| SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES | SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates —The preparation of the Company’s 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 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 consolidated financial statements; therefore, actual results could differ from management’s estimates. Foreign Currency Translation —The consolidated financial statements of the Company’s foreign subsidiaries are measured using the local currency as the functional currency. Assets and liabilities of foreign subsidiaries are translated at exchange rates in effect as of the balance sheet date. Revenues and expenses are translated at average exchange rates in effect during the year. Translation adjustments are recorded within accumulated other comprehensive loss, a separate component of stockholders’ equity. Cash and Cash Equivalents —The Company considers all highly liquid investments, such as treasury bills, commercial paper, certificates of deposit and money market instruments with maturities of three months or less at the time of acquisition to be cash equivalents. Cash and cash equivalents primarily consist of amounts held in interest-bearing money market funds that were readily convertible to cash. The fair value of cash and cash equivalents approximates their carrying value. Marketable Securities —The Company has a policy that generally requires securities to be investment grade (i.e. rated ‘A+’ or higher by bond rating firms) with the objective of minimizing the potential risk of principal loss. In the event that the rating drops below that investment grade, the Company will sell the security prior to maturity. The Company determines the classification of its marketable securities at the time of purchase and re-evaluates these determinations at each balance sheet date. Debt securities are classified as held-to-maturity when the Company has the positive intent and ability to hold the securities to maturity. Held-to-maturity securities are stated at amortized cost and are periodically assessed for other-than-temporary impairment. Amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, and is included in interest income. The Company considers highly liquid treasury notes, U.S. agency securities, corporate debt securities, money market funds and other funds with maturities of more than three months to be marketable securities. Held-to-maturity securities with less than one year to maturity are included in short-term marketable securities. All other held-to-maturity securities are classified as long-term marketable securities. Concentrations of Credit Risk —Financial instruments that potentially subject the Company to concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. The Company places its cash and cash equivalents with major financial institutions, which management assesses to be of high credit quality, in order to limit the exposure of each investment. Credit risk with respect to accounts receivable is dispersed due to the Company’s large number of customers. In addition, the Company’s credit risk is mitigated by the relatively short collection period. Collateral is not required for accounts receivable. Accounts Receivable, Net and Payment Terms —The timing of revenue recognition may differ from the timing of invoicing to customers. The Company records an accounts receivable balance when revenue is recognized prior to or at the time of invoicing the customer. Payment terms and conditions vary by contract type and the service being provided. For advertising services, the Company typically invoices customers on a monthly basis, one month in arrears, with payment due either at the end of each billing period or up to 30 days after the end of the billing period. For transaction services, the Company collects its commission fee on each transaction either at the time of the transaction or up to 30 days after the end of the billing period. For subscription services, the Company typically invoices customers one month in advance, with payment due at the beginning of each billing period. Allowance for Doubtful Accounts —The Company maintains an allowance for doubtful accounts receivable. The allowance reflects the Company's best estimate of probable losses associated with the accounts receivable balance. It is based upon historical experience and loss patterns, the number of days that billings are past due, an evaluation of the potential risk of loss associated with delinquent accounts and known delinquent accounts. When new information becomes available that allows the Company to more accurately estimate the allowance, it makes an adjustment, which is considered a change in accounting estimate. The carrying value of accounts receivable approximates their fair value. Deferred Contract Costs —The Company has determined that certain sales incentive compensation costs are incremental costs to obtain the related contract. These costs are capitalized in the period in which they are incurred and amortized on a straight-line basis over the expected customer life of the associated contract. The Company uses a straight-line basis as it expects the benefit of these costs to be realized uniformly over the amortization period. The amortization periods for contract costs, which extend up to 41 months, were determined based on both qualitative and quantitative factors, including product life cycle attributes and customer retention historical data. For contract costs with amortization periods of less than 12 months, the Company applies a practical expedient to expense such costs as incurred. The Company assesses deferred contract costs for impairment on a quarterly basis. Amortized contract costs are recorded within sales and marketing expense in the consolidated statements of operations. Deferred contract costs are included within other non-current assets on the Company's consolidated balance sheets (see Note 11 , " Other Non-Current Assets "). Deferred Revenue —The Company records deferred revenue when it has received consideration, or has the right to receive consideration, in advance of the transfer of the performance obligations of the contract to the customer. Property, Equipment and Software —Property, equipment and software are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, which are approximately three Website and Internal-Use Software Development Costs —Costs related to website and internal-use software are primarily related to the Company’s website and mobile app, including support systems. The Company capitalizes its costs to develop software when preliminary development efforts are successfully completed, management has authorized and committed project funding and it is probable that the project will be completed and the software will be used as intended. Costs incurred for enhancements that are expected to result in additional material functionality are capitalized and amortized over the estimated useful life of the upgrades. Such costs are amortized on a straight-line basis over the estimated useful life of the related asset, which is generally three years. Leases —The Company leases its office facilities under operating lease agreements that expire from 2020 to 2029, some of which include options to renew at the Company's sole discretion. If exercised, such options would extend the lease terms by up to ten years. Additionally, certain lease agreements contain options to terminate the leases, which require 6 to 12 months prior written notice to the landlord. The Company does not have any finance lease agreements. The Company recognizes on its consolidated balance sheet operating lease liabilities representing the present value of future lease payments, and an associated operating lease right-of-use asset for any operating lease with a term greater than one year. The Company recognizes the amortization of the right-of-use asset each month within lease expense. The Company elected to use the practical expedient for short-term leases, and therefore does not record operating lease right-of-use assets or lease liabilities associated with leases with durations of 12 months or less. When recording the present value of lease liabilities, a discount rate is required. The Company has concluded that the rates implicit in the various operating lease agreements are not readily determinable. As a result, the Company instead uses its incremental borrowing rate, which is calculated based on hypothetical borrowings to fund each respective lease over the lease term, as of the lease commencement date, assuming that borrowings are secured by the various leased properties. The incremental borrowing rates are determined based on an assessment of the Company’s implied credit rating, using ratings scales from reputable rating agencies that consider a number of qualitative and quantitative factors. Market rates are derived as of the lease commencement dates with reference to companies with the same debt rating that operate in a similar industry to the Company. The Company does not recognize its renewal options as part of its right-of-use assets and lease liabilities until it is reasonably certain that it will exercise such renewal options. The Company does not combine lease and non-lease components; its lease agreements provide specific allocations of the Company's obligations between lease and non-lease components. As a result, the Company is not required to exercise any judgment in determining such allocations. Business Combinations —The Company accounts for acquisitions of entities that consist of inputs and processes that have the ability to contribute to the creation of outputs as business combinations. The Company allocates the purchase price of the acquisition to the tangible assets, liabilities and identifiable intangible assets acquired based on their estimated fair values. The excess of the purchase price over those fair values is recorded as goodwill. Acquisition-related expenses and integration costs are expensed as incurred. During the measurement period, the Company records adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill. After the measurement period, which could be up to one year after the transaction date, subsequent adjustments are recorded to the Company’s consolidated statements of operations. Goodwill —Goodwill represents the excess of the purchase price in a business combination over the fair value of net tangible and intangible assets acquired. The carrying amount of goodwill is reviewed at least annually, or more frequently if events or changes in circumstances indicate that the carrying value of goodwill may not be recoverable. The Company has the option to first assess qualitative factors 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 under the authoritative guidance. If the Company determines that it is more likely than not that its fair value is less than the carrying amount, or opts not to perform a qualitative assessment, then the two-step goodwill impairment test will be performed. The first step, identifying a potential impairment, compares the fair value of the reporting unit with its carrying amount. If the carrying amount exceeds its fair value, the second step will be performed; otherwise, no further step is required. The second step, measuring the impairment loss, compares the implied fair value of the goodwill with the carrying amount of the goodwill. Any excess of the goodwill carrying amount over the applied fair value is recognized as an impairment loss, and the carrying value of goodwill is written down to fair value. 0 impairment charges associated with goodwill have been recorded by the Company to date. Intangible Assets —Intangible assets include acquired intangible assets identified through business combinations, which are carried at fair value less accumulated amortization, and purchased intangible assets, which are carried at cost less accumulated amortization. Amortization is recorded over the estimated useful lives of the assets, generally two years to 12 years. The Company reviews amortizable intangible assets to be held and used for impairment whenever events or changes in circumstances indicate that the carrying value of the assets may not be recoverable. Determination of recoverability is based on the lowest level of identifiable estimated undiscounted cash flows resulting from the use of the asset and its eventual disposition. Measurement of any impairment loss is based on the excess of the carrying value of the asset over its fair value. No impairment charges have been recorded to date. Impairment of Long-Lived Assets and Long-Lived Assets to Be Disposed of —The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. Stock Repurchases —The Company accounts for repurchases of its common stock by recording the cost to repurchase those shares to treasury stock, a separate component of stockholders' equity. Upon retirement, the carrying amount of treasury stock is reduced with a corresponding reduction to par value of common stock, with any excess of the cost incurred to repurchase shares over their par value recorded as an adjustment to retained earnings (accumulated deficit) on the date of retirement. Assets and Liabilities Held for Sale —The Company considers an asset to be held for sale when: management approves and commits to a formal plan to actively market the asset for sale at a reasonable price in relation to its fair value; the asset is available for immediate sale in its present condition; an active program to locate a buyer and other actions required to complete the sale have been initiated; the sale of the asset is expected to be completed within one year; and it is unlikely that significant changes will be made to the plan. Upon designation as held for sale, the Company records the carrying value of the assets at the lower of its carrying value or its estimated fair value, less costs to sell. The Company ceases to record depreciation and amortization expense associated with assets upon their designation as held for sale. Revenue Recognition —The Company generates revenue from the sale of advertising products, transactions and other services, which correspond to the Company's major product lines. The Company recognizes revenue by applying the following steps: the contract with the customer is identified; the performance obligations in the contract are identified; the transaction price is determined; the transaction price is allocated to the performance obligations in the contract; and revenue is recognized when (or as) the Company satisfies these performance obligations in an amount that reflects the consideration it expects to be entitled to in exchange for those services. The Company applies the portfolio practical expedient to account for contracts with customers in each category of revenue. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which revenue is recognized in the amount to which the Company has a right to invoice. Contracts with customers can include multiple performance obligations, where the transaction price is allocated to each performance obligation based on its relative standalone selling price ("SSP"). The Company determines SSP based on the prices of the promised goods or services charged when sold separately to customers, which are determined using contractually stated prices. The Company allocates revenue to each of the performance obligations included in a contract with multiple performance obligations at the inception of the contract. The various products and services comprising contracts with multiple performance obligations are typically capable of being distinguished and accounted for as separate performance obligations. For all contracts with customers, estimates and assumptions include determining variable consideration and identifying the nature and timing of satisfaction of performance obligations. Because the Company considers contracts month-to-month, variable consideration is resolved at the time of invoicing, which eliminates the use of estimates in determining the transaction price. For contracts satisfied over time, the Company applies the invoice practical expedient to depict the value transferred to the customer and measure of progress towards completion of its obligations. The Company considers the right to receive consideration from a customer to correspond directly with the value to the customer of its performance completed to date. The Company does not consider the effects of the time value of money as substantially all of the Company’s contracts are invoiced on a monthly basis, one month in arrears. Revenue is recognized net of any taxes collected from customers, which are remitted to governmental authorities. The Company does not typically refund customers for services once it determines the performance obligations of the contract have been satisfied, but will assess any refund requests from customers and partners on a case by case basis. The Company records an allowance for potential future refunds, which is estimated based on historical trends and recorded as a reduction of net revenue. Advertising . The Company generates advertising revenue primarily through the display of advertising products on its website and mobile app. These arrangements are evidenced by either written or electronic acceptance of a contract that stipulates the types of advertising to be delivered, the timing and pricing. Performance-based advertising placements are priced on a cost-per-click basis, while impression-based advertising placements are priced on a cost per thousand impressions basis. The Company recognizes revenue from the delivery of performance-based ads and impression-based ads in the period of delivery, in each case net of customer discounts. The Company also offers businesses premium features in connection with their business listing pages pursuant to fixed monthly fees, and recognizes revenue from such offerings over the service period. The Company also generates advertising revenue through indirect sales of advertising products, such as through reseller contracts that allow partners to sell Yelp Branded Profiles to their clients and the monetization of remnant advertising inventory through third-party ad networks, and recognizes revenue in the period of delivery. Transactions . The Company generates transactions revenue primarily from revenue-sharing partner contracts and, through October 10, 2017, Yelp Eat24 as a standalone product. The Company's transactions platform provides consumers with the ability to complete food delivery and other transactions through third parties directly on Yelp. The Company earns a per-transaction commission fee pursuant to partnership contracts for acting as an agent for these transactions, which it recognizes on a net basis and includes in revenue upon completion of a transaction. Prior to the disposal of Eat24, the Company's Yelp Eat24 business generated revenue through arrangements with restaurants, in which restaurants paid a commission percentage fee on orders placed through the Yelp Eat24 platform. The Company recorded revenue associated with Yelp Eat24 transactions on a net basis as the restaurant is primarily responsible for providing the underlying service and the Company does not control the service provided by the restaurant to the consumer. Concurrently with the disposal of Eat24 on October 10, 2017, the Company entered into a partnership agreement with Grubhub; as a result, following the sale, the Company generates revenue from transactions placed through the Grubhub network, which includes the Eat24 restaurant network, that originate on Yelp. Other Services . The Company generates other services revenue through subscription services contracts, such as sales of monthly subscriptions to Yelp Reservations and Yelp Waitlist, licensing contracts for access to Yelp data, and other non-advertising, non-transaction partnerships. Subscription revenues are recognized ratably over the contract terms beginning on the commencement date of each contract, which is the date the service is made available to customers. Cost of Revenue —The Company’s cost of revenue primarily consists of credit card processing fees, web hosting costs, and salaries, benefits and stock-based compensation expense for its infrastructure teams related to operating the Company’s website and mobile app. It also includes confirmation services expenses and delivery-related costs as well as video production expenses. Research and Development —The Company incurs research and development expenses for costs it incurs in research aimed at developing, and in translating the results of such research into new products and services or significant improvements to existing products or services, whether intended for sale or for internal use. Such costs are considered research and development expense up to the point in time at which the product or service achieves technological feasibility. These expenses primarily consist of employee-related costs (including stock-based compensation) for the Company's engineers and other employees engaged in the research and development of its products and services, as well as allocated indirect overhead costs. Research and development costs were $225.5 million, $205.8 million and $171.2 million for the years ended December 31, 2019, 2018 and 2017, respectively, and are recorded to costs and expenses in the consolidated statements of operations for those periods, primarily within product development costs. Stock-Based Compensation —The Company accounts for stock-based employee compensation plans under the fair value recognition and measurement provisions, which require all stock-based payments to employees, including grants of stock options, restricted stock awards, restricted stock units ("RSUs"), performance-based restricted stock units ("PRSUs") and issuances under its 2012 Employee Stock Purchase Plan, as amended (“ESPP”), to be measured based on the grant-date fair value of the awards. The Company accounts for forfeitures as they occur. The fair value of options granted to employees is estimated on the grant date using the Black-Scholes-Merton option valuation model. This valuation model for stock-based compensation expense requires the Company to make assumptions and judgments about the variables used in the calculation, including the expected term (weighted-average period of time that the options granted are expected to be outstanding), the expected volatility in the fair market value of the Company’s common stock, a risk-free interest rate and expected dividends. No compensation cost is recorded for options that do not vest. The Company uses the simplified calculation of expected life as the contractual term for options of 10 years is longer than the Company has been publicly traded. Expected volatility is based on an average of the historical volatilities of the common stock of several entities with characteristics similar to those of the Company. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option. The Company uses the straight-line method for expense attribution. The fair value of RSUs is measured using to the closing price of the Company's common stock on the New York Stock Exchange on the grant date. The Company uses the straight-line method for expense attribution. No compensation cost is recorded for RSUs that do not vest. Shares for these grants are issued upon vesting, net of tax withholding to be paid by the Company on behalf of its employees. The vesting of PRSUs outstanding as of December 31, 2019 was subject to both a market performance condition and a time-based vesting schedule. As a result of these multiple vesting requirements, the Company uses a Monte Carlo model to determine the fair value of the PRSUs. The Company uses the accelerated method for expense attribution. Compensation costs are recorded if the service condition is met regardless of whether the market performance condition is satisfied. No compensation cost is recorded if the service condition is not met. Advertising Expenses —Advertising costs are expensed in the period in which the advertising takes place. Costs of producing advertising are expensed in the period in which production takes place. Total advertising expenses incurred were $20.7 million, $38.0 million and $50.3 million for the years ended December 31, 2019, 2018 and 2017, respectively. Comprehensive Income —Comprehensive income consists of net income and other comprehensive (loss) income, which consists of foreign currency translation adjustments. Income Taxes —The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the Company’s financial statements or tax returns. In estimating future tax consequences, the Company generally considers all expected future events other than enactments or changes in the tax law or rates. In assessing the realization of deferred tax assets, the Company considers whether it is more likely than not that all or some portion of deferred tax assets will not be realized. The ultimate realization of the deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Valuation allowances are provided to reduce deferred tax assets to the amount that is more likely than not to be realized. In determining the need for a valuation allowance, the weight given to positive and negative evidence is commensurate with the extent to which the evidence may be objectively verified. The Company evaluates the ability to realize net deferred tax assets and the related valuation allowance on a quarterly basis. The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. The Company provides for tax contingencies whenever it is deemed probable that a tax asset has been impaired or a tax liability has been incurred for events such as tax claims or changes in tax laws. Tax contingencies are based upon their technical merits, relative tax law and the specific facts and circumstances as of each reporting period. Changes in facts and circumstances could result in material changes to the amounts recorded for such tax contingencies. The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities based on the technical merits of the position. The tax benefits recognized in the financial statements from such a position are then measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. Employee Benefit Plan —The Company sponsors a qualified 401(k) defined contribution plan covering eligible employees. Participants may contribute a portion of their annual compensation up to a maximum annual amount set by the Internal Revenue Service (“IRS”). Employer contributions under this plan were $9.5 million, $12.0 million and $4.8 million for the years ended December 31, 2019, 2018 and 2017, respectively. Insurance —The Company is self-insured for certain employee benefits include medical, detail and vision; however, the Company obtains third-party excess insurance coverage to limit its exposure to certain claims. Liabilities associated with these benefits include estimates of both claims filed and losses incurred but not yet reported. The Company utilizes valuations provided by reputable, independent third-party actuaries. The Company's self-insured liabilities are included in the consolidated balance sheets within accounts payable and accrued liabilities. Recently Adopted Accounting Pronouncements Lease Accounting —In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2016-02, "Leases (Topic 842)" ("ASC 842"). ASC 842 supersedes the previous accounting guidance for leases included within Accounting Standards Codification 840, "Leases" ("ASC 840"). The new guidance generally requires lessees to recognize operating and financial lease liabilities and corresponding right-of-use assets on the balance sheet and to provide enhanced disclosures on the amount, timing and uncertainty of cash flows arising from lease arrangements. The Company adopted and began applying ASC 842 on January 1, 2019 in accordance with Accounting Standards Update No. 2018-11, "Targeted Improvements to ASC 842," using a modified retrospective approach. Based on its lease portfolio in place at the time of adoption, the Company determined that a cumulative-effect adjustment to the opening balance of accumulated deficit was not needed because there was no difference between the operating lease expense recorded to its condensed consolidated statement of operations following its adoption of ASC 842 and the amount that would have been recorded under ASC 840. The Company will continue to disclose comparative reporting periods prior to January 1, 2019 under ASC 840. The Company elected the practical expedient available under ASC 842 to not record operating lease right-of-use assets or lease liabilities associated with leases with durations of 12 months or less. Those leases will be recorded on a straight line basis to the consolidated statement of operations over the lease term. The Company recorded operating lease right-of-use assets and lease liabilities for all of its leases that met the definition of a lease under ASC 842 and that had terms of greater than 12 months in duration upon its adoption of ASC 842. The Company elected not to take the package of practical expedients permitted under the transition guidance within ASC 842, which allows an entity to not reassess whether any expired or existing contracts contain leases, the lease classification for any expired or existing leases, and treatment of initial direct costs for any existing leases. Additionally, the Company did not elect the hindsight practical expedient to determine the lease terms for existing leases. The most significant changes as a result of ASC 842 were the recognition on the Company's consolidated balance sheet upon adoption on January 1, 2019 of operating lease right-of-use assets of $233.0 million, current operating lease liabilities of $55.2 million and long-term operating lease liabilities of $212.5 million. These balances consist of the Company's office lease portfolio and, to a much lesser extent, its computer equipment lease portfolio. The Company de-recognized deferred rent liabilities associated with its office lease portfolio of $34.8 million upon adoption. Callable Debt Securities —In March 2017, FASB issued Accounting Standards Update No. 2017-08, "Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities" ("ASU 2017-08"). ASU 2017-08 requires entities to amortize purchased callable debt securities held at a premium to the earliest call date. The Company adopted ASU 2017-08 effective January 1, 2019 using t |
