Description of Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements as of September 30, 2017 and for the three and nine months ended September 30, 2017 and 2016 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, 2017, and the consolidated results of operations, comprehensive loss and cash flows for the interim periods ended September 30, 2017 and 2016. 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, 2016 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, 2016 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 10, 2017.
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 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update 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 May 2017, FASB issued Accounting Standards Update No. 2017-09, "Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting" (“ASU 2017-09”). This update clarifies and reduces both (i) diversity in practice and (ii) cost and complexity when applying the guidance in Topic 718, to a change to the terms and conditions of a share-based payment award. ASU 2017-09 is effective for financial statements issued for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted. The amendments in this ASU should be applied prospectively to an award modified on or after the adoption date. 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 January 2017, FASB issued Accounting Standards Update 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 January 2017, the FASB issued Accounting Standards Update No. 2017-01, "Business Combinations (Topic 805): Clarifying the Definition of a Business" (“ASU 2017-01”). This update clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of businesses. The amendments in this update provide a screen to determine when a set is not a business. If the screen is not met, it (1) requires that to be considered a business, a set must include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create output and (2) removes the evaluation of whether a market participant could replace the missing elements. ASU 2017-01 is effective for financial statements issued for annual periods beginning after December 15, 2017, and interim periods within those annual periods. The Company does not expect the adoption of ASU 2017-01 to have a material effect on its financial position, results of operations or cash flows. In March 2016, the FASB issued Accounting Standards Update No. 2016-09, “Compensation -Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”). This update is intended to improve the accounting for employee share-based payments and affects all organizations that issue share-based payment awards to their employees. Several aspects of the accounting for share-based payment award transactions are simplified, including:(a) income tax consequences; (b) classification of awards as either equity or liabilities; and (c) classification on the statement of cash flows. The Company adopted this ASU as of the beginning of the first quarter of 2017 and has elected to continue to estimate expected forfeitures over the course of a vesting period. Further, the ASU eliminates the requirement to delay the recognition of excess tax benefits until they reduce current taxes payable. The adoption of ASU 2016-09 did not have any material impact on the Company’s financial statements. In February 2016, the FASB issued Accounting Standards Update 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. Certain targeted improvements were made to align, where necessary, lessor accounting with the lessee accounting model and Topic 606, “Revenue from Contracts with Customers”. 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) must 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. ASU 2016-02 is effective for financial statements issued for annual periods beginning after December 15, 2018. While the Company is currently assessing the impact ASU 2016-02 will have on the consolidated financial statements, the Company expects the primary impact to its consolidated financial position upon adoption will be the recognition, on a discounted basis, of its minimum commitments under non-cancelable operating leases on the consolidated balance sheets resulting in the recording of right of use assets and lease obligations. The Company is also currently evaluating the timing of adoption and the impact that the standard will have on its condensed consolidated financial statements and related disclosures. In May 2014, the FASB issued ASC Update No. 2014-09, Revenue from Contracts with Customers (“Topic 606”), which has been subsequently updated. The purpose of Update No. 2014-09 is to provide enhancements to the quality and consistency of how revenue is reported while also improving comparability in the financial statements of companies using U.S. GAAP and International Financial Reporting Standards. The core principle requires entities to recognize revenue in a manner that depicts the transfer of goods or services to customers in amounts that reflect the consideration an entity expects to be entitled to in exchange for those goods or services. Topic 606, as amended, becomes effective for annual periods beginning after December 15, 2017, at which point we plan to adopt the standard. The Company currently plans to adopt the standard using the “modified retrospective method.” Under that method, the Company will apply the rules to contracts that are not completed as of January 1, 2018, and recognize the cumulative effect of the initial adoption as an adjustment to the opening balance of retained earnings. The Company has reached preliminary conclusions on our key revenue streams related to the standard and are finalizing our accounting policies. Based on its initial assessment, the Company believes the timing of revenue recognition for its primary revenue stream, hosted services within its Business segment, will not materially change. Upon adopting Topic 606, the Company will provide additional disclosures in the notes to the consolidated financial statements, specifically related to disaggregated revenue, contract balances and performance obligations. In the third quarter of 2017, the Company provided global training to its finance team on Topic 606. In the fourth quarter of 2017, the Company will perform a simulation of its new accounting processes and procedures to prepare its team for the month-end close process upon adoption of Topic 606. The Company will implement new internal controls to address risks associated with applying the five-step model, specifically related to judgments made in connection to variable consideration and applying the constraint. Additionally, the Company will establish monitoring controls to identify new sales arrangements and changes in its business environment that could impact its current accounting assessment. The Company expects to finalize its impact assessment and redesign impacted processes, policies and controls during the fourth quarter of 2017.
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. Because the Company provides its application as a service, the Company follows the provisions of FASB Accounting Standards Codification (“ASC”) 605-10-S99, “Revenue Recognition” and ASC 605-25, “Revenue Recognition with Multiple-Element Arrangements.” The Company charges a monthly, quarterly or annual fee, which varies by type of service, the level of customer usage and website traffic, and in some cases, the number of orders placed via the Company’s online engagement solutions. 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 605-45, “Principal Agent Considerations,” the Company records revenue for transactions in which it acts as an agent on a net basis, and revenue for transactions in which it acts as a principal on a gross basis. The Company also sells certain of the LivePerson services directly via Internet download. These services are marketed as LiveEngage for small to medium-sized businesses, and are paid for almost exclusively by credit card. Credit card payments accelerate cash flow and reduce the Company’s collection risk, subject to the merchant bank’s right to hold back cash pending settlement of the transactions. Sales of LiveEngage may occur with or without the assistance of an online sales representative, rather than through face-to-face or telephone contact that is typically required for traditional direct sales. The Company recognizes monthly service revenue based upon the fee charged for the LivePerson services, provided that there is persuasive evidence of an arrangement, no significant Company obligations remain, collection of the resulting receivable is probable and the amount of fees to be paid is fixed or determinable. The Company’s service agreements typically have twelve month terms and, in some cases, are terminable or may terminate upon 30 to 90 days’ notice without penalty. When professional service fees add value to the customer on a standalone basis, the Company recognizes professional service fees upon completion and customer acceptance. The Company establishes a selling price hierarchy for determining the selling price of a deliverable, which is based on: (a) vendor-specific objective evidence; (b) third-party evidence; or (c) best estimated selling price. If a professional services arrangement does not qualify for separate accounting, the Company recognizes the fees, and the related labor costs, ratably over the contracted period. For revenue from the Company’s Consumer segment generated from online transactions between Experts and Users, the Company recognizes revenue net of the Expert fees in accordance with ASC 605-45, “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 User and retains a portion of the fee, and then remits the balance to the Expert. Revenue from these transactions is recognized when there is persuasive evidence of an arrangement, no significant Company obligations remain, collection of the resulting receivable is probable and the amount of fees to be paid is fixed and determinable.
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 facilitates real-time online interactions – chat, voice and content delivery across multiple channels and screens for global corporations of all sizes. The Consumer segment facilitates online transactions between Experts and Users and sells its services to consumers. 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 (with limited exceptions). Incremental compensation costs arising from subsequent modifications of awards after the grant date must be recognized.