Zendesk (ZEN) 10-Q 2 Aug 19 2019 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2019	Jul. 31, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-36456
Entity Registrant Name	ZENDESK, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-4411091
Entity Address, Address Line One	1019 Market Street
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94103
City Area Code	415
Local Phone Number	418-7506
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	ZEN
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Smaller Reporting Company	false
Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		110,983,797
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001463172
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 171,218	$ 126,518
Marketable securities	255,930	300,213
Accounts receivable, net of allowance for doubtful accounts of $3,252 and $2,571 as of June 30, 2019 and December 31, 2018, respectively	105,806	85,280
Deferred costs	30,259	24,712
Prepaid expenses and other current assets	45,697	35,873
Total current assets	608,910	572,596
Marketable securities, noncurrent	371,245	393,671
Property and equipment, net	87,520	75,654
Deferred costs, noncurrent	31,805	26,914
Lease right-of-use assets	102,702
Goodwill and intangible assets, net	212,436	146,327
Other assets	24,379	22,717
Total assets	1,438,997	1,237,879
Current liabilities:
Accounts payable	38,887	16,820
Accrued liabilities	36,598	34,097
Accrued compensation and related benefits	51,955	46,603
Deferred revenue	286,552	245,243
Lease liabilities	22,784
Convertible senior notes, net	470,641	0
Total current liabilities	907,417	342,763
Convertible senior notes, net	0	458,176
Deferred revenue, noncurrent	797	2,719
Lease liabilities, noncurrent	97,860
Other liabilities	5,946	17,300
Total liabilities	1,012,020	820,958
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock	0	0
Common stock	1,106	1,080
Additional paid-in capital	1,053,488	950,693
Accumulated other comprehensive gain (loss)	772	(5,724)
Accumulated deficit	(628,389)	(529,128)
Total stockholders’ equity	426,977	416,921
Total liabilities and stockholders’ equity	$ 1,438,997	$ 1,237,879

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 3,252	$ 2,571

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Income Statement [Abstract]
Revenue		$ 194,583		$ 141,882		$ 376,068		$ 271,673
Cost of revenue	[1]	57,670		44,160		113,324		83,216
Gross profit		136,913		97,722		262,744		188,457
Operating expenses:
Research and development	[1]	50,510		37,624		97,301		74,708
Sales and marketing		94,746	[1]	69,450	[1]	186,447	[1]	134,508
General and administrative	[1]	43,019		24,245		74,271		46,452
Total operating expenses	[1]	188,275		131,319		358,019		255,668
Operating loss		(51,362)		(33,597)		(95,275)		(67,211)
Other income (expense), net:
Interest income		5,294		3,826		10,766		5,344
Interest expense		(6,614)		(6,289)		(13,158)		(7,053)
Other income (expense), net		(1,268)		27		(570)		272
Total other income (expense), net		(2,588)		(2,436)		(2,962)		(1,437)
Loss before provision for (benefit from) income taxes		(53,950)		(36,033)		(98,237)		(68,648)
Provision for (benefit from) income taxes		591		(1,667)		1,024		(4,957)
Net loss		$ (54,541)		$ (34,366)		$ (99,261)		$ (63,691)
Net loss per share, basic and diluted (usd per share)		$ (0.50)		$ (0.33)		$ (0.91)		$ (0.61)
Weighted-average shares used to compute net loss per share, basic and diluted (in shares)		109,986		105,000		109,312		104,350
[1]	Includes share-based compensation expense as follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Cost of revenue $ 5,246 $ 3,474 $ 10,183 $ 6,572 Research and development 11,911 9,529 23,548 19,758 Sales and marketing 13,575 9,178 25,973 17,186 General and administrative 13,019 5,967 20,704 11,619

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based compensation			$ 80,408	$ 55,135
Cost of revenue
Share-based compensation	$ 5,246	$ 3,474	10,183	6,572
Research and development
Share-based compensation	11,911	9,529	23,548	19,758
Sales and marketing
Share-based compensation	13,575	9,178	25,973	17,186
General and administrative
Share-based compensation	$ 13,019	$ 5,967	$ 20,704	$ 11,619

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (54,541)	$ (34,366)	$ (99,261)	$ (63,691)
Other comprehensive gain (loss), before tax:
Net unrealized gain (loss) on available-for-sale investments	2,291	13	5,633	(623)
Foreign currency translation loss	0	0	0	(12)
Net unrealized gain (loss) on derivative instruments	1,452	(3,132)	2,576	(3,874)
Other comprehensive gain (loss), before tax	3,743	(3,119)	8,209	(4,509)
Tax effect	(641)	1,082	(1,713)	1,082
Other comprehensive gain (loss), net of tax	3,102	(2,037)	6,496	(3,427)
Comprehensive loss	$ (51,439)	$ (36,403)	$ (92,765)	$ (67,118)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		103,121
Beginning balance at Dec. 31, 2017	$ 354,184	$ 1,031	$ 753,568	$ (2,372)	$ (398,043)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		674
Issuance of common stock upon exercise of stock options	9,747	$ 7	9,740
Issuance of common stock for settlement of RSUs (in shares)		1,498
Issuance of common stock for settlement of RSUs	(2,148)	$ 14	(2,162)
Issuance of common stock in connection with employee stock purchase plan (in shares)		390
Issuance of common stock in connection with employee stock purchase plan	9,474	$ 4	9,470
Share-based compensation	56,440		56,440
Equity component of convertible senior notes	44,304		44,304
Other comprehensive gain (loss), net of tax	(3,427)			(3,427)
Net loss	(63,691)				(63,691)
Other	(17)		(17)
Ending balance (in shares) at Jun. 30, 2018		105,683
Ending balance at Jun. 30, 2018	404,866	$ 1,056	871,343	(5,799)	(461,734)
Beginning balance (in shares) at Mar. 31, 2018		104,263
Beginning balance at Mar. 31, 2018	400,653	$ 1,042	830,741	(3,762)	(427,368)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		220
Issuance of common stock upon exercise of stock options	3,553	$ 2	3,551
Issuance of common stock for settlement of RSUs (in shares)		810
Issuance of common stock for settlement of RSUs	(1,413)	$ 8	(1,421)
Issuance of common stock in connection with employee stock purchase plan (in shares)		390
Issuance of common stock in connection with employee stock purchase plan	9,474	$ 4	9,470
Share-based compensation	28,953		28,953
Equity component of convertible senior notes	49		49
Other comprehensive gain (loss), net of tax	(2,037)			(2,037)
Net loss	(34,366)				(34,366)
Ending balance (in shares) at Jun. 30, 2018		105,683
Ending balance at Jun. 30, 2018	404,866	$ 1,056	871,343	(5,799)	(461,734)
Beginning balance (in shares) at Dec. 31, 2018		108,037
Beginning balance at Dec. 31, 2018	$ 416,921	$ 1,080	950,693	(5,724)	(529,128)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	626	626
Issuance of common stock upon exercise of stock options	$ 13,209	$ 5	13,204
Issuance of common stock for settlement of RSUs (in shares)		1,661
Issuance of common stock for settlement of RSUs	(5,079)	$ 17	(5,096)
Issuance of common stock in connection with employee stock purchase plan (in shares)		374
Issuance of common stock in connection with employee stock purchase plan	15,312	$ 4	15,308
Share-based compensation	79,379		79,379
Equity component of convertible senior notes	0
Other comprehensive gain (loss), net of tax	6,496			6,496
Net loss	(99,261)				(99,261)
Other	0
Ending balance (in shares) at Jun. 30, 2019		110,698
Ending balance at Jun. 30, 2019	426,977	$ 1,106	1,053,488	772	(628,389)
Beginning balance (in shares) at Mar. 31, 2019		109,260
Beginning balance at Mar. 31, 2019	418,945	$ 1,092	994,031	(2,330)	(573,848)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		250
Issuance of common stock upon exercise of stock options	4,772	$ 2	4,770
Issuance of common stock for settlement of RSUs (in shares)		814
Issuance of common stock for settlement of RSUs	(2,663)	$ 8	(2,671)
Issuance of common stock in connection with employee stock purchase plan (in shares)		374
Issuance of common stock in connection with employee stock purchase plan	15,312	$ 4	15,308
Share-based compensation	42,050		42,050
Equity component of convertible senior notes	0
Other comprehensive gain (loss), net of tax	3,102			3,102
Net loss	(54,541)				(54,541)
Ending balance (in shares) at Jun. 30, 2019		110,698
Ending balance at Jun. 30, 2019	$ 426,977	$ 1,106	$ 1,053,488	$ 772	$ (628,389)

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net loss	$ (99,261)	$ (63,691)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	17,701	18,663
Share-based compensation	80,408	55,135
Amortization of deferred costs	14,540	9,530
Amortization of debt discount and issuance costs	12,465	6,650
Other	846	2,299
Changes in operating assets and liabilities:
Accounts receivable	(22,867)	(13,896)
Prepaid expenses and other current assets	(9,154)	(7,425)
Deferred costs	(24,313)	(17,579)
Lease right-of-use assets	9,107
Other assets and liabilities	(1,740)	(9,311)
Accounts payable	21,333	10,266
Accrued liabilities	455	11,576
Accrued compensation and related benefits	4,258	4,120
Deferred revenue	39,443	33,601
Lease liabilities	(6,394)
Net cash provided by operating activities	36,827	39,938
Cash flows from investing activities
Purchases of property and equipment	(14,154)	(20,036)
Internal-use software development costs	(2,966)	(4,161)
Purchases of marketable securities	(270,823)	(249,011)
Proceeds from maturities of marketable securities	100,296	94,580
Proceeds from sales of marketable securities	243,112	8,848
Cash paid for the acquisition of Smooch, net of cash acquired	(70,794)	0
Purchase of strategic investment	(500)	0
Net cash used in investing activities	(15,829)	(169,780)
Cash flows from financing activities
Proceeds from issuance of convertible senior notes, net of issuance costs paid of $13,506	0	561,493
Purchase of capped call related to convertible senior notes	0	(63,940)
Proceeds from exercises of employee stock options	13,210	9,747
Proceeds from employee stock purchase plan	15,310	9,949
Taxes paid related to net share settlement of share-based awards	(5,079)	(2,146)
Other	0	(1,716)
Net cash provided by financing activities	23,441	513,387
Effect of exchange rate changes on cash, cash equivalents and restricted cash	66	(36)
Net increase in cash, cash equivalents and restricted cash	44,505	383,509
Cash, cash equivalents and restricted cash at beginning of period	128,876	110,888
Cash, cash equivalents and restricted cash at end of period	173,381	494,397
Reconciliation of cash, cash equivalents and restricted cash to condensed consolidated balance sheets
Total cash, cash equivalents and restricted cash	128,876	110,888
Supplemental cash flow data
Cash paid for interest	719	0
Cash paid for taxes	2,219	1,545
Non-cash investing and financing activities
Balance of property and equipment in accounts payable and accrued expenses	12,636	4,921
Asset retirement obligations incurred	1,196	200
Property and equipment acquired through tenant improvement allowances	414	4,261
Estimated convertible senior notes offering costs incurred but not yet paid	0	55
Internal-Use Software Development Costs
Non-cash investing and financing activities
Share-based compensation capitalized in deferred costs and in internal-use software development costs	800	1,499
Deferred Costs
Non-cash investing and financing activities
Share-based compensation capitalized in deferred costs and in internal-use software development costs	$ 666	$ 370

CONDENSED CONSOLIDATED STATEM_6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (PARENTHETICAL) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Payments of debt issuance costs	$ 0	$ 13,506

Overview and Basis of Presentat

Overview and Basis of Presentation	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Overview and Basis of Presentation	Overview and Basis of Presentation Company and Background Zendesk was founded in Denmark in 2007 and reincorporated in Delaware in April 2009. We are a software development company that provides software as a service, or SaaS, products that are intended to help organizations and their customers build better experiences. Our product family is built upon a modern architecture that enables us and our customers to rapidly innovate, adapt our technology in novel ways, and easily integrate with other products and applications. With our origins in customer service, we have evolved our offerings over time to a family of products and platform that work together to help organizations understand the broader customer journey, improve communications across all channels, and engage where and when it’s needed most. References to Zendesk, the “Company,” “our,” or “we” in these notes refer to Zendesk, Inc. and its subsidiaries on a consolidated basis. Basis of Presentation These unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in our Annual Report on Form 10-K, for the year ended December 31, 2018, filed with the SEC on February 14, 2019. There have been no changes to our significant accounting policies described in the Annual Report on Form 10-K that have had a material impact on our condensed consolidated financial statements and related notes, except as described below. The consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly our financial position, results of operations, comprehensive loss, stockholders' equity, and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year ending December 31, 2019 . Use of Estimates The preparation of our consolidated financial statements in conformity with GAAP requires management to make certain estimates, judgments, and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenue and expenses during the reported periods. Significant items subject to such estimates and assumptions include: • the estimate of variable consideration related to revenue recognition; • the fair value and useful lives of acquired intangible assets; • the capitalization and useful life of capitalized costs to obtain customer contracts; • the valuation of strategic investments; • the useful lives of property and equipment; • the capitalization and useful lives of internal-use software; • the lease term and incremental borrowing rate for lease liabilities; • the fair value of our convertible senior notes; • the fair value of asset retirement obligations; • the fair value and expense recognition for certain share-based awards; • the preparation of financial forecasts used in currency hedging; and • the recognition of tax benefits. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ from those estimates. Concentrations of Risk As of June 30, 2019 and December 31, 2018, no customers represented 10% or greater of our total accounts receivable balance. There were no customers that individually exceeded 10% of our revenue during the three and six months ended June 30, 2019 or 2018 . Recently Issued Accounting Pronouncements In June 2016, the Financial Accounting Standards Board, or FASB, issued ASU 2016-13, including subsequent amendments, regarding ASC Topic 326 “ Measurement of Credit Losses on Financial Instruments, ” which modifies the accounting methodology for most financial instruments. The guidance establishes a new “expected loss model” that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Additionally, any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. This guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted. We are currently evaluating the impact of the adoption of this standard on our consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, regarding ASC Topic 350 “ Simplifying the Test for Goodwill Impairment, ” which simplifies the required methodology to calculate an impairment charge for goodwill. The standard is effective for fiscal years beginning after December 15, 2019, however early adoption is permitted. We do not expect the adoption of this standard to have a material effect on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, regarding ASC Topic 820 “ Fair Value Measurement, ” which modifies the disclosure requirements for fair value measurements for certain types of investments. The guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted. We do not expect the adoption of this standard to have a material effect on our consolidated financial statements. Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, regarding ASC Topic 842 “ Leases, ” including subsequent amendments. We refer to the new guidance as “ASC 842.” This new guidance requires lessees to recognize most leases on their balance sheets as lease right-of-use assets with corresponding lease liabilities and eliminates certain real estate-specific provisions. The new guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted ASC 842 in the first quarter of 2019 and applied the following practical expedients: • comparative periods prior to the adoption date are not adjusted to reflect the new guidance (the modified retrospective method of transition); and • the historical determination as to the existence and classification of leases is carried forward for existing contracts as of the adoption date. The effect of adopting ASC 842 resulted in the recognition of lease right-of-use assets and corresponding lease liabilities on our condensed consolidated balance sheets. As of March 31, 2019, the first quarter of adoption, the aggregate balance of lease right-of-use assets and lease liabilities was $99 million and $114 million , respectively. The standard did not affect our consolidated statement of operations or cash flows. In August 2017, the FASB issued ASU 2017-12, regarding ASC Topic 815 “ Derivatives and Hedging. ” This guidance simplifies various aspects of hedge accounting, including the measurement and presentation of hedge ineffectiveness and certain documentation and assessment requirements. The guidance also makes more hedging strategies eligible for hedge accounting. We adopted this standard in the first quarter of 2019. Upon adoption, we no longer recognize hedge ineffectiveness immediately in our consolidated statements of operations, but we instead recognize the entire change in the fair value of the hedge contract in other comprehensive income. The cumulative-effect adjustment to eliminate ineffectiveness was not material. The presentation and disclosures have been modified on a prospective basis, as required by the guidance. In February 2018, the FASB issued ASU 2018-02, “ Income Statement - Reporting Comprehensive Income ,” which provides for the reclassification of the effect of remeasuring deferred tax balances related to items within accumulated other comprehensive income to retained earnings resulting from the Tax Cuts and Jobs Act, or Tax Act. The guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted this standard in the first quarter of 2019. We have elected not to reclassify the income tax effects of the Tax Act from accumulated other comprehensive income to retained earnings, therefore the adoption did not have an effect on our consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, regarding ASC Topic 718 “ Compensation - Stock Compensation, ” which largely aligns the accounting for share-based compensation for non-employees with employees. The guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted this standard in the first quarter of 2019. The adoption did not have an effect on our consolidated financial statements. In June 2018, the FASB issued ASU 2018-08, regarding ASC Topic 958 “ Not-for-Profit Entities ,” which clarified the guidance on how entities determine whether to account for a transfer of assets as an exchange transaction or a contribution. The guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted the standard in the first quarter of 2019. The adoption did not have an effect on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, regarding ASC Topic 350-40 “ Intangibles - Internal-Use Software, ” which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. We early adopted the standard in the first quarter of 2019. The adoption did not have an effect on our consolidated financial statements.

Business Combinations

Business Combinations	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Business Combinations	Business Combinations Smooch Technologies Holdings ULC On May 14, 2019, we completed the acquisition of Smooch Technologies Holdings ULC, or Smooch, a developer of messaging technology. We acquired Smooch for purchase consideration of $72 million in cash. In connection with the acquisition, we incurred transaction costs of $3 million within general and administrative expenses and share-based compensation expense of $5 million , primarily within general and administrative expenses, resulting from the accelerated vesting of certain unvested Smooch stock options because post-combination service requirements were eliminated. The fair value of assets acquired and liabilities assumed was based on a preliminary valuation, and our estimates and assumptions are subject to change within the measurement period. The primary area that remains preliminary relates to the evaluation of certain tax-related items. The total purchase consideration was allocated to the assets acquired and liabilities assumed as set forth below (in thousands). The excess of the purchase price over the net assets acquired was recorded as goodwill. Goodwill generated from the acquisition is primarily attributable to assembled workforce and expected growth from the expansion of the scope of and market opportunity for our products. Goodwill will not be amortized but instead will be tested for impairment at least annually and more frequently if certain indicators of impairment are present. As a result of the structure of the transaction, the balance of goodwill is deductible in the U.S. over 15 years for income tax purposes. Net tangible assets $ 2,053 Net deferred tax liability (1,326 ) Identifiable intangible assets: Developed technology 8,000 Customer relationships 3,900 Backlog 1,000 Goodwill 58,245 Total purchase consideration $ 71,872 The developed technology, customer relationships, and backlog intangible assets were assigned useful lives of 5.5 , 8.0 , and 2.0 years, respectively. In connection with the acquisition, we granted cash-based retention awards to certain employees of Smooch, which vest over a required service period. The awards will be recorded as expense and were not included in the total purchase consideration. From the date of the acquisition, the results of operations of Smooch have been included in and are immaterial to our consolidated financial statements. Pro forma revenue and results of operations have not been presented because the historical results of Smooch are not material to our consolidated financial statements in any period presented. FutureSimple Inc. On September 10, 2018, we completed the acquisition of FutureSimple Inc., or FutureSimple, the developer of Base, a sales force automation software product. We acquired FutureSimple for purchase consideration of $81 million in cash. We incurred transaction costs of $2 million in connection with the acquisition, which were included within general and administrative expenses. The fair value of assets acquired and liabilities assumed was based on a preliminary valuation, and our estimates and assumptions are subject to change within the measurement period. The primary areas that remain preliminary relate to the evaluation of certain tax-related items. The total purchase consideration was allocated to the assets acquired and liabilities assumed as set forth below (in thousands). During the three months ended June 30, 2019 , we made certain immaterial adjustments to the preliminary purchase price allocation, which are reflected in the table below. The excess of the purchase price over the net assets acquired was recorded as goodwill. Goodwill generated from the acquisition is primarily attributable to assembled workforce and expected growth from the expansion of the scope of and market opportunity for our products. Goodwill is not deductible for income tax purposes. Goodwill will not be amortized but instead will be tested for impairment at least annually and more frequently if certain indicators of impairment are present. Net tangible liabilities $ (2,966 ) Identifiable intangible assets: Developed technology 19,000 Customer relationships 10,400 Backlog 2,200 Goodwill 52,389 Total purchase consideration $ 81,023 The developed technology, customer relationships, and backlog intangible assets were assigned useful lives of 6.5 , 5.0 , and 2.0 years, respectively. In connection with the acquisition, we granted cash and share-based retention awards to certain employees of FutureSimple. The cash awards vest over a required service period and the share-based awards vest upon fulfillment of certain service and performance conditions. Each retention award will be recorded as expense based on the fulfillment of such service and performance conditions, as applicable, and is not included in the total purchase consideration. From the date of the acquisition, the results of operations of FutureSimple have been included in and are immaterial to our consolidated financial statements. Pro forma revenue and results of operations have not been presented because the historical results of FutureSimple are not material to our consolidated financial statements in any period presented.

Financial Instruments

Financial Instruments	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Financial Instruments	Financial Instruments Investments The following tables present information about our financial assets measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): Fair Value Measurement at Level 1 Level 2 Total Description Corporate bonds $ — $ 436,124 $ 436,124 Asset-backed securities — 130,291 130,291 Money market funds 63,341 — 63,341 U.S. treasury securities — 55,932 55,932 Commercial paper — 6,927 6,927 Certificates of deposit — 650 650 Total $ 63,341 $ 629,924 $ 693,265 Included in cash and cash equivalents $ 66,090 Included in marketable securities $ 627,175 Fair Value Measurement at Level 1 Level 2 Total Description Corporate bonds $ — $ 460,210 $ 460,210 Asset-backed securities — 127,078 127,078 U.S. treasury securities — 58,039 58,039 Money market funds 57,758 — 57,758 Commercial paper — 38,900 38,900 Agency securities — 11,256 11,256 Certificates of deposit and time deposits — 3,200 3,200 Total $ 57,758 $ 698,683 $ 756,441 Included in cash and cash equivalents $ 62,557 Included in marketable securities $ 693,884 As of June 30, 2019 and December 31, 2018 , there were no securities within Level 3 of the fair value hierarchy. There were no transfers between fair value measurement levels during the three and six months ended June 30, 2019 . Gross unrealized gains and losses for cash equivalents and marketable securities as of June 30, 2019 were $5 million and not material, respectively. The aggregate amortized cost basis for cash equivalents and marketable securities as of June 30, 2019 was $689 million . Gross unrealized gains and losses for cash equivalents and marketable securities as of December 31, 2018 were no t material. Unrealized losses for securities that have been in an unrealized loss position for more than 12 months as of June 30, 2019 and December 31, 2018 were no t material. The following table classifies our marketable securities by contractual maturity (in thousands): June 30, December 31, Due in one year or less $ 255,930 $ 300,213 Due after one year and within five years 371,245 393,671 Total $ 627,175 $ 693,884 As of June 30, 2019 and December 31, 2018 , the balance of strategic investments without readily determinable fair values was $11 million and $10 million , respectively. There have been no adjustments to the carrying values of strategic investments resulting from impairments or observable price changes. For our other financial instruments, including accounts receivable, accounts payable, and other current liabilities, the carrying amounts approximate their fair values due to the relatively short maturity of these balances. Derivative Instruments and Hedging Our foreign currency exposures typically arise from expenditures associated with foreign operations and sales in foreign currencies of our products. To mitigate the effect of foreign currency fluctuations on our future cash flows and earnings, we enter into foreign currency forward contracts with certain financial institutions and designate those contracts as cash flow hedges. Our foreign currency forward contracts generally have maturities of 15 months or less. Upon the adoption of ASU 2017-12 in the first quarter of 2019, we include time value related to our cash flow hedges for effectiveness testing purposes and the entire change in the unrecognized value of our hedge contracts is recorded in accumulated other comprehensive income (loss), or AOCI. Prior to adoption, we excluded time value for effectiveness testing purposes and we recognized changes in time value immediately in other income (expense), net. As of June 30, 2019 , the balance of AOCI included an unrecognized net gain of $1 million related to the changes in the fair value of foreign currency forward contracts designated as cash flow hedges. We expect to reclassify a net gain of $1 million into earnings over the next 12 months associated with our cash flow hedges. The following tables present information about our derivative instruments on our consolidated balance sheets (in thousands): June 30, 2019 Asset Derivatives Liability Derivatives Derivative Instrument Balance Sheet Location Fair Value (Level 2) Balance Sheet Location Fair Value (Level 2) Foreign currency forward contracts Other current assets $ 1,905 Accrued liabilities $ 2,500 Total $ 1,905 $ 2,500 December 31, 2018 Asset Derivatives Liability Derivatives Derivative Instrument Balance Sheet Location Fair Value (Level 2) Balance Sheet Location Fair Value (Level 2) Foreign currency forward contracts Other current assets $ 2,047 Accrued liabilities $ 4,862 Total $ 2,047 $ 4,862 Our foreign currency forward contracts had a total notional value of $227 million and $200 million as of June 30, 2019 and December 31, 2018 , respectively. We have a master netting arrangement with each of our counterparties, which permit net settlement of multiple, separate derivative contracts with a single payment. We may also be required to exchange cash collateral with certain of our counterparties on a regular basis. GAAP permits companies to present the fair value of derivative instruments on a net basis according to master netting arrangements. We have elected to present our derivative instruments on a gross basis in our consolidated financial statements. We do not enter into any derivative contracts for trading or speculative purposes. As of June 30, 2019 and December 31, 2018 , there was no cash collateral posted with counterparties. All derivatives have been designated as hedging instruments. The following table presents information about our foreign currency forward contracts on our condensed consolidated statements of operations for the three and six months ended June 30, 2019 (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Classification Gain (Loss) Reclassified from AOCI into Earnings Gain (Loss) Reclassified from AOCI into Earnings Revenue $ 589 $ 1,032 Cost of revenue (393 ) (867 ) Research and development (331 ) (765 ) Sales and marketing (630 ) (1,420 ) General and administrative (221 ) (497 ) Total $ (986 ) $ (2,517 ) The gain recognized in AOCI related to foreign currency forward contracts was no t material for the three and six months ended June 30, 2019 . The loss recognized in AOCI related to foreign currency forward contracts was $3 million for both the three and six months ended June 30, 2018 . The gain reclassified from AOCI into earnings related to foreign currency forward contracts was no t material and $ 1 million for the three and six months ended June 30, 2018 , which was included within revenue, cost of revenue and operating expenses on our consolidated statements of operations. The cash flow effects related to foreign currency forward contracts are included within operating activities on our consolidated statements of cash flows. Convertible Senior Notes As of June 30, 2019 , the fair value of our convertible senior notes was $877 million . The fair value was determined based on the quoted price of the convertible senior notes in an inactive market on the last traded day of the quarter and has been classified as Level 2 in the fair value hierarchy. Based on the closing price of our common stock of $89.03 on the last trading day of the quarter, the if-converted value of our convertible senior notes exceeded the principal amount of $575 million as of June 30, 2019 .

Costs to Obtain Customer Contra

Costs to Obtain Customer Contracts	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Costs to Obtain Customer Contracts	Costs to Obtain Customer Contracts The balances of deferred costs to obtain customer contracts were $62 million and $52 million as of June 30, 2019 and December 31, 2018 , respectively. Amortization expense for these deferred costs was $8 million and $5 million for the three months ended June 30, 2019 and 2018 , respectively, and $15 million and $10 million for the six months ended June 30, 2019 and 2018 , respectively. There were no impairment losses related to these deferred costs for the periods presented. During the three months ended June 30, 2019 and 2018 , $126 million and $93 million of revenue was recognized that was included in the deferred revenue balances at the beginning of each period, respectively. During the six months ended June 30, 2019 and 2018 , $189 million and $139 million of revenue was recognized that was included in the deferred revenue balances at the beginning of each period, respectively. The aggregate balance of remaining performance obligations as of June 30, 2019 was $526 million . We expect to recognize $390 million of the balance as revenue in the next 12 months and the remainder thereafter. The aggregate balance of remaining performance obligations represents contracted revenue that has not yet been recognized and does not include contract amounts which are cancelable by the customer and amounts associated with optional renewal periods.

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment, net consists of the following (in thousands): June 30, December 31, Leasehold improvements $ 58,844 $ 51,832 Capitalized internal-use software 39,264 36,444 Computer equipment and licensed software and patents 23,345 21,100 Furniture and fixtures 12,055 11,550 Construction in progress 19,026 10,538 Hosting equipment — 34,105 Total 152,534 165,569 Less: accumulated depreciation and amortization (65,014 ) (89,915 ) Property and equipment, net $ 87,520 $ 75,654 Depreciation expense was $5 million and $7 million for the three months ended June 30, 2019 and 2018 , respectively, and $10 million and $13 million for the six months ended June 30, 2019 and 2018 , respectively. Amortization expense of capitalized internal-use software was $2 million and $1 million for the three months ended June 30, 2019 and 2018 , respectively, and $3 million for each of the six months ended June 30, 2019 and 2018 . The carrying value of capitalized internal-use software as of June 30, 2019 and December 31, 2018 was $20 million and $19 million , respectively, including $3 million in construction in progress for both periods. During the first quarter of 2019, we completed the transition from our self-managed colocation data centers to third-party managed hosting services, at which time, we concluded that these assets met the criteria to be classified as held for sale. Accordingly, these assets were written down to their estimated salvage value and reclassified from property and equipment to other current assets, with $34 million and $33 million being reclassified from hosting equipment and accumulated depreciation respectively, for a net amount of $1 million .

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases We lease office space under noncancelable operating leases with various expiration dates. Additionally, we are the sublessor for certain office space. All of our office leases are classified as operating leases with lease expense recognized on a straight-line basis over the lease term. Lease right-of-use assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. As our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The lease right-of-use assets also include any lease payments made and exclude lease incentives such as tenant improvement allowances. Options to extend the lease term are included in the lease term when it is reasonably certain that we will exercise the extension option. Our operating leases typically include non-lease components such as common-area maintenance costs. We have elected to include non-lease components with lease payments for the purpose of calculating lease right-of-use assets and liabilities, to the extent that they are fixed. Non-lease components that are not fixed are expensed as incurred as variable lease payments. Leases with a term of one year or less are not recognized on our consolidated balance sheet; we recognize lease expense for these leases on a straight-line basis over the lease term. The following tables present information about leases on our consolidated balance sheet (in thousands): June 30, 2019 Assets Lease right-of-use assets $ 102,702 Liabilities Lease liabilities 22,784 Lease liabilities, noncurrent 97,860 As of June 30, 2019 , the weighted average remaining lease term was 6.1 years and the weighted average discount rate was 5.3% . The following table presents information about leases on our consolidated statement of operations (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Operating lease expense $ 5,794 $ 10,839 Short-term lease expense 995 1,869 Variable lease expense 2,343 3,228 Sublease income 392 793 The following table presents supplemental cash flow information about our leases (in thousands): Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities $ 8,343 Operating lease assets obtained in exchange for new lease liabilities 27,541 As of June 30, 2019 , remaining maturities of lease liabilities are as follows: Remainder of 2019 $ 13,474 2020 27,741 2021 25,263 2022 23,768 2023 17,137 Thereafter 33,076 Total lease payments 140,459 Less imputed interest 19,815 Total $ 120,644 The table above excludes future payments of $3 million related to signed leases that have not yet commenced.

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Intangible Assets	Goodwill and Acquired Intangible Assets The changes in the carrying amount of goodwill for the six months ended June 30, 2019 are as follows (in thousands): Balance as of December 31, 2018 $ 111,584 Goodwill acquired 58,245 Goodwill adjustments (240 ) Balance as of June 30, 2019 $ 169,589 Acquired intangible assets subject to amortization consist of the following (in thousands): As of June 30, 2019 Cost Accumulated Amortization Net Weighted Average Remaining Useful Life (In years) Developed technology $ 39,000 $ (11,078 ) $ 27,922 5.2 Customer relationships 15,210 (2,485 ) 12,725 5.2 Backlog 3,200 (1,000 ) 2,200 1.5 $ 57,410 $ (14,563 ) $ 42,847 As of December 31, 2018 Cost Accumulated Amortization Net Weighted Average Remaining Useful Life (In years) Developed technology $ 31,000 $ (8,151 ) $ 22,849 5.5 Customer relationships 11,310 (1,249 ) 10,061 4.6 Backlog 2,200 (367 ) 1,833 1.7 $ 44,510 $ (9,767 ) $ 34,743 Amortization expense of acquired intangible assets was $3 million and $1 million for the three months ended June 30, 2019 and 2018 , respectively, and $5 million and $1 million for the six months ended June 30, 2019 and 2018 , respectively. Estimated future amortization expense as of June 30, 2019 is as follows (in thousands): Remainder of 2019 $ 5,647 2020 9,270 2021 7,596 2022 7,430 2023 6,659 Thereafter 6,245 $ 42,847

0.25% Convertible Senior Notes

0.25% Convertible Senior Notes and Capped Call	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
0.25% Convertible Senior Notes and Capped Call	0.25% Convertible Senior Notes and Capped Call In March 2018, we issued $575 million aggregate principal amount of 0.25% convertible senior notes due March 15, 2023 in a private offering (the “Notes”). The Notes are unsecured obligations and bear interest at a fixed rate of 0.25% per annum, payable semi-annually in arrears on March 15 and September 15 of each year, commencing on September 15, 2018. The total net proceeds from the offering, after deducting initial purchase discounts and estimated debt issuance costs, were approximately $561 million . Each $1,000 principal amount of the Notes will initially be convertible into 15.8554 shares of our common stock, the “Conversion Option,” which is equivalent to an initial conversion price of approximately $63.07 per share, subject to adjustment upon the occurrence of specified events. The Notes will be convertible at the option of the holders at any time prior to the close of business on the business day immediately preceding December 15, 2022, only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2018 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period, the “Measurement Period,” in which the trading price per $1,000 principal amount of notes for each trading day of the Measurement Period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events (as set forth in the indenture). On or after December 15, 2022 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their Notes at any time, regardless of the foregoing circumstances. Upon conversion, we will pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election. If certain specified fundamental changes occur (as set forth in the indenture governing the Notes) prior to the maturity date, holders of the Notes may require us to repurchase for cash all or any portion of their notes at a repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In addition, if specific corporate events occur prior to the applicable maturity date, we will increase the conversion rate for a holder who elects to convert their notes in connection with such a corporate event in certain circumstances. It is our current intent and policy to settle conversions through combination settlement with a specified dollar amount of $1,000 per $1,000 principal amount of Notes. For more than 20 trading days during the 30 consecutive trading days ended June 30, 2019 , the last reported sale price of our common stock was equal to or exceeded 130% of the conversion price of the Notes. As a result, the Notes will be convertible at the option of the holders during the quarter ending September 30, 2019 and were classified as current liabilities on our consolidated balance sheet as of June 30, 2019 . As of the date of this filing, none of the holders of the Notes have submitted requests for conversion. In accounting for the transaction, the Notes were separated into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar debt instrument that does not have an associated conversion feature. The carrying amount of the equity component representing the Conversion Option was $125 million and was determined by deducting the fair value of the liability component from the par value of the Notes. The equity component was recorded in additional paid-in capital and is not remeasured as long as it continues to meet the conditions for equity classification. The excess of the principal amount of the liability component over its carrying amount, the “Debt Discount,” is amortized to interest expense over the contractual term of the Notes at an effective interest rate of 5.26% . In accounting for the debt issuance costs of $14 million related to the Notes, we allocated the total amount incurred to the liability and equity components of the Notes based on their relative values. Issuance costs attributable to the liability component were $11 million and are amortized to interest expense using the effective interest method over the contractual term of the Notes. Issuance costs attributable to the equity component were netted with the equity component in additional paid-in capital. The net carrying amount of the liability component of the Notes is as follows (in thousands): June 30, December 31, Principal $ 575,000 $ 575,000 Unamortized Debt Discount (95,917 ) (107,494 ) Unamortized issuance costs (8,442 ) (9,330 ) Net carrying amount $ 470,641 $ 458,176 The net carrying amount of the equity component of the Notes is as follows (in thousands): June 30, December 31, Debt Discount for Conversion Option $ 124,976 $ 124,976 Issuance costs (2,948 ) (2,948 ) Net carrying amount $ 122,028 $ 122,028 Interest expense related to the Notes is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Contractual interest expense $ 359 $ 359 $ 719 $ 403 Amortization of Debt Discount 5,826 5,531 11,577 6,202 Amortization of issuance costs 451 399 888 448 Total interest expense $ 6,636 $ 6,289 $ 13,184 $ 7,053 In connection with the pricing of the Notes, we entered into privately negotiated capped call transactions with certain counterparties, the “Capped Calls.” The Capped Calls each have an initial strike price of approximately $63.07 per share, subject to certain adjustments, which correspond to the initial conversion price of the Notes. The Capped Calls have initial cap prices of $95.20 per share, subject to certain adjustments. The Capped Calls cover, subject to anti-dilution adjustments, approximately 9.1 million shares of our common stock. Conditions that cause adjustments to the initial strike price of the Capped Calls mirror conditions that result in corresponding adjustments for the Notes. The Capped Calls are generally intended to reduce or offset the potential dilution to our common stock upon any conversion of the Notes with such reduction or offset, as the case may be, subject to a cap based on the cap price. For accounting purposes, the Capped Calls are separate transactions, and not part of the terms of the Notes. As these transactions meet certain accounting criteria, the Capped Calls are recorded in stockholders' equity and are not accounted for as derivatives. The cost of $64 million incurred in connection with the Capped Calls was recorded as a reduction to additional paid-in capital. The net impact to our stockholders' equity, included in additional paid-in capital, of the above components of the Notes is as follows (in thousands): Conversion Option $ 124,976 Purchase of Capped Calls (63,940 ) Issuance costs (2,948 ) Net deferred tax liability (13,784 ) Total $ 44,304

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments As of June 30, 2019 , there were no material changes in our commitments under contractual obligations, as disclosed in our audited consolidated financial statements for the year ended December 31, 2018. Litigation and Loss Contingencies We accrue estimates for resolution of legal and other contingencies when losses are probable and estimable. From time to time, we may become a party to litigation and subject to claims that arise in the ordinary course of business, including intellectual property claims, labor and employment claims, threatened claims, breach of contract claims, tax, and other matters. We currently have no material pending litigation. We are not currently aware of any litigation matters or loss contingencies that would be expected to have a material adverse effect on our business, consolidated balance sheets, results of operations, comprehensive loss, or cash flows. Indemnifications In the ordinary course of business, we enter into contractual arrangements under which we agree to provide indemnification of varying scope and terms to customers, business partners, and other parties with respect to certain matters, including, but not limited to, losses arising out of the breach of such agreements, intellectual property infringement claims made by third parties, and other liabilities relating to or arising from our products or our acts or omissions. In these circumstances, payment may be conditional on the other party making a claim pursuant to the procedures specified in the particular contract. Further, our obligations under these agreements may be limited in terms of time and/or amount, and in some instances, we may have recourse against third parties for certain payments. In addition, we have indemnification agreements with our directors and executive officers that require us, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The terms of such obligations may vary. To date, we have not incurred any material costs, and we have not accrued any liabilities in our consolidated financial statements, as a result of these obligations. Certain of our product offerings include service-level agreements warranting defined levels of uptime reliability and performance, which permit those customers to receive credits for future services in the event that we fail to meet those levels. To date, we have not accrued for any significant liabilities in our consolidated financial statements as a result of these service-level agreements.

Common Stock and Stockholders'

Common Stock and Stockholders' Equity	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Common Stock and Stockholders' Equity	10. Common Stock and Stockholders’ Equity Common Stock As of June 30, 2019 and December 31, 2018 , there were 400 million shares of common stock authorized for issuance with a par value of $0.01 per share and 110.7 million and 108.0 million shares were issued and outstanding, respectively. Preferred Stock As of each of June 30, 2019 and December 31, 2018 , there were 10 million shares of preferred stock authorized for issuance with a par value of $0.01 per share and no shares of preferred stock were issued or outstanding. Employee Equity Plans Employee Stock Purchase Plan Under our Employee Stock Purchase Plan, or ESPP, eligible employees are granted options to purchase shares of our common stock through payroll deductions. The ESPP provides for 18 -month offering periods, which include three six -month purchase periods. At the end of each purchase period, employees are able to purchase shares at 85% of the lower of the fair market value of our common stock at the beginning of an offering period or the fair market value of our common stock at the end of the purchase period. During the three and six months ended June 30, 2019 , 0.4 million shares of common stock were purchased under the ESPP. Pursuant to the terms of the ESPP, the number of shares reserved under the ESPP increased by 1.1 million shares on January 1, 2019. As of June 30, 2019 , 4.6 million shares of common stock were available for issuance under the ESPP. Stock Option and Grant Plans Our board of directors adopted the 2009 Stock Option and Grant Plan, or the 2009 Plan, in July 2009. The 2009 Plan was terminated in connection with our initial public offering in May 2014, and accordingly, no shares are available for issuance under this plan. The 2009 Plan continues to govern outstanding awards granted thereunder. Our 2014 Stock Option and Incentive Plan, or the 2014 Plan, serves as the successor to our 2009 Plan. Pursuant to the terms of the 2014 Plan, the number of shares reserved for issuance under the 2014 Plan increased by 5.4 million shares on January 1, 2019. As of June 30, 2019 , we had 11.8 million shares of common stock available for future grants under the 2014 Plan. On May 6, 2016, the compensation committee of our board of directors granted equity awards representing 1.2 million shares of common stock. These awards were granted outside of the 2014 Plan pursuant to an exemption provided for “employment inducement awards” within the meaning of Section 303A.08 of the New York Stock Exchange Listed Company Manual and accordingly did not require approval from our stockholders. A summary of our share-based award activity for the six months ended June 30, 2019 is as follows (in thousands, except per share information): Options Outstanding RSUs Outstanding Shares Available for Grant Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding RSUs Weighted Average Grant Date Fair Value Aggregate Intrinsic Value (In years) Outstanding — January 1, 2019 8,232 5,938 $ 20.85 6.58 $ 222,959 6,611 $ 37.77 $ 385,891 Increase in authorized shares 5,402 Stock options granted (336 ) 336 73.27 RSUs granted (2,003 ) 2,003 69.61 Stock options exercised (626 ) 21.09 RSUs vested (1,661 ) 36.06 Stock options forfeited or canceled 81 (81 ) 42.48 RSUs forfeited or canceled 476 (476 ) 41.95 RSUs forfeited or canceled and unavailable for grant (15 ) 23.44 Outstanding — June 30, 2019 11,852 5,567 $ 23.67 6.29 $ 363,982 6,462 $ 47.80 $ 575,132 The restricted stock units, or RSUs, forfeited or canceled and unavailable for grant relate to our employment inducement awards. The aggregate intrinsic value for options outstanding represents the difference between the closing market price of our common stock on the last trading day of the reporting period and the exercise price of outstanding, in-the-money options. The total intrinsic value of stock options exercised during six months ended June 30, 2019 and 2018 was $38 million and $21 million , respectively. The intrinsic value for options exercised represents the difference between the exercise price and the market value on the date of exercise. The weighted-average grant date fair value of stock options granted during the six months ended June 30, 2019 and 2018 was $28.65 and $17.53 , respectively. The total fair value of RSUs vested during the six months ended June 30, 2019 and 2018 was $132 million and $74 million , respectively. The fair value of RSUs vested represents market value on the vesting date. The weighted-average grant date fair value of RSUs granted during the six months ended June 30, 2019 and 2018 was $69.61 , and $39.43 , respectively. As of June 30, 2019 , we had a total of $329 million in future expense related to our stock options and RSUs to be recognized over a weighted average period of 2.8 years. Performance Restricted Stock Units During the three months ended September 30, 2018 , the compensation committee of our board of directors granted performance-based restricted stock units, or PRSUs, representing 0.2 million shares of common stock, the substantial majority of which were granted in connection with the acquisition of FutureSimple. The PRSUs vest in four semi-annual tranches through March 2021. The PRSUs include a service condition and a performance condition related to the attainment of semi-annual performance targets approved and communicated in advance of each performance period. For the three and six months ended June 30, 2019 , we recorded $3 million and $4 million of share-based compensation expense, respectively, related to the PRSUs, including a one-time charge related to accelerated retention compensation. For the three and six months ended June 30, 2019 , no PRSUs were vested. The total future expense related to the PRSUs will be based on the fair value of the underlying shares on the grant date for each performance tranche.

Deferred Revenue and Performanc

Deferred Revenue and Performance Obligations	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Deferred Revenue and Performance Obligations	Costs to Obtain Customer Contracts The balances of deferred costs to obtain customer contracts were $62 million and $52 million as of June 30, 2019 and December 31, 2018 , respectively. Amortization expense for these deferred costs was $8 million and $5 million for the three months ended June 30, 2019 and 2018 , respectively, and $15 million and $10 million for the six months ended June 30, 2019 and 2018 , respectively. There were no impairment losses related to these deferred costs for the periods presented. During the three months ended June 30, 2019 and 2018 , $126 million and $93 million of revenue was recognized that was included in the deferred revenue balances at the beginning of each period, respectively. During the six months ended June 30, 2019 and 2018 , $189 million and $139 million of revenue was recognized that was included in the deferred revenue balances at the beginning of each period, respectively. The aggregate balance of remaining performance obligations as of June 30, 2019 was $526 million . We expect to recognize $390 million of the balance as revenue in the next 12 months and the remainder thereafter. The aggregate balance of remaining performance obligations represents contracted revenue that has not yet been recognized and does not include contract amounts which are cancelable by the customer and amounts associated with optional renewal periods.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potential shares of common stock, including those related to outstanding share-based awards and our convertible senior notes, to the extent dilutive. Basic and diluted net loss per share were the same for each period presented as the inclusion of all potential common stock outstanding would have been anti-dilutive. The following table presents the calculation of basic and diluted net loss per share for the periods presented (in thousands, except per share data): Three Months Ended Six Months Ended 2019 2018 2019 2018 Net loss $ (54,541 ) $ (34,366 ) $ (99,261 ) $ (63,691 ) Weighted-average shares used to compute basic and diluted net loss per share 109,986 105,000 109,312 104,350 Net loss per share, basic and diluted $ (0.50 ) $ (0.33 ) $ (0.91 ) $ (0.61 ) The anti-dilutive securities excluded from the shares used to calculate diluted net loss per share are as follows (in thousands): As of June 30, 2019 2018 Shares subject to outstanding common stock options and employee stock purchase plan 5,647 6,358 Restricted stock units 6,462 7,472 Shares related to convertible senior notes 2,426 — 14,535 13,830 The shares related to convertible senior notes calculated in the table above are calculated based on the average market price of our common stock for the three months ended June 30, 2019 . We expect to settle the principal amount of the convertible senior notes in cash and therefore use the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The conversion spread has a dilutive impact on diluted net income per share when the average market price of our common stock for a given reporting period exceeds the initial conversion price of $63.07 per share for the convertible senior notes. Based on the initial conversion price, potential dilution related to the convertible senior notes is approximately 9.1 million shares. The convertible senior notes will be convertible during the quarter ending September 30, 2019.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We reported income tax expense of $1 million in each of the three and six months ended June 30, 2019 . We reported a benefit from income taxes of $2 million and $5 million in the three and six months ended June 30, 2018, primarily due to the recognition of an income tax benefit related to taxable temporary differences of the convertible senior notes and the capped call. The effective tax rate for each period differs from the statutory rate primarily as a result of not recognizing a deferred tax asset for U.S. losses due to having a full valuation allowance against U.S. deferred tax assets.

Geographic Information

Geographic Information	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Geographic Information	Geographic Information Our chief operating decision maker reviews the financial information presented on a consolidated basis for purposes of allocating resources and evaluating our financial performance. Accordingly, we have determined that we operate in a single reporting segment. Revenue The following table presents our revenue by geographic area, as determined based on the billing address of our customers (in thousands): Three Months Ended Six Months Ended 2019 2018 2019 2018 United States $ 101,014 $ 73,019 $ 195,916 $ 141,373 EMEA 55,457 41,765 107,532 79,637 APAC 21,258 16,111 40,734 30,107 Other 16,854 10,987 31,886 20,556 Total $ 194,583 $ 141,882 $ 376,068 $ 271,673 Long-Lived Assets The following table presents our long-lived assets by geographic area (in thousands): As of As of United States $ 82,009 $ 32,351 EMEA: Republic of Ireland 44,971 14,698 Other EMEA 7,171 2,450 Total EMEA 52,142 17,148 APAC: Singapore 29,326 1,117 Other APAC 7,142 5,772 Total APAC 36,468 6,889 Total $ 170,619 $ 56,388 The carrying values of capitalized internal-use software and intangible assets are excluded from the balance of long-lived assets presented in the table above.

Overview and Basis of Present_2

Overview and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	These unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in our Annual Report on Form 10-K, for the year ended December 31, 2018, filed with the SEC on February 14, 2019. There have been no changes to our significant accounting policies described in the Annual Report on Form 10-K that have had a material impact on our condensed consolidated financial statements and related notes, except as described below. The consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly our financial position, results of operations, comprehensive loss, stockholders' equity, and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year ending December 31, 2019 .
Use of Estimates	The preparation of our consolidated financial statements in conformity with GAAP requires management to make certain estimates, judgments, and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenue and expenses during the reported periods. Significant items subject to such estimates and assumptions include: • the estimate of variable consideration related to revenue recognition; • the fair value and useful lives of acquired intangible assets; • the capitalization and useful life of capitalized costs to obtain customer contracts; • the valuation of strategic investments; • the useful lives of property and equipment; • the capitalization and useful lives of internal-use software; • the lease term and incremental borrowing rate for lease liabilities; • the fair value of our convertible senior notes; • the fair value of asset retirement obligations; • the fair value and expense recognition for certain share-based awards; • the preparation of financial forecasts used in currency hedging; and • the recognition of tax benefits.
Concentrations of Risk	As of June 30, 2019 and December 31, 2018, no customers represented 10% or greater of our total accounts receivable balance. There were no customers that individually exceeded 10% of our revenue during the three and six months ended June 30, 2019 or 2018 .
Recently Issued and Adopted Accounting Pronouncements	In June 2016, the Financial Accounting Standards Board, or FASB, issued ASU 2016-13, including subsequent amendments, regarding ASC Topic 326 “ Measurement of Credit Losses on Financial Instruments, ” which modifies the accounting methodology for most financial instruments. The guidance establishes a new “expected loss model” that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Additionally, any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. This guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted. We are currently evaluating the impact of the adoption of this standard on our consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, regarding ASC Topic 350 “ Simplifying the Test for Goodwill Impairment, ” which simplifies the required methodology to calculate an impairment charge for goodwill. The standard is effective for fiscal years beginning after December 15, 2019, however early adoption is permitted. We do not expect the adoption of this standard to have a material effect on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, regarding ASC Topic 820 “ Fair Value Measurement, ” which modifies the disclosure requirements for fair value measurements for certain types of investments. The guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted. We do not expect the adoption of this standard to have a material effect on our consolidated financial statements. Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, regarding ASC Topic 842 “ Leases, ” including subsequent amendments. We refer to the new guidance as “ASC 842.” This new guidance requires lessees to recognize most leases on their balance sheets as lease right-of-use assets with corresponding lease liabilities and eliminates certain real estate-specific provisions. The new guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted ASC 842 in the first quarter of 2019 and applied the following practical expedients: • comparative periods prior to the adoption date are not adjusted to reflect the new guidance (the modified retrospective method of transition); and • the historical determination as to the existence and classification of leases is carried forward for existing contracts as of the adoption date. The effect of adopting ASC 842 resulted in the recognition of lease right-of-use assets and corresponding lease liabilities on our condensed consolidated balance sheets. As of March 31, 2019, the first quarter of adoption, the aggregate balance of lease right-of-use assets and lease liabilities was $99 million and $114 million , respectively. The standard did not affect our consolidated statement of operations or cash flows. In August 2017, the FASB issued ASU 2017-12, regarding ASC Topic 815 “ Derivatives and Hedging. ” This guidance simplifies various aspects of hedge accounting, including the measurement and presentation of hedge ineffectiveness and certain documentation and assessment requirements. The guidance also makes more hedging strategies eligible for hedge accounting. We adopted this standard in the first quarter of 2019. Upon adoption, we no longer recognize hedge ineffectiveness immediately in our consolidated statements of operations, but we instead recognize the entire change in the fair value of the hedge contract in other comprehensive income. The cumulative-effect adjustment to eliminate ineffectiveness was not material. The presentation and disclosures have been modified on a prospective basis, as required by the guidance. In February 2018, the FASB issued ASU 2018-02, “ Income Statement - Reporting Comprehensive Income ,” which provides for the reclassification of the effect of remeasuring deferred tax balances related to items within accumulated other comprehensive income to retained earnings resulting from the Tax Cuts and Jobs Act, or Tax Act. The guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted this standard in the first quarter of 2019. We have elected not to reclassify the income tax effects of the Tax Act from accumulated other comprehensive income to retained earnings, therefore the adoption did not have an effect on our consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, regarding ASC Topic 718 “ Compensation - Stock Compensation, ” which largely aligns the accounting for share-based compensation for non-employees with employees. The guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted this standard in the first quarter of 2019. The adoption did not have an effect on our consolidated financial statements. In June 2018, the FASB issued ASU 2018-08, regarding ASC Topic 958 “ Not-for-Profit Entities ,” which clarified the guidance on how entities determine whether to account for a transfer of assets as an exchange transaction or a contribution. The guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period. We adopted the standard in the first quarter of 2019. The adoption did not have an effect on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, regarding ASC Topic 350-40 “ Intangibles - Internal-Use Software, ” which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. We early adopted the standard in the first quarter of 2019. The adoption did not have an effect on our consolidated financial statements.
Leases	Lease right-of-use assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. As our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The lease right-of-use assets also include any lease payments made and exclude lease incentives such as tenant improvement allowances. Options to extend the lease term are included in the lease term when it is reasonably certain that we will exercise the extension option.

Business Combinations (Tables)

Business Combinations (Tables)	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Summary of Assets Acquired and Liabilities Assumed	Goodwill will not be amortized but instead will be tested for impairment at least annually and more frequently if certain indicators of impairment are present. Net tangible liabilities $ (2,966 ) Identifiable intangible assets: Developed technology 19,000 Customer relationships 10,400 Backlog 2,200 Goodwill 52,389 Total purchase consideration $ 81,023 15 years for income tax purposes. Net tangible assets $ 2,053 Net deferred tax liability (1,326 ) Identifiable intangible assets: Developed technology 8,000 Customer relationships 3,900 Backlog 1,000 Goodwill 58,245 Total purchase consideration $ 71,872

Financial Instruments (Tables)

Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value on Recurring Basis	The following tables present information about our financial assets measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): Fair Value Measurement at Level 1 Level 2 Total Description Corporate bonds $ — $ 436,124 $ 436,124 Asset-backed securities — 130,291 130,291 Money market funds 63,341 — 63,341 U.S. treasury securities — 55,932 55,932 Commercial paper — 6,927 6,927 Certificates of deposit — 650 650 Total $ 63,341 $ 629,924 $ 693,265 Included in cash and cash equivalents $ 66,090 Included in marketable securities $ 627,175 Fair Value Measurement at Level 1 Level 2 Total Description Corporate bonds $ — $ 460,210 $ 460,210 Asset-backed securities — 127,078 127,078 U.S. treasury securities — 58,039 58,039 Money market funds 57,758 — 57,758 Commercial paper — 38,900 38,900 Agency securities — 11,256 11,256 Certificates of deposit and time deposits — 3,200 3,200 Total $ 57,758 $ 698,683 $ 756,441 Included in cash and cash equivalents $ 62,557 Included in marketable securities $ 693,884
Schedule of Marketable Securities Classified by Contractual Maturity	The following table classifies our marketable securities by contractual maturity (in thousands): June 30, December 31, Due in one year or less $ 255,930 $ 300,213 Due after one year and within five years 371,245 393,671 Total $ 627,175 $ 693,884
Schedule of Derivative Instruments on Consolidated Balance Sheets	The following tables present information about our derivative instruments on our consolidated balance sheets (in thousands): June 30, 2019 Asset Derivatives Liability Derivatives Derivative Instrument Balance Sheet Location Fair Value (Level 2) Balance Sheet Location Fair Value (Level 2) Foreign currency forward contracts Other current assets $ 1,905 Accrued liabilities $ 2,500 Total $ 1,905 $ 2,500 December 31, 2018 Asset Derivatives Liability Derivatives Derivative Instrument Balance Sheet Location Fair Value (Level 2) Balance Sheet Location Fair Value (Level 2) Foreign currency forward contracts Other current assets $ 2,047 Accrued liabilities $ 4,862 Total $ 2,047 $ 4,862
Schedule of Derivative Instruments on Statement of Operations	The following table presents information about our foreign currency forward contracts on our condensed consolidated statements of operations for the three and six months ended June 30, 2019 (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Classification Gain (Loss) Reclassified from AOCI into Earnings Gain (Loss) Reclassified from AOCI into Earnings Revenue $ 589 $ 1,032 Cost of revenue (393 ) (867 ) Research and development (331 ) (765 ) Sales and marketing (630 ) (1,420 ) General and administrative (221 ) (497 ) Total $ (986 ) $ (2,517 )

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment, net consists of the following (in thousands): June 30, December 31, Leasehold improvements $ 58,844 $ 51,832 Capitalized internal-use software 39,264 36,444 Computer equipment and licensed software and patents 23,345 21,100 Furniture and fixtures 12,055 11,550 Construction in progress 19,026 10,538 Hosting equipment — 34,105 Total 152,534 165,569 Less: accumulated depreciation and amortization (65,014 ) (89,915 ) Property and equipment, net $ 87,520 $ 75,654

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Schedule of Lease Impact on Balance Sheet	The following tables present information about leases on our consolidated balance sheet (in thousands): June 30, 2019 Assets Lease right-of-use assets $ 102,702 Liabilities Lease liabilities 22,784 Lease liabilities, noncurrent 97,860
Schedule of Lease Cost and Supplemental Cash Flow Information	The following table presents supplemental cash flow information about our leases (in thousands): Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities $ 8,343 Operating lease assets obtained in exchange for new lease liabilities 27,541 The following table presents information about leases on our consolidated statement of operations (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Operating lease expense $ 5,794 $ 10,839 Short-term lease expense 995 1,869 Variable lease expense 2,343 3,228 Sublease income 392 793
Schedule of Maturities of Leases	As of June 30, 2019 , remaining maturities of lease liabilities are as follows: Remainder of 2019 $ 13,474 2020 27,741 2021 25,263 2022 23,768 2023 17,137 Thereafter 33,076 Total lease payments 140,459 Less imputed interest 19,815 Total $ 120,644

Goodwill and Acquired Intangi_2

Goodwill and Acquired Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the six months ended June 30, 2019 are as follows (in thousands): Balance as of December 31, 2018 $ 111,584 Goodwill acquired 58,245 Goodwill adjustments (240 ) Balance as of June 30, 2019 $ 169,589
Summary of Intangible Assets Acquired	Acquired intangible assets subject to amortization consist of the following (in thousands): As of June 30, 2019 Cost Accumulated Amortization Net Weighted Average Remaining Useful Life (In years) Developed technology $ 39,000 $ (11,078 ) $ 27,922 5.2 Customer relationships 15,210 (2,485 ) 12,725 5.2 Backlog 3,200 (1,000 ) 2,200 1.5 $ 57,410 $ (14,563 ) $ 42,847 As of December 31, 2018 Cost Accumulated Amortization Net Weighted Average Remaining Useful Life (In years) Developed technology $ 31,000 $ (8,151 ) $ 22,849 5.5 Customer relationships 11,310 (1,249 ) 10,061 4.6 Backlog 2,200 (367 ) 1,833 1.7 $ 44,510 $ (9,767 ) $ 34,743
Summary of Estimated Future Amortization Expense	Estimated future amortization expense as of June 30, 2019 is as follows (in thousands): Remainder of 2019 $ 5,647 2020 9,270 2021 7,596 2022 7,430 2023 6,659 Thereafter 6,245 $ 42,847

0.25% Convertible Senior Note_2

0.25% Convertible Senior Notes and Capped Call (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of Net Carrying Amount of Liability and Equity Component of Convertible Notes	The net carrying amount of the liability component of the Notes is as follows (in thousands): June 30, December 31, Principal $ 575,000 $ 575,000 Unamortized Debt Discount (95,917 ) (107,494 ) Unamortized issuance costs (8,442 ) (9,330 ) Net carrying amount $ 470,641 $ 458,176 The net carrying amount of the equity component of the Notes is as follows (in thousands): June 30, December 31, Debt Discount for Conversion Option $ 124,976 $ 124,976 Issuance costs (2,948 ) (2,948 ) Net carrying amount $ 122,028 $ 122,028 The net impact to our stockholders' equity, included in additional paid-in capital, of the above components of the Notes is as follows (in thousands): Conversion Option $ 124,976 Purchase of Capped Calls (63,940 ) Issuance costs (2,948 ) Net deferred tax liability (13,784 ) Total $ 44,304
Schedule of Interest Expense	Interest expense related to the Notes is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Contractual interest expense $ 359 $ 359 $ 719 $ 403 Amortization of Debt Discount 5,826 5,531 11,577 6,202 Amortization of issuance costs 451 399 888 448 Total interest expense $ 6,636 $ 6,289 $ 13,184 $ 7,053

Common Stock and Stockholders_2

Common Stock and Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Summary of Stock Option and RSU Award Activity	A summary of our share-based award activity for the six months ended June 30, 2019 is as follows (in thousands, except per share information): Options Outstanding RSUs Outstanding Shares Available for Grant Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding RSUs Weighted Average Grant Date Fair Value Aggregate Intrinsic Value (In years) Outstanding — January 1, 2019 8,232 5,938 $ 20.85 6.58 $ 222,959 6,611 $ 37.77 $ 385,891 Increase in authorized shares 5,402 Stock options granted (336 ) 336 73.27 RSUs granted (2,003 ) 2,003 69.61 Stock options exercised (626 ) 21.09 RSUs vested (1,661 ) 36.06 Stock options forfeited or canceled 81 (81 ) 42.48 RSUs forfeited or canceled 476 (476 ) 41.95 RSUs forfeited or canceled and unavailable for grant (15 ) 23.44 Outstanding — June 30, 2019 11,852 5,567 $ 23.67 6.29 $ 363,982 6,462 $ 47.80 $ 575,132

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss per Share	The following table presents the calculation of basic and diluted net loss per share for the periods presented (in thousands, except per share data): Three Months Ended Six Months Ended 2019 2018 2019 2018 Net loss $ (54,541 ) $ (34,366 ) $ (99,261 ) $ (63,691 ) Weighted-average shares used to compute basic and diluted net loss per share 109,986 105,000 109,312 104,350 Net loss per share, basic and diluted $ (0.50 ) $ (0.33 ) $ (0.91 ) $ (0.61 )
Schedule of Anti-Dilutive Securities Excluded from the Diluted per Share Calculation	The anti-dilutive securities excluded from the shares used to calculate diluted net loss per share are as follows (in thousands): As of June 30, 2019 2018 Shares subject to outstanding common stock options and employee stock purchase plan 5,647 6,358 Restricted stock units 6,462 7,472 Shares related to convertible senior notes 2,426 — 14,535 13,830

Geographic Information (Tables)

Geographic Information (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Schedule of Revenue by Geographic Areas	The following table presents our revenue by geographic area, as determined based on the billing address of our customers (in thousands): Three Months Ended Six Months Ended 2019 2018 2019 2018 United States $ 101,014 $ 73,019 $ 195,916 $ 141,373 EMEA 55,457 41,765 107,532 79,637 APAC 21,258 16,111 40,734 30,107 Other 16,854 10,987 31,886 20,556 Total $ 194,583 $ 141,882 $ 376,068 $ 271,673
Schedule of Long-Lived Assets by Geographic Areas	The following table presents our long-lived assets by geographic area (in thousands): As of As of United States $ 82,009 $ 32,351 EMEA: Republic of Ireland 44,971 14,698 Other EMEA 7,171 2,450 Total EMEA 52,142 17,148 APAC: Singapore 29,326 1,117 Other APAC 7,142 5,772 Total APAC 36,468 6,889 Total $ 170,619 $ 56,388

Overview and Basis of Present_3

Overview and Basis of Presentation - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Lease right-of-use assets	$ 102,702	$ 99,000
Operating lease liabilities	$ 120,644	$ 114,000

Business Combinations - Narrati

Business Combinations - Narrative (Details) - USD ($) $ in Millions	May 14, 2019	Sep. 10, 2018
Smooch Technologies Holding ULC
Business Acquisition [Line Items]
Cash consideration	$ 72
Transaction costs associated with transaction	3
Share based compensation expense as a result of acquisition	$ 5
Amortization period for goodwill acquired and eligible for income tax deductions	15 years
Smooch Technologies Holding ULC | Developed technology
Business Acquisition [Line Items]
Acquired intangible assets weighted average useful life	5 years 6 months
Smooch Technologies Holding ULC | Customer relationships
Business Acquisition [Line Items]
Acquired intangible assets weighted average useful life	8 years
Smooch Technologies Holding ULC | Backlog
Business Acquisition [Line Items]
Acquired intangible assets weighted average useful life	2 years
FutureSimple Inc.
Business Acquisition [Line Items]
Cash consideration		$ 81
Transaction costs associated with transaction		$ 2
FutureSimple Inc. | Developed technology
Business Acquisition [Line Items]
Acquired intangible assets weighted average useful life		6 years 6 months
FutureSimple Inc. | Customer relationships
Business Acquisition [Line Items]
Acquired intangible assets weighted average useful life		5 years
FutureSimple Inc. | Backlog
Business Acquisition [Line Items]
Acquired intangible assets weighted average useful life		2 years

Business Combinations - Summary

Business Combinations - Summary of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Jun. 30, 2019	May 14, 2019	Dec. 31, 2018	Sep. 10, 2018
Business Acquisition [Line Items]
Goodwill	$ 169,589		$ 111,584
Smooch Technologies Holding ULC
Business Acquisition [Line Items]
Net tangible assets		$ 2,053
Net deferred tax liability		(1,326)
Goodwill		58,245
Total purchase price		71,872
FutureSimple Inc.
Business Acquisition [Line Items]
Net tangible liabilities				$ (2,966)
Goodwill				52,389
Total purchase price				81,023
Developed technology | Smooch Technologies Holding ULC
Business Acquisition [Line Items]
Identifiable intangible assets:		8,000
Developed technology | FutureSimple Inc.
Business Acquisition [Line Items]
Identifiable intangible assets:				19,000
Customer relationships | Smooch Technologies Holding ULC
Business Acquisition [Line Items]
Identifiable intangible assets:		3,900
Customer relationships | FutureSimple Inc.
Business Acquisition [Line Items]
Identifiable intangible assets:				10,400
Backlog | Smooch Technologies Holding ULC
Business Acquisition [Line Items]
Identifiable intangible assets:		$ 1,000
Backlog | FutureSimple Inc.
Business Acquisition [Line Items]
Identifiable intangible assets:				$ 2,200

Financial Instruments - Financi

Financial Instruments - Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Included in marketable securities	$ 627,175	$ 693,884
Fair Value Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	693,265	756,441
Included in cash and cash equivalents	66,090	62,557
Included in marketable securities	627,175	693,884
Fair Value Measurements, Recurring | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	436,124	460,210
Fair Value Measurements, Recurring | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	130,291	127,078
Fair Value Measurements, Recurring | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	63,341	57,758
Fair Value Measurements, Recurring | U.S. treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	55,932	58,039
Fair Value Measurements, Recurring | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	6,927	38,900
Fair Value Measurements, Recurring | Agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets		11,256
Fair Value Measurements, Recurring | Certificates of deposit and time deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	650	3,200
Fair Value Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	63,341	57,758
Fair Value Measurements, Recurring | Level 1 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value Measurements, Recurring | Level 1 | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value Measurements, Recurring | Level 1 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	63,341	57,758
Fair Value Measurements, Recurring | Level 1 | U.S. treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value Measurements, Recurring | Level 1 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value Measurements, Recurring | Level 1 | Agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets		0
Fair Value Measurements, Recurring | Level 1 | Certificates of deposit and time deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	629,924	698,683
Fair Value Measurements, Recurring | Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	436,124	460,210
Fair Value Measurements, Recurring | Level 2 | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	130,291	127,078
Fair Value Measurements, Recurring | Level 2 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value Measurements, Recurring | Level 2 | U.S. treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	55,932	58,039
Fair Value Measurements, Recurring | Level 2 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	6,927	38,900
Fair Value Measurements, Recurring | Level 2 | Agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets		11,256
Fair Value Measurements, Recurring | Level 2 | Certificates of deposit and time deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	$ 650	$ 3,200

Financial Instruments - Narrati

Financial Instruments - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross unrealized gain (loss)			$ 5,000,000		$ 0
Amortized cost of cash equivalents and marketable securities	$ 689,000,000		689,000,000
Unrealized losses recognized by securities in continuous loss position for twelve months or longer	0		0		0
Balance of strategic investment	11,000,000		11,000,000		10,000,000
Adjustments to carrying value of strategic investments			0
Unrealized gain in accumulated other comprehensive loss	426,977,000	$ 404,866,000	426,977,000	$ 404,866,000	416,921,000	$ 418,945,000	$ 400,653,000	$ 354,184,000
Cash collateral posted	$ 0		$ 0		0
Closing price of common stock (usd per share)	$ 89.03		$ 89.03
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of financial assets	$ 0		$ 0		0
Shares related to convertible senior notes | Convertible Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Convertible debt, if-convertible value in excess of principal amount			575,000,000
Shares related to convertible senior notes | Convertible Debt | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value	877,000,000		877,000,000
Foreign Currency Forward Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Reclassification of net gain	1,000,000		1,000,000
Notional value	227,000,000		227,000,000		$ 200,000,000
Gain reclassified from accumulated other comprehensive income into earnings before adoption		0		1,000,000
Gain (loss) recognized in AOCI	0	$ (3,000,000)	$ 0	$ (3,000,000)
Foreign Currency Forward Contracts | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative, maturity			15 months
AOCI, Derivative Qualifying as Hedge, Excluded Component, Parent | Foreign Currency Forward Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain in accumulated other comprehensive loss	$ 1,000,000		$ 1,000,000

Financial Instruments - Marketa

Financial Instruments - Marketable Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Due in one year or less	$ 255,930	$ 300,213
Due after one year and within five years	371,245	393,671
Total	$ 627,175	$ 693,884

Financial Instruments - Schedul

Financial Instruments - Schedule of Derivative Instruments on Consolidated Balance Sheets (Details) - Designated as Hedging Instrument - Level 2 - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivatives Fair Value [Line Items]
Asset Derivatives	$ 1,905	$ 2,047
Liability Derivatives	2,500	4,862
Foreign Currency Forward Contracts | Other current assets
Derivatives Fair Value [Line Items]
Asset Derivatives	1,905	2,047
Foreign Currency Forward Contracts | Accrued liabilities
Derivatives Fair Value [Line Items]
Liability Derivatives	$ 2,500	$ 4,862

Financial Instruments - Sched_2

Financial Instruments - Schedule of Derivative Instruments on Statement of Operations (Details) - Foreign Currency Forward Contracts - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	$ (986)	$ (2,517)
Revenue
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	589	1,032
Cost of revenue
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	(393)	(867)
Research and development
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	(331)	(765)
Sales and marketing
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	(630)	(1,420)
General and administrative
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	$ (221)	$ (497)

Costs to Obtain Customer Cont_2

Costs to Obtain Customer Contracts (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Deferred costs to obtain customer contracts	$ 62,000,000		$ 62,000,000		$ 52,000,000
Amortization of deferred costs	8,000,000	$ 5,000,000	14,540,000	$ 9,530,000
Impairment related to deferred costs	$ 0	$ 0	$ 0	$ 0

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total	$ 152,534	$ 165,569
Less: accumulated depreciation and amortization	(65,014)	(89,915)
Property and equipment, net	87,520	75,654
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	58,844	51,832
Capitalized internal-use software
Property, Plant and Equipment [Line Items]
Total	39,264	36,444
Computer equipment and licensed software and patents
Property, Plant and Equipment [Line Items]
Total	23,345	21,100
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	12,055	11,550
Construction in progress
Property, Plant and Equipment [Line Items]
Total	19,026	10,538
Hosting equipment
Property, Plant and Equipment [Line Items]
Total	$ 0	$ 34,105

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 5		$ 7	$ 10	$ 13
Amortization expense of capitalized internal-use software	2		$ 1	3	$ 3
Carrying value of capitalized internal-use software	20			20		$ 19
Capitalized internal-use software included in construction in progress	$ 3			$ 3		$ 3
Hosting equipment
Property, Plant and Equipment [Line Items]
Reclassification from property and equipment, gross		$ 34
Reclassification of accumulated depreciations associated with property and equipment		33
Reclassification from property and equipment, net of accumulated depreciation		$ 1

Leases - Schedule of Lease Impa

Leases - Schedule of Lease Impact on Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019
Assets
Lease right-of-use assets	$ 102,702	$ 99,000
Liabilities
Lease liabilities	22,784
Lease liabilities, noncurrent	$ 97,860

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	Jun. 30, 2019USD ($)
Leases [Abstract]
Weighted average remaining lease term	6 years 1 month 6 days
Weighted average discount rate	5.30%
Operating lease payments for leases that have not yet commenced	$ 3

Leases - Schedule of Lease Cost

Leases - Schedule of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease expense	$ 5,794	$ 10,839
Short-term lease expense	995	1,869
Variable lease expense	2,343	3,228
Sublease income	$ 392	$ 793

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 8,343
Operating lease assets obtained in exchange for new lease liabilities	$ 27,541

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remainder of 2019	$ 13,474
2020	27,741
2021	25,263
2022	23,768
2023	17,137
Thereafter	33,076
Total lease payments	140,459
Less imputed interest	19,815
Total	$ 120,644	$ 114,000

Goodwill and Acquired Intangi_3

Goodwill and Acquired Intangible Assets - Schedule of Carrying Amount of Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2018	$ 111,584
Goodwill acquired	58,245
Goodwill adjustments	(240)
Balance as of June 30, 2019	$ 169,589

Goodwill and Acquired Intangi_4

Goodwill and Acquired Intangible Assets - Acquired Intangible Assets Subject to Amortization (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Cost	$ 57,410	$ 44,510
Accumulated Amortization	(14,563)	(9,767)
Net	42,847	34,743
Developed technology
Finite Lived Intangible Assets [Line Items]
Cost	39,000	31,000
Accumulated Amortization	(11,078)	(8,151)
Net	$ 27,922	$ 22,849
Weighted Average Remaining Useful Life	5 years 2 months 12 days	5 years 6 months
Customer relationships
Finite Lived Intangible Assets [Line Items]
Cost	$ 15,210	$ 11,310
Accumulated Amortization	(2,485)	(1,249)
Net	$ 12,725	$ 10,061
Weighted Average Remaining Useful Life	5 years 2 months 12 days	4 years 7 months 6 days
Backlog
Finite Lived Intangible Assets [Line Items]
Cost	$ 3,200	$ 2,200
Accumulated Amortization	(1,000)	(367)
Net	$ 2,200	$ 1,833
Weighted Average Remaining Useful Life	1 year 6 months	1 year 8 months 12 days

Goodwill and Acquired Intangi_5

Goodwill and Acquired Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 3	$ 1	$ 5	$ 1

Goodwill and Acquired Intangi_6

Goodwill and Acquired Intangible Assets - Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2019	$ 5,647
2020	9,270
2021	7,596
2022	7,430
2023	6,659
Thereafter	6,245
Total estimated future amortization expense	$ 42,847	$ 34,743

0.25% Convertible Senior Note_3

0.25% Convertible Senior Notes and Capped Call - Narrative (Details) $ / shares in Units, shares in Millions	Mar. 15, 2018USD ($)day$ / sharesshares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes, net of issuance costs				$ 0	$ 561,493,000
Cost incurred related to capped calls		$ 0	$ (49,000)	$ 0	$ (44,304,000)
Convertible Debt | Shares related to convertible senior notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 575,000,000
Interest rate	0.25%
Proceeds from issuance of convertible senior notes, net of issuance costs	$ 561,000,000
Initial conversion rate of common stock				0.0158554
Conversion price (usd per share) | $ / shares	$ 63.07
Limitation on sale of common stock, sale price threshold, number of trading days | day	20
Limitation on sale of common stock, sale price threshold, trading period | day	30
Threshold percentage of stock price trigger	130.00%
Number of consecutive business days	5 days
Percentage of closing sale price in excess of convertible notes	98.00%
Redemption price percentage	100.00%
Conversion Option	$ 125,000,000	$ 124,976,000		$ 124,976,000		$ 124,976,000
Effective interest rate		5.26%		5.26%
Debt issuance costs, gross		$ 14,000,000		$ 14,000,000
Issuance costs attributable to the liability component	$ 11,000,000	8,442,000		8,442,000		$ 9,330,000
Capped calls, initial cap price (in usd per share) | $ / shares	$ 95.20
Number of shares covered by cap call (in shares) | shares	9.1
Cost incurred related to capped calls	$ (64,000,000)			(44,304,000)
Net deferred tax liability related to cap call		$ 13,784,000		$ 13,784,000

0.25% Convertible Senior Note_4

0.25% Convertible Senior Notes and Capped Call - Schedule of Net Carrying Amount of Liability and Equity Component of Convertible Notes (Details) - Convertible Debt - Shares related to convertible senior notes - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Mar. 15, 2018
Net Carrying Amount of Liability Component of Convertible Notes [Abstract]
Principal	$ 575,000	$ 575,000
Unamortized Debt Discount	(95,917)	(107,494)
Unamortized issuance costs	(8,442)	(9,330)	$ (11,000)
Net carrying amount	470,641	458,176
Net Carrying Amount of Equity Component of Convertible Notes [Abstract]
Debt Discount for Conversion Option	124,976	124,976	$ 125,000
Issuance costs	(2,948)	(2,948)
Net carrying amount	$ 122,028	$ 122,028

0.25% Convertible Senior Note_5

0.25% Convertible Senior Notes and Capped Call - Schedule of Interest Expense (Details) - Convertible Debt - Shares related to convertible senior notes - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Contractual interest expense	$ 359	$ 359	$ 719	$ 403
Amortization of Debt Discount	5,826	5,531	11,577	6,202
Amortization of issuance costs	451	399	888	448
Total interest expense	$ 6,636	$ 6,289	$ 13,184	$ 7,053

0.25% Convertible Senior Note_6

0.25% Convertible Senior Notes and Capped Call - Summary of Impact to Stockholder's Equity (Details) - USD ($) $ in Thousands	Mar. 15, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Net impact to stockholder's equity		$ 0	$ 49	$ 0	$ 44,304
Convertible Debt | Shares related to convertible senior notes
Debt Instrument [Line Items]
Conversion Option	$ 125,000	124,976		124,976		$ 124,976
Purchase of Capped Calls				(63,940)
Issuance costs		(2,948)		(2,948)		$ (2,948)
Net deferred tax liability		$ (13,784)		(13,784)
Net impact to stockholder's equity	$ 64,000			$ 44,304

Common Stock and Stockholders_3

Common Stock and Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Millions	Jan. 01, 2019shares	Jan. 01, 2018shares	May 06, 2016shares	Jun. 30, 2019USD ($)number_of_semi_annual_tranches$ / sharesshares	Sep. 30, 2018shares	Jun. 30, 2019USD ($)offering_period$ / sharesshares	Jun. 30, 2018USD ($)$ / shares	Dec. 31, 2018$ / sharesshares
Class Of Stock [Line Items]
Common stock, shares authorized (in shares)				400,000,000		400,000,000		400,000,000
Common stock, par value (usd per share) | $ / shares				$ 0.01		$ 0.01		$ 0.01
Common stock, shares issued (in shares)				110,700,000		110,700,000		109,300,000
Common stock, shares outstanding (in shares)				108,000,000		108,000,000		108,000,000
Preferred stock, shares authorized (in shares)				10,000,000		10,000,000		10,000,000
Preferred stock, par value (usd per share) | $ / shares				$ 0.01		$ 0.01		$ 0.01
Preferred stock, shares issued (in shares)				0		0		0
Preferred stock, shares outstanding (in shares)				0		0		0
Increase in authorized shares (in shares)						5,402,000
Shares of common stock available for issuance (in shares)				11,852,000		11,852,000		8,232,000
Stock options granted (in shares)			1,200,000			336,000
Intrinsic value of options exercised (usd per share) | $						$ 38	$ 21
Weighted-average grant date fair value of stock options (usd per share) | $ / shares						$ 28.65	$ 17.53
Future period share-based compensation expense | $				$ 329		$ 329
Future period share-based compensation expense, period to recognized						2 years 9 months 18 days
Employee Stock Option
Class Of Stock [Line Items]
Offering period						18 months
Number of offering periods | offering_period						3,000
Length of purchase period						6 months
Restricted Stock Units
Class Of Stock [Line Items]
Intrinsic value of shares vested | $						$ 132	$ 74
Weighted average grant date fair value (usd per share) | $ / shares						$ 69.61	$ 39.43
Shares granted (in shares)						2,003,000
Number of shares vested (in shares)						1,661,000
Performance-Based Restricted Stock Units
Class Of Stock [Line Items]
Number of vesting periods | number_of_semi_annual_tranches				4
2009 Stock Option and Grant Plan
Class Of Stock [Line Items]
Shares of common stock available for issuance (in shares)				0		0
2014 Plan | Employee Stock Option
Class Of Stock [Line Items]
Increase in authorized shares (in shares)		5,400,000
Shares of common stock available for issuance (in shares)				11,800,000		11,800,000
PSU Retention Plan | Performance-Based Restricted Stock Units
Class Of Stock [Line Items]
Shares granted (in shares)					200,000
Share-based compensation expense | $				$ 3		$ 4
Number of shares vested (in shares)						0
Employee Stock Purchase Plan
Class Of Stock [Line Items]
Percentage of purchase price of shares lower of the fair market value of common stock employees are able to purchase shares						85.00%
Common shares purchased (in shares)				400,000
Increase in authorized shares (in shares)	1,100,000
Shares of common stock available for issuance (in shares)				4,600,000		4,600,000

Common Stock and Stockholders_4

Common Stock and Stockholders' Equity - Summary of Stock Option and RSU Award Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	May 06, 2016	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Shares Available for Grant
Outstanding at beginning of period (in shares)		8,232
Increase in authorized shares (in shares)		5,402
Stock options granted (in shares)		(336)
RSUs granted (in shares)		(2,003)
Stock options forfeited or canceled (in shares)		81
RSUs forfeited or canceled (in shares)		476
Outstanding at end of period (in shares)		11,852		8,232
Number of Shares
Balance at the beginning of the period (in shares)		5,938
Stock options granted (in shares)	1,200	336
Stock options exercised (in shares)		(626)
Stock options forfeited or canceled (in shares)		(81)
Balance at the end of the period (in shares)		5,567		5,938
Weighted Average Exercise Price
Balance at the beginning of the period (usd per share)		$ 20.85
Stock options granted (usd per share)		73.27
Stock options exercised (usd per share)		21.09
Stock options forfeited or canceled (usd per share)		42.48
Balance at the end of the period (usd per share)		$ 23.67		$ 20.85
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term		6 years 3 months 14 days		6 years 6 months 29 days
Aggregate Intrinsic Value
Aggregate intrinsic value, options		$ 363,982		$ 222,959
Aggregate intrinsic value, restricted stock units		$ 575,132		$ 385,891
Restricted Stock Units
Outstanding RSUs
Balance at the beginning of the period (in shares)		6,611
RSUs granted (in shares)		2,003
RSUs vested (in shares)		(1,661)
RSUs forfeited or canceled (in shares)		(476)
RSUs forfeited and unavailable for grant (in shares)		(15)
Balance at the end of the period (in shares)		6,462		6,611
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (usd per share)		$ 37.77
Weighted average grant date fair value, RSUs granted (usd per share)		69.61	$ 39.43
Weighted average grant date fair value, RSUs vested (usd per share)		36.06
Weighted average grant date fair value, RSUs forfeited or canceled (usd per share)		41.95
Weighted average grant date fair value, forfeited and unavailable for grant (usd per share)		23.44
Balance at the end of the period (usd per share)		$ 47.80		$ 37.77

Deferred Revenue and Performa_2

Deferred Revenue and Performance Obligations - Deferred Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue recognized and included in deferred revenue	$ 126	$ 93	$ 189	$ 139

Deferred Revenue and Performa_3

Deferred Revenue and Performance Obligations - Performance Obligations (Details) $ in Millions	Jun. 30, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 526
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 390
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	1 year

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss	$ (54,541)	$ (34,366)	$ (99,261)	$ (63,691)
Weighted-average shares used to compute basic and diluted net loss per share	109,986	105,000	109,312	104,350
Net loss per share, basic and diluted (usd per share)	$ (0.50)	$ (0.33)	$ (0.91)	$ (0.61)

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Anti-Dilutive Securities Excluded from the Diluted per Share Calculation (Details) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (in shares)	14,535	13,830
Shares subject to outstanding common stock options and employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (in shares)	5,647	6,358
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (in shares)	6,462	7,472
Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (in shares)	2,426	0

Net Loss Per Share - Narrative

Net Loss Per Share - Narrative (Details) - $ / shares shares in Millions	6 Months Ended
	Jun. 30, 2019	Mar. 15, 2018
Debt Instrument [Line Items]
Potential dilution based on initial conversion price (in shares)	9.1
Convertible Debt | Shares related to convertible senior notes
Debt Instrument [Line Items]
Conversion price (usd per share)		$ 63.07

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 591	$ (1,667)	$ 1,024	$ (4,957)

Geographic Information - Narrat

Geographic Information - Narrative (Details)	6 Months Ended
	Jun. 30, 2019segment
Segment Reporting [Abstract]
Number of reportable segments	1

Geographic Information - Schedu

Geographic Information - Schedule of Revenue by Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$ 194,583	$ 141,882	$ 376,068	$ 271,673
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	101,014	73,019	195,916	141,373
EMEA
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	55,457	41,765	107,532	79,637
APAC
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	21,258	16,111	40,734	30,107
Other
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$ 16,854	$ 10,987	$ 31,886	$ 20,556

Geographic Information - Sche_2

Geographic Information - Schedule of Long-Lived Assets by Geographic Areas (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	$ 170,619	$ 56,388
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	82,009	32,351
Republic of Ireland
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	44,971	14,698
Other EMEA
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	7,171	2,450
EMEA
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	52,142	17,148
Singapore
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	29,326	1,117
Other APAC
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	7,142	5,772
APAC
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets	$ 36,468	$ 6,889

Uncategorized Items - zen10-qq2

Label	Element	Value
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	$ 1,021,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	1,443,000
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	720,000
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	$ 624,000