LivePerson (LPSN) 10-Q 9 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 05, 2018
Document And Entity Information [Abstract]
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Trading Symbol	LPSN
Entity Registrant Name	LIVEPERSON INC
Entity Central Index Key	1,102,993
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		63,415,683

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 66,351,000	$ 56,115,000
Cash held as collateral	0	1,451,000
Accounts receivable, net of allowance for doubtful accounts of $1,951 and $1,318 as of September 30, 2018 and December 31, 2017, respectively	51,727,000	37,926,000
Prepaid expenses and other current assets	18,722,000	7,352,000
Total current assets	136,800,000	102,844,000
Property and equipment, net	39,788,000	34,705,000
Intangibles, net	13,249,000	12,366,000
Goodwill	85,467,000	80,531,000
Deferred tax assets	732,000	753,000
Other assets	1,818,000	1,600,000
Total assets	277,854,000	232,799,000
CURRENT LIABILITIES:
Accounts payable	6,603,000	5,481,000
Accrued expenses and other current liabilities	41,124,000	48,011,000
Deferred revenue	56,117,000	35,563,000
Total current liabilities	103,844,000	89,055,000
Deferred revenue	2,067,000	0
Other liabilities	3,972,000	2,766,000
Deferred tax liability	1,073,000	915,000
Total liabilities	110,956,000	92,736,000
Commitments and contingencies
STOCKHOLDERS’ EQUITY:
Common stock	63,000	60,000
Additional paid-in capital	351,702,000	305,676,000
Treasury stock	(3,000)	(3,000)
Accumulated deficit	(181,026,000)	(163,135,000)
Accumulated other comprehensive loss	(3,838,000)	(2,535,000)
Total stockholders’ equity	166,898,000	140,063,000
Total liabilities and stockholders’ equity	$ 277,854,000	$ 232,799,000

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 1,951	$ 1,318

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue	$ 64,213	$ 56,493	$ 184,114	$ 161,486
Costs and expenses
Cost of revenue	15,689	14,541	45,679	43,456
Sales and marketing	26,748	21,603	76,271	66,695
General and administrative	11,972	10,398	33,594	30,528
Product development	13,484	9,726	40,955	29,011
Restructuring costs	722	0	2,806	2,315
Amortization of purchased intangibles	424	470	1,272	1,412
Total costs and expenses	69,039	56,738	200,577	173,417
Loss from operations	(4,826)	(245)	(16,463)	(11,931)
Other (expense) income , net	(213)	191	(53)	412
Loss before provision for income taxes	(5,039)	(54)	(16,516)	(11,519)
Provision for income taxes	2,004	1,256	2,051	3,000
Net loss	$ (7,043)	$ (1,310)	$ (18,567)	$ (14,519)
Net loss per share of common stock:
Basic net loss per common share (in dollars per share)	$ (0.12)	$ (0.02)	$ (0.32)	$ (0.26)
Diluted net loss per common share (in dollars per share)	$ (0.12)	$ (0.02)	$ (0.32)	$ (0.26)
Weighted-average shares used to compute net loss per share:
Weighted average shares outstanding used in basic net loss per common share calculation (in shares)	60,014,246	56,524,990	58,667,289	56,153,428
Weighted average shares outstanding used in diluted net loss per common share calculation (in shares)	60,014,246	56,524,990	58,667,289	56,153,428
Cost of revenue
Additional Information on Operating Expenses
Stock-based compensation expense	$ 220	$ 108	$ 604	$ 301
Depreciation expense	1,934	1,715	5,781	5,350
Amortization of purchased intangibles	285	639	859	2,556
Sales and marketing
Additional Information on Operating Expenses
Stock-based compensation expense	1,472	576	3,731	1,984
Depreciation expense	388	417	1,115	1,206
General and administrative
Additional Information on Operating Expenses
Stock-based compensation expense	1,368	622	3,390	2,058
Depreciation expense	275	321	795	911
Product development
Additional Information on Operating Expenses
Stock-based compensation expense	1,014	537	2,613	1,760
Depreciation expense	$ 960	$ 726	$ 2,652	$ 1,550

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (7,043)	$ (1,310)	$ (18,567)	$ (14,519)
Foreign currency translation adjustment	376	317	1,303	(4,301)
Comprehensive loss	$ (6,667)	$ (993)	$ (17,264)	$ (18,820)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
OPERATING ACTIVITIES:
Net loss	$ (18,567)	$ (14,519)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	10,338	6,103
Depreciation	10,343	9,017
Amortization of purchased intangibles	2,131	3,968
Amortization of tenant allowance	(204)	(125)
Deferred income taxes	179	823
Provision for doubtful accounts, net	1,326	1,363
Changes in operating assets and liabilities:
Accounts receivable	(15,127)	(1,719)
Prepaid expenses and other current assets	(11,370)	(2,248)
Other assets	(218)	75
Accounts payable	571	(4,352)
Accrued expenses and other current liabilities	(8,849)	(2,954)
Deferred revenue	22,381	8,549
Other liabilities	(42)	(463)
Net cash (used in) provided by operating activities	(7,108)	3,518
INVESTING ACTIVITIES:
Purchases of property and equipment, including capitalized software	(13,832)	(12,176)
Cash held as collateral for foreign exchange forward contracts	1,451	2,511
Payments for acquisitions and intangible assets, net of cash acquired	(1,502)	(345)
Net cash used in investing activities	(13,883)	(10,010)
FINANCING ACTIVITIES:
Proceeds from issuance of common stock in connection with the exercise of options	32,712	7,748
Repurchase of common stock	(1,345)	(1,741)
Net cash provided by financing activities	31,367	6,007
EFFECT OF FOREIGN EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(140)	3,957
CHANGE IN CASH AND CASH EQUIVALENTS	10,236	3,472
CASH AND CASH EQUIVALENTS - Beginning of the period	56,115	50,889
CASH AND CASH EQUIVALENTS - End of the period	66,351	54,361
SUPPLEMENTAL DISCLOSURE OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes	5,524	540
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchase of property and equipment recorded in accounts payable	550	507
Leasehold improvements funded by landlord	1,449	0
Contingent earn-out in connection with the acquisition of Conversable recorded in accrued expenses and common stock	2,124	0
BotCentral
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	1,000	0
Conversable, Inc.
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Issuance of shares of common stock in connection with acquisition	$ 3,000	$ 0

Description of Business and Bas

Description of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation LivePerson, Inc. (the “Company” or “LivePerson”) was incorporated in the State of Delaware in November 1995 and the LivePerson service was introduced in November 1998. In April 2000, the Company completed an initial public offering and is currently traded on the NASDAQ Global Select Market and the Tel Aviv Stock Exchange. LivePerson is headquartered in New York City with U.S. offices in Alpharetta (Georgia), Austin (Texas), San Francisco (California) and Seattle (Washington), and international offices in Amsterdam (Netherlands), Berlin (Germany), London (United Kingdom), Mannheim (Germany), Melbourne (Australia), Milan (Italy), Paris (France), Ra'anana (Israel), Reading (United Kingdom), Tel Aviv (Israel), and Tokyo (Japan). LivePerson provides mobile and online business messaging solutions that power digital communication between brands and consumers. LiveEngage, the Company’s enterprise-class, cloud-based platform, enables businesses and consumers to connect through conversational interfaces, such as in-app and mobile messaging, while leveraging bots and artificial intelligence (AI) to increase efficiency. As consumers have reoriented their digital lives around the smartphone, messaging apps have become their preferred communication channel to connect with each other. LivePerson allows brands to align with this new consumer preference, and deploy messaging at scale for customer care, marketing, and sales, instead of requiring that consumers use email or call a 1-800 number. LiveEngage was designed to securely deploy messaging, coupled with bots and AI, at scale for brands with tens of millions of customers and many thousands of customer care agents. LiveEngage powers conversations across each of a brand’s primary digital channels, including mobile apps, mobile and desktop web browsers, short message services (SMS), social media and third-party consumer messaging platforms. Brands can also use LiveEngage to message consumers when they dial a 1-800 number instead of having them navigate interactive voice response systems (IVR) and wait on hold. The platform seamlessly integrates with third-party bots, enabling brands to manage both AI- based agents and human agents from a single console. LivePerson optimizes campaign outcomes for sales and service transactions by combining website visitor data with other historical, behavioral, and operational information to develop insights into each step of a consumer’s journey. LivePerson’s products, coupled with its domain knowledge, industry expertise and consulting services, have been proven to maximize the effectiveness of consumer engagement. The Company’s primary revenue source is from the sale of LivePerson services to businesses of all sizes. The Company also offers an online marketplace that connects independent service providers (“Experts”) who provide information and knowledge for a fee via real-time chat with individual consumers (“Users”). Basis of Presentation The accompanying condensed consolidated financial statements as of September 30, 2018 and for the three and nine months ended September 30, 2018 and 2017 are unaudited. In the opinion of management, the unaudited condensed consolidated financial statements have been prepared on the same basis as the annual financial statements and reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the consolidated financial position of LivePerson as of September 30, 2018 , and the consolidated results of operations, comprehensive loss and cash flows for the interim periods ended September 30, 2018 and 2017 . The financial data and other information disclosed in these notes to the condensed consolidated financial statements related to these periods are unaudited. The results of operations for any interim period are not necessarily indicative of the results of operations for any other future interim period or for a full fiscal year. The condensed consolidated balance sheet at December 31, 2017 has been derived from audited consolidated financial statements at that date. Certain information and note disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 15, 2018 . Principles of Consolidation The condensed consolidated financial statements include the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated. Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of income and expenses during the reporting period. These estimates are based on information available as of the date of the condensed consolidated financial statements; therefore, actual results could differ from management’s estimates. Recently Issued Accounting Standards In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") No. 2018-15 "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract; Disclosures for Implementation Costs Incurred for Internal-Use Software and Cloud Computing Arrangements". This standard aligns the accounting for implementation costs incurred in a hosting arrangement that is a service contract with the accounting for implementation costs incurred to develop or obtain internal-use software under Accounting Standards Codification ("ASC") 350-40, in order to determine which costs to capitalize and recognize as an asset. ASU 2018-15 is effective for annual reporting periods, and interim periods within those years, beginning after December 15, 2019, and can be applied either prospectively to implementation costs incurred after the date of adoption or retrospectively to all arrangements. The Company is currently in the process of evaluating the impact of the adoption of ASU 2018-230 on its consolidated financial statements. In June 2018, the FASB issued ASU No. 2018-07 "Compensation —Stock Compensation (Topic 718) —Improvements to Nonemployee Share-Based Payment Accounting" ("ASU 2018-07"). This new standard expands the scope of Topic 718, Compensation—Stock Compensation (which currently only includes share-based payments to employees) to include share-based payments issued to non-employees for goods or services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. ASU 2018-07 is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company is currently evaluating the impact of this updated standard, but does not believe this update will have a significant impact on its consolidated financial statements. In March 2018, the FASB issued ASU No. 2018-05 "Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118" ("ASU 2018-05"). This new standard adds SEC paragraphs pursuant to the SEC Staff Accounting Bulletin No. 118, which expresses the view of the staff regarding application of Topic 740, Income Taxes, in the reporting period that includes December 22, 2017, the date on which the Tax Cuts and Jobs Act (H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018) was signed into law. ASU 2018-05 is effective upon inclusion in the FASB Codification. The Company evaluated the impact of this updated standard and determined that the tax on unremitted earnings is zero due to the overall accumulated deficit in earnings and profits. In February 2018, the FASB issued ASU No. 2018-02 "Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU 2018-02"). This new standard allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017. The amendments in ASU 2018-02 affects any entity that is required to apply the provisions of Topic 220 and has items of other comprehensive income for which the related tax effects are presented in other comprehensive income as required by GAAP. ASU 2018-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, for public companies. Early adoption is permitted in any interim period or fiscal years before the effective date of the standard. The Company does not expect the adoption of ASU 2018-02 to have a material effect on its financial position, results of operations or cash flows. In August 2017, the FASB issued ASU No. 2017-12 "Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities" ("ASU 2017-12"). This new standard refines and expands hedge accounting for both financial (e.g., interest rate) and commodity risks. Its provisions create more transparency around how economic results are presented, both on the face of the financial statements and in the footnotes, for investors and analysts. ASU 2017-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, for public companies. Early adoption is permitted in any interim period or fiscal years before the effective date of the standard. The Company does not expect the adoption of ASU 2017-12 to have a material effect on its financial position, results of operations or cash flows. In January 2017, FASB issued ASU No. 2017-04, "Intangibles —Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment" (“ASU 2017-04”). This update addresses concerns over the cost and complexity of the two-step goodwill impairment test. The amendments in this update remove the second step of the test. An entity will apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. ASU 2017-04 is effective for financial statements issued for annual periods beginning after December 15, 2019, and interim periods within those annual periods. The Company does not expect the adoption of ASU 2017-04 to have a material effect on its financial position, results of operations or cash flows. In February 2016, the FASB issued ASU No. 2016-02, “Leases” (“ASU 2016-02”). ASU 2016-02 requires lessees to recognize the following for all leases (with the exception of short-term leases) at the commencement date: a lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under the new guidance, lessor accounting is largely unchanged. The new lease guidance also simplified the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. Lessees will no longer be provided with a source of off-balance sheet financing. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) may apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. Lessees and lessors may not apply a full retrospective transition approach. The Company is currently evaluating adopting the standard using the modified transition approach or the transition option available where the Company would recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. ASU 2016-02 is effective for financial statements issued for annual periods beginning after December 15, 2018. The Company is currently assessing the provisions of this guidance and evaluating the timing and impact the guidance will have on its consolidated financial statements and related disclosures. The Company is also in the process of aggregating lease documentation for review. The adoption of this ASU primarily impacts the balance sheet through the recognition of a right-of-use asset and a lease liability for all leases with terms in excess of twelve months. This guidance is effective January 1, 2019 using a modified retrospective transition approach with early adoption permitted. Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("Topic 606"). Topic 606 supersedes the revenue recognition requirements in ASC Topic 605, "Revenue Recognition" ("Topic 605"), and requires the recognition of revenue when promised goods or services are transferred to customers in an amount that reflects the considerations to which the entity expects to be entitled to in exchange for those goods or services. Topic 606 also includes Subtopic 340-40, "Other Assets and Deferred Costs - Contracts with Customers", which requires the deferral of incremental costs of obtaining a contract with a customer. Collectively, the Company refers to Topic 606 and Subtopic 340-40 as the "new standard." The Company adopted the requirements of the new standard as of January 1, 2018, utilizing the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. Results for the reporting periods beginning after January 1, 2018 are presented under the new standard, while prior period amounts are not adjusted and continue to be reported in accordance with its historic accounting under Topic 605. The impact of adopting the new standard as of January 1, 2018 on revenues was not material. The primary impact of adopting the new standard relates to the deferral of incremental commission costs of obtaining subscription contracts. The Company recorded an addition to opening retained earnings of $0.7 million as of January 1, 2018 due to the impact of adopting the new standard, with the impact related to the deferral of incremental commission costs. Under Topic 605, the Company deferred only direct and incremental commission costs to obtain a contract and amortized those costs on a straight-line basis over the term of the related subscription contract, which was generally one year. Under the new standard, the Company defers all incremental commission costs to obtain the contract. The prepaid commission balance as of September 30, 2018 is $10.9 million . The Company amortizes these costs over the related period of benefit using the customer expected life that the Company determined to be three to five years which is consistent with the transfer to the customer of the services to which the asset relates.

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition The majority of the Company’s revenue is generated from monthly service revenues and related professional services from the sale of the LivePerson services. Revenues are recognized when control of these services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those services. The Company determines revenue recognition through the following steps: • Identification of the contract, or contracts, with a customer; • Identification of the performance obligations in the contract; • Determination of the transaction price; • Allocation of the transaction price to the performance obligations in the contract; and • Recognition of revenue when, or as, the Company satisfies a performance obligation. Total revenue of $64.2 million and $184.1 million recognized during the three months and nine months ended September 30, 2018 , respectively, under Topic 606, was not materially different from what would have been recognized under Topic 605. Hosted Services- Business Revenue Hosted Services Business revenue is reported at the amount that reflects the ultimate consideration expected to be received and primarily consist of fees that provide customers access to LiveEngage, the Company’s enterprise-class, cloud-based platform. The Company has determined such access represents a stand-ready service provided continually throughout the contract term. As such, control and satisfaction of this stand-ready performance obligation is deemed to occur over time. The Company recognizes this revenue over time on a ratable basis over the contract term, beginning on the date that access to the LiveEngage platform is made available to the customer. The passage of time is deemed to be the most faithful depiction of the transfer of control of the services as the customer simultaneously receives and consumes the benefit provided by the Company’s performance. Subscription contracts are generally one year or longer in length, billed, monthly, quarterly or annually in advance. There is no significant variable consideration related to these arrangements. Additionally, for certain of the Company's larger customers, the Company may provide call center labor through an arrangement with one or more of several qualified vendors. For most of these customers, the Company passes the fee it incurs with the labor provider and its fee for the hosted services through to its customers in the form of a fixed fee for each order placed via the Company's online engagement solutions. For these Pay for Performance ("PFP") arrangements in accordance with ASC-606, "Principal Agent Considerations", the Company acts as a principal in a transaction if it controls the specified goods or services before they are transferred to the customer. Professional Services Revenues Professional services revenue primarily consists of fees for deployment and optimization services, as well as training delivered on an on-demand basis which is deemed to represent a distinct stand-ready performance obligation. Professional Services Revenues are reported at the amount that reflects the ultimate consideration the Company expects to receive in exchange for such services. Control for the majority of the Company's Professional Services contracts passes over time to the customer and is recognized ratably over the contracted period, as the passage of time is deemed to be the most faithful depiction of the transfer of control. For certain deployment services, which are not deemed to represent a distinct performance obligation, revenue will be recognized in the same manner as the fee for access to the LiveEngage platform, and as such will be recognized on a straight-line basis over the contract term. For services billed on a fixed price basis, revenue is recognized over time based on the proportion performed using inputs as the measure of progress toward complete satisfaction of the performance obligation. Professional service contracts are generally one year or longer in length, billed, monthly, quarterly or annually in advance. There is no significant variable consideration related to these arrangements. Contracts with Multiple Performance Obligations Some of the Company's contracts with customers contain multiple performance obligations. For these contracts, the Company accounts for individual performance obligations separately if they are distinct. The transaction price is allocated to the separate performance obligations on a relative standalone selling price basis. The Company determines the standalone selling prices based on its overall pricing objectives, taking into consideration market conditions and other factors, including the value of its contracts, the cloud applications sold, and the number and types of users within its contracts. Hosted Services- Consumer Revenue For revenue from the Company's Consumer segment generated from online transactions between Experts and Users, revenue is recognized at an amount net of Expert fees in accordance with ASC 606, “Principal Agent Considerations,” due primarily to the fact that the Expert is the primary obligor. Additionally, the Company performs as an agent without any risk of loss for collection, and is not involved in selecting the Expert or establishing the Expert’s fee. The Company collects a fee from the consumer and retains a portion of the fee, and then remits the balance to the Expert. Revenue from these transactions is recognized at the point in time when the transaction is complete and no significant performance obligations remain. Deferred Revenues The Company records deferred revenues when cash payments are received or due in advance of its performance. The increase in the deferred revenue balance for the nine months ended September 30, 2018 is primarily driven by cash payments received or due in advance of satisfying its performance obligations, partially offset by $31.7 million of revenues recognized that were included in the deferred revenue balance as of December 31, 2017 . The following table presents deferred revenue by revenue source (amounts in thousands): Deferred Revenue As of September 30, 2018 December 31, 2017 Hosted services – Business $ 45,225 $ 27,011 Professional services – Business 10,892 8,552 Total deferred revenue - short term $ 56,117 $ 35,563 Hosted services – Business $ 1,653 $ — Professional services – Business 414 — Total deferred revenue - long term $ 2,067 $ — Disaggregated Revenue The following table presents the Company's revenues disaggregated by revenue source (amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 (1) 2018 2017 (1) Revenue: Hosted services – Business $ 50,046 $ 46,378 $ 145,805 $ 131,798 Hosted services – Consumer 4,876 4,355 14,508 12,985 Professional services 9,291 5,760 23,801 16,703 Total revenue $ 64,213 $ 56,493 $ 184,114 $ 161,486 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method. Revenue by Geographic Location The following table presents the Company’s revenues attributable to domestic and foreign operations for the periods presented (amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 United States $ 37,033 $ 35,519 $ 106,676 $ 101,282 Other Americas (1) 2,402 1,744 6,208 5,684 Total Americas 39,435 37,263 112,884 106,966 EMEA (2) (4) 18,536 14,175 52,974 41,640 APAC (3) 6,242 5,055 18,256 12,880 Total revenue $ 64,213 $ 56,493 $ 184,114 $ 161,486 (1) Canada, Latin America and South America (2) Europe, the Middle East and Africa (“EMEA”) (3) Asia-Pacific (“APAC”) (4) Includes revenues from the United Kingdom of $11.1 million and $10.2 million for the three months ended September 30, 2018 and 2017 , respectively, and $34.7 million and $28.4 million nine months ended September 30, 2018 and 2017 , respectively. Information about Contract Balances Amounts collected in advance of services being provided are accounted for as deferred revenue. Nearly all of the Company's deferred revenue balance is related to Hosted Services- Business Revenue. In some arrangements, the Company allows customers to pay for access to LiveEngage over the term of the software license. The Company refers to these as subscription transactions. Amounts recognized as revenue in excess of amounts billed are recorded as unbilled receivables. Unbilled receivables, anticipated to be invoiced in the next twelve months, are included in accounts receivable on the consolidated balance sheet. The opening and closing balances of the Company's accounts receivable, unbilled receivables, and deferred revenues are as follows (amounts in thousands): Accounts Receivable Unbilled Receivable Deferred Revenue (current) Deferred Revenue (long term) Opening Balance as of December 31, 2017 $ 30,342 $ 7,584 $ 35,563 $ — Increase (decrease), net 10,300 3,501 20,554 2,067 Ending Balance as of September 30, 2018 $ 40,642 $ 11,085 $ 56,117 $ 2,067 As of September 30, 2018 , the Company expects to recognize the long term performance obligations in 2019.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The Company calculates earnings per share (“EPS”) in accordance with the provisions of ASC 260-10 and the guidance of SEC Staff Accounting Bulletin (“SAB”) No. 98. Under ASC 260-10, basic EPS excludes dilution for common stock equivalents and is computed by dividing net income or loss attributable to common shareholders by the weighted average number of common shares outstanding for the period. All options, warrants or other potentially dilutive instruments issued for nominal consideration are required to be included in the calculation of basic and diluted net income attributable to common stockholders. Diluted EPS is calculated using the treasury stock method and reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock and resulted in the issuance of common stock. Diluted net loss per common share for the three and nine months ended September 30, 2018 does not include the effect of 9,168,450 outstanding common stock awards, as the effect of their inclusion is anti-dilutive. Diluted net loss per common share for the three and nine months ended September 30, 2017 does not include the effect of 8,653,000 outstanding common stock awards, as the effect of their inclusion is anti-dilutive. A reconciliation of shares used in calculating basic and diluted net loss per share follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Basic 60,014,246 56,524,990 58,667,289 56,153,428 Effect of assumed exercised options — — — — Diluted 60,014,246 56,524,990 58,667,289 56,153,428

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The Company accounts for its segment information in accordance with the provisions of ASC 280-10, “Segment Reporting.” ASC 280-10 establishes annual and interim reporting standards for operating segments of a company. ASC 280-10 requires disclosures of selected segment-related financial information about products, major customers, and geographic areas based on the Company’s internal accounting methods. The Company is organized into two operating segments for purposes of making operating decisions and assessing performance. The Business segment enables brands to leverage LiveEngage’s sophisticated intelligence engine to connect with consumers through an integrated suite of mobile and online business messaging technologies. The Consumer segment facilitates online transactions between independent service providers (“Experts”) and individual consumers (“Users”) seeking information and knowledge for a fee via mobile and online messaging. Both segments currently generate their revenue primarily in the United States. The chief operating decision maker, who is the chief executive officer, evaluates performance, makes operating decisions, and allocates resources based on the operating income of each segment. The reporting segments follow the same accounting polices used in the preparation of the Company’s condensed consolidated financial statements which are described in the summary of significant accounting policies. The Company allocates cost of revenue, sales and marketing and amortization of purchased intangibles to the segments, but it does not allocate product development expenses, general and administrative expenses, restructuring costs and income tax expense because management does not use this information to measure performance of the operating segments. There are currently no inter-segment sales. Summarized financial information by segment for the three months ended September 30, 2018 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 50,046 $ — $ — $ 50,046 Hosted services – Consumer — 4,876 — 4,876 Professional services 9,291 — — 9,291 Total revenue 59,337 4,876 — 64,213 Cost of revenue 14,695 994 — 15,689 Sales and marketing 24,391 2,357 — 26,748 Amortization of purchased intangibles 424 — — 424 Unallocated corporate expenses — — 26,178 26,178 Operating income (loss) $ 19,827 $ 1,525 $ (26,178 ) $ (4,826 ) Summarized financial information by segment for the three months ended September 30, 2017 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 46,378 $ — $ — $ 46,378 Hosted services – Consumer — 4,355 — 4,355 Professional services 5,760 — — 5,760 Total revenue 52,138 4,355 — 56,493 Cost of revenue 13,681 860 — 14,541 Sales and marketing 19,554 2,049 — 21,603 Amortization of purchased intangibles 470 — — 470 Unallocated corporate expenses — — 20,124 20,124 Operating income (loss) $ 18,433 $ 1,446 $ (20,124 ) $ (245 ) Summarized financial information by segment for the nine months ended September 30, 2018 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 145,805 $ — $ — $ 145,805 Hosted services – Consumer — 14,508 — 14,508 Professional services 23,801 — — 23,801 Total revenue 169,606 14,508 — 184,114 Cost of revenue 42,699 2,980 — 45,679 Sales and marketing 69,453 6,818 — 76,271 Amortization of purchased intangibles 1,272 — — 1,272 Unallocated corporate expenses — — 77,355 77,355 Operating income (loss) $ 56,182 $ 4,710 $ (77,355 ) $ (16,463 ) Summarized financial information by segment for the nine months ended September 30, 2017 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 131,798 $ — $ — $ 131,798 Hosted services – Consumer — 12,985 — 12,985 Professional services 16,703 — — 16,703 Total revenue 148,501 12,985 — 161,486 Cost of revenue 40,794 2,662 — 43,456 Sales and marketing 60,338 6,357 — 66,695 Amortization of purchased intangibles 1,412 — — 1,412 Unallocated corporate expenses — — 61,854 61,854 Operating income (loss) $ 45,957 $ 3,966 $ (61,854 ) $ (11,931 ) Geographic Information The Company is domiciled in the United States and has international operations in Israel, the United Kingdom, Asia-Pacific and Australia, Latin America and Western Europe, particularly France, Germany and the Netherlands. The following table presents the Company’s long-lived assets by geographic region as of the dates presented (amounts in thousands): September 30, December 31, 2018 2017 United States $ 108,016 $ 95,716 Israel 13,490 13,079 Australia 8,744 9,504 Netherlands 7,677 8,363 Other (1) 3,127 3,293 Total long-lived assets $ 141,054 $ 129,955 (1) United Kingdom, Germany, Japan, France and Italy No individual customer accounted for 10% or more of consolidated revenue for any of the periods presented. No individual customer accounted for 10% or more of accounts receivable as of September 30, 2018 and December 31, 2017 .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill The changes in the carrying amount of goodwill for the nine months ended September 30, 2018 are as follows (amounts in thousands): Business Consumer Consolidated Balance as of December 31, 2017 $ 72,507 $ 8,024 $ 80,531 Adjustments to goodwill: Acquisitions 5,010 — 5,010 Foreign exchange adjustment (74 ) — (74 ) Balance as of September 30, 2018 $ 77,443 $ 8,024 $ 85,467 Intangible Assets Intangible assets are summarized as follows (amounts in thousands): As of September 30, 2018 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Amortization Period Amortizing intangible assets: Technology $ 30,640 $ (23,221 ) $ 7,419 5.3 years Customer relationships 15,971 (11,436 ) 4,535 8.0 years Trade names 1,287 (1,287 ) — 2.1 years Non-compete agreements 1,437 (1,437 ) — 2.3 years Patents 1,867 (599 ) 1,268 13.4 years Other 262 (235 ) 27 2.7 years Total $ 51,464 $ (38,215 ) $ 13,249 As of December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Amortization Period Amortizing intangible assets: Technology $ 27,882 $ (22,197 ) $ 5,685 5.3 years Customer relationships 15,978 (10,457 ) 5,521 8.0 years Trade names 1,289 (1,283 ) 6 2.1 years Non-compete agreements 1,439 (1,439 ) — 2.3 years Patents 1,620 (493 ) 1,127 13.1 years Other 262 (235 ) 27 2.7 years Total $ 48,470 $ (36,104 ) $ 12,366 Amortization expense is calculated over the estimated useful life of the asset. Aggregate amortization expense for intangible assets was $0.7 million and $1.1 million for the three months ended September 30, 2018 and 2017 , respectively, and $2.1 million and $4.0 million for the nine months ended September 30, 2018 and 2017 , respectively. For the three and nine months ended September 30, 2018 and 2017 , respectively, a portion of this amortization is included in cost of revenue. Estimated amortization expense for the next five years is as follows (amounts in thousands): Estimated Amortization Expense Remaining 2018 $ 792 2019 2,963 2020 2,775 2021 2,565 2022 2,216 Thereafter 1,938 Total $ 13,249

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment The following table presents the detail of property and equipment for the periods presented (amounts in thousands): September 30, December 31, Computer equipment and software $ 113,463 $ 100,392 Furniture, equipment and building improvements 15,154 13,546 128,617 113,938 Less: accumulated depreciation (88,829 ) (79,233 ) Total $ 39,788 $ 34,705

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities The following table presents the detail of accrued expenses and other current liabilities for the periods presented (amounts in thousands): September 30, December 31, Payroll and other employee related costs $ 16,942 $ 16,431 Professional services and consulting and other vendor fees 12,688 15,674 Unrecognized tax benefits 2,332 4,924 Sales commissions 5,719 5,259 Contingent earn-out (see Note 8) 1,800 — Restructuring (see Note 12) 1,249 2,338 Other 394 3,385 Total $ 41,124 $ 48,011 8. Acquisitions Conversable, Inc. In September 2018, the Company acquired the employees and technology assets of Conversable, Inc. a SaaS based Artificial Intelligence powered conversational platform, headquartered in Austin, Texas, for an aggregated estimated purchase price of $6.6 million . The estimated purchase price consisted of $1.2 million in cash, approximately $3.0 million in shares of common stock of the Company, a potential earn-out consideration of $1.8 million in cash and $0.3 million of common stock of the Company, and $0.3 million of deferred revenue. This transaction was accounted for under the purchase method of accounting and was based upon the estimated fair value of Conversable, Inc.'s net tangible and identifiable intangible assets as of the date of acquisition. The preliminary purchase price allocation resulted in approximately $5.0 million of goodwill and approximately $1.6 million of intangible assets. The goodwill will be deductible for tax purposes. The intangible assets are being amortized over their expected period of benefit. There is a potential earn-out consideration payment to Conversable Inc.'s shareholders for $2.1 million , which is based on achieving certain targeted financial, strategic, and integration objectives. There is another $0.6 million potential earn-out consideration payment to Conversable Inc.'s employees, which is considered compensation and is being expensed over 12 months. Conversable Inc.’s capabilities will accelerate the ongoing expansion of the Company's conversational commerce solutions and enhance the Company’s ability to deliver proactive and personalized content and services when and where the customer needs it, helping consumers find immediate service through messaging. The Company is in the process of finalizing all fair value and asset purchase accounting adjustments. The effect of this acquisition is included in the Company's results from September 27, 2018 to September 30, 2018 and is not material, thus no pro-forma disclosure is provided. BotCentral, Inc. In January 2018, the Company acquired the employees and technology assets of BotCentral, Inc., a Silicon Valley based startup, for an approximate purchase price of $1.0 million in common stock of the Company. The Company incurred an additional $0.2 million related to acquisition costs. This transaction was accounted for as an asset purchase. The aggregate amount of approximately $1.2 million is included in "Intangibles, net" on the Company's September 30, 2018 condensed consolidated balance sheet. While an active participant in the LiveEngage for Bots partner program, the BotCentral team created a number of bot solutions for major brands in banking, insurance, and travel, running on LivePerson's conversational platform. With the team's expertise and knowledge of the LiveEngage platform, the team is bringing valuable insight for LivePerson's customers and partners, and enabling the company to more rapidly optimize its bot deployment capabilities, and grow the ecosystem.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisitions	Acquisitions Conversable, Inc. In September 2018, the Company acquired the employees and technology assets of Conversable, Inc. a SaaS based Artificial Intelligence powered conversational platform, headquartered in Austin, Texas, for an aggregated estimated purchase price of $6.6 million . The estimated purchase price consisted of $1.2 million in cash, approximately $3.0 million in shares of common stock of the Company, a potential earn-out consideration of $1.8 million in cash and $0.3 million of common stock of the Company, and $0.3 million of deferred revenue. This transaction was accounted for under the purchase method of accounting and was based upon the estimated fair value of Conversable, Inc.'s net tangible and identifiable intangible assets as of the date of acquisition. The preliminary purchase price allocation resulted in approximately $5.0 million of goodwill and approximately $1.6 million of intangible assets. The goodwill will be deductible for tax purposes. The intangible assets are being amortized over their expected period of benefit. There is a potential earn-out consideration payment to Conversable Inc.'s shareholders for $2.1 million , which is based on achieving certain targeted financial, strategic, and integration objectives. There is another $0.6 million potential earn-out consideration payment to Conversable Inc.'s employees, which is considered compensation and is being expensed over 12 months. Conversable Inc.’s capabilities will accelerate the ongoing expansion of the Company's conversational commerce solutions and enhance the Company’s ability to deliver proactive and personalized content and services when and where the customer needs it, helping consumers find immediate service through messaging. The Company is in the process of finalizing all fair value and asset purchase accounting adjustments. The effect of this acquisition is included in the Company's results from September 27, 2018 to September 30, 2018 and is not material, thus no pro-forma disclosure is provided. BotCentral, Inc. In January 2018, the Company acquired the employees and technology assets of BotCentral, Inc., a Silicon Valley based startup, for an approximate purchase price of $1.0 million in common stock of the Company. The Company incurred an additional $0.2 million related to acquisition costs. This transaction was accounted for as an asset purchase. The aggregate amount of approximately $1.2 million is included in "Intangibles, net" on the Company's September 30, 2018 condensed consolidated balance sheet. While an active participant in the LiveEngage for Bots partner program, the BotCentral team created a number of bot solutions for major brands in banking, insurance, and travel, running on LivePerson's conversational platform. With the team's expertise and knowledge of the LiveEngage platform, the team is bringing valuable insight for LivePerson's customers and partners, and enabling the company to more rapidly optimize its bot deployment capabilities, and grow the ecosystem.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures its cash equivalents at fair value based on an expected exit price as defined by the authoritative guidance on fair value measurements, which represents the amount that would be received on the sale of an asset or paid to transfer a liability, as the case may be, in an orderly transaction between market participants. As such, fair value may be based on assumptions that market participants would use in pricing an asset or liability. The authoritative guidance on fair value measurements establishes a consistent framework for measuring fair value on either a recurring or nonrecurring basis whereby inputs, used in valuation techniques, are assigned a hierarchical level. The following are the hierarchical levels of inputs to measure fair value: • Level 1: Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2: Inputs reflect: quoted prices for identical assets or liabilities in markets that are not active; quoted prices for similar assets or liabilities in active markets; inputs other than quoted prices that are observable for the assets or liabilities; or inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3: Unobservable inputs reflecting the Company’s assumptions incorporated in valuation techniques used to determine fair value. These assumptions are required to be consistent with market participant assumptions that are reasonably available. Financial Assets and Liabilities The carrying amount of cash, accounts receivable, and accounts payable approximate their fair value due to their short-term nature. The Company ’ s assets and liabilities that are measured at fair value on a recurring basis, by level, within the fair value hierarchy as of September 30, 2018 and December 31, 2017 , are summarized as follows (amounts in thousands). The Company has no restricted cash balance at September 30, 2018 . The Company's restricted cash balance of $1.5 million at December 31, 2017 was not held in a money market account and is not included in the following table. September 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 2,828 $ — $ — $ 2,828 $ 2,806 $ — $ — $ 2,806 Foreign currency derivative contracts — — — — — 65 — 65 Total assets $ 2,828 $ — $ — $ 2,828 $ 2,806 $ 65 $ — $ 2,871 Liabilities: Contingent earn-out $ — $ — $ 1,800 $ 1,800 $ — $ — $ — $ — Foreign currency derivative contracts — — — — — 2 — 2 Total liabilities $ — $ — $ 1,800 $ 1,800 $ — $ 2 $ — $ 2 In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value. Observable or market inputs reflect market data obtained from independent sources, while unobservable inputs reflect the Company’s assumptions based on the best information available. The Company's money market funds are measured at fair value on a recurring basis based on quoted market prices in active markets and are classified as level 1 within the fair value hierarchy. The Company's only liability that is measured at fair value on a recurring basis is the contingent earn-out and is classified as level 3 within the fair value hierarchy. On a nonrecurring basis, the Company uses fair value measures when analyzing asset impairment. Long-lived tangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If it is determined such indicators are present and the review indicates that the assets will not be fully recoverable, based on undiscounted estimated cash flows over the remaining amortization periods, their carrying values are reduced to estimated fair value. The Company uses an income approach and inputs that constitute level 3. During the third quarter of each year, the Company evaluates goodwill for impairment at the reporting unit level. The Company uses qualitative factors in accordance with ASU No. 2011-08 to determine whether it is “more likely than not” that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. This measurement is classified based on level 3 input. The Company recorded a contingent earn-out of $1.8 million in September 2018 in connection with the acquisition of Conversable, Inc. The contingent earn-out is based on achieving certain targeted financial, strategic, and integration objectives. The unobservable inputs considered are probability factors and the time value of money. See Note 8 of the Notes to Condensed Consolidated Financial Statements for a full description of the acquisition. The changes in fair value of the Level 3 liabilities are as follows (amounts in thousands): Contingent Earn-Out September 30, 2018 December 31, 2017 Balance, Beginning of year $ — $ — Conversable, Inc. addition (see Note 8) 1,800 — Cash payment — — Changes in fair value — — Balance, End of year $ 1,800 $ — Derivative Financial Instruments The Company is exposed to foreign exchange risks that in part are managed by using derivative financial instruments. The Company entered into foreign currency forward contracts related to risks associated with foreign operations. The Company does not use derivatives for trading purposes. Derivatives are recorded at their estimated fair values based upon Level 2 inputs. Derivatives designated and effective as cash flow hedges are reported as a component of other comprehensive income and reclassified to earnings in the same periods in which the hedged transactions impact earnings. Gains and losses related to derivatives not meeting the requirements of hedge accounting and the portion of derivatives related to hedge ineffectiveness are recognized in current earnings. As of September 30, 2018 , the Company is not party to any foreign currency forward contracts and does not have any restricted cash balance. At December 31, 2017 , in accordance with the foreign currency forward contracts, the Company was required to pledge cash as collateral security to be maintained at an Israeli bank. The collateral security would remain in control of the bank, to be available in order to satisfy outstanding obligations under the foreign currency forward contracts. Accordingly, the Company had cash at an Israeli bank of approximately $1.5 million at December 31, 2017 , which is recorded as cash held as collateral in current assets. The following summarizes certain information regarding the Company’s outstanding foreign currency derivative contracts related primarily to intercompany receivables and payables for the periods presented (in thousands): As of September 30, 2018 As of December 31, 2017 Notional amount of foreign currency derivative contracts $ — $ 2,866 Fair value of foreign currency derivatives contracts $ — $ 63 The fair value of the Company’s derivative instruments is summarized below (in thousands): Fair Value of Derivative Instruments Balance Sheet Location As of September 30, 2018 As of December 31, 2017 Derivative Assets Derivatives not designated as hedging instruments: Foreign currency derivatives contracts Prepaid expenses and other current assets $ — $ 65 Derivative Liabilities Derivatives not designated as hedging instruments: Foreign currency derivatives contracts Accrued expenses and other liabilities $ — $ 2 The following summarizes certain information regarding the Company’s derivatives that are not designated or are not effective as hedges (in thousands): Gain (losses) on Derivative Instruments Recognized in Statements of Operations Three Months Ended September 30, Nine Months Ended September 30, Location 2018 2017 2018 2017 Foreign currency derivatives contracts Other (income) expense $ — $ (19 ) $ (50 ) $ 194

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Contractual Obligations The Company leases facilities and certain equipment under agreements accounted for as operating leases. These leases generally require the Company to pay all executory costs such as maintenance and insurance. Rental expense for operating leases for the three months ended September 30, 2018 and 2017 was approximately $2.9 million and $2.3 million , respectively. Rental expense for operating leases for the nine months ended September 30, 2018 and 2017 was approximately $7.2 million and $7.3 million , respectively. Employee Benefit Plans The Company has a 401(k) defined contribution plan covering all eligible employees. The Company provides for employer matching contributions equal to 50% of employee contributions, up to the lesser of 5% of eligible compensation or $6,000 . Matching contributions are deposited into the employee’s 401(k) account and are subject to 5 year graded vesting. Salaries and related expenses include $0.4 million and $0.3 million of employer matching contributions for both the three months ended September 30, 2018 and 2017 , respectively. Salaries and related expenses include $1.2 million and $1.1 million of employer matching contributions for the nine months ended September 30, 2018 and 2017 , respectively. Letters of Credit As of September 30, 2018 , the Company has a $1.8 million letter of credit outstanding substantially in favor of a certain landlord for office space. In addition, the Company has a letter of credit totaling $0.1 million as a security deposit for the due performance by the Company of the terms and conditions of a supply contract. There were no draws against these letters of credit during the nine months ended September 30, 2018 .

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholders' Equity	Stockholders ’ Equity Common Stock As of September 30, 2018 , there were 100,000,000 shares of common stock authorized, and 63,201,497 shares issued and outstanding. As of December 31, 2017 , there were 100,000,000 shares of common stock authorized, and 59,663,969 shares issued and outstanding. The par value for common shares is $0.001 . Preferred Stock As of September 30, 2018 and December 31, 2017 , there were 5,000,000 shares of preferred stock authorized, and zero shares issued and outstanding. The par value for preferred shares is $0.001 . Stock Repurchase Program On December 10, 2012, the Company’s Board of Directors approved a stock repurchase program through June 30, 2014. Under the stock repurchase program, the Company is authorized to repurchase shares of its common stock, in the open market or privately negotiated transactions, at times and prices considered appropriate by the Board of Directors depending upon prevailing market conditions and other corporate considerations. On March 13, 2014, the Company’s Board of Directors increased the aggregate purchase price of the stock repurchase program from $30.0 million to $40.0 million . On July 23, 2014, the Company’s Board of Directors increased the aggregate purchase price of the stock repurchase program from $40.0 million to $50.0 million . On February 16, 2016, the Company's Board of Directors increased the aggregate purchase price of the total stock repurchase program by an additional $14.0 million . On November 21, 2016, the Company's Board of Directors increased the aggregate purchase price of the stock repurchase program from $64.0 million to $74.0 million and extended the expiration date of the program out to December 31, 2017. On May 7, 2018, the Company's Board of Directors ratified the extension to December 31, 2018 of the repurchase program, effective as of January 1, 2018. There were 93,750 shares repurchased under this program during the nine months ended September 30, 2018 , which were recorded in treasury stock at par on the condensed consolidated balance sheets as of September 30, 2018 . As of September 30, 2018 , approximately $17.1 million remained available for purchase under the program. Stock-Based Compensation The Company follows FASB ASC 718-10, “Stock Compensation,” which addresses the accounting for transactions in which an entity exchanges its equity instruments for goods or services, with a primary focus on transactions in which an entity obtains employee services in share-based payment transactions. ASC 718-10 requires measurement of the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. Incremental compensation costs arising from subsequent modifications of awards after the grant date must be recognized. The per share weighted average fair value of stock options granted was $10.13 and $5.02 during the three months ended September 30, 2018 and 2017, respectively, and $6.62 and $3.63 during the nine months ended September 30, 2018 and 2017, respectively. The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Dividend yield 0.0% 0.0% 0.0% 0.0% Risk-free interest rate 2.8% - 2.9% 1.8% 2.5% - 2.9% 1.7% - 1.9% Expected life (in years) 5 5 5 5 Historical volatility 43.5% - 43.7% 47.3% 43.5% - 48.4% 46.6% - 47.6% A description of the methods used in the significant assumptions used to estimate the fair value of stock-based compensation awards follows: Dividend yield – The Company uses 0% as it has never issued dividends and does not anticipate issuing dividends in the near term. Risk-free interest rate – The Company uses the market yield on U.S. Treasury securities at five years with constant maturity, representing the current expected life of stock options in years. Expected life – The Company uses historical data to estimate the expected life of a stock option. Historical volatility – The Company uses a trailing five year from grant date to determine volatility. Stock Option Plans During 1998, the Company established the Stock Option and Restricted Stock Purchase Plan (the “1998 Plan”). Under the 1998 Plan, the Board of Directors could issue incentive stock options or nonqualified stock options or other equity-based awards in respect of up to 5,850,000 shares of common stock. The 2000 Stock Incentive Plan (the “2000 Plan”) succeeded the 1998 Plan. Under the 2000 Plan, the options which had been outstanding under the 1998 Plan were incorporated in the 2000 Plan increasing the number of shares available for issuance under the 2000 Plan by approximately 4,150,000 , thereby reserving for issuance 10,000,000 shares of common stock in the aggregate. The Company established the 2009 Stock Incentive Plan (as amended and restated, the “2009 Plan”) as a successor to the 2000 Plan. Under the 2009 Plan, the options which had been outstanding under the 2000 Plan were incorporated into the 2009 Plan and the Company increased the number of shares available for issuance under the plan by 6,000,000 . The Company amended the 2009 Plan (the “Amended 2009 Plan”) effective June 7, 2012. The Amended 2009 Plan increased the number of shares authorized for issuance under the plan by an additional 4,250,000 . On June 2, 2017, the Company's Board of Directors amended and restated the Amended 2009 Plan effective April 30, 2017. The amended and restated plan increased the number of shares authorized for issuance under the plan by an additional 4,000,000 , thereby reserving for issuance 27,817,744 shares of common stock in the aggregate. Options to acquire common stock granted thereunder have 10 -year terms. As of September 30, 2018 , approximately 2.4 million shares of common stock were reserved for issuance under the Amended 2009 Plan (taking into account all option exercises and other equity award settlements through September 30, 2018 ). Employee Stock Purchase Plan In June 2010, the Company’s stockholders approved the 2010 Employee Stock Purchase Plan with 1,000,000 shares of common stock initially reserved for issuance. Subject to stockholder approval, which was obtained on June 2, 2017, the Company's Board of Directors amended and restated the 2010 Employee Stock Purchase Plan effective April 30, 2017. The amended and restated plan increased the number of shares authorized for issuance under the plan by an additional 1,000,000 , thereby reserving for issuance 2,000,000 shares of common stock in the aggregate. As of September 30, 2018 , approximately 0.9 million shares of common stock were reserved for issuance under the Employee Stock Purchase Plan (taking into account all share purchases through September 30, 2018 ). Inducement Plan During January 2018, the Company established the Inducement Plan (the “2018 Plan”). Under the 2018 Plan, the Board of Directors can issue incentive stock options or nonqualified stock options or other equity-based awards in respect of up to 1,500,000 shares of common stock. On April 25, 2018, the Company's Board of Directors amended and restated the 2018 Plan (the "Amended 2018 Plan"). The Amended 2018 Plan increased the number of shares authorized for issuance under the plan by an additional 500,000 shares, thereby reserving for issuance 2,000,000 shares of common stock in the aggregate. As of September 30, 2018 , approximately 0.2 million shares of common stock were reserved for issuance under the Amended 2018 Plan (taking into account all option exercises and other equity award settlements through September 30, 2018 ). Stock Option Activity A summary of the Company’s stock option activity and weighted average exercise prices follows: Stock Option Activity Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Options (in thousands) Weighted Average Exercise Price Balance outstanding at December 31, 2017 7,959 $ 10.71 Granted 1,952 15.03 Exercised (2,874 ) 10.72 Cancelled or expired (554 ) 9.91 Balance outstanding at September 30, 2018 6,483 $ 12.07 6.91 $ 90,038 Options vested and expected to vest 5,614 $ 11.80 6.55 $ 79,474 Options exercisable at September 30, 2018 3,250 $ 11.00 4.78 $ 48,604 The total fair value of stock options exercised during the nine months ended September 30, 2018 was approximately $15.2 million . As of September 30, 2018 , there was approximately $16.1 million of total unrecognized compensation cost related to nonvested share-based compensation arrangements. That cost is expected to be recognized over a weighted average period of approximately 2.9 years. The following table summarizes information about outstanding and vested stock options as of September 30, 2018 : Options Outstanding Options Exercisable Range of Exercise Prices Number of Shares Outstanding (in thousands) Weighted-Average Remaining Contractual Life (Years) Weighted-Average Exercise Price Number of Shares (in thousands) Weighted-Average Exercise Price $1.79 - $7.60 1,152 6.47 $ 6.92 583 $ 6.43 $7.95 - $9.55 664 6.35 9.21 479 9.21 $9.90 - $10.13 659 5.72 10.09 655 10.09 $10.31 - $11.96 674 7.06 11.27 395 11.01 $12.09 - $12.32 41 2.85 12.29 41 12.29 $12.45 - $12.45 930 9.38 12.45 — — $12.46 - $13.59 759 3.76 13.28 702 13.26 $14.30- $15.96 697 8.72 14.72 61 15.94 $16.05 - $21.75 721 6.92 18.09 334 17.44 $22.35 - $27.25 186 9.82 23.84 — — 6,483 6.91 $ 12.07 3,250 $ 11.00 Restricted Stock Unit Activity A summary of the Company’s restricted stock units (“RSUs”) activity and weighted average exercise prices follows: Restricted Stock Unit Activity Number of Shares (in thousands) Weighted Average Grant Date Fair Value (Per Share) Aggregate Fair Value (in thousands) Balance outstanding at December 31, 2017 1,123 $ 9.03 $ — Awarded 2,130 16.35 — Released (334 ) 9.04 — Forfeited (234 ) 10.42 — Non-vested and outstanding at September 30, 2018 2,685 $ 14.71 $ 69,673 Expected to vest 1,878 $ 13.93 $ 48,741 RSUs granted to employees generally vest over a three to four -year period or upon achievement of certain performance conditions. In accordance with ASU 2017-09, as of September 30, 2018 , total unrecognized compensation cost, adjusted for estimated forfeitures, related to nonvested RSUs was approximately $35.9 million and the weighted-average remaining vesting period was 2.8 years.

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2018
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring The Company’s restructuring costs relate to the wind-down of our legacy platform and severance costs associated with re-prioritizing and reallocating resources to focus on areas showing high growth potential within our Business Segment. The expense associated with this restructuring was approximately $0.7 million during the three months ended September 30, 2018 and approximately $2.8 million and $2.3 million during the nine months ended September 30, 2018 and 2017 , respectively. There were no restructuring costs during the three months ended September 30, 2017 . The Company expects to incur additional restructuring costs through December 31, 2019. The restructuring liability was approximately $1.2 million as of September 30, 2018 and $2.3 million as of December 31, 2017 . It is classified as accrued expenses and other current liabilities on the condensed consolidated balance sheets. The following table presents the detail of the liability for the Company's restructuring charges for the periods presented (amounts in thousands): September 30, 2018 December 31, 2017 Balance, Beginning of the year $ 2,338 $ 2,551 Severance and other associated costs 2,806 648 Cash payments (3,895 ) (2,807 ) Wind down cost legacy platform — 1,946 Balance, End of period $ 1,249 $ 2,338 The following table presents the detail of expenses for the Company's restructuring charges for the three months ended September 30, 2018 (amounts in thousands): September 30, 2018 September 30, 2017 Severance and other associated costs $ 722 $ (31 ) Wind down cost legacy platform — 31 Total restructuring costs $ 722 $ — The following table presents the detail of expenses for the Company's restructuring charges for the nine months ended September 30, 2018 (amounts in thousands): September 30, 2018 September 30, 2017 Severance and other associated costs $ 2,806 $ 399 Wind down cost legacy platform — 1,916 Total restructuring costs $ 2,806 $ 2,315

Legal Matters

Legal Matters	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Legal Matters	Legal Matters The Company previously filed an intellectual property suit against [24]7 Customer, Inc. in the Southern District of New York on March 6, 2014 seeking damages on the grounds that [24]7 reverse engineered and misappropriated the Company's technology to develop competing products and misused the Company's business information. On June 22, 2015, [24]7 Customer, Inc. filed suit against the Company in the Northern District of California alleging patent infringement. On December 7, 2015, [24]7 Customer Inc. filed a second patent infringement suit against the Company, also in the Northern District of California. On March 16, 2017, the New York case was voluntarily transferred and consolidated with the two California cases in the Northern District of California for all pre-trial purposes. Recent rulings by both the Court and the United States Patent Office in the Company’s favor have invalidated the majority of [24]7 patents that were asserted in the patent cases. Trial for the Company’s intellectual property and other claims asserted against [24]7 in the original litigation is currently set for April 1, 2019. The Company believes the claims filed by [24]7 are without merit and intends to defend them vigorously. The Company routinely assesses all of its litigation and threatened litigation as to the probability of ultimately incurring a liability, and records its best estimate of the ultimate loss in situations where the Company assesses the likelihood of loss as probable. From time to time, the Company is involved in or subject to legal, administrative and regulatory proceedings, claims, demands and investigations arising in the ordinary course of business, including direct claims brought by or against the Company with respect to intellectual property, contracts, employment and other matters, as well as claims brought against the Company’s customers for whom the Company has a contractual indemnification obligation. The Company accrues for a liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Significant judgment is required in both the determination of probability and the determination as to whether a loss is reasonably estimable. In addition, in the event the Company determines that a loss is not probable, but is reasonably possible, and it becomes possible to develop what the Company believes to be a reasonable range of possible loss, then the Company will include disclosure related to such matter as appropriate and in compliance with ASC 450. The accruals or estimates, if any, resulting from the foregoing analysis, are reviewed at least quarterly and adjusted to reflect the impact of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular matter. To the extent there is a reasonable possibility that the losses could exceed the amounts already accrued, the Company will, as applicable, adjust the accrual in the period the determination is made, disclose an estimate of the additional loss or range of loss, indicate that the estimate is immaterial with respect to its financial statements as a whole or, if the amount of such adjustment cannot be reasonably estimated, disclose that an estimate cannot be made. From time to time, third parties assert claims against the Company regarding intellectual property rights, privacy issues and other matters arising in the ordinary course of business. Although the Company cannot be certain of the outcome of any litigation or the disposition of any claims, nor the amount of damages and exposure, if any, that the Company could incur, the Company currently believes that the final disposition of all existing matters will not have a material adverse effect on our business, results of operations, financial condition or cash flows. In addition, in the ordinary course of business, the Company is also subject to periodic threats of lawsuits, investigations and claims. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events AdvantageTec Inc. In October 2018, the Company entered into a stock purchase agreement to acquire the outstanding equity interest of AdvantageTec, Inc. (“AdvantageTec”), a leading provider of texting solutions for service departments of automotive dealerships that helps enable conversational commerce across the entire dealership, including variable and fixed operations. The purchase agreement was for total consideration of approximately $16.6 million , which includes approximately $6.0 million in cash, approximately $4.5 million in shares of common stock and approximately $5.7 million of potential earn-out consideration in cash and shares of common stock. The earn-out is contingent upon achieving certain targeted financial, strategic and integration objectives and milestones and is included as part of the purchase price. The acquisition enhances the Company’s messaging platform available for the automotive industry. The transaction will be accounted for under the purchase method of accounting. The Company is in the process of finalizing all fair value and purchase accounting adjustments.

Description of Business and B_2

Description of Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements as of September 30, 2018 and for the three and nine months ended September 30, 2018 and 2017 are unaudited. In the opinion of management, the unaudited condensed consolidated financial statements have been prepared on the same basis as the annual financial statements and reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the consolidated financial position of LivePerson as of September 30, 2018 , and the consolidated results of operations, comprehensive loss and cash flows for the interim periods ended September 30, 2018 and 2017 . The financial data and other information disclosed in these notes to the condensed consolidated financial statements related to these periods are unaudited. The results of operations for any interim period are not necessarily indicative of the results of operations for any other future interim period or for a full fiscal year. The condensed consolidated balance sheet at December 31, 2017 has been derived from audited consolidated financial statements at that date. Certain information and note disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 15, 2018 .
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of income and expenses during the reporting period. These estimates are based on information available as of the date of the condensed consolidated financial statements; therefore, actual results could differ from management’s estimates.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") No. 2018-15 "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract; Disclosures for Implementation Costs Incurred for Internal-Use Software and Cloud Computing Arrangements". This standard aligns the accounting for implementation costs incurred in a hosting arrangement that is a service contract with the accounting for implementation costs incurred to develop or obtain internal-use software under Accounting Standards Codification ("ASC") 350-40, in order to determine which costs to capitalize and recognize as an asset. ASU 2018-15 is effective for annual reporting periods, and interim periods within those years, beginning after December 15, 2019, and can be applied either prospectively to implementation costs incurred after the date of adoption or retrospectively to all arrangements. The Company is currently in the process of evaluating the impact of the adoption of ASU 2018-230 on its consolidated financial statements. In June 2018, the FASB issued ASU No. 2018-07 "Compensation —Stock Compensation (Topic 718) —Improvements to Nonemployee Share-Based Payment Accounting" ("ASU 2018-07"). This new standard expands the scope of Topic 718, Compensation—Stock Compensation (which currently only includes share-based payments to employees) to include share-based payments issued to non-employees for goods or services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. ASU 2018-07 is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company is currently evaluating the impact of this updated standard, but does not believe this update will have a significant impact on its consolidated financial statements. In March 2018, the FASB issued ASU No. 2018-05 "Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118" ("ASU 2018-05"). This new standard adds SEC paragraphs pursuant to the SEC Staff Accounting Bulletin No. 118, which expresses the view of the staff regarding application of Topic 740, Income Taxes, in the reporting period that includes December 22, 2017, the date on which the Tax Cuts and Jobs Act (H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018) was signed into law. ASU 2018-05 is effective upon inclusion in the FASB Codification. The Company evaluated the impact of this updated standard and determined that the tax on unremitted earnings is zero due to the overall accumulated deficit in earnings and profits. In February 2018, the FASB issued ASU No. 2018-02 "Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU 2018-02"). This new standard allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017. The amendments in ASU 2018-02 affects any entity that is required to apply the provisions of Topic 220 and has items of other comprehensive income for which the related tax effects are presented in other comprehensive income as required by GAAP. ASU 2018-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, for public companies. Early adoption is permitted in any interim period or fiscal years before the effective date of the standard. The Company does not expect the adoption of ASU 2018-02 to have a material effect on its financial position, results of operations or cash flows. In August 2017, the FASB issued ASU No. 2017-12 "Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities" ("ASU 2017-12"). This new standard refines and expands hedge accounting for both financial (e.g., interest rate) and commodity risks. Its provisions create more transparency around how economic results are presented, both on the face of the financial statements and in the footnotes, for investors and analysts. ASU 2017-12 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, for public companies. Early adoption is permitted in any interim period or fiscal years before the effective date of the standard. The Company does not expect the adoption of ASU 2017-12 to have a material effect on its financial position, results of operations or cash flows. In January 2017, FASB issued ASU No. 2017-04, "Intangibles —Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment" (“ASU 2017-04”). This update addresses concerns over the cost and complexity of the two-step goodwill impairment test. The amendments in this update remove the second step of the test. An entity will apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. ASU 2017-04 is effective for financial statements issued for annual periods beginning after December 15, 2019, and interim periods within those annual periods. The Company does not expect the adoption of ASU 2017-04 to have a material effect on its financial position, results of operations or cash flows. In February 2016, the FASB issued ASU No. 2016-02, “Leases” (“ASU 2016-02”). ASU 2016-02 requires lessees to recognize the following for all leases (with the exception of short-term leases) at the commencement date: a lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under the new guidance, lessor accounting is largely unchanged. The new lease guidance also simplified the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. Lessees will no longer be provided with a source of off-balance sheet financing. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) may apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. Lessees and lessors may not apply a full retrospective transition approach. The Company is currently evaluating adopting the standard using the modified transition approach or the transition option available where the Company would recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. ASU 2016-02 is effective for financial statements issued for annual periods beginning after December 15, 2018. The Company is currently assessing the provisions of this guidance and evaluating the timing and impact the guidance will have on its consolidated financial statements and related disclosures. The Company is also in the process of aggregating lease documentation for review. The adoption of this ASU primarily impacts the balance sheet through the recognition of a right-of-use asset and a lease liability for all leases with terms in excess of twelve months. This guidance is effective January 1, 2019 using a modified retrospective transition approach with early adoption permitted. Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("Topic 606"). Topic 606 supersedes the revenue recognition requirements in ASC Topic 605, "Revenue Recognition" ("Topic 605"), and requires the recognition of revenue when promised goods or services are transferred to customers in an amount that reflects the considerations to which the entity expects to be entitled to in exchange for those goods or services. Topic 606 also includes Subtopic 340-40, "Other Assets and Deferred Costs - Contracts with Customers", which requires the deferral of incremental costs of obtaining a contract with a customer. Collectively, the Company refers to Topic 606 and Subtopic 340-40 as the "new standard." The Company adopted the requirements of the new standard as of January 1, 2018, utilizing the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. Results for the reporting periods beginning after January 1, 2018 are presented under the new standard, while prior period amounts are not adjusted and continue to be reported in accordance with its historic accounting under Topic 605. The impact of adopting the new standard as of January 1, 2018 on revenues was not material. The primary impact of adopting the new standard relates to the deferral of incremental commission costs of obtaining subscription contracts. The Company recorded an addition to opening retained earnings of $0.7 million as of January 1, 2018 due to the impact of adopting the new standard, with the impact related to the deferral of incremental commission costs. Under Topic 605, the Company deferred only direct and incremental commission costs to obtain a contract and amortized those costs on a straight-line basis over the term of the related subscription contract, which was generally one year. Under the new standard, the Company defers all incremental commission costs to obtain the contract. The prepaid commission balance as of September 30, 2018 is $10.9 million . The Company amortizes these costs over the related period of benefit using the customer expected life that the Company determined to be three to five years which is consistent with the transfer to the customer of the services to which the asset relates.
Revenue Recognition	Revenue Recognition The majority of the Company’s revenue is generated from monthly service revenues and related professional services from the sale of the LivePerson services. Revenues are recognized when control of these services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those services. The Company determines revenue recognition through the following steps: • Identification of the contract, or contracts, with a customer; • Identification of the performance obligations in the contract; • Determination of the transaction price; • Allocation of the transaction price to the performance obligations in the contract; and • Recognition of revenue when, or as, the Company satisfies a performance obligation. Total revenue of $64.2 million and $184.1 million recognized during the three months and nine months ended September 30, 2018 , respectively, under Topic 606, was not materially different from what would have been recognized under Topic 605. Hosted Services- Business Revenue Hosted Services Business revenue is reported at the amount that reflects the ultimate consideration expected to be received and primarily consist of fees that provide customers access to LiveEngage, the Company’s enterprise-class, cloud-based platform. The Company has determined such access represents a stand-ready service provided continually throughout the contract term. As such, control and satisfaction of this stand-ready performance obligation is deemed to occur over time. The Company recognizes this revenue over time on a ratable basis over the contract term, beginning on the date that access to the LiveEngage platform is made available to the customer. The passage of time is deemed to be the most faithful depiction of the transfer of control of the services as the customer simultaneously receives and consumes the benefit provided by the Company’s performance. Subscription contracts are generally one year or longer in length, billed, monthly, quarterly or annually in advance. There is no significant variable consideration related to these arrangements. Additionally, for certain of the Company's larger customers, the Company may provide call center labor through an arrangement with one or more of several qualified vendors. For most of these customers, the Company passes the fee it incurs with the labor provider and its fee for the hosted services through to its customers in the form of a fixed fee for each order placed via the Company's online engagement solutions. For these Pay for Performance ("PFP") arrangements in accordance with ASC-606, "Principal Agent Considerations", the Company acts as a principal in a transaction if it controls the specified goods or services before they are transferred to the customer. Professional Services Revenues Professional services revenue primarily consists of fees for deployment and optimization services, as well as training delivered on an on-demand basis which is deemed to represent a distinct stand-ready performance obligation. Professional Services Revenues are reported at the amount that reflects the ultimate consideration the Company expects to receive in exchange for such services. Control for the majority of the Company's Professional Services contracts passes over time to the customer and is recognized ratably over the contracted period, as the passage of time is deemed to be the most faithful depiction of the transfer of control. For certain deployment services, which are not deemed to represent a distinct performance obligation, revenue will be recognized in the same manner as the fee for access to the LiveEngage platform, and as such will be recognized on a straight-line basis over the contract term. For services billed on a fixed price basis, revenue is recognized over time based on the proportion performed using inputs as the measure of progress toward complete satisfaction of the performance obligation. Professional service contracts are generally one year or longer in length, billed, monthly, quarterly or annually in advance. There is no significant variable consideration related to these arrangements. Contracts with Multiple Performance Obligations Some of the Company's contracts with customers contain multiple performance obligations. For these contracts, the Company accounts for individual performance obligations separately if they are distinct. The transaction price is allocated to the separate performance obligations on a relative standalone selling price basis. The Company determines the standalone selling prices based on its overall pricing objectives, taking into consideration market conditions and other factors, including the value of its contracts, the cloud applications sold, and the number and types of users within its contracts. Hosted Services- Consumer Revenue For revenue from the Company's Consumer segment generated from online transactions between Experts and Users, revenue is recognized at an amount net of Expert fees in accordance with ASC 606, “Principal Agent Considerations,” due primarily to the fact that the Expert is the primary obligor. Additionally, the Company performs as an agent without any risk of loss for collection, and is not involved in selecting the Expert or establishing the Expert’s fee. The Company collects a fee from the consumer and retains a portion of the fee, and then remits the balance to the Expert. Revenue from these transactions is recognized at the point in time when the transaction is complete and no significant performance obligations remain. Deferred Revenues The Company records deferred revenues when cash payments are received or due in advance of its performance. The increase in the deferred revenue balance for the nine months ended September 30, 2018 is primarily driven by cash payments received or due in advance of satisfying its performance obligations, partially offset by $31.7 million of revenues recognized that were included in the deferred revenue balance as of December 31, 2017 . The following table presents deferred revenue by revenue source (amounts in thousands): Deferred Revenue As of September 30, 2018 December 31, 2017 Hosted services – Business $ 45,225 $ 27,011 Professional services – Business 10,892 8,552 Total deferred revenue - short term $ 56,117 $ 35,563 Hosted services – Business $ 1,653 $ — Professional services – Business 414 — Total deferred revenue - long term $ 2,067 $ — Disaggregated Revenue The following table presents the Company's revenues disaggregated by revenue source (amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 (1) 2018 2017 (1) Revenue: Hosted services – Business $ 50,046 $ 46,378 $ 145,805 $ 131,798 Hosted services – Consumer 4,876 4,355 14,508 12,985 Professional services 9,291 5,760 23,801 16,703 Total revenue $ 64,213 $ 56,493 $ 184,114 $ 161,486 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method. Revenue by Geographic Location The following table presents the Company’s revenues attributable to domestic and foreign operations for the periods presented (amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 United States $ 37,033 $ 35,519 $ 106,676 $ 101,282 Other Americas (1) 2,402 1,744 6,208 5,684 Total Americas 39,435 37,263 112,884 106,966 EMEA (2) (4) 18,536 14,175 52,974 41,640 APAC (3) 6,242 5,055 18,256 12,880 Total revenue $ 64,213 $ 56,493 $ 184,114 $ 161,486 (1) Canada, Latin America and South America (2) Europe, the Middle East and Africa (“EMEA”) (3) Asia-Pacific (“APAC”) (4) Includes revenues from the United Kingdom of $11.1 million and $10.2 million for the three months ended September 30, 2018 and 2017 , respectively, and $34.7 million and $28.4 million nine months ended September 30, 2018 and 2017 , respectively. Information about Contract Balances Amounts collected in advance of services being provided are accounted for as deferred revenue. Nearly all of the Company's deferred revenue balance is related to Hosted Services- Business Revenue. In some arrangements, the Company allows customers to pay for access to LiveEngage over the term of the software license. The Company refers to these as subscription transactions. Amounts recognized as revenue in excess of amounts billed are recorded as unbilled receivables. Unbilled receivables, anticipated to be invoiced in the next twelve months, are included in accounts receivable on the consolidated balance sheet. The opening and closing balances of the Company's accounts receivable, unbilled receivables, and deferred revenues are as follows (amounts in thousands): Accounts Receivable Unbilled Receivable Deferred Revenue (current) Deferred Revenue (long term) Opening Balance as of December 31, 2017 $ 30,342 $ 7,584 $ 35,563 $ — Increase (decrease), net 10,300 3,501 20,554 2,067 Ending Balance as of September 30, 2018 $ 40,642 $ 11,085 $ 56,117 $ 2,067 As of September 30, 2018 , the Company expects to recognize the long term performance obligations in 2019.
Net Loss Per Share	Net Loss Per Share The Company calculates earnings per share (“EPS”) in accordance with the provisions of ASC 260-10 and the guidance of SEC Staff Accounting Bulletin (“SAB”) No. 98. Under ASC 260-10, basic EPS excludes dilution for common stock equivalents and is computed by dividing net income or loss attributable to common shareholders by the weighted average number of common shares outstanding for the period. All options, warrants or other potentially dilutive instruments issued for nominal consideration are required to be included in the calculation of basic and diluted net income attributable to common stockholders. Diluted EPS is calculated using the treasury stock method and reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock and resulted in the issuance of common stock.
Segment Information	Segment Information The Company accounts for its segment information in accordance with the provisions of ASC 280-10, “Segment Reporting.” ASC 280-10 establishes annual and interim reporting standards for operating segments of a company. ASC 280-10 requires disclosures of selected segment-related financial information about products, major customers, and geographic areas based on the Company’s internal accounting methods. The Company is organized into two operating segments for purposes of making operating decisions and assessing performance. The Business segment enables brands to leverage LiveEngage’s sophisticated intelligence engine to connect with consumers through an integrated suite of mobile and online business messaging technologies. The Consumer segment facilitates online transactions between independent service providers (“Experts”) and individual consumers (“Users”) seeking information and knowledge for a fee via mobile and online messaging. Both segments currently generate their revenue primarily in the United States. The chief operating decision maker, who is the chief executive officer, evaluates performance, makes operating decisions, and allocates resources based on the operating income of each segment. The reporting segments follow the same accounting polices used in the preparation of the Company’s condensed consolidated financial statements which are described in the summary of significant accounting policies. The Company allocates cost of revenue, sales and marketing and amortization of purchased intangibles to the segments, but it does not allocate product development expenses, general and administrative expenses, restructuring costs and income tax expense because management does not use this information to measure performance of the operating segments. There are currently no inter-segment sales.
Goodwill and Intangible Assets	Amortization expense is calculated over the estimated useful life of the asset.
Stock-Based Compensation	Stock-Based Compensation The Company follows FASB ASC 718-10, “Stock Compensation,” which addresses the accounting for transactions in which an entity exchanges its equity instruments for goods or services, with a primary focus on transactions in which an entity obtains employee services in share-based payment transactions. ASC 718-10 requires measurement of the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. Incremental compensation costs arising from subsequent modifications of awards after the grant date must be recognized.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Deferred Revenues and Contract Balances	The following table presents deferred revenue by revenue source (amounts in thousands): Deferred Revenue As of September 30, 2018 December 31, 2017 Hosted services – Business $ 45,225 $ 27,011 Professional services – Business 10,892 8,552 Total deferred revenue - short term $ 56,117 $ 35,563 Hosted services – Business $ 1,653 $ — Professional services – Business 414 — Total deferred revenue - long term $ 2,067 $ — The opening and closing balances of the Company's accounts receivable, unbilled receivables, and deferred revenues are as follows (amounts in thousands): Accounts Receivable Unbilled Receivable Deferred Revenue (current) Deferred Revenue (long term) Opening Balance as of December 31, 2017 $ 30,342 $ 7,584 $ 35,563 $ — Increase (decrease), net 10,300 3,501 20,554 2,067 Ending Balance as of September 30, 2018 $ 40,642 $ 11,085 $ 56,117 $ 2,067 As of September 30, 2018 , the Company expects to recognize the long term performance obligations in 2019.
Schedule of Disaggregation of Revenue	The following table presents the Company's revenues disaggregated by revenue source (amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 (1) 2018 2017 (1) Revenue: Hosted services – Business $ 50,046 $ 46,378 $ 145,805 $ 131,798 Hosted services – Consumer 4,876 4,355 14,508 12,985 Professional services 9,291 5,760 23,801 16,703 Total revenue $ 64,213 $ 56,493 $ 184,114 $ 161,486 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method.
Schedule of Revenue by Geographic Region	The following table presents the Company’s revenues attributable to domestic and foreign operations for the periods presented (amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 United States $ 37,033 $ 35,519 $ 106,676 $ 101,282 Other Americas (1) 2,402 1,744 6,208 5,684 Total Americas 39,435 37,263 112,884 106,966 EMEA (2) (4) 18,536 14,175 52,974 41,640 APAC (3) 6,242 5,055 18,256 12,880 Total revenue $ 64,213 $ 56,493 $ 184,114 $ 161,486 (1) Canada, Latin America and South America (2) Europe, the Middle East and Africa (“EMEA”) (3) Asia-Pacific (“APAC”) (4) Includes revenues from the United Kingdom of $11.1 million and $10.2 million for the three months ended September 30, 2018 and 2017 , respectively, and $34.7 million and $28.4 million nine months ended September 30, 2018 and 2017 , respectively.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Reconciliation of Shares Used in Calculating Basic and Diluted Earnings Per Share	A reconciliation of shares used in calculating basic and diluted net loss per share follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Basic 60,014,246 56,524,990 58,667,289 56,153,428 Effect of assumed exercised options — — — — Diluted 60,014,246 56,524,990 58,667,289 56,153,428

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Summary of Financial Information by Segment	Summarized financial information by segment for the three months ended September 30, 2018 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 50,046 $ — $ — $ 50,046 Hosted services – Consumer — 4,876 — 4,876 Professional services 9,291 — — 9,291 Total revenue 59,337 4,876 — 64,213 Cost of revenue 14,695 994 — 15,689 Sales and marketing 24,391 2,357 — 26,748 Amortization of purchased intangibles 424 — — 424 Unallocated corporate expenses — — 26,178 26,178 Operating income (loss) $ 19,827 $ 1,525 $ (26,178 ) $ (4,826 ) Summarized financial information by segment for the three months ended September 30, 2017 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 46,378 $ — $ — $ 46,378 Hosted services – Consumer — 4,355 — 4,355 Professional services 5,760 — — 5,760 Total revenue 52,138 4,355 — 56,493 Cost of revenue 13,681 860 — 14,541 Sales and marketing 19,554 2,049 — 21,603 Amortization of purchased intangibles 470 — — 470 Unallocated corporate expenses — — 20,124 20,124 Operating income (loss) $ 18,433 $ 1,446 $ (20,124 ) $ (245 ) Summarized financial information by segment for the nine months ended September 30, 2018 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 145,805 $ — $ — $ 145,805 Hosted services – Consumer — 14,508 — 14,508 Professional services 23,801 — — 23,801 Total revenue 169,606 14,508 — 184,114 Cost of revenue 42,699 2,980 — 45,679 Sales and marketing 69,453 6,818 — 76,271 Amortization of purchased intangibles 1,272 — — 1,272 Unallocated corporate expenses — — 77,355 77,355 Operating income (loss) $ 56,182 $ 4,710 $ (77,355 ) $ (16,463 ) Summarized financial information by segment for the nine months ended September 30, 2017 , based on the Company’s internal financial reporting system utilized by the Company’s chief operating decision maker, follows (amounts in thousands): Business Consumer Corporate Consolidated Revenue: Hosted services – Business $ 131,798 $ — $ — $ 131,798 Hosted services – Consumer — 12,985 — 12,985 Professional services 16,703 — — 16,703 Total revenue 148,501 12,985 — 161,486 Cost of revenue 40,794 2,662 — 43,456 Sales and marketing 60,338 6,357 — 66,695 Amortization of purchased intangibles 1,412 — — 1,412 Unallocated corporate expenses — — 61,854 61,854 Operating income (loss) $ 45,957 $ 3,966 $ (61,854 ) $ (11,931 )
Long-Lived Assets by Geographic Region	The following table presents the Company’s long-lived assets by geographic region as of the dates presented (amounts in thousands): September 30, December 31, 2018 2017 United States $ 108,016 $ 95,716 Israel 13,490 13,079 Australia 8,744 9,504 Netherlands 7,677 8,363 Other (1) 3,127 3,293 Total long-lived assets $ 141,054 $ 129,955 (1) United Kingdom, Germany, Japan, France and Italy

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amount of goodwill for the nine months ended September 30, 2018 are as follows (amounts in thousands): Business Consumer Consolidated Balance as of December 31, 2017 $ 72,507 $ 8,024 $ 80,531 Adjustments to goodwill: Acquisitions 5,010 — 5,010 Foreign exchange adjustment (74 ) — (74 ) Balance as of September 30, 2018 $ 77,443 $ 8,024 $ 85,467
Summary of Intangible Assets	Intangible assets are summarized as follows (amounts in thousands): As of September 30, 2018 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Amortization Period Amortizing intangible assets: Technology $ 30,640 $ (23,221 ) $ 7,419 5.3 years Customer relationships 15,971 (11,436 ) 4,535 8.0 years Trade names 1,287 (1,287 ) — 2.1 years Non-compete agreements 1,437 (1,437 ) — 2.3 years Patents 1,867 (599 ) 1,268 13.4 years Other 262 (235 ) 27 2.7 years Total $ 51,464 $ (38,215 ) $ 13,249 As of December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Amortization Period Amortizing intangible assets: Technology $ 27,882 $ (22,197 ) $ 5,685 5.3 years Customer relationships 15,978 (10,457 ) 5,521 8.0 years Trade names 1,289 (1,283 ) 6 2.1 years Non-compete agreements 1,439 (1,439 ) — 2.3 years Patents 1,620 (493 ) 1,127 13.1 years Other 262 (235 ) 27 2.7 years Total $ 48,470 $ (36,104 ) $ 12,366
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Estimated amortization expense for the next five years is as follows (amounts in thousands): Estimated Amortization Expense Remaining 2018 $ 792 2019 2,963 2020 2,775 2021 2,565 2022 2,216 Thereafter 1,938 Total $ 13,249

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	The following table presents the detail of property and equipment for the periods presented (amounts in thousands): September 30, December 31, Computer equipment and software $ 113,463 $ 100,392 Furniture, equipment and building improvements 15,154 13,546 128,617 113,938 Less: accumulated depreciation (88,829 ) (79,233 ) Total $ 39,788 $ 34,705

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	The following table presents the detail of accrued expenses and other current liabilities for the periods presented (amounts in thousands): September 30, December 31, Payroll and other employee related costs $ 16,942 $ 16,431 Professional services and consulting and other vendor fees 12,688 15,674 Unrecognized tax benefits 2,332 4,924 Sales commissions 5,719 5,259 Contingent earn-out (see Note 8) 1,800 — Restructuring (see Note 12) 1,249 2,338 Other 394 3,385 Total $ 41,124 $ 48,011

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The carrying amount of cash, accounts receivable, and accounts payable approximate their fair value due to their short-term nature. The Company ’ s assets and liabilities that are measured at fair value on a recurring basis, by level, within the fair value hierarchy as of September 30, 2018 and December 31, 2017 , are summarized as follows (amounts in thousands). The Company has no restricted cash balance at September 30, 2018 . The Company's restricted cash balance of $1.5 million at December 31, 2017 was not held in a money market account and is not included in the following table. September 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 2,828 $ — $ — $ 2,828 $ 2,806 $ — $ — $ 2,806 Foreign currency derivative contracts — — — — — 65 — 65 Total assets $ 2,828 $ — $ — $ 2,828 $ 2,806 $ 65 $ — $ 2,871 Liabilities: Contingent earn-out $ — $ — $ 1,800 $ 1,800 $ — $ — $ — $ — Foreign currency derivative contracts — — — — — 2 — 2 Total liabilities $ — $ — $ 1,800 $ 1,800 $ — $ 2 $ — $ 2
Schedule of Changes in Fair Value of Level 3 Liabilities	The changes in fair value of the Level 3 liabilities are as follows (amounts in thousands): Contingent Earn-Out September 30, 2018 December 31, 2017 Balance, Beginning of year $ — $ — Conversable, Inc. addition (see Note 8) 1,800 — Cash payment — — Changes in fair value — — Balance, End of year $ 1,800 $ —
Schedule of Derivative Instruments	The following summarizes certain information regarding the Company’s outstanding foreign currency derivative contracts related primarily to intercompany receivables and payables for the periods presented (in thousands): As of September 30, 2018 As of December 31, 2017 Notional amount of foreign currency derivative contracts $ — $ 2,866 Fair value of foreign currency derivatives contracts $ — $ 63
Schedule of Derivative Liabilities at Fair Value	The fair value of the Company’s derivative instruments is summarized below (in thousands): Fair Value of Derivative Instruments Balance Sheet Location As of September 30, 2018 As of December 31, 2017 Derivative Assets Derivatives not designated as hedging instruments: Foreign currency derivatives contracts Prepaid expenses and other current assets $ — $ 65 Derivative Liabilities Derivatives not designated as hedging instruments: Foreign currency derivatives contracts Accrued expenses and other liabilities $ — $ 2
Gain (Losses) on Derivative Instruments Recognized in Income Statement	The following summarizes certain information regarding the Company’s derivatives that are not designated or are not effective as hedges (in thousands): Gain (losses) on Derivative Instruments Recognized in Statements of Operations Three Months Ended September 30, Nine Months Ended September 30, Location 2018 2017 2018 2017 Foreign currency derivatives contracts Other (income) expense $ — $ (19 ) $ (50 ) $ 194

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted Average Assumptions of Fair Value Options Using Black-Scholes Option-Pricing Model	The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Dividend yield 0.0% 0.0% 0.0% 0.0% Risk-free interest rate 2.8% - 2.9% 1.8% 2.5% - 2.9% 1.7% - 1.9% Expected life (in years) 5 5 5 5 Historical volatility 43.5% - 43.7% 47.3% 43.5% - 48.4% 46.6% - 47.6%
Summary of Stock Option Activity and Weighted Average Exercise Prices	A summary of the Company’s stock option activity and weighted average exercise prices follows: Stock Option Activity Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Options (in thousands) Weighted Average Exercise Price Balance outstanding at December 31, 2017 7,959 $ 10.71 Granted 1,952 15.03 Exercised (2,874 ) 10.72 Cancelled or expired (554 ) 9.91 Balance outstanding at September 30, 2018 6,483 $ 12.07 6.91 $ 90,038 Options vested and expected to vest 5,614 $ 11.80 6.55 $ 79,474 Options exercisable at September 30, 2018 3,250 $ 11.00 4.78 $ 48,604
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range	The following table summarizes information about outstanding and vested stock options as of September 30, 2018 : Options Outstanding Options Exercisable Range of Exercise Prices Number of Shares Outstanding (in thousands) Weighted-Average Remaining Contractual Life (Years) Weighted-Average Exercise Price Number of Shares (in thousands) Weighted-Average Exercise Price $1.79 - $7.60 1,152 6.47 $ 6.92 583 $ 6.43 $7.95 - $9.55 664 6.35 9.21 479 9.21 $9.90 - $10.13 659 5.72 10.09 655 10.09 $10.31 - $11.96 674 7.06 11.27 395 11.01 $12.09 - $12.32 41 2.85 12.29 41 12.29 $12.45 - $12.45 930 9.38 12.45 — — $12.46 - $13.59 759 3.76 13.28 702 13.26 $14.30- $15.96 697 8.72 14.72 61 15.94 $16.05 - $21.75 721 6.92 18.09 334 17.44 $22.35 - $27.25 186 9.82 23.84 — — 6,483 6.91 $ 12.07 3,250 $ 11.00
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity	A summary of the Company’s restricted stock units (“RSUs”) activity and weighted average exercise prices follows: Restricted Stock Unit Activity Number of Shares (in thousands) Weighted Average Grant Date Fair Value (Per Share) Aggregate Fair Value (in thousands) Balance outstanding at December 31, 2017 1,123 $ 9.03 $ — Awarded 2,130 16.35 — Released (334 ) 9.04 — Forfeited (234 ) 10.42 — Non-vested and outstanding at September 30, 2018 2,685 $ 14.71 $ 69,673 Expected to vest 1,878 $ 13.93 $ 48,741

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2018
Restructuring and Related Activities [Abstract]
Schedule of Restructuring and Related Costs	The following table presents the detail of the liability for the Company's restructuring charges for the periods presented (amounts in thousands): September 30, 2018 December 31, 2017 Balance, Beginning of the year $ 2,338 $ 2,551 Severance and other associated costs 2,806 648 Cash payments (3,895 ) (2,807 ) Wind down cost legacy platform — 1,946 Balance, End of period $ 1,249 $ 2,338 The following table presents the detail of expenses for the Company's restructuring charges for the three months ended September 30, 2018 (amounts in thousands): September 30, 2018 September 30, 2017 Severance and other associated costs $ 722 $ (31 ) Wind down cost legacy platform — 31 Total restructuring costs $ 722 $ — The following table presents the detail of expenses for the Company's restructuring charges for the nine months ended September 30, 2018 (amounts in thousands): September 30, 2018 September 30, 2017 Severance and other associated costs $ 2,806 $ 399 Wind down cost legacy platform — 1,916 Total restructuring costs $ 2,806 $ 2,315

Description of Business and B_3

Description of Business and Basis of Presentation (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid commissions	$ 10.9
ASU No. 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings		$ 0.7

Revenue Recognition (Narrative)

Revenue Recognition (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from Contract with Customer [Abstract]
Revenue	$ 64,213	$ 56,493	$ 184,114	$ 161,486
Recognition of deferred revenue			$ 31,700

Revenue Recognition (Deferred R

Revenue Recognition (Deferred Revenue) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total deferred revenue - short term	$ 56,117	$ 35,563
Total deferred revenue - long term	2,067	0
Hosted Services - Business
Disaggregation of Revenue [Line Items]
Total deferred revenue - short term	45,225	27,011
Total deferred revenue - long term	1,653	0
Professional Services
Disaggregation of Revenue [Line Items]
Total deferred revenue - short term	10,892	8,552
Total deferred revenue - long term	$ 414	$ 0

Revenue Recognition (Disaggrega

Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 64,213	$ 56,493	$ 184,114	$ 161,486
Hosted Services - Business
Disaggregation of Revenue [Line Items]
Revenue	50,046	46,378	145,805	131,798
Hosted Services - Consumer
Disaggregation of Revenue [Line Items]
Revenue	4,876	4,355	14,508	12,985
Professional Services
Disaggregation of Revenue [Line Items]
Revenue	$ 9,291	$ 5,760	$ 23,801	$ 16,703

Revenue Recognition (Revenue by

Revenue Recognition (Revenue by Geographic Region) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue		$ 64,213	$ 56,493	$ 184,114	$ 161,486
United States
Disaggregation of Revenue [Line Items]
Revenue		37,033	35,519	106,676	101,282
Other Americas
Disaggregation of Revenue [Line Items]
Revenue	[1]	2,402	1,744	6,208	5,684
Total Americas
Disaggregation of Revenue [Line Items]
Revenue		39,435	37,263	112,884	106,966
EMEA
Disaggregation of Revenue [Line Items]
Revenue	[2],[3]	18,536	14,175	52,974	41,640
APAC
Disaggregation of Revenue [Line Items]
Revenue	[4]	6,242	5,055	18,256	12,880
United Kingdom
Disaggregation of Revenue [Line Items]
Revenue		$ 11,100	$ 10,200	$ 34,700	$ 28,400
[1]	Canada, Latin America and South America
[2]	Europe, the Middle East and Africa (“EMEA”)
[3]	Includes revenues from the United Kingdom of $11.1 million and $10.2 million for the three months ended September 30, 2018 and 2017, respectively, and $34.7 million and $28.4 million nine months ended September 30, 2018 and 2017, respectively.
[4]	Asia-Pacific (“APAC”)

Revenue Recognition (Receivable

Revenue Recognition (Receivables and Deferred Revenue) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Contract Balances [Roll Forward]
Opening balance, Receivable	$ 37,926
Ending balance, Receivable	51,727
Opening balance, Deferred Revenue (current)	35,563
Increase (decrease) in current deferred revenue, net	20,554
Ending balance, Deferred Revenue (current)	56,117
Opening balance, Deferred Revenue (long-term)	0
Increase (decrease) in long-term deferred revenue, net	2,067
Ending balance, Deferred Revenue (long-term)	2,067
Accounts Receivable
Contract Balances [Roll Forward]
Opening balance, Receivable	30,342
Increase (decrease) in accounts receivable, net	10,300
Ending balance, Receivable	40,642
Unbilled Receivable
Contract Balances [Roll Forward]
Opening balance, Receivable	7,584
Increase (decrease) in unbilled receivables, net	3,501
Ending balance, Receivable	11,085
Hosted Services - Business
Contract Balances [Roll Forward]
Opening balance, Deferred Revenue (current)	27,011
Ending balance, Deferred Revenue (current)	45,225
Opening balance, Deferred Revenue (long-term)	0
Ending balance, Deferred Revenue (long-term)	1,653
Professional Services
Contract Balances [Roll Forward]
Opening balance, Deferred Revenue (current)	8,552
Ending balance, Deferred Revenue (current)	10,892
Opening balance, Deferred Revenue (long-term)	0
Ending balance, Deferred Revenue (long-term)	$ 414

Net Loss Per Share (Narrative)

Net Loss Per Share (Narrative) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Anti-dilutive common stock awards not included in earnings per share calculation (in shares)	9,784,690	9,423,000	9,168,450	8,653,000

Net Loss Per Share (Reconciliat

Net Loss Per Share (Reconciliation of Shares Used in Calculating Basic and Diluted Earnings Per Share) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Basic (in shares)	60,014,246	56,524,990	58,667,289	56,153,428
Effect of assumed exercised options (in shares)	0	0	0	0
Diluted (in shares)	60,014,246	56,524,990	58,667,289	56,153,428

Segment Information (Narrative)

Segment Information (Narrative) (Details)	9 Months Ended
	Sep. 30, 2018segment
Segment Reporting [Abstract]
Number of operating segments	2

Segment Information (Summary of

Segment Information (Summary of Financial Information by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Revenue	$ 64,213	$ 56,493	$ 184,114	$ 161,486
Cost of revenue	15,689	14,541	45,679	43,456
Sales and marketing	26,748	21,603	76,271	66,695
Amortization of purchased intangibles	424	470	1,272	1,412
Unallocated corporate expenses	26,178	20,124	77,355	61,854
Loss from operations	(4,826)	(245)	(16,463)	(11,931)
Corporate
Revenue:
Unallocated corporate expenses	26,178	20,124	77,355	61,854
Loss from operations	(26,178)	(20,124)	(77,355)	(61,854)
Business | Operating Segments
Revenue:
Revenue	59,337	52,138	169,606	148,501
Cost of revenue	14,695	13,681	42,699	40,794
Sales and marketing	24,391	19,554	69,453	60,338
Amortization of purchased intangibles	424	470	1,272	1,412
Loss from operations	19,827	18,433	56,182	45,957
Consumer | Operating Segments
Revenue:
Revenue	4,876	4,355	14,508	12,985
Cost of revenue	994	860	2,980	2,662
Sales and marketing	2,357	2,049	6,818	6,357
Loss from operations	1,525	1,446	4,710	3,966
Hosted Services - Business
Revenue:
Revenue	50,046	46,378	145,805	131,798
Hosted Services - Business | Business | Operating Segments
Revenue:
Revenue	50,046	46,378	145,805	131,798
Hosted Services - Consumer
Revenue:
Revenue	4,876	4,355	14,508	12,985
Hosted Services - Consumer | Consumer | Operating Segments
Revenue:
Revenue	4,876	4,355	14,508	12,985
Professional Services
Revenue:
Revenue	9,291	5,760	23,801	16,703
Professional Services | Business | Operating Segments
Revenue:
Revenue	$ 9,291	$ 5,760	$ 23,801	$ 16,703

Segment Information (Long-Lived

Segment Information (Long-Lived Assets by Geographic Region) (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total long-lived assets		$ 141,054	$ 129,955
United States
Segment Reporting Information [Line Items]
Total long-lived assets		108,016	95,716
Israel
Segment Reporting Information [Line Items]
Total long-lived assets		13,490	13,079
Australia
Segment Reporting Information [Line Items]
Total long-lived assets		8,744	9,504
Netherlands
Segment Reporting Information [Line Items]
Total long-lived assets		7,677	8,363
Other
Segment Reporting Information [Line Items]
Total long-lived assets	[1]	$ 3,127	$ 3,293
[1]	United Kingdom, Germany, Japan, France and Italy

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Changes in Carrying Amount of Goodwill) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 80,531
Acquisitions	5,010
Foreign exchange adjustment	(74)
Goodwill, ending balance	85,467
Business
Goodwill [Roll Forward]
Goodwill, beginning balance	72,507
Acquisitions	5,010
Foreign exchange adjustment	(74)
Goodwill, ending balance	77,443
Consumer
Goodwill [Roll Forward]
Goodwill, beginning balance	8,024
Acquisitions	0
Foreign exchange adjustment	0
Goodwill, ending balance	$ 8,024

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 51,464	$ 48,470
Accumulated Amortization	(38,215)	(36,104)
Net Carrying Amount	13,249	12,366
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	30,640	27,882
Accumulated Amortization	(23,221)	(22,197)
Net Carrying Amount	$ 7,419	$ 5,685
Weighted Average Amortization Period	5 years 3 months 18 days	5 years 3 months 18 days
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 15,971	$ 15,978
Accumulated Amortization	(11,436)	(10,457)
Net Carrying Amount	$ 4,535	$ 5,521
Weighted Average Amortization Period	8 years	8 years 18 days
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,287	$ 1,289
Accumulated Amortization	(1,287)	(1,283)
Net Carrying Amount	$ 0	$ 6
Weighted Average Amortization Period	2 years 1 month	2 years 1 month 12 days
Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,437	$ 1,439
Accumulated Amortization	(1,437)	(1,439)
Net Carrying Amount	$ 0	$ 0
Weighted Average Amortization Period	2 years 3 months 12 days	2 years 3 months 12 days
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,867	$ 1,620
Accumulated Amortization	(599)	(493)
Net Carrying Amount	$ 1,268	$ 1,127
Weighted Average Amortization Period	13 years 5 months	13 years 1 month 18 days
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 262	$ 262
Accumulated Amortization	(235)	(235)
Net Carrying Amount	$ 27	$ 27
Weighted Average Amortization Period	2 years 8 months 12 days	2 years 8 months 18 days

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization	$ 700	$ 1,100	$ 2,131	$ 3,968

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets (Future Amortization Expense) (Details) $ in Thousands	Sep. 30, 2018USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 792
2,019	2,963
2,020	2,775
2,021	2,565
2,022	2,216
Thereafter	1,938
Total	$ 13,249

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 128,617	$ 113,938
Less: accumulated depreciation	(88,829)	(79,233)
Total	39,788	34,705
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	113,463	100,392
Furniture, equipment and building improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,154	$ 13,546

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Payroll and other employee related costs	$ 16,942	$ 16,431
Professional services and consulting and other vendor fees	12,688	15,674
Unrecognized tax benefits	2,332	4,924
Sales commissions	5,719	5,259
Contingent earn-out	1,800	0
Restructuring	1,249	2,338	$ 2,551
Other	394	3,385
Total	$ 41,124	$ 48,011

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended		9 Months Ended
	Sep. 30, 2018	Jan. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Contingent earn-out consideration in cash	$ 1,800		$ 1,800	$ 0
Goodwill acquired in acquisition			5,010
Conversable, Inc.
Business Acquisition [Line Items]
Aggregate purchase price	6,600
Cash payment in acquisition	1,200
Equity consideration in acquisition	3,000
Contingent earn-out consideration in cash	1,800		1,800
Contingent earn-out consideration in equity	300		$ 300
Deferred revenue in acquisition	300
Goodwill acquired in acquisition	5,000
Aggregate amount of intangibles acquired	1,600
Potential earn-out consideration payments based on achieving targets	2,100
Potential earn-out consideration payments for compensation	$ 600
Period for recognizing compensation-related potential earn-out consideration payments	12 months
BotCentral
Business Acquisition [Line Items]
Equity consideration in acquisition		$ 1,000
Aggregate amount of intangibles acquired		1,200
Acquisition costs		$ 200

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets and Liabilities) (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Restricted cash balance	$ 0	$ 1,451,000
Liabilities:
Contingent earn-out	1,800,000	0
Recurring
Assets:
Assets	2,828,000	2,871,000
Liabilities:
Liabilities	1,800,000	2,000
Recurring | Money market funds
Assets:
Money market funds	2,828,000	2,806,000
Recurring | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	65,000
Liabilities:
Foreign currency derivative contracts	0	2,000
Recurring | Contingent earn-out
Liabilities:
Contingent earn-out	1,800,000	0
Recurring | Level 1
Assets:
Assets	2,828,000	2,806,000
Liabilities:
Liabilities	0	0
Recurring | Level 1 | Money market funds
Assets:
Money market funds	2,828,000	2,806,000
Recurring | Level 1 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Recurring | Level 1 | Contingent earn-out
Liabilities:
Contingent earn-out	0	0
Recurring | Level 2
Assets:
Assets	0	65,000
Liabilities:
Liabilities	0	2,000
Recurring | Level 2 | Money market funds
Assets:
Money market funds	0	0
Recurring | Level 2 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	65,000
Liabilities:
Foreign currency derivative contracts	0	2,000
Recurring | Level 2 | Contingent earn-out
Liabilities:
Contingent earn-out	0	0
Recurring | Level 3
Assets:
Assets	0	0
Liabilities:
Liabilities	1,800,000	0
Recurring | Level 3 | Money market funds
Assets:
Money market funds	0	0
Recurring | Level 3 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Recurring | Level 3 | Contingent earn-out
Liabilities:
Contingent earn-out	$ 1,800,000	$ 0

Fair Value Measurements (Change

Fair Value Measurements (Changes in Fair Value of Level 3 Liabilities) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Change in Fair Value of Level 3 Liabilities
Beginning balance	$ 0	$ 0
Conversable, Inc. addition	1,800	0
Cash payment	0	0
Changes in fair value	0	0
Ending balance	$ 1,800	$ 0

Fair Value Measurements (Deriva

Fair Value Measurements (Derivative Financial Instruments) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Cash held as collateral	$ 0		$ 0		$ 1,451,000
Foreign currency derivative contracts
Derivative [Line Items]
Notional amount of foreign currency derivative contracts	0		0		2,866,000
Fair value of foreign currency derivatives contracts	0		0		$ 63,000
Foreign currency derivative contracts | Other (income) expense
Derivative [Line Items]
Gain (losses) on Derivative Instruments Recognized in Statements of Operations	$ 0	$ (19,000)	$ (50,000)	$ 194,000

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Derivative Instruments) (Details) - Derivatives not designated as hedging instruments - Foreign currency derivative contracts - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Prepaid expenses and other current assets
Derivative Assets
Foreign currency derivative contracts	$ 0	$ 65
Accrued expenses and other liabilities
Derivative Liabilities
Foreign currency derivative contracts	$ 0	$ 2

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Rental expense for operating leases	$ 2,900,000	$ 2,300,000	$ 7,200,000	$ 7,300,000
Defined benefit plan employer matching contribution on first five percent of employee compensation			50.00%
Percentage of employees' eligible compensation for employer matching contribution			5.00%
Defined benefit plan employer contribution limit			$ 6,000
Defined benefit plan employer contribution vesting period			5 years
Defined benefit plan employer contribution	400,000	$ 300,000	$ 1,200,000	$ 1,100,000
Letter of Credit
Line of Credit Facility [Line Items]
Proceeds from amounts drawn against letters of credit			0
Letter of Credit | LOC for Office Space
Line of Credit Facility [Line Items]
Letters of credit outstanding	1,800,000		1,800,000
Letter of Credit | LOC for Security Deposit
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 100,000		$ 100,000

Stockholders' Equity (Narrative

Stockholders' Equity (Narrative) (Details) - USD ($)	Apr. 25, 2018	Apr. 30, 2017	Jun. 07, 2012	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 31, 2018	Dec. 31, 2017	Nov. 21, 2016	Feb. 16, 2016	Jul. 23, 2014	Mar. 13, 2014	Dec. 10, 2012	Jun. 30, 2010
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, shares authorized (in shares)				100,000,000		100,000,000			100,000,000
Common stock, shares issued (in shares)				63,201,497		63,201,497			59,663,969
Common stock, shares outstanding (in shares)				60,537,707		60,537,707			59,663,969
Common stock, par value (in dollars per share)				$ 0.001		$ 0.001			$ 0.001
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred stock, shares authorized (in shares)				5,000,000		5,000,000			5,000,000
Preferred stock, shares issued (in shares)				0		0			0
Preferred stock, shares outstanding (in shares)				0		0			0
Preferred stock, par value (in dollars per share)				$ 0.001		$ 0.001			$ 0.001
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased during period (in shares)						93,750
Stock repurchase program, remaining authorized repurchase amount				$ 17,100,000		$ 17,100,000
Per share weighed average fair value of stock options granted during the period (in dollars per share)				$ 10.13	$ 5.02	$ 6.62	$ 3.63
Dividend yield				0.00%	0.00%	0.00%	0.00%
Expected life				5 years	5 years	5 years	5 years
Period used to determine volatility						5 years
Total value of stock options exercised						$ 15,200,000
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested share-based compensation arrangements				$ 16,100,000		$ 16,100,000
Weighted average recognition period of unrecognized compensation cost						2 years 10 months 24 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested share-based compensation arrangements				$ 35,900,000		$ 35,900,000
Weighted average recognition period of unrecognized compensation cost						2 years 10 months 2 days
Vesting period						4 years
1998 Plan | Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)				5,850,000		5,850,000
2000 Plan | Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares of common stock available for issuance						4,150,000
1998 and 2000 Plan | Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)				10,000,000		10,000,000
2009 Plan | Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares of common stock available for issuance						6,000,000
2009 Plan, Amended | Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)		27,817,744		2,400,000		2,400,000
Increase in number of shares of common stock available for issuance		4,000,000	4,250,000
Stock option term						10 years
2010 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)		2,000,000		900,000		900,000									1,000,000
Increase in number of shares of common stock available for issuance		1,000,000
2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)	2,000,000							1,500,000
Increase in number of shares of common stock available for issuance	500,000
2018 Plan | Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance				200,000		200,000
2012 Stock Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount										$ 74,000,000	$ 64,000,000	$ 50,000,000	$ 40,000,000	$ 30,000,000
Increase to authorized amount											$ 14,000,000

Stockholders' Equity (Weighted

Stockholders' Equity (Weighted Average Assumptions of Fair Value Options Using Black-Scholes Option-Pricing Model) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%	0.00%
Expected life	5 years	5 years	5 years	5 years
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.80%	1.80%	2.50%	1.70%
Historical volatility	43.50%	47.30%	43.50%	46.60%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.90%	1.80%	2.90%	1.90%
Historical volatility	43.70%	47.30%	48.40%	47.60%

Stockholders' Equity (Summary o

Stockholders' Equity (Summary of Stock Option Activity and Weighted Average Exercise Prices) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Options
Beginning balance (in shares) | shares	7,959
Granted (in shares) | shares	1,952
Exercised (in shares) | shares	(2,874)
Cancelled or expired (in shares) | shares	(554)
Ending balance (in shares) | shares	6,483
Options vested and expected to vest (in shares) | shares	5,614
Options exercisable at end of period (in shares) | shares	3,250
Weighted Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 10.71
Granted (in dollars per share) | $ / shares	15.03
Exercised (in dollars per share) | $ / shares	10.72
Cancelled or expired (in dollars per share) | $ / shares	9.91
Ending balance (in dollars per share) | $ / shares	12.07
Options vested and expected to vest (in dollars per share) | $ / shares	11.80
Options exercisable at end of period (in dollars per share) | $ / shares	$ 11
Weighted Average Remaining Contractual Term (in years)
Options outstanding at end of period	6 years 10 months 28 days
Options vested and expected to vest	6 years 6 months 18 days
Options exercisable at end of period	4 years 9 months 11 days
Aggregate Intrinsic Value
Options outstanding at end of period | $	$ 90,038
Options vested and expected to vest | $	79,474
Options exercisable at end of period | $	$ 48,604

Stockholders' Equity (Summary_2

Stockholders' Equity (Summary of Options by Range of Exercise Prices) (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of shares outstanding (in shares) | shares	6,483
Options outstanding, Weighted-average remaining contractual life	6 years 10 months 28 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 12.07
Options exercisable, Number of shares (in shares) | shares	3,250
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 11
$1.79 - $7.60
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	1.79
Exercise price range, maximum (in dollars per share)	$ 7.33
Options outstanding, Number of shares outstanding (in shares) | shares	1,152
Options outstanding, Weighted-average remaining contractual life	6 years 5 months 19 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 6.92
Options exercisable, Number of shares (in shares) | shares	583
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 6.43
$7.95 - $9.55
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	7.45
Exercise price range, maximum (in dollars per share)	$ 7.60
Options outstanding, Number of shares outstanding (in shares) | shares	664
Options outstanding, Weighted-average remaining contractual life	6 years 4 months 6 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 9.21
Options exercisable, Number of shares (in shares) | shares	479
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 9.21
$9.90 - $10.13
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	7.95
Exercise price range, maximum (in dollars per share)	$ 9.55
Options outstanding, Number of shares outstanding (in shares) | shares	659
Options outstanding, Weighted-average remaining contractual life	5 years 8 months 19 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 10.09
Options exercisable, Number of shares (in shares) | shares	655
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 10.09
$10.31 - $11.96
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	9.90
Exercise price range, maximum (in dollars per share)	$ 10.13
Options outstanding, Number of shares outstanding (in shares) | shares	674
Options outstanding, Weighted-average remaining contractual life	7 years 22 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 11.27
Options exercisable, Number of shares (in shares) | shares	395
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 11.01
$12.09 - $12.32
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	10.31
Exercise price range, maximum (in dollars per share)	$ 11.95
Options outstanding, Number of shares outstanding (in shares) | shares	41
Options outstanding, Weighted-average remaining contractual life	2 years 10 months 6 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 12.29
Options exercisable, Number of shares (in shares) | shares	41
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 12.29
$12.45 - $12.45
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	11.96
Exercise price range, maximum (in dollars per share)	$ 12.32
Options outstanding, Number of shares outstanding (in shares) | shares	930
Options outstanding, Weighted-average remaining contractual life	9 years 4 months 17 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 12.45
Options exercisable, Number of shares (in shares) | shares	0
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 0
$12.46 - $13.59
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	12.45
Exercise price range, maximum (in dollars per share)	$ 12.45
Options outstanding, Number of shares outstanding (in shares) | shares	759
Options outstanding, Weighted-average remaining contractual life	3 years 9 months 4 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 13.28
Options exercisable, Number of shares (in shares) | shares	702
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 13.26
$14.30- $15.96
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	12.46
Exercise price range, maximum (in dollars per share)	$ 13.37
Options outstanding, Number of shares outstanding (in shares) | shares	697
Options outstanding, Weighted-average remaining contractual life	8 years 8 months 19 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 14.72
Options exercisable, Number of shares (in shares) | shares	61
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 15.94
$16.05 - $21.75
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	13.59
Exercise price range, maximum (in dollars per share)	$ 15.55
Options outstanding, Number of shares outstanding (in shares) | shares	721
Options outstanding, Weighted-average remaining contractual life	6 years 11 months 1 day
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 18.09
Options exercisable, Number of shares (in shares) | shares	334
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 17.44
$22.35 - $27.25
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, minimum (in dollars per share)	15.66
Exercise price range, maximum (in dollars per share)	$ 18.24
Options outstanding, Number of shares outstanding (in shares) | shares	186
Options outstanding, Weighted-average remaining contractual life	9 years 9 months 26 days
Options outstanding, Weighted-average exercise price (in dollars per share)	$ 23.84
Options exercisable, Number of shares (in shares) | shares	0
Options exercisable, Weighted-average exercise price (in dollars per share)	$ 0

Stockholders' Equity (Summary_3

Stockholders' Equity (Summary of Restricted Stock Unit Activity and Weighted Average Exercise Price) (Details) - Restricted Stock Units (RSUs) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Number of Shares (in thousands)
Beginning balance outstanding (in shares) | shares	1,123
Awarded (in shares) | shares	2,130
Released (in shares) | shares	(334)
Forfeited (in shares) | shares	(234)
Non-vested and outstanding at end of period (in shares) | shares	2,685
Expected to vest (in shares) | shares	1,878
Weighted Average Grant Date Fair Value (usd per share)
Beginning balance outstanding (in dollars per share) | $ / shares	$ 9.03
Awarded (in dollars per share) | $ / shares	16.35
Released (in dollars per share) | $ / shares	9.04
Forfeited (in dollars per share) | $ / shares	10.42
Non-vested and outstanding at end of period (in dollars per share) | $ / shares	14.71
Expected to vest (in dollars per share) | $ / shares	$ 13.93
Aggregate Fair Value (in thousands)
Non-vested and outstanding at September 30, 2018 | $	$ 69,673
Expected to vest | $	$ 48,741

Restructuring (Narrative) (Deta

Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring expense	$ 722	$ 0	$ 2,806	$ 2,315
Restructuring liability	$ 1,249		$ 1,249		$ 2,338	$ 2,551

Restructuring (Restructuring Li

Restructuring (Restructuring Liability) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Balance, Beginning of the year	$ 2,338	$ 2,551
Severance and other associated costs	2,806	648
Cash payments	(3,895)	(2,807)
Wind down cost legacy platform	0	1,946
Balance, End of period	$ 1,249	$ 2,338

Restructuring (Restructuring Ex

Restructuring (Restructuring Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 722	$ 0	$ 2,806	$ 2,315
Severance and other associated costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	722		2,806	399
Restructuring costs		(31)
Wind down cost legacy platform
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 0		$ 0	$ 1,916
Restructuring costs		$ 31

Subsequent Events (Narrative) (

Subsequent Events (Narrative) (Details) - Subsequent Event - AdvantageTec $ in Millions	1 Months Ended
	Oct. 31, 2018USD ($)
Subsequent Event [Line Items]
Aggregate purchase price	$ 16.6
Cash payment in acquisition	6
Equity consideration in acquisition	4.5
Potential earn-out consideration payments based on achieving targets	$ 5.7