)
Forfeited/Cancelled	(800,855)	(656,230)	(797,252)
Outstanding, ending balance	11,068,859	11,525,279	13,190,420
Total exercisable at December 31, 2015 (in shares)	6,873,262
Total vested and expected to vest at December 31, 2015 (in shares)	10,574,276
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 5.34	$ 3.10	$ 2.36
Granted	16.19	10.28	5.52
Exercised	2.76	1.89	1.30
Forfeited/Cancelled	9.94	6.58	3.80
Outstanding, ending balance (in dollars per share)	6.94	$ 5.34	$ 3.10
Total exercisable at December 31, 2015 (in dollars per share)	4.43
Total vested and expected to vest at December 31, 2015 (in dollars per share)	$ 6.79
Weighted-Average Remaining Contract Term (in years)
Outstanding at December 31, 2015, Weighted-Average Remaining Contract Term	7 years 4 days
Total exercisable at December 31, 2015, Weighted-Average Remaining Contract Term	6 years 1 month 21 days
Total vested and expected to vest at December 31, 2015, Weighted-Average Remaining Contract Term	6 years 11 months 9 days
Outstanding at December 31, 2015, Aggregate Intrinsic Value	$ 31,932,259
Total exercisable at December 31, 2015, Aggregate Intrinsic Value	28,485,307
Total vested and expected to vest at December 31, 2015, Aggregate Intrinsic Value	$ 31,678,517

Stock-based Compensation - Su62

Stock-based Compensation - Summary of the Unvested RSUs (Details) - RSUs	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Shares
Unvested at December 31, 2014 (in shares) | shares	0
Granted | shares	407,368
Vested | shares	0
Forfeited/Cancelled | shares	(11,522)
Unvested at December 31, 2015 | shares	395,846
Total expected to vest at December 31, 2015 (in shares) | shares	343,291
Weighted-Average Grant Date Fair Value
Unvested at December 31, 2014 (in dollars per share) | $ / shares	$ 0
Granted | $ / shares	13.78
Vested | $ / shares	0
Forfeited/Cancelled | $ / shares	16.76
Unvested at December 31, 2015 | $ / shares	13.70
Total expected to vest at December 31, 2015 (in dollars per share) | $ / shares	$ 13.68

Stock-based Compensation - Allo

Stock-based Compensation - Allocated Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 10,841	$ 10,050	$ 3,834
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	871	1,113	200
Marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	560	216	79
Product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	2,860	1,461	785
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 6,550	$ 7,260	$ 2,770

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 04, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		1,660,170	3,206,717	3,076,101
Stock-based compensation expense-acquisitions		$ 1,860	$ 4,130	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value		15,100	24,800	4,000
Fair value of awards vested		8,300	$ 4,700	$ 3,500
Unrecognized compensation for stock options		$ 15,800
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period for unrecognized compensation		2 years 7 months 6 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock granted in period (in shares)		407,368
Granted		$ 13.78
Unrecognized compensation for restricted stock units		$ 4,200
Weighted-average period for unrecognized compensation		3 years 1 month 10 days
2006 Stock Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized			24,252,967
Number of shares available for grant			1,518,002
Term for options		10 years
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of additional shares issued annually		7,050,000
Percentage of outstanding stock		5.00%
Shares reserved for future issuance		14,100,000
Number of shares authorized		14,735,179
Number of shares available for grant		14,362,827
Weighted average grant date fair value of options		$ 6.89	$ 4.86	$ 2.60
2015 Equity Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term for options		10 years
Stock option requisite service period		4 years
2015 Equity Incentive Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock granted in period (in shares)		201,875
Granted		$ 16.53
2006 Plan Eligible for 2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance		12,653,075
25% Vest After First Year of Service | 2006 Stock Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting rights, percentage		25.00%
25% Vest After First Year of Service | 2015 Equity Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting rights, percentage		25.00%
25% Vest After First Year of Service | 2015 Equity Incentive Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting rights, percentage		25.00%
Vest Ratably Each Month Over a 36-Month Period | 2006 Stock Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period		36 months
Vest Ratably Each Month Over a 36-Month Period | 2015 Equity Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period		36 months
Vest Ratably Each Month Over a 36-Month Period | 2015 Equity Incentive Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period		3 years
Subsequent Event | 2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of additional shares issued annually	2,814,083

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]
Excess tax deductions on share-based compensation		$ (3,944)	$ (4,877)	$ (22)
U.S. federal statutory income tax rate		35.00%
Alternative minimum tax credit		$ 717	163
Research and development credit carryforwards		898	0
Valuation allowance		9,540	1,892
Deferred tax assets considered realizable		9,677	7,196
Unrecognized tax benefits		22,229	398	0	$ 0
Deferred tax liability for gain in revised corporate structure transaction	$ 66,000	$ 71,097	7,345
Deferred charge amortization period	5 years	5 years
Deferred charge amortized to income tax expense		$ 13,200
Amortization of deferred charges related to unrecognized tax benefits		3,900
Deferred charge related to unrecognized tax benefits		19,700
Unrecognized tax benefits that would impact effective tax rate favorably		6,500
Tax benefit recognized from research and development tax credit		7,684	0	0
Other Liabilities
Income Tax Contingency [Line Items]
Unrecognized tax benefits		22,200	400
Increase in unrecognized tax benefits		21,800
Additional Paid-in Capital
Income Tax Contingency [Line Items]
Excess tax deductions on share-based compensation		(3,900)	(4,900)	$ (22)
Internal Revenue Service (IRS)
Income Tax Contingency [Line Items]
Operating loss carryforwards		200	6,900
Alternative minimum tax credit		700	200
Research and development credit carryforwards		2,800
New York State Division of Taxation and Finance
Income Tax Contingency [Line Items]
Operating loss carryforwards		$ 0	$ 4,300
Foreign Tax Authority
Income Tax Contingency [Line Items]
Term of cumulative foreign loss		3 years

Income Taxes - Domestic and For

Income Taxes - Domestic and Foreign Components of (Loss) Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic	$ 25,627	$ 6,084	$ (544)
International	(53,621)	(16,344)	602
Income (loss) before income taxes	$ (27,994)	$ (10,260)	$ 58

Income Taxes - Income Tax (Bene

Income Taxes - Income Tax (Benefit) Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 24,524	$ 5,378	$ 91
State	3,843	21	(614)
Foreign	579	401	95
Total current	28,946	5,800	(428)
Deferred:
Federal	(2,863)	(50)	871
State	108	(186)	411
Foreign	(122)	(581)	0
Total deferred	(2,877)	(817)	1,282
Total income tax provision	$ 26,069	$ 4,983	$ 854

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Income Tax (Benefit) Provision at the U.S. Federal Statutory Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax provision (benefit) at federal statutory rate	$ (9,798)	$ (3,488)	$ 20
State and local taxes net of federal benefit	2,575	(109)	(135)
Foreign income tax rate differential	11,584	3,255	(131)
Non-deductible stock-based compensation	1,571	1,963	611
Net unrealized loss on warrant and other liabilities	1,097	140	143
Non-deductible items	1,314	152	114
Uncertain tax positions	5,523	398	0
Return to provision adjustment	(25)	36	240
Non-deductible acquisition costs	10	582	0
Change in valuation allowance	7,957	2,065	0
Research and development credit	(7,684)	0	0
Deferred charge on restructuring	12,168	0	0
Other	(223)	(11)	(8)
Total income tax provision	$ 26,069	$ 4,983	$ 854

Income Taxes - Significant Comp

Income Taxes - Significant Component of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Jan. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 7,961		$ 3,274
Research and development credit carryforwards	898		0
Stock-based compensation expense	3,953		2,222
Accrued VAT liability	74		612
Alternative minimum tax credit	717		163
Allowance for doubtful accounts	650		701
Deferred rent	146		108
Accrued vacation	640		413
Unrealized loss on foreign currency	3,035		554
Other, net	1,143		1,041
Total deferred tax assets	19,217		9,088
Less valuation allowance	9,540		1,892
Total net deferred tax asset	9,677		7,196
Deferred tax liabilities:
Depreciation and amortization	(4,490)		(5,467)
Restructuring liability	(65,585)		0
Other liabilities	(1,022)		(1,878)
Total deferred tax liabilities	(71,097)	$ (66,000)	(7,345)
Net deferred tax liabilities	$ (61,420)		$ (149)

Income Taxes - Summary of Valua

Income Taxes - Summary of Valuation Allowance Activity (Details) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance as of the beginning of period	$ 1,892	$ 0	$ 0
Additions charged to expense	7,983	3,915	0
Deletions credited to expense	0	(1,850)	0
Currency translation	(335)	(173)	0
Balance as of the end of period	$ 9,540	$ 1,892	$ 0

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of the beginning of period	$ 398	$ 0	$ 0
Additions based on tax positions related to the current year	21,797	398	0
Additions for tax positions of prior years	34	0	0
Reductions for tax provisions of prior years	0	0	0
Settlements	0	0	0
Balance as of the end of period	$ 22,229	$ 398	$ 0

Net Loss Per Share - Calculatio

Net Loss Per Share - Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss	$ (54,063)	$ (15,243)	$ (796)
Basic and diluted shares:
Weighted average common shares outstanding	91,122,291	40,246,663	32,667,242
Net loss per share attributable to common stockholders:
Basic and diluted net loss per share applicable to common stockholders (in dollars per share)	$ (0.59)	$ (0.38)	$ (0.02)

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Shares Excluded from the Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	28,370,974	64,959,514	66,073,549
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	11,806,620	11,308,241	12,422,276
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	128,200	0	0
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	182,031	203,030	203,030
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	16,254,123	53,448,243	53,448,243

Segment and Geographic Inform74

Segment and Geographic Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue, Major Customer [Line Items]
Revenue	$ 273,499	$ 195,591	$ 125,022
United States
Revenue, Major Customer [Line Items]
Revenue	213,389	153,866	103,428
International
Revenue, Major Customer [Line Items]
Revenue	$ 60,110	$ 41,725	$ 21,594

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ / shares in Units, ft² in Thousands	1 Months Ended	12 Months Ended
	May. 31, 2014ft²	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013USD ($)	Jan. 03, 2014USD ($)
Loss Contingencies [Line Items]
Gross balance of leased equipment			$ 17,221,000	$ 6,000,000
Capital leases, interest expense		$ 1,200,000	400,000	200,000
Operating leases, rent expense		5,100,000	3,600,000	$ 2,400,000
Collateral account		5,341,000	5,341,000
Non-income Tax Obligations
Loss Contingencies [Line Items]
Non-income tax obligation reserve		2,600,000	$ 3,500,000
Capital Lease Obligations | ePlus Group, Inc
Loss Contingencies [Line Items]
Line of credit, maximum borrowing capacity		$ 18,000,000			$ 8,000,000
Term of lease		36 months
Buyout option		$ 1
Capital Lease Obligations | TriplePoint Capital, LLC
Loss Contingencies [Line Items]
Line of credit, maximum borrowing capacity					$ 20,000,000
Term of lease		36 months
Interest rate		8.25%
Series E preferred stock
Loss Contingencies [Line Items]
Conversion of preferred stock warrants into common stock warrants | shares			4,723
Exercise price of warrant | $ / shares			$ 15.88
Office Building
Loss Contingencies [Line Items]
Build-to-suit leases, term of contract	10 years
Area of real estate property | ft²	199
Office Building | Build-to-Suit Lease
Loss Contingencies [Line Items]
Area of real estate property | ft²	172
Collateral account		$ 5,300,000
Office Building | Operating Lease
Loss Contingencies [Line Items]
Area of real estate property | ft²	27
Computer Equipment | ePlus Group, Inc
Loss Contingencies [Line Items]
Gross balance of leased equipment		$ 17,200,000

Commitments and Contingencies76

Commitments and Contingencies - Summary of Lease Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Capital Lease Obligations
2,016	$ 7,011
2,017	5,946
2,018	2,413
2,019	0
2,020	0
Thereafter	0
Capital Leases, Future Minimum Payments Due	15,370
Operating Leases
2,016	3,716
2,017	2,912
2,018	3,901
2,019	3,951
2,020	3,604
Thereafter	13,801
Operating Leases, Future Minimum Payments Due	31,885
Build-to-Suit Lease
2,016	0
2,017	5,883
2,018	9,381
2,019	9,451
2,020	9,522
Thereafter	59,188
Build-to-Suit Leases, Future Minimum Payments Due	93,425
Amounts representing interest	2,189
Present value of net minimum payments	13,181
Current maturities	5,610	$ 1,755
Long-term payment obligations	$ 7,571	$ 3,148