Yelp (YELP) 10-Q 8 Nov 19 2019 Q3 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-35444
Entity Registrant Name	YELP INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-1854266
Entity Address, Address Line One	140 New Montgomery Street, 9th Floor
Entity Address, City or Town	San Francisco,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	(415)
Local Phone Number	908-3801
Title of 12(b) Security	Common Stock, par value $0.000001 per share
Trading Symbol	YELP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		70,201,693
Amendment Flag	false
Entity Central Index Key	0001345016
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 123,402	$ 332,764
Short-term marketable securities	258,414	423,096
Accounts receivable (net of allowance for doubtful accounts of $7,779 and $8,685 at September 30, 2019 and December 31, 2018, respectively)	101,441	87,305
Prepaid expenses and other current assets	16,042	17,104
Total current assets	499,299	860,269
Long-term marketable securities	34,964	0
Property, equipment and software, net	113,935	114,800
Operating lease right-of-use assets	207,852	0
Goodwill	103,459	105,620
Intangibles, net	10,778	13,359
Restricted cash	22,127	22,071
Other non-current assets	36,355	59,444
Total assets	1,028,769	1,175,563
Current liabilities:
Accounts payable	3,139	6,540
Accrued liabilities	71,739	54,522
Operating lease liabilities — current	57,013	0
Deferred revenue	4,222	3,843
Total current liabilities	136,113	64,905
Operating lease liabilities — long-term	186,056	0
Other long-term liabilities	4,036	35,140
Total liabilities	326,205	100,045
Commitments and contingencies (Note 13)
Stockholders' equity:
Common stock, $0.000001 par value, 200,000,000 shares authorized – 70,199,923 and 81,996,839 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	0	0
Additional paid-in capital	1,220,048	1,139,462
Accumulated other comprehensive loss	(13,297)	(11,021)
Accumulated deficit	(504,187)	(52,923)
Total stockholders' equity	702,564	1,075,518
Total liabilities and stockholders' equity	$ 1,028,769	$ 1,175,563

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 7,779	$ 8,685	$ 8,885	$ 8,602
Common stock, par value (in USD per share)	$ 0.000001	$ 0.000001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	70,199,923	81,996,839
Common stock, shares outstanding (in shares)	70,199,923	81,996,839

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net revenue	$ 262,474	$ 241,096	$ 745,371	$ 699,033
Costs and expenses:
Cost of revenue (exclusive of depreciation and amortization shown separately below)	16,514	14,177	45,754	43,618
Sales and marketing	127,655	121,759	374,016	362,054
Product development	56,661	53,764	169,302	158,046
General and administrative	39,703	30,302	101,927	90,892
Depreciation and amortization	12,391	10,713	36,507	31,250
Total costs and expenses	252,924	230,715	727,506	685,860
Income from operations	9,550	10,381	17,865	13,173
Other income, net	3,063	3,921	11,645	9,950
Income before income taxes	12,613	14,302	29,510	23,123
(Provision for) benefit from income taxes	(2,552)	684	(5,781)	281
Net income attributable to common stockholders	$ 10,061	$ 14,986	$ 23,729	$ 23,404
Net income per share attributable to common stockholders
Basic (in USD per share)	$ 0.14	$ 0.18	$ 0.31	$ 0.28
Diluted (in USD per share)	$ 0.14	$ 0.17	$ 0.30	$ 0.26
Weighted-average shares used to compute net income per share attributable to common stockholders
Basic (in shares)	70,773	84,008	75,975	83,865
Diluted (in shares)	73,712	88,724	79,315	89,271

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 10,061	$ 14,986	$ 23,729	$ 23,404
Other comprehensive loss:
Foreign currency translation adjustments	(2,134)	(193)	(2,276)	(1,811)
Foreign currency adjustments to net income upon liquidation of investment in foreign entities	0	0	0	30
Other comprehensive loss	(2,134)	(193)	(2,276)	(1,781)
Comprehensive income	$ 7,927	$ 14,793	$ 21,453	$ 21,623

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Retained Earnings (Accumulated Deficit)
Balance (in shares) at Dec. 31, 2017		83,724,916
Balance at beginning at Dec. 31, 2017	$ 1,108,697	$ 0	$ 1,038,017	$ (46)	$ (8,444)	$ 79,170
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)		737,986
Issuance of common stock upon exercises of employee stock options	14,696		14,696
Issuance of common stock upon vesting of RSUs (in shares)		1,470,127
Issuance of common stock for employee stock purchase plan (in shares)		195,987
Issuance of common stock for employee stock purchase plan	7,139		7,139
Stock-based compensation (inclusive of capitalized stock-based compensation)	90,567		90,567
Shares withheld related to net share settlement of equity awards	(41,220)		(41,220)
Treasury Stock, Value, Acquired, Cost Method	72,008			72,008
Retirement of common stock (in shares)		(1,753,995)
Retirement of common stock				72,054		(72,054)
Foreign currency adjustments	(1,781)				(1,781)
Net income	23,404					23,404
Balance (in shares) at Sep. 30, 2018		84,375,021
Balance at end at Sep. 30, 2018	1,129,494	$ 0	1,109,199	0	(10,225)	30,520
Balance (in shares) at Jun. 30, 2018		83,792,697
Balance at beginning at Jun. 30, 2018	1,098,434	$ 0	1,086,727	0	(10,032)	21,739
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)		237,981
Issuance of common stock upon exercises of employee stock options	5,614		5,614
Issuance of common stock upon vesting of RSUs (in shares)		504,681
Stock-based compensation (inclusive of capitalized stock-based compensation)	30,380		30,380
Shares withheld related to net share settlement of equity awards	(13,522)		(13,522)
Treasury Stock, Value, Acquired, Cost Method	6,205			6,205
Retirement of common stock (in shares)		(160,338)
Retirement of common stock				6,205		(6,205)
Foreign currency adjustments	(193)				(193)
Net income	14,986					14,986
Balance (in shares) at Sep. 30, 2018		84,375,021
Balance at end at Sep. 30, 2018	$ 1,129,494	$ 0	1,109,199	0	(10,225)	30,520
Balance (in shares) at Dec. 31, 2018	81,996,839	81,996,839
Balance at beginning at Dec. 31, 2018	$ 1,075,518	$ 0	1,139,462	0	(11,021)	(52,923)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)	399,320	399,320
Issuance of common stock upon exercises of employee stock options	$ 8,276		8,276
Issuance of common stock upon vesting of RSUs (in shares)		1,510,144
Issuance of common stock for employee stock purchase plan (in shares)		288,529
Issuance of common stock for employee stock purchase plan	7,537		7,537
Stock-based compensation (inclusive of capitalized stock-based compensation)	97,810		97,810
Shares withheld related to net share settlement of equity awards	(33,037)		(33,037)
Treasury Stock, Value, Acquired, Cost Method	474,993			474,993
Retirement of common stock (in shares)		(13,994,909)
Retirement of common stock				474,993		(474,993)
Foreign currency adjustments	(2,276)				(2,276)
Net income	$ 23,729					23,729
Balance (in shares) at Sep. 30, 2019	70,199,923	70,199,923
Balance at end at Sep. 30, 2019	$ 702,564	$ 0	1,220,048	0	(13,297)	(504,187)
Balance (in shares) at Jun. 30, 2019		71,931,789
Balance at beginning at Jun. 30, 2019	746,455	$ 0	1,194,486	(5,952)	(11,163)	(430,916)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)		225,364
Issuance of common stock upon exercises of employee stock options	4,615		4,615
Issuance of common stock upon vesting of RSUs (in shares)		527,233
Stock-based compensation (inclusive of capitalized stock-based compensation)	31,140		31,140
Shares withheld related to net share settlement of equity awards	(10,193)		(10,193)
Treasury Stock, Value, Acquired, Cost Method	77,380			77,380
Retirement of common stock (in shares)		(2,484,463)
Retirement of common stock				83,332		(83,332)
Foreign currency adjustments	(2,134)				(2,134)
Net income	$ 10,061					10,061
Balance (in shares) at Sep. 30, 2019	70,199,923	70,199,923
Balance at end at Sep. 30, 2019	$ 702,564	$ 0	$ 1,220,048	$ 0	$ (13,297)	$ (504,187)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating Activities
Net income attributable to common stockholders	$ 23,729	$ 23,404
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	36,507	31,250
Provision for doubtful accounts	15,259	19,285
Stock-based compensation	91,006	85,732
Noncash lease cost	31,379	0
Deferred income taxes	(673)	0
Other adjustments	(2,559)	(2,793)
Changes in operating assets and liabilities:
Accounts receivable	(29,395)	(24,956)
Prepaid expenses and other assets	(2,312)	(2,085)
Operating lease liabilities	(31,002)	0
Accounts payable, accrued liabilities and other liabilities	17,329	(13,722)
Net cash provided by operating activities	149,268	116,115
Investing Activities
Purchases of marketable securities	(396,648)	(572,788)
Maturities of marketable securities	530,597	460,800
Release of escrow deposit	28,750	0
Purchases of property, equipment and software	(29,950)	(33,937)
Other investing activities	383	64
Net cash provided by (used in) investing activities	133,132	(145,861)
Financing Activities
Proceeds from issuance of common stock for employee stock-based plans	15,813	21,835
Repurchases of common stock	(474,993)	(71,993)
Taxes paid related to the net share settlement of equity awards	(32,784)	(41,081)
Net cash used in financing activities	(491,964)	(91,239)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	258	197
Change in cash, cash equivalents and restricted cash	(209,306)	(120,788)
Cash, cash equivalents and restricted cash — Beginning of period	354,835	566,404
Cash, cash equivalents and restricted cash — End of period	145,529	445,616
Supplemental Disclosures of Other Cash Flow Information
Cash paid for income taxes, net of refunds	5,702	28,820
Supplemental Disclosures of Noncash Investing and Financing Activities
Purchases of property, equipment and software recorded in accounts payable and accrued liabilities	1,856	2,393
Tax liability related to net share settlement of equity awards included in accrued liabilities	896	1,679
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities	$ 6,325	$ 0

DESCRIPTION OF BUSINESS AND BAS

DESCRIPTION OF BUSINESS AND BASIS FOR PRESENTATION	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis for Presentation	DESCRIPTION OF BUSINESS AND BASIS FOR PRESENTATION Yelp Inc. was incorporated in Delaware on September 3, 2004. Except where specifically noted or the context otherwise requires, the use of terms such as the "Company" and "Yelp" in these Notes to Condensed Consolidated Financial Statements refers to Yelp Inc. and its subsidiaries. Yelp connects consumers with great local businesses. Yelp's trusted local platform delivers significant value to both consumers and businesses by helping each discover and interact with the other: its content and transaction capabilities help consumers save time and money, while its advertising and other products help businesses gain visibility and engage with its large audience of purchase-oriented consumers. Basis of Presentation The accompanying interim condensed consolidated financial statements are unaudited. These unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and the applicable rules and regulations of the U.S. Securities and Exchange Commission ("SEC") regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 , filed with the SEC on March 1, 2019 (the "Annual Report"). The unaudited condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited consolidated financial statements as of that date, but does not include all disclosures required by GAAP, including certain notes to the financial statements. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements, except as set forth under "Recently Adopted Accounting Pronouncements" below. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments of a normally recurring nature necessary for the fair presentation of the interim periods presented. Principles of Consolidation These unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated upon consolidation. Use of Estimates The preparation of the Company’s unaudited interim 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. Significant Accounting Policies Except as set forth below, there have been no material changes to the Company's significant accounting policies from those described in the Annual Report. Leases —The Company leases its office facilities under operating lease agreements that expire from 2019 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 condensed 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 has 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. 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 an entity to recognize on its balance sheet operating and finance lease liabilities and corresponding right-of-use assets, as well as to recognize the associated lease expenses on its statements of operations in a manner similar to that required under ASC 840. 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 has elected to use 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. The Company will record those leases on a straight line basis to its consolidated statements of operations over the lease terms. 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 upon its adoption of ASC 842. The Company has elected not to take the package of practical expedients permitted under the transition guidance within the new standard, 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 Company's recognition on its condensed 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, the 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"). This new guidance 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 the modified retrospective method. The Company does not hold any callable debt securities at a premium upon the adoption date, and, accordingly, no adjustment to opening retained earnings was required. Non-employee Share-Based Payment Accounting —In June 2018, the FASB issued Accounting Standards Update No. 2018-07, "Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting" ("ASU 2018-07"). This new guidance changes the accounting for non-employee share-based payments to align with the accounting for employee stock compensation. The Company adopted ASU 2018-07 effective January 1, 2019, and the adoption did not have a material impact on its consolidated financial statements. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income —In February 2018, the FASB issued Accounting Standards Update No. 2018-02, "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU 2018-02"). This new guidance permits a company to reclassify the income tax effects of the U.S. Tax Cuts and Jobs Act on items within accumulated other comprehensive income to retained earnings. ASU 2018-02 is effective for all entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company adopted ASU 2018-02 effective January 1, 2019 and elected to not reclassify the income tax effects of the U.S. Tax Cuts and Jobs Act from accumulated other comprehensive income to retained earnings. Recent Accounting Pronouncements Not Yet Effective In June 2016, the FASB issued Accounting Standards Update No. 2016-13, “Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). This guidance requires certain types of financial instruments, including trade receivables and held-to-maturity investments measured at amortized cost, to be presented at the net amount expected to be collected based on historical events, current conditions and forecast information. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The impact on the Company's consolidated financial statements will depend on the composition and credit quality of its financial instruments, the historical credit loss activity of that portfolio, and reasonable and supportable economic forecast and conditions at the time of adoption. Considering such factors as of September 30, 2019, the adoption of ASU 2016-13 would not have a material impact on its consolidated financial statements. In January 2017, the FASB issued Accounting Standards Update No. 2017-04, "Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment" ("ASU 2017-04"). This new guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the new standard, entities will perform goodwill impairment tests by comparing fair value of a reporting unit with its carrying amount, and will recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company does not expect the adoption of ASU 2017-04 to have a material impact on its consolidated financial statements. In August 2018, the FASB issued Accounting Standards Update No. 2018-13, "Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement" (“ASU 2018-13”), which amends Accounting Standards Codification 820, "Fair Value Measurement." ASU 2018-13 modifies the disclosure requirements for fair value measurements by removing, modifying and adding certain disclosures. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company does not expect the adoption of ASU 2018-13 to have a material impact on its consolidated financial statements. In August 2018, the FASB issued Accounting Standards Update No. 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract" ("ASU 2018-15"). This new guidance requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification 350-40 to determine which implementation costs to defer and recognize as an asset. ASU 2018-15 generally aligns the guidance on recognizing implementation costs incurred in a cloud computing arrangement that is a service contract with that for implementation costs incurred to develop or obtain internal-use software, including hosting arrangements that include an internal-use software license. ASU 2018-15 is effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently assessing the impact of ASU 2018-15 on its consolidated financial statements.

CASH, CASH EQUIVALENTS AND REST

CASH, CASH EQUIVALENTS AND RESTRICTED CASH	9 Months Ended
	Sep. 30, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Restricted Cash	CASH, CASH EQUIVALENTS AND RESTRICTED CASH Cash, cash equivalents and restricted cash as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Cash $ 31,729 $ 81,055 Cash equivalents 91,673 251,709 Total cash and cash equivalents $ 123,402 $ 332,764 Restricted cash 22,127 22,071 Total cash, cash equivalents and restricted cash $ 145,529 $ 354,835 As of September 30, 2019 and December 31, 2018 , the Company had letters of credit collateralized fully by bank deposits that totaled $22.1 million and $22.1 million , respectively. These letters of credit primarily relate to lease agreements for certain of the Company’s offices, which are required to be maintained and issued to the landlords of each facility. Each letter of credit is subject to renewal annually until the applicable lease expires. As the bank deposits have restrictions on their use, they are classified as restricted cash on the Company's condensed consolidated balance sheets.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s investments in money market accounts are recorded as cash equivalents at fair value on the condensed consolidated balance sheets. All other financial instruments are classified as held-to-maturity investments and, accordingly, are recorded at amortized cost; however, the Company is required to determine the fair value of these investments on a recurring basis to identify any potential impairment. The accounting guidance for fair value measurements prioritizes the inputs used in measuring fair value in the following hierarchy: Level 1 —Observable inputs, such as quoted prices in active markets, Level 2 —Inputs other than quoted prices in active markets that are observable either directly or indirectly, or Level 3 —Unobservable inputs in which there are little or no market data, which require the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, to minimize the use of unobservable inputs when determining fair value. The Company’s money market funds are classified within Level 1 of the fair value hierarchy because they are valued using quoted prices in active markets. The Company’s commercial paper, corporate bonds, U.S. government bonds and agency bonds are classified within Level 2 of the fair value hierarchy because they have been valued using inputs other than quoted prices in active markets that are observable directly or indirectly. The following table represents the fair value of the Company’s financial instruments, including those measured at fair value on a recurring basis and those held-to-maturity, as of September 30, 2019 and December 31, 2018 (in thousands): September 30, 2019 December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 91,673 $ — $ — $ 91,673 $ 221,173 $ — $ — $ 221,173 Commercial paper — — — — — 30,536 — 30,536 Marketable securities: Commercial paper — 129,500 — 129,500 — 175,070 — 175,070 Corporate bonds — 85,154 — 85,154 — 131,496 — 131,496 Agency bonds — 79,210 — 79,210 — 50,846 — 50,846 U.S. government bonds — — — — — 65,502 — 65,502 Total cash equivalents and marketable securities $ 91,673 $ 293,864 $ — $ 385,537 $ 221,173 $ 453,450 $ — $ 674,623

MARKETABLE SECURITIES

MARKETABLE SECURITIES	9 Months Ended
	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	MARKETABLE SECURITIES The amortized cost, gross unrealized gains and losses, and fair value of marketable securities classified as held-to-maturity as of September 30, 2019 and December 31, 2018 were as follows (in thousands): September 30, 2019 Amortized Gross Gross Fair Short-term marketable securities: Commercial paper $ 129,454 $ 50 $ (4 ) $ 129,500 Corporate bonds 74,865 247 — 75,112 Agency bonds 54,095 118 (1 ) 54,212 Total short-term marketable securities 258,414 415 (5 ) 258,824 Long-term marketable securities: Agency bonds 25,000 2 (4 ) 24,998 Corporate bonds 9,964 78 — 10,042 Total long-term marketable securities 34,964 80 (4 ) 35,040 Total marketable securities $ 293,378 $ 495 $ (9 ) $ 293,864 December 31, 2018 Amortized Gross Gross Fair Cash equivalents: Commercial paper $ 30,536 $ — $ — $ 30,536 Total cash equivalents 30,536 — — 30,536 Short-term marketable securities: Commercial paper 175,070 — — 175,070 Corporate bonds 131,626 8 (138 ) 131,496 U.S. government bonds 65,513 — (11 ) 65,502 Agency bonds 50,887 — (41 ) 50,846 Total short-term marketable securities 423,096 8 (190 ) 422,914 Total marketable securities $ 453,632 $ 8 $ (190 ) $ 453,450 The following tables present gross unrealized losses and fair values for those securities that were in an unrealized loss position as of September 30, 2019 and December 31, 2018 , aggregated by investment category and the length of time that the individual securities have been in a continuous loss position (in thousands): September 30, 2019 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Commercial paper $ 41,817 $ (4 ) $ — $ — $ 41,817 $ (4 ) Agency bonds 19,994 (5 ) — — 19,994 (5 ) Total $ 61,811 $ (9 ) $ — $ — $ 61,811 $ (9 ) December 31, 2018 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 121,566 $ (138 ) $ — $ — $ 121,566 $ (138 ) U.S. government bonds 65,502 (11 ) — — 65,502 (11 ) Agency bonds 50,846 (41 ) — — 50,846 (41 ) Total $ 237,914 $ (190 ) $ — $ — $ 237,914 $ (190 ) The Company periodically reviews its investment portfolio for other-than-temporary impairment. The Company considers such factors as the duration, severity and reason for the decline in value, and the potential recovery period. The Company also considers whether it is more likely than not that it will be required to sell the securities before the recovery of their amortized cost basis, and whether the amortized cost basis cannot be recovered as a result of credit losses. During the three and nine months ended September 30, 2019 and 2018 , the Company did not recognize any other-than-temporary impairment losses.

PREPAID EXPENSES AND OTHER CURR

PREPAID EXPENSES AND OTHER CURRENT ASSETS	9 Months Ended
	Sep. 30, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	PREPAID EXPENSES AND OTHER CURRENT ASSETS Prepaid expenses and other current assets as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Prepaid expenses $ 11,970 $ 9,436 Other current assets 4,072 7,668 Total prepaid expenses and other current assets $ 16,042 $ 17,104

PROPERTY, EQUIPMENT AND SOFTWAR

PROPERTY, EQUIPMENT AND SOFTWARE, NET	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Property, Equipment and Software, Net	PROPERTY, EQUIPMENT AND SOFTWARE, NET Property, equipment and software, net as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Capitalized website and internal-use software development costs $ 133,551 $ 108,590 Leasehold improvements 85,983 83,811 Computer equipment 43,276 40,801 Furniture and fixtures 18,372 17,839 Telecommunication 4,855 4,691 Software 2,217 1,651 Total 288,254 257,383 Less accumulated depreciation (174,319 ) (142,583 ) Property, equipment and software, net $ 113,935 $ 114,800 Depreciation expense was approximately $11.6 million and $9.8 million for the three months ended September 30, 2019 and 2018 , respectively, and approximately $33.9 million and $28.6 million for the nine months ended September 30, 2019 and 2018 , respectively.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	GOODWILL AND INTANGIBLE ASSETS The Company’s goodwill is the result of its acquisitions of other businesses, and represents the excess of purchase consideration over the fair value of assets acquired and liabilities assumed. The Company performed its annual goodwill impairment analysis as of August 31, 2019 and concluded that goodwill was not impaired, as the fair value of each reporting unit exceeded its carrying value. The changes in carrying amount of goodwill during the nine months ended September 30, 2019 were as follows (in thousands): Balance as of December 31, 2018 $ 105,620 Effect of currency translation (2,161 ) Balance as of September 30, 2019 $ 103,459 Intangible assets at September 30, 2019 and December 31, 2018 consisted of the following (dollars in thousands): September 30, 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life Business relationships $ 9,918 $ (2,598 ) $ 7,320 8.8 years Developed technology 7,832 (4,640 ) 3,192 2.5 years Content 3,750 (3,750 ) — 0.0 years Domains and data licenses 2,869 (2,699 ) 170 1.6 years Trademarks 877 (798 ) 79 0.4 years User relationships 146 (129 ) 17 0.5 years Total $ 25,392 $ (14,614 ) $ 10,778 December 31, 2018 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life Business relationships $ 9,918 $ (1,868 ) $ 8,050 9.4 years Developed technology 7,832 (3,562 ) 4,270 3.1 years Content 3,873 (3,696 ) 177 0.8 years Domain and data licenses 2,869 (2,359 ) 510 1.5 years Trademarks 877 (579 ) 298 1.2 years User relationships 146 (92 ) 54 1.2 years Total $ 25,515 $ (12,156 ) $ 13,359 Amortization expense was $0.8 million and $0.9 million for the three months ended September 30, 2019 and 2018 , respectively, and $2.6 million and $2.7 million for the nine months ended September 30, 2019 and 2018 , respectively. As of September 30, 2019 , the estimated future amortization of purchased intangible assets for (i) the remaining three months of 2019 , (ii) each of the succeeding five years, and (iii) thereafter was as follows (in thousands): Year Ending December 31, Amount 2019 (from October 1, 2019) $ 696 2020 2,402 2021 2,262 2022 1,045 2023 714 2024 708 Thereafter 2,951 Total amortization $ 10,778

LEASES

LEASES	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	LEASES The components of lease cost as of September 30, 2019 were as follows (in thousands): Three Months Ended Nine Months Ended Operating lease cost $ 13,544 $ 40,878 Short-term lease cost (12 months or less) 291 938 Sublease income (1,475 ) (2,764 ) Total lease cost, net $ 12,360 $ 39,052 The Company will continue to disclose comparative reporting periods prior to January 1, 2019 under ASC 840. During the three and nine months ended September 30, 2018 , the Company recognized rent expense, net of sublease rental income, on a straight-line basis over the lease period. Rent expense, net, was $13.7 million and $37.7 million for the three and nine months ended September 30, 2018 , respectively. The Company has subleased certain office facilities under operating lease agreements that expire in 2025. The sublease agreements do not contain any options to renew. The Company recognizes sublease rental income as a reduction in rent expense on a straight-line basis over the lease period. Sublease rental income was $0.5 million and $1.7 million for the three and nine months ended September 30, 2018 . 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 was not required to exercise any judgment in determining such allocations. The Company's leases and subleases do not include any variable lease payments, residual value guarantees, related-party leases, or restrictions or covenants which would limit or prevent the Company's right to obtain substantially all of economic benefits from use of the respective assets during the lease term. Supplemental cash flow information related to leases for the nine months ended September 30, 2019 was as follows (in thousands): September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 42,323 As of September 30, 2019 , maturities of lease liabilities for (i) the remaining three months of 2019 , (ii) each of the succeeding five years, and (iii) thereafter were as follows (in thousands): Year Ending December 31, Operating 2019 (from October 1, 2019) $ 14,495 2020 59,435 2021 52,055 2022 44,712 2023 41,652 2024 39,420 Thereafter 37,112 Total minimum lease payments 288,881 Less imputed interest (45,812 ) Present value of lease liabilities $ 243,069 As of December 31, 2018 , maturities of lease liabilities for (i) each of the succeeding five years and (ii) thereafter were as follows (in thousands): Year Ending December 31, Operating 2019 $ 56,703 2020 59,009 2021 51,429 2022 43,603 2023 40,517 Thereafter 69,980 Total minimum lease payments $ 321,241 As of September 30, 2019 , the weighted-average remaining lease term and weighted-average discount rate were as follows: September 30, 2019 Weighted-average remaining lease term (years) — operating leases 5.8 Weighted-average discount rate — operating leases 6.0 % In October 2019, the Company entered into a lease agreement for an office facility in London, U.K., which expires in 2030 and we expect to classify as an operating lease. The Company expects to record $15 million of operating lease cost over the life of the lease.

OTHER NON-CURRENT ASSETS

OTHER NON-CURRENT ASSETS	9 Months Ended
	Sep. 30, 2019
Other Assets, Noncurrent Disclosure [Abstract]
Other Non-Current Assets	OTHER NON-CURRENT ASSETS Other non-current assets as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Deferred tax assets $ 19,076 $ 17,240 Deferred contract costs 13,993 12,345 Escrow deposit — 28,750 Other non-current assets 3,286 1,109 Total other non-current assets $ 36,355 $ 59,444 The escrow deposit as of December 31, 2018 consisted of the funds held in escrow in connection with the Company's sale of its wholly owned subsidiary, Eat24, LLC ("Eat24") to Grubhub Holdings Inc. ("Purchaser") in October 2017. A portion of the purchase price was held in escrow for an initial 18-month period after closing to secure the Purchaser's rights of indemnification in the transaction. Following the expiration of the escrow period in April 2019, the deposit was released to the Company. Deferred contract costs as of September 30, 2019 and December 31, 2018 , and changes in deferred contract costs during the nine months ended September 30, 2019 , were as follows (in thousands): Nine Months Ended Balance, beginning of period $ 12,345 Add: costs deferred on new contracts 10,236 Less: amortization recorded in sales and marketing expenses (8,588 ) Balance, end of period $ 13,993

CONTRACT BALANCES

CONTRACT BALANCES	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Contract Balances	CONTRACT BALANCES The allowance for doubtful accounts as of September 30, 2019 and 2018 and changes in the allowance for doubtful accounts during the nine months ended September 30, 2019 and 2018 were as follows (in thousands): Nine Months Ended 2019 2018 Balance, beginning of period $ 8,685 $ 8,602 Add: provision for doubtful accounts 15,259 19,285 Less: write-offs, net of recoveries (16,165 ) (19,002 ) Balance, end of period $ 7,779 $ 8,885 Contract liabilities consist of deferred revenue, which is recorded on the consolidated balance sheets when the Company has received consideration, or has the right to receive consideration, in advance of transferring the performance obligations under the contract to the customer. As of September 30, 2019 , deferred revenue was $4.2 million , the majority of which is expected to be recognized as revenue in the subsequent three-month period ending December 31, 2019. Changes in deferred revenue during the nine months ended September 30, 2019 were as follows (in thousands): Nine Months Ended Balance, beginning of period $ 3,843 Less: recognition of deferred revenue from beginning balance (3,539 ) Add: net increase in current period contract liabilities 3,918 Balance, end of period $ 4,222 The net increase in contract liabilities primarily relates to new contracts with customers during the periods presented. No other contract assets or liabilities are recorded on the Company's condensed consolidated balance sheets as of September 30, 2019 and December 31, 2018 .

ACCRUED LIABILITIES

ACCRUED LIABILITIES	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Accrued Liabilities	ACCRUED LIABILITIES Accrued liabilities as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Accrued employee compensation and related $ 44,258 $ 21,580 Accrued tax liabilities 5,831 5,491 Accrued cost of revenue 6,875 5,463 Accrued sales and marketing expenses 3,880 4,536 Other accrued liabilities 10,895 17,452 Total accrued liabilities $ 71,739 $ 54,522

OTHER LONG-TERM LIABILITIES

OTHER LONG-TERM LIABILITIES	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Other Long-Term Liabilities	OTHER LONG-TERM LIABILITIES Other long-term liabilities as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Deferred rent $ — $ 31,253 Other long-term liabilities 4,036 3,887 Total other long-term liabilities $ 4,036 $ 35,140 The Company de-recognized the deferred rent balance as of December 31, 2018 upon its adoption of ASC 842 on January 1, 2019. See " Note 1. Description of Business and Basis for Presentation ".

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Legal Proceedings —In January 2018, a putative class action lawsuit alleging violations of the federal securities laws was filed in the U.S. District Court for the Northern District of California, naming as defendants the Company and certain of its officers. The complaint, which the plaintiff amended on June 25, 2018, alleges violations of the Exchange Act by the Company and its officers for allegedly making materially false and misleading statements regarding its business and operations on February 9, 2017. The plaintiff seeks unspecified monetary damages and other relief. On August 2, 2018, the Company and the other defendants filed a motion to dismiss the amended complaint, which the court granted in part and denied in part on November 27, 2018. On October 22, 2019, the Court approved a stipulation to certify a class in this action. The case remains pending. Due to the preliminary nature of this lawsuit, the Company is unable to reasonably estimate either the probability of incurring a loss or an estimated range of such loss, if any, from the lawsuit. The Company is subject to other legal proceedings arising in the ordinary course of business. Although the results of litigation and claims cannot be predicted with certainty, the Company currently does not believe that the final outcome of any of these other matters will have a material effect on the Company’s business, financial position, results of operations or cash flows. Indemnification Agreements —In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to customers, vendors, lessors, business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements, services to be provided by the Company or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with directors and certain officers and employees that will require the Company to, among other things, indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. While the outcome of claims cannot be predicted with certainty, the Company does not believe that the outcome of any claims under the indemnification arrangements will have a material effect on the Company’s financial position, results of operations or cash flows.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	9 Months Ended
	Sep. 30, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY The following table presents the number of shares authorized and issued as of the dates indicated: September 30, 2019 December 31, 2018 Shares Authorized Shares Issued Shares Authorized Shares Issued Stockholders’ equity: Common stock, $0.000001 par value 200,000,000 70,199,923 200,000,000 81,996,839 Undesignated preferred stock 10,000,000 — 10,000,000 — Stock Repurchase Program On July 31, 2017 , the Company’s board of directors authorized a stock repurchase program under which the Company was authorized to repurchase up to $200.0 million of its outstanding common stock. This program was completed on November 16, 2018 . On November 27, 2018 , the Company's board of directors authorized the Company to repurchase up to an additional $250.0 million of its outstanding common stock, which it subsequently increased by an additional $250.0 million on February 11, 2019, bringing the total amount of repurchases authorized under its stock repurchase program to $500.0 million . The Company may purchase shares at management’s discretion in the open market, in privately negotiated transactions, in transactions structured through investment banking institutions, or a combination of the foregoing. During the nine months ended September 30, 2019 , the Company repurchased on the open market and retired 13,994,909 shares for an aggregate purchase price of $475.0 million . The Company had no treasury stock balance as of September 30, 2019 . During the nine months ended September 30, 2018 , the Company repurchased on the open market and retired 1,752,895 shares for an aggregate purchase price of $72.0 million . The Company had no treasury stock balance as of September 30, 2018 . Equity Incentive Plans The Company has outstanding awards under three equity incentive plans: the Amended and Restated 2005 Equity Incentive Plan (the "2005 Plan"), the 2011 Equity Incentive Plan (the "2011 Plan") and the 2012 Equity Incentive Plan, as amended (the "2012 Plan"). In July 2011, the Company adopted the 2011 Plan, terminated the 2005 Plan and provided that no further stock awards were to be granted under the 2005 Plan. All outstanding stock awards under the 2005 Plan continue to be governed by their existing terms. Upon the effectiveness of the underwriting agreement in connection with the Company’s initial public offering ("IPO"), the Company terminated the 2011 Plan and all shares that were reserved under the 2011 Plan but not issued were assumed by the 2012 Plan. No further awards have been or will be granted pursuant to the 2011 Plan. All outstanding stock awards under the 2011 Plan continue to be governed by their existing terms. Under the 2012 Plan, the Company has the ability to issue incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock units ("RSUs"), restricted stock awards, performance units and performance shares. Additionally, the 2012 Plan provides for the grant of performance cash awards to employees, directors and consultants. Stock Options Stock options granted under the 2012 Plan are granted at a price per share not less than the fair value of a share of the Company’s common stock at date of grant. Options granted to date generally vest over a three - or four -year period, on one of four schedules: (a) 25% vesting at the end of one year and the remaining shares vesting monthly thereafter; (b) 10% vesting over the first year, 20% vesting over the second year, 30% vesting over the third year and 40% vesting over the fourth year; (c) ratably on a monthly basis; or (d) 35% vesting over the first year, 40% vesting over the second year and 25% vesting over the third year. Options granted are generally exercisable for contractual terms of up to 10 years . The Company issues new shares when stock options are exercised. A summary of stock option activity for the nine months ended September 30, 2019 is as follows: Number of Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 6,818,682 $ 24.54 5.11 $ 88,983 Granted 662,150 36.06 Exercised (399,320 ) 20.74 Canceled (339,301 ) 40.88 Outstanding at September 30, 2019 6,742,211 $ 25.11 4.36 $ 81,195 Options vested and exercisable at September 30, 2019 5,683,209 $ 22.78 3.59 $ 80,712 Aggregate intrinsic value represents the difference between the closing price of the Company’s common stock as quoted on the New York Stock Exchange on a given date and the exercise price of outstanding, in-the-money options. The total intrinsic value of options exercised was approximately $3.4 million and $5.3 million for the three months ended September 30, 2019 and 2018 , respectively, and $6.2 million and $18.1 million for the nine months ended September 30, 2019 and 2018 , respectively. There were no options granted in the three months ended September 30, 2019 . The weighted-average grant date fair value of options granted was $23.41 per share for the three months ended September 30, 2018 and $17.64 and $18.89 per share for the nine months ended September 30, 2019 and 2018 , respectively. As of September 30, 2019 , total unrecognized compensation costs related to nonvested stock options was approximately $17.6 million , which the Company expects to recognize over a weighted-average time period of 2.5 years . RSUs The cost of RSUs is determined using the fair value of the Company’s common stock on the date of grant. RSUs generally vest over a four -year period, on one of three schedules: (a) 25% vesting at the end of one year and the remaining vesting quarterly or annually thereafter; (b) 10% vesting over the first year, 20% vesting over the second year, 30% vesting over the third year and 40% vesting over the fourth year; or (c) ratably on a quarterly basis. RSUs also include performance-based restricted stock units ("PRSUs") for which the expense is recognized from the date of grant. The PRSUs are subject to both a performance goal and a time-based vesting schedule. The shares underlying each PRSU award will be eligible to vest only if the average closing price of the Company's common stock equals or exceeds $45.3125 over any 60-day trading period during the four years following the grant date of February 7, 2019 (the "Performance Goal"). If the Performance Goal is met, the shares underlying each PRSU award will vest quarterly over four years from the grant date (the "Time-Based Vesting Schedule"). Any shares subject to the PRSUs that have met the Time-Based Vesting Schedule at the time the Performance Goal is achieved will fully vest as of such date; thereafter, any remaining nonvested shares subject to the PRSUs will continue vesting solely according to the Time-Based Vesting Schedule. Due to the multiple obligations that exist for the PRSUs, a Monte Carlo model was used to determine the fair value of these awards. As the PRSU activity during the nine months ended September 30, 2019 was not material, it is presented together with the RSU activity in the table below. A summary of RSU activity for the nine months ended September 30, 2019 is as follows: Number of Shares Weighted-Average Grant Date Fair Value Nonvested at December 31, 2018 6,563,863 $ 38.67 Granted 4,361,791 35.06 Vested (1) (2,469,190 ) 35.97 Canceled (1,462,739 ) 37.99 Nonvested at September 30, 2019 6,993,725 $ 37.51 (1) Includes 959,046 shares that vested but were not issued due to net share settlement for payment of employee taxes. The aggregate fair value as of the vest date of RSUs that vested during the nine months ended September 30, 2019 and 2018 was $84.9 million and $107.4 million , respectively. As of September 30, 2019 , the Company had approximately $251.1 million of unrecognized stock-based compensation expense related to RSUs, which it expects to recognize over the remaining weighted-average vesting period of approximately 2.7 years . Employee Stock Purchase Plan The 2012 Employee Stock Purchase Plan, as amended ("ESPP"), allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations, during designated offering periods. At the end of each offering period, employees are able to purchase shares at 85% of the fair market value of the Company’s common stock on the last day of the offering period, based on the closing sales price of the Company's common stock as quoted on the New York Stock Exchange on such date. There were no shares purchased by employees under the ESPP in the three months ended September 30, 2019 and 2018 . Employees purchased 288,529 shares and 195,987 shares under the ESPP in the nine months ended September 30, 2019 and 2018 , respectively, at weighted-average purchase prices of $26.12 and $36.42 per share, respectively. The Company recognized stock-based compensation expense related to the ESPP of $0.7 million and $0.7 million in the three months ended September 30, 2019 and 2018 , respectively, and $2.0 million and $2.0 million in the nine months ended September 30, 2019 and 2018 , respectively. Stock-Based Compensation The following table summarizes the effects of stock-based compensation expense related to stock-based awards in the condensed consolidated statements of operations during the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Cost of revenue $ 1,054 $ 1,162 $ 3,415 $ 3,345 Sales and marketing 7,683 7,941 23,143 23,514 Product development 15,250 14,536 46,572 41,878 General and administrative 5,249 5,555 17,876 16,995 Total stock-based compensation recorded to income before income taxes 29,236 29,194 91,006 85,732 Benefit from income taxes (7,661 ) (167 ) (23,766 ) (476 ) Total stock-based compensation recorded to net income $ 21,575 $ 29,027 $ 67,240 $ 85,256 The Company capitalized $2.6 million and $1.9 million of stock-based compensation expense as website development costs in the three months ended September 30, 2019 and 2018 , respectively, and $7.6 million and $5.9 million in the nine months ended September 30, 2019 and 2018 , respectively.

OTHER INCOME, NET

OTHER INCOME, NET	9 Months Ended
	Sep. 30, 2019
Other Income and Expenses [Abstract]
Other Income, Net	OTHER INCOME, NET Other income, net for the three and nine months ended September 30, 2019 and 2018 consisted of the following (in thousands): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Interest income, net $ 2,830 $ 3,705 $ 10,946 $ 9,606 Transaction gain (loss) on foreign exchange (20 ) 75 93 89 Other non-operating income, net 253 141 606 255 Other income, net $ 3,063 $ 3,921 $ 11,645 $ 9,950

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The Company is subject to income tax in the United States as well as other tax jurisdictions in which it conducts business. Earnings from non-U.S. activities are subject to local country income tax. The provision for income taxes for the nine months ended September 30, 2019 was $5.8 million , which was due to $5.5 million U.S. federal, state and foreign income tax expense and $0.3 million of net discrete tax expense. The benefit from income taxes for the nine months ended September 30, 2018 was $0.3 million , which was due to $1.2 million U.S. federal, state and foreign income tax expense, offset by $1.5 million of net discrete tax benefits. Accounting for income taxes for interim periods generally requires the provision for income taxes to be determined by applying an estimate of the annual effective tax rate for the full fiscal year to income or loss before income taxes, excluding unusual or infrequently occurring discrete items ("Ordinary" income), for the reporting period. For the three and nine months ended September 30, 2019 , the difference between the effective tax rate and the federal statutory tax rate primarily relates to tax credits and non-deductible expenses. For the three and nine months ended September 30, 2018 , rather than applying an estimate of the annual effective tax rate for the full year Ordinary income, a discrete effective tax rate method was used in jurisdictions where a small change in estimated Ordinary income had a significant impact on the annual effective tax rate. As of September 30, 2019 , the total amount of gross unrecognized tax benefits was $38.6 million , $16.3 million of which is subject to a full valuation allowance and would not affect the Company’s effective tax rate if recognized. In the nine months ended September 30, 2019 , the Company has recorded an immaterial amount of interest and penalties. As of September 30, 2019 , the Company estimates that it had accumulated undistributed earnings generated by its foreign subsidiaries of approximately $3.5 million . Any taxes due with respect to such earnings or the excess of the amount for financial reporting over the tax basis of the Company's foreign investments would generally be limited to foreign and state taxes. The Company has not recognized a deferred tax liability related to un-remitted foreign earnings, as it intends to indefinitely reinvest these earnings, and expects future U.S. cash generation to be sufficient to meet future U.S. cash needs. In addition, the Company is subject to the continuous examination of its income tax returns by the Internal Revenue Service and other tax authorities. The Company’s federal and state income tax returns for tax years subsequent to 2003 remain open to examination. In the Company’s most significant foreign jurisdictions — Canada, Ireland, the United Kingdom and Germany — the tax years subsequent to 2014 remain open to examination. The Company regularly assesses the likelihood of adverse outcomes resulting from examinations to determine the adequacy of its provision for income taxes, and monitors the progress of ongoing discussions with tax authorities and the impact, if any, of the expected expiration of the statute of limitations in various taxing jurisdictions. The Company believes that an adequate provision has been made for any adjustments that may result from tax examinations. However, the outcome of tax audits cannot be predicted with certainty. If any issues addressed in the Company’s tax audits are resolved in a manner not consistent with management’s expectations, the Company could be required to adjust its provision for income taxes in the period such resolution occurs. As of September 30, 2019 , although the timing of the resolution or closure of audits is not certain, the Company believes it is reasonably possible that its unrecognized tax benefits could be reduced by an immaterial amount over the next 12 months.

NET INCOME PER SHARE

NET INCOME PER SHARE	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Income Per Share	NET INCOME PER SHARE Basic net income per share is computed using the weighted-average number of outstanding shares of common stock during the period. Diluted net income per share is computed using the weighted-average number of outstanding shares of common stock and, when dilutive, potential shares of common stock outstanding during the period. Potential common shares consist of the incremental shares of common stock issuable upon the exercise of stock options, shares issuable upon the vesting of RSUs and, to a lesser extent, purchase rights related to the ESPP. The following table presents the calculation of basic and diluted net income per share for the periods presented (in thousands, except per share data): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Basic net income per share: Net income $ 10,061 $ 14,986 $ 23,729 $ 23,404 Shares used in computation: Weighted-average common shares outstanding 70,773 84,008 75,975 83,865 Basic net income per share attributable to common stockholders $ 0.14 $ 0.18 $ 0.31 $ 0.28 Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Diluted net income per share: Net income $ 10,061 $ 14,986 $ 23,729 $ 23,404 Shares used in computation: Weighted-average common shares outstanding 70,773 84,008 75,975 83,865 Stock options 2,345 3,011 2,429 3,096 Restricted stock units 478 1,656 870 2,240 Employee stock purchase program 116 49 41 70 Number of shares used in diluted calculation 73,712 88,724 79,315 89,271 Diluted net income per share attributable to common stockholders $ 0.14 $ 0.17 $ 0.30 $ 0.26 The following weighted-average stock-based instruments were excluded from the calculation of diluted net income per share because their effect would have been anti-dilutive for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Stock options 2,718 1,694 2,629 1,681 Restricted stock units 2,718 591 2,530 106

INFORMATION ABOUT REVENUE AND G

INFORMATION ABOUT REVENUE AND GEOGRAPHIC AREAS	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Information About Revenue and Geographic Areas	INFORMATION ABOUT REVENUE AND GEOGRAPHIC AREAS The Company has concluded that it has one operating segment, with its Chief Executive Officer as its Chief Operating Decision Maker ("CODM"). While the Company has expanded its product offerings in recent years to increase the value provided to both consumers and businesses, those product offerings operate on, interact with, or are complementary to Yelp's local platform. In addition, the Company’s CODM regularly reviews financial information, makes decisions to allocate resources, and assesses performance on a consolidated basis. When the Company communicates results externally, it disaggregates net revenue into major product lines. The disaggregation of revenue by major product lines is based on the type of service provided and also aligns with the timing of revenue recognition. Net Revenue The following table presents the Company’s net revenue by major product line for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Net revenue by product: Advertising $ 253,098 $ 232,502 $ 717,973 $ 672,712 Transactions 3,074 3,042 9,528 10,402 Other services 6,302 5,552 17,870 15,919 Total net revenue $ 262,474 $ 241,096 $ 745,371 $ 699,033 During the three and nine months ended September 30, 2019 and 2018 , no individual customer accounted for 10% or more of consolidated net revenue. The following table presents the Company’s net revenue by major geographic region for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 United States $ 258,820 $ 237,597 $ 735,169 $ 689,096 All other countries 3,654 3,499 10,202 9,937 Total net revenue $ 262,474 $ 241,096 $ 745,371 $ 699,033 Long-Lived Assets The following table presents the Company’s long-lived assets by major geographic region for the periods presented (in thousands): September 30, December 31, United States $ 112,700 $ 112,984 All other countries 1,235 1,816 Total long-lived assets $ 113,935 $ 114,800

DESCRIPTION OF BUSINESS AND B_2

DESCRIPTION OF BUSINESS AND BASIS FOR PRESENTATION (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements are unaudited. These unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and the applicable rules and regulations of the U.S. Securities and Exchange Commission ("SEC") regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 , filed with the SEC on March 1, 2019 (the "Annual Report"). The unaudited condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited consolidated financial statements as of that date, but does not include all disclosures required by GAAP, including certain notes to the financial statements. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements, except as set forth under "Recently Adopted Accounting Pronouncements" below. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments of a normally recurring nature necessary for the fair presentation of the interim periods presented.
Principles of Consolidation	Principles of Consolidation These unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of the Company’s unaudited interim 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.
Leases	Leases —The Company leases its office facilities under operating lease agreements that expire from 2019 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 condensed 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 has 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.
Recently Adopted Accounting Pronouncements and Recent Accounting Pronouncements Not Yet Effective	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 an entity to recognize on its balance sheet operating and finance lease liabilities and corresponding right-of-use assets, as well as to recognize the associated lease expenses on its statements of operations in a manner similar to that required under ASC 840. 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 has elected to use 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. The Company will record those leases on a straight line basis to its consolidated statements of operations over the lease terms. 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 upon its adoption of ASC 842. The Company has elected not to take the package of practical expedients permitted under the transition guidance within the new standard, 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 Company's recognition on its condensed 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, the 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"). This new guidance 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 the modified retrospective method. The Company does not hold any callable debt securities at a premium upon the adoption date, and, accordingly, no adjustment to opening retained earnings was required. Non-employee Share-Based Payment Accounting —In June 2018, the FASB issued Accounting Standards Update No. 2018-07, "Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting" ("ASU 2018-07"). This new guidance changes the accounting for non-employee share-based payments to align with the accounting for employee stock compensation. The Company adopted ASU 2018-07 effective January 1, 2019, and the adoption did not have a material impact on its consolidated financial statements. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income —In February 2018, the FASB issued Accounting Standards Update No. 2018-02, "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU 2018-02"). This new guidance permits a company to reclassify the income tax effects of the U.S. Tax Cuts and Jobs Act on items within accumulated other comprehensive income to retained earnings. ASU 2018-02 is effective for all entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company adopted ASU 2018-02 effective January 1, 2019 and elected to not reclassify the income tax effects of the U.S. Tax Cuts and Jobs Act from accumulated other comprehensive income to retained earnings. Recent Accounting Pronouncements Not Yet Effective In June 2016, the FASB issued Accounting Standards Update No. 2016-13, “Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). This guidance requires certain types of financial instruments, including trade receivables and held-to-maturity investments measured at amortized cost, to be presented at the net amount expected to be collected based on historical events, current conditions and forecast information. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The impact on the Company's consolidated financial statements will depend on the composition and credit quality of its financial instruments, the historical credit loss activity of that portfolio, and reasonable and supportable economic forecast and conditions at the time of adoption. Considering such factors as of September 30, 2019, the adoption of ASU 2016-13 would not have a material impact on its consolidated financial statements. In January 2017, the FASB issued Accounting Standards Update No. 2017-04, "Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment" ("ASU 2017-04"). This new guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the new standard, entities will perform goodwill impairment tests by comparing fair value of a reporting unit with its carrying amount, and will recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company does not expect the adoption of ASU 2017-04 to have a material impact on its consolidated financial statements. In August 2018, the FASB issued Accounting Standards Update No. 2018-13, "Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement" (“ASU 2018-13”), which amends Accounting Standards Codification 820, "Fair Value Measurement." ASU 2018-13 modifies the disclosure requirements for fair value measurements by removing, modifying and adding certain disclosures. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company does not expect the adoption of ASU 2018-13 to have a material impact on its consolidated financial statements. In August 2018, the FASB issued Accounting Standards Update No. 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract" ("ASU 2018-15"). This new guidance requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification 350-40 to determine which implementation costs to defer and recognize as an asset. ASU 2018-15 generally aligns the guidance on recognizing implementation costs incurred in a cloud computing arrangement that is a service contract with that for implementation costs incurred to develop or obtain internal-use software, including hosting arrangements that include an internal-use software license. ASU 2018-15 is effective for the first interim period within annual reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently assessing the impact of ASU 2018-15 on its consolidated financial statements.

CASH, CASH EQUIVALENTS AND RE_2

CASH, CASH EQUIVALENTS AND RESTRICTED CASH (Tables)	9 Months Ended
	Sep. 30, 2019
Cash and Cash Equivalents [Abstract]
Schedule of Cash and Cash Equivalents	Cash, cash equivalents and restricted cash as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Cash $ 31,729 $ 81,055 Cash equivalents 91,673 251,709 Total cash and cash equivalents $ 123,402 $ 332,764 Restricted cash 22,127 22,071 Total cash, cash equivalents and restricted cash $ 145,529 $ 354,835
Restrictions on Cash and Cash Equivalents	Cash, cash equivalents and restricted cash as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Cash $ 31,729 $ 81,055 Cash equivalents 91,673 251,709 Total cash and cash equivalents $ 123,402 $ 332,764 Restricted cash 22,127 22,071 Total cash, cash equivalents and restricted cash $ 145,529 $ 354,835

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value	The following table represents the fair value of the Company’s financial instruments, including those measured at fair value on a recurring basis and those held-to-maturity, as of September 30, 2019 and December 31, 2018 (in thousands): September 30, 2019 December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 91,673 $ — $ — $ 91,673 $ 221,173 $ — $ — $ 221,173 Commercial paper — — — — — 30,536 — 30,536 Marketable securities: Commercial paper — 129,500 — 129,500 — 175,070 — 175,070 Corporate bonds — 85,154 — 85,154 — 131,496 — 131,496 Agency bonds — 79,210 — 79,210 — 50,846 — 50,846 U.S. government bonds — — — — — 65,502 — 65,502 Total cash equivalents and marketable securities $ 91,673 $ 293,864 $ — $ 385,537 $ 221,173 $ 453,450 $ — $ 674,623

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of the Fair Value to Amortized Cost Basis of Securities Held-to-Maturity	The amortized cost, gross unrealized gains and losses, and fair value of marketable securities classified as held-to-maturity as of September 30, 2019 and December 31, 2018 were as follows (in thousands): September 30, 2019 Amortized Gross Gross Fair Short-term marketable securities: Commercial paper $ 129,454 $ 50 $ (4 ) $ 129,500 Corporate bonds 74,865 247 — 75,112 Agency bonds 54,095 118 (1 ) 54,212 Total short-term marketable securities 258,414 415 (5 ) 258,824 Long-term marketable securities: Agency bonds 25,000 2 (4 ) 24,998 Corporate bonds 9,964 78 — 10,042 Total long-term marketable securities 34,964 80 (4 ) 35,040 Total marketable securities $ 293,378 $ 495 $ (9 ) $ 293,864 December 31, 2018 Amortized Gross Gross Fair Cash equivalents: Commercial paper $ 30,536 $ — $ — $ 30,536 Total cash equivalents 30,536 — — 30,536 Short-term marketable securities: Commercial paper 175,070 — — 175,070 Corporate bonds 131,626 8 (138 ) 131,496 U.S. government bonds 65,513 — (11 ) 65,502 Agency bonds 50,887 — (41 ) 50,846 Total short-term marketable securities 423,096 8 (190 ) 422,914 Total marketable securities $ 453,632 $ 8 $ (190 ) $ 453,450
Schedule of Securities in an Unrealized Loss Position	The following tables present gross unrealized losses and fair values for those securities that were in an unrealized loss position as of September 30, 2019 and December 31, 2018 , aggregated by investment category and the length of time that the individual securities have been in a continuous loss position (in thousands): September 30, 2019 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Commercial paper $ 41,817 $ (4 ) $ — $ — $ 41,817 $ (4 ) Agency bonds 19,994 (5 ) — — 19,994 (5 ) Total $ 61,811 $ (9 ) $ — $ — $ 61,811 $ (9 ) December 31, 2018 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 121,566 $ (138 ) $ — $ — $ 121,566 $ (138 ) U.S. government bonds 65,502 (11 ) — — 65,502 (11 ) Agency bonds 50,846 (41 ) — — 50,846 (41 ) Total $ 237,914 $ (190 ) $ — $ — $ 237,914 $ (190 )

PREPAID EXPENSES AND OTHER CU_2

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)	9 Months Ended
	Sep. 30, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Prepaid expenses $ 11,970 $ 9,436 Other current assets 4,072 7,668 Total prepaid expenses and other current assets $ 16,042 $ 17,104

PROPERTY, EQUIPMENT, AND SOFTWA

PROPERTY, EQUIPMENT, AND SOFTWARE, NET (Tables)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property, Equipment and Software, Net	Property, equipment and software, net as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Capitalized website and internal-use software development costs $ 133,551 $ 108,590 Leasehold improvements 85,983 83,811 Computer equipment 43,276 40,801 Furniture and fixtures 18,372 17,839 Telecommunication 4,855 4,691 Software 2,217 1,651 Total 288,254 257,383 Less accumulated depreciation (174,319 ) (142,583 ) Property, equipment and software, net $ 113,935 $ 114,800

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in carrying amount of goodwill during the nine months ended September 30, 2019 were as follows (in thousands): Balance as of December 31, 2018 $ 105,620 Effect of currency translation (2,161 ) Balance as of September 30, 2019 $ 103,459
Schedule of Intangible Assets	Intangible assets at September 30, 2019 and December 31, 2018 consisted of the following (dollars in thousands): September 30, 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life Business relationships $ 9,918 $ (2,598 ) $ 7,320 8.8 years Developed technology 7,832 (4,640 ) 3,192 2.5 years Content 3,750 (3,750 ) — 0.0 years Domains and data licenses 2,869 (2,699 ) 170 1.6 years Trademarks 877 (798 ) 79 0.4 years User relationships 146 (129 ) 17 0.5 years Total $ 25,392 $ (14,614 ) $ 10,778 December 31, 2018 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life Business relationships $ 9,918 $ (1,868 ) $ 8,050 9.4 years Developed technology 7,832 (3,562 ) 4,270 3.1 years Content 3,873 (3,696 ) 177 0.8 years Domain and data licenses 2,869 (2,359 ) 510 1.5 years Trademarks 877 (579 ) 298 1.2 years User relationships 146 (92 ) 54 1.2 years Total $ 25,515 $ (12,156 ) $ 13,359
Schedule of Future Amortization Expense	As of September 30, 2019 , the estimated future amortization of purchased intangible assets for (i) the remaining three months of 2019 , (ii) each of the succeeding five years, and (iii) thereafter was as follows (in thousands): Year Ending December 31, Amount 2019 (from October 1, 2019) $ 696 2020 2,402 2021 2,262 2022 1,045 2023 714 2024 708 Thereafter 2,951 Total amortization $ 10,778

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Lease Cost and Supplemental Cash Flow Information	Supplemental cash flow information related to leases for the nine months ended September 30, 2019 was as follows (in thousands): September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 42,323 The components of lease cost as of September 30, 2019 were as follows (in thousands): Three Months Ended Nine Months Ended Operating lease cost $ 13,544 $ 40,878 Short-term lease cost (12 months or less) 291 938 Sublease income (1,475 ) (2,764 ) Total lease cost, net $ 12,360 $ 39,052
Lessee, Operating Lease, Liability, Maturity	As of September 30, 2019 , maturities of lease liabilities for (i) the remaining three months of 2019 , (ii) each of the succeeding five years, and (iii) thereafter were as follows (in thousands): Year Ending December 31, Operating 2019 (from October 1, 2019) $ 14,495 2020 59,435 2021 52,055 2022 44,712 2023 41,652 2024 39,420 Thereafter 37,112 Total minimum lease payments 288,881 Less imputed interest (45,812 ) Present value of lease liabilities $ 243,069 As of December 31, 2018 , maturities of lease liabilities for (i) each of the succeeding five years and (ii) thereafter were as follows (in thousands): Year Ending December 31, Operating 2019 $ 56,703 2020 59,009 2021 51,429 2022 43,603 2023 40,517 Thereafter 69,980 Total minimum lease payments $ 321,241
Assets And Liabilities, Lessee Information	As of September 30, 2019 , the weighted-average remaining lease term and weighted-average discount rate were as follows: September 30, 2019 Weighted-average remaining lease term (years) — operating leases 5.8 Weighted-average discount rate — operating leases 6.0 %

OTHER NON-CURRENT ASSETS (Table

OTHER NON-CURRENT ASSETS (Tables)	9 Months Ended
	Sep. 30, 2019
Other Assets, Noncurrent Disclosure [Abstract]
Schedule of Other Non-Current Assets	Other non-current assets as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Deferred tax assets $ 19,076 $ 17,240 Deferred contract costs 13,993 12,345 Escrow deposit — 28,750 Other non-current assets 3,286 1,109 Total other non-current assets $ 36,355 $ 59,444
Capitalized Contract Cost	Deferred contract costs as of September 30, 2019 and December 31, 2018 , and changes in deferred contract costs during the nine months ended September 30, 2019 , were as follows (in thousands): Nine Months Ended Balance, beginning of period $ 12,345 Add: costs deferred on new contracts 10,236 Less: amortization recorded in sales and marketing expenses (8,588 ) Balance, end of period $ 13,993

CONTRACT BALANCES (Tables)

CONTRACT BALANCES (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Schedule of Allowance for Doubtful Accounts Receivable	The allowance for doubtful accounts as of September 30, 2019 and 2018 and changes in the allowance for doubtful accounts during the nine months ended September 30, 2019 and 2018 were as follows (in thousands): Nine Months Ended 2019 2018 Balance, beginning of period $ 8,685 $ 8,602 Add: provision for doubtful accounts 15,259 19,285 Less: write-offs, net of recoveries (16,165 ) (19,002 ) Balance, end of period $ 7,779 $ 8,885
Contract with Customer, Liability	Changes in deferred revenue during the nine months ended September 30, 2019 were as follows (in thousands): Nine Months Ended Balance, beginning of period $ 3,843 Less: recognition of deferred revenue from beginning balance (3,539 ) Add: net increase in current period contract liabilities 3,918 Balance, end of period $ 4,222

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Accrued employee compensation and related $ 44,258 $ 21,580 Accrued tax liabilities 5,831 5,491 Accrued cost of revenue 6,875 5,463 Accrued sales and marketing expenses 3,880 4,536 Other accrued liabilities 10,895 17,452 Total accrued liabilities $ 71,739 $ 54,522

LONG-TERM LIABILITIES (Tables)

LONG-TERM LIABILITIES (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Schedule of Other Long-Term Liabilities	Other long-term liabilities as of September 30, 2019 and December 31, 2018 consisted of the following (in thousands): September 30, December 31, Deferred rent $ — $ 31,253 Other long-term liabilities 4,036 3,887 Total other long-term liabilities $ 4,036 $ 35,140

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	9 Months Ended
	Sep. 30, 2019
Stockholders' Equity Note [Abstract]
Schedule of Stock by Class	The following table presents the number of shares authorized and issued as of the dates indicated: September 30, 2019 December 31, 2018 Shares Authorized Shares Issued Shares Authorized Shares Issued Stockholders’ equity: Common stock, $0.000001 par value 200,000,000 70,199,923 200,000,000 81,996,839 Undesignated preferred stock 10,000,000 — 10,000,000 —
Schedule of Stock Option Activity	A summary of stock option activity for the nine months ended September 30, 2019 is as follows: Number of Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 6,818,682 $ 24.54 5.11 $ 88,983 Granted 662,150 36.06 Exercised (399,320 ) 20.74 Canceled (339,301 ) 40.88 Outstanding at September 30, 2019 6,742,211 $ 25.11 4.36 $ 81,195 Options vested and exercisable at September 30, 2019 5,683,209 $ 22.78 3.59 $ 80,712
Schedule of RSU Activity	A summary of RSU activity for the nine months ended September 30, 2019 is as follows: Number of Shares Weighted-Average Grant Date Fair Value Nonvested at December 31, 2018 6,563,863 $ 38.67 Granted 4,361,791 35.06 Vested (1) (2,469,190 ) 35.97 Canceled (1,462,739 ) 37.99 Nonvested at September 30, 2019 6,993,725 $ 37.51
Schedule of Stock-Based Compensation Expense	The following table summarizes the effects of stock-based compensation expense related to stock-based awards in the condensed consolidated statements of operations during the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Cost of revenue $ 1,054 $ 1,162 $ 3,415 $ 3,345 Sales and marketing 7,683 7,941 23,143 23,514 Product development 15,250 14,536 46,572 41,878 General and administrative 5,249 5,555 17,876 16,995 Total stock-based compensation recorded to income before income taxes 29,236 29,194 91,006 85,732 Benefit from income taxes (7,661 ) (167 ) (23,766 ) (476 ) Total stock-based compensation recorded to net income $ 21,575 $ 29,027 $ 67,240 $ 85,256

OTHER INCOME, NET (Tables)

OTHER INCOME, NET (Tables)	9 Months Ended
	Sep. 30, 2019
Other Income and Expenses [Abstract]
Schedule of Other Income, Net	Other income, net for the three and nine months ended September 30, 2019 and 2018 consisted of the following (in thousands): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Interest income, net $ 2,830 $ 3,705 $ 10,946 $ 9,606 Transaction gain (loss) on foreign exchange (20 ) 75 93 89 Other non-operating income, net 253 141 606 255 Other income, net $ 3,063 $ 3,921 $ 11,645 $ 9,950

NET INCOME PER SHARE (Tables)

NET INCOME PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Calculation of Basic and Diluted Net Income (Loss) Per Share	The following table presents the calculation of basic and diluted net income per share for the periods presented (in thousands, except per share data): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Basic net income per share: Net income $ 10,061 $ 14,986 $ 23,729 $ 23,404 Shares used in computation: Weighted-average common shares outstanding 70,773 84,008 75,975 83,865 Basic net income per share attributable to common stockholders $ 0.14 $ 0.18 $ 0.31 $ 0.28 Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Diluted net income per share: Net income $ 10,061 $ 14,986 $ 23,729 $ 23,404 Shares used in computation: Weighted-average common shares outstanding 70,773 84,008 75,975 83,865 Stock options 2,345 3,011 2,429 3,096 Restricted stock units 478 1,656 870 2,240 Employee stock purchase program 116 49 41 70 Number of shares used in diluted calculation 73,712 88,724 79,315 89,271 Diluted net income per share attributable to common stockholders $ 0.14 $ 0.17 $ 0.30 $ 0.26
Schedule of Anti-dilutive Securities	The following weighted-average stock-based instruments were excluded from the calculation of diluted net income per share because their effect would have been anti-dilutive for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Stock options 2,718 1,694 2,629 1,681 Restricted stock units 2,718 591 2,530 106

INFORMATION ABOUT REVENUE AND_2

INFORMATION ABOUT REVENUE AND GEOGRAPHIC AREAS (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Schedule of Revenue by Product Line	The following table presents the Company’s net revenue by major product line for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Net revenue by product: Advertising $ 253,098 $ 232,502 $ 717,973 $ 672,712 Transactions 3,074 3,042 9,528 10,402 Other services 6,302 5,552 17,870 15,919 Total net revenue $ 262,474 $ 241,096 $ 745,371 $ 699,033
Schedule of Net Revenue by Geographic Region	The following table presents the Company’s net revenue by major geographic region for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 United States $ 258,820 $ 237,597 $ 735,169 $ 689,096 All other countries 3,654 3,499 10,202 9,937 Total net revenue $ 262,474 $ 241,096 $ 745,371 $ 699,033
Schedule of Long-Lived Assets by Geographic Location	The following table presents the Company’s long-lived assets by major geographic region for the periods presented (in thousands): September 30, December 31, United States $ 112,700 $ 112,984 All other countries 1,235 1,816 Total long-lived assets $ 113,935 $ 114,800

DESCRIPTION OF BUSINESS AND B_3

DESCRIPTION OF BUSINESS AND BASIS FOR PRESENTATION (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Option to extend lease term, period	10 years
Operating lease right-of-use assets	$ 207,852	$ 233,000	$ 0
Operating lease liabilities — current	57,013	55,200	0
Operating lease liabilities — long-term	$ 186,056	212,500	$ 0
De-recognized deferred rent liabilities associated with its office lease portfolio		$ 34,800
Maximum
Lessee, Lease, Description [Line Items]
Option to terminate	P12M
Minimum
Lessee, Lease, Description [Line Items]
Option to terminate	P6M

CASH, CASH EQUIVALENTS AND RE_3

CASH, CASH EQUIVALENTS AND RESTRICTED CASH (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash	$ 31,729	$ 81,055
Cash equivalents	91,673	251,709
Total cash and cash equivalents	123,402	332,764
Restricted cash	22,127	22,071
Total cash, cash equivalents and restricted cash	$ 145,529	$ 354,835	$ 445,616	$ 566,404

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	$ 293,864	$ 453,450
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	385,537	674,623
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	91,673	221,173
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	293,864	453,450
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	129,500	175,070
Recurring | Commercial paper | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | Commercial paper | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	129,500	175,070
Recurring | Commercial paper | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	85,154	131,496
Recurring | Corporate bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | Corporate bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	85,154	131,496
Recurring | Corporate bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | Agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	79,210	50,846
Recurring | Agency bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | Agency bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	79,210	50,846
Recurring | Agency bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | U.S. government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	65,502
Recurring | U.S. government bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | U.S. government bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	65,502
Recurring | U.S. government bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	91,673	221,173
Recurring | Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	91,673	221,173
Recurring | Money market funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Recurring | Money market funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	30,536
Recurring | Commercial paper | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Recurring | Commercial paper | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	30,536
Recurring | Commercial paper | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	$ 0	$ 0

MARKETABLE SECURITIES (Schedule

MARKETABLE SECURITIES (Schedule of the Fair Value to Amortized Cost Basis of Securities Held-to-Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash equivalents and Short-term marketable securities:
Amortized Cost	$ 258,414	$ 423,096
Gross Unrealized Gains	415	8
Gross Unrealized Losses	(5)	(190)
Fair Value	258,824	422,914
Long-term marketable securities:
Amortized Cost	34,964
Gross Unrealized Gains	80
Gross Unrealized Losses	(4)
Fair Value	35,040
Amortized Cost	293,378	453,632
Gross Unrealized Gains	495	8
Gross Unrealized Losses	(9)	(190)
Fair Value	293,864	453,450
Commercial paper
Cash equivalents and Short-term marketable securities:
Amortized Cost	129,454	175,070
Gross Unrealized Gains	50	0
Gross Unrealized Losses	(4)	0
Fair Value	129,500	175,070
Corporate bonds
Cash equivalents and Short-term marketable securities:
Amortized Cost	74,865	131,626
Gross Unrealized Gains	247	8
Gross Unrealized Losses	0	(138)
Fair Value	75,112	131,496
Long-term marketable securities:
Amortized Cost	9,964
Gross Unrealized Gains	78
Gross Unrealized Losses	0
Fair Value	10,042
U.S. government bonds
Cash equivalents and Short-term marketable securities:
Amortized Cost		65,513
Gross Unrealized Gains		0
Gross Unrealized Losses		(11)
Fair Value		65,502
Agency bonds
Cash equivalents and Short-term marketable securities:
Amortized Cost	54,095	50,887
Gross Unrealized Gains	118	0
Gross Unrealized Losses	(1)	(41)
Fair Value	54,212	50,846
Long-term marketable securities:
Amortized Cost	25,000
Gross Unrealized Gains	2
Gross Unrealized Losses	(4)
Fair Value	$ 24,998
Commercial paper
Cash equivalents and Short-term marketable securities:
Amortized Cost		30,536
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		$ 30,536

MARKETABLE SECURITIES (Schedu_2

MARKETABLE SECURITIES (Schedule of Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value
Less Than 12 Months	$ 61,811	$ 237,914
12 Months or Greater	0	0
Total	61,811	237,914
Unrealized Loss
Less Than 12 Months	(9)	(190)
12 Months or Greater	0	0
Total	(9)	(190)
Commercial paper
Fair Value
Less Than 12 Months	41,817
12 Months or Greater	0
Total	41,817
Unrealized Loss
Less Than 12 Months	(4)
12 Months or Greater	0
Total	(4)
Corporate bonds
Fair Value
Less Than 12 Months		121,566
12 Months or Greater		0
Total		121,566
Unrealized Loss
Less Than 12 Months		(138)
12 Months or Greater		0
Total		(138)
U.S. government bonds
Fair Value
Less Than 12 Months		65,502
12 Months or Greater		0
Total		65,502
Unrealized Loss
Less Than 12 Months		(11)
12 Months or Greater		0
Total		(11)
Agency bonds
Fair Value
Less Than 12 Months	19,994	50,846
12 Months or Greater	0	0
Total	19,994	50,846
Unrealized Loss
Less Than 12 Months	(5)	(41)
12 Months or Greater	0	0
Total	$ (5)	$ (41)

PREPAID EXPENSES AND OTHER CU_3

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 11,970	$ 9,436
Other current assets	4,072	7,668
Total prepaid expenses and other current assets	$ 16,042	$ 17,104

PROPERTY, EQUIPMENT AND SOFTW_2

PROPERTY, EQUIPMENT AND SOFTWARE, NET (Schedule of Property, Equipment and Software) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	$ 288,254	$ 257,383
Less accumulated depreciation	(174,319)	(142,583)
Property, equipment and software, net	113,935	114,800
Capitalized website and internal-use software development costs
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	133,551	108,590
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	85,983	83,811
Computer equipment
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	43,276	40,801
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	18,372	17,839
Telecommunication
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	4,855	4,691
Software
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	$ 2,217	$ 1,651

PROPERTY, EQUIPMENT, AND SOFT_2

PROPERTY, EQUIPMENT, AND SOFTWARE, NET (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 11.6	$ 9.8	$ 33.9	$ 28.6

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS (Schedule of Goodwill) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 105,620
Effect of currency translation	(2,161)
Ending balance	$ 103,459

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 25,392	$ 25,515
Accumulated Amortization	(14,614)	(12,156)
Total amortization	10,778	13,359
Business relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	9,918	9,918
Accumulated Amortization	(2,598)	(1,868)
Total amortization	$ 7,320	$ 8,050
Weighted Average Remaining Life (in years)	8 years 9 months 18 days	9 years 4 months 24 days
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 7,832	$ 7,832
Accumulated Amortization	(4,640)	(3,562)
Total amortization	$ 3,192	$ 4,270
Weighted Average Remaining Life (in years)	2 years 6 months	3 years 1 month 6 days
Content
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,750	$ 3,873
Accumulated Amortization	(3,750)	(3,696)
Total amortization	$ 0	$ 177
Weighted Average Remaining Life (in years)	0 years	9 months 18 days
Domains and data licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,869	$ 2,869
Accumulated Amortization	(2,699)	(2,359)
Total amortization	$ 170	$ 510
Weighted Average Remaining Life (in years)	1 year 7 months 6 days	1 year 6 months
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 877	$ 877
Accumulated Amortization	(798)	(579)
Total amortization	$ 79	$ 298
Weighted Average Remaining Life (in years)	4 months 24 days	1 year 2 months 12 days
User relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 146	$ 146
Accumulated Amortization	(129)	(92)
Total amortization	$ 17	$ 54
Weighted Average Remaining Life (in years)	6 months	1 year 2 months 12 days

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 0.8	$ 0.9	$ 2.6	$ 2.7

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS (Schedule of Future Amortization Expense) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Year Ending December 31,
2019 (from October 1, 2019)	$ 696
2020	2,402
2021	2,262
2022	1,045
2023	714
2024	708
Thereafter	2,951
Total amortization	$ 10,778	$ 13,359

LEASES (Narrative) (Details)

LEASES (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Lessee, Lease, Description [Line Items]
Operating Leases, Rent Expense, Net			$ 13,700		$ 37,700
Lease cost		$ 12,360		$ 39,052
Sublease Income		$ 1,475	$ 500	$ 2,764	$ 1,700
Subsequent Event | UNITED KINGDOM
Lessee, Lease, Description [Line Items]
Lease cost	$ 15,000

LEASES (Lease Cost) (Details)

LEASES (Lease Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating lease cost	$ 13,544		$ 40,878
Short-term lease cost (12 months or less)	291		938
Sublease income	(1,475)	$ (500)	(2,764)	$ (1,700)
Total lease cost, net	$ 12,360		$ 39,052

LEASES (Supplemental Cash Flow

LEASES (Supplemental Cash Flow Information) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 42,323

LEASES (Operating Lease Maturit

LEASES (Operating Lease Maturities) (Details) $ in Thousands	Sep. 30, 2019USD ($)
Leases [Abstract]
2019 (from October 1, 2019)	$ 14,495
2020	59,435
2021	52,055
2022	44,712
2023	41,652
2024	39,420
Thereafter	37,112
Total minimum lease payments	288,881
Less imputed interest	(45,812)
Present value of lease liabilities	$ 243,069

LEASES (Maturities Prior to Ado

LEASES (Maturities Prior to Adoption of ASC 842) (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 56,703
2020	59,009
2021	51,429
2022	43,603
2023	40,517
Thereafter	69,980
Total minimum lease payments	$ 321,241

LEASES (Additional Information)

LEASES (Additional Information) (Details)	Sep. 30, 2019
Leases [Abstract]
Weighted-average remaining lease term (years) — operating leases	5 years 9 months 18 days
Weighted-average discount rate — operating leases	6.00%

OTHER NON-CURRENT ASSETS (Detai

OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Other Assets, Noncurrent Disclosure [Abstract]
Deferred tax assets	$ 19,076	$ 17,240
Deferred contract costs	13,993	12,345
Escrow deposit	0	28,750
Other non-current assets	3,286	1,109
Total other non-current assets	$ 36,355	$ 59,444

OTHER NON-CURRENT ASSETS (Chang

OTHER NON-CURRENT ASSETS (Changes in Deferred Contract Costs) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Changes In Capitalized Contract Costs [Roll Forward]
Balance, beginning of period	$ 12,345
Add: costs deferred on new contracts	10,236
Less: amortization recorded in sales and marketing expenses	(8,588)
Balance, end of period	$ 13,993

CONTRACT BALANCES (Schedule of

CONTRACT BALANCES (Schedule of Changes in Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 8,685	$ 8,602
Add: provision for doubtful accounts	15,259	19,285
Less: write-offs, net of recoveries	(16,165)	(19,002)
Balance, end of period	$ 7,779	$ 8,885

CONTRACT BALANCES (Narrative) (

CONTRACT BALANCES (Narrative) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Deferred revenue	$ 4,222	$ 3,843

CONTRACT BALANCES (Changes in D

CONTRACT BALANCES (Changes in Deferred Revenue) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Change in Contract with Customer, Liability [Roll Forward]
Balance, beginning of period	$ 3,843
Less: recognition of deferred revenue from beginning balance	(3,539)
Add: net increase in current period contract liabilities	3,918
Balance, end of period	$ 4,222

ACCRUED LIABILITIES (Details)

ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued employee compensation and related	$ 44,258	$ 21,580
Accrued tax liabilities	5,831	5,491
Accrued cost of revenue	6,875	5,463
Accrued sales and marketing expenses	3,880	4,536
Other accrued liabilities	10,895	17,452
Total accrued liabilities	$ 71,739	$ 54,522

LONG-TERM LIABILITIES (Schedule

LONG-TERM LIABILITIES (Schedule of Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Deferred rent	$ 0	$ 31,253
Other long-term liabilities	4,036	3,887
Total other long-term liabilities	$ 4,036	$ 35,140

STOCKHOLDERS' EQUITY (Schedule

STOCKHOLDERS' EQUITY (Schedule of Stock by Class) (Details) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Stockholders’ equity:
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	70,199,923	81,996,839
Undesignated preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Undesignated preferred stock, shares issued (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.000001	$ 0.000001

STOCKHOLDERS' EQUITY (Narrative

STOCKHOLDERS' EQUITY (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Sep. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2019USD ($)planschedule$ / sharesshares	Sep. 30, 2018USD ($)$ / sharesshares	Feb. 11, 2019USD ($)	Nov. 27, 2018USD ($)	Jul. 31, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury stock (in shares) | shares	0		0
Number of equity incentive plans | plan			3
Granted (in shares) | shares			662,150
Fair value of vested shares			$ 84,900,000	$ 107,400,000
Stock-based compensation	$ 29,236,000	$ 29,194,000	91,006,000	85,732,000
Capitalized stock-based compensation expense	2,600,000	1,900,000	$ 7,600,000	5,900,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of vesting schedules | schedule			4
Exercisable period			10 years
Intrinsic value of options exercised	$ 3,400,000	$ 5,300,000	$ 6,200,000	$ 18,100,000
Granted (in shares) | shares	0
Weighted average grant date fair value (in USD per share) | $ / shares		$ 23.41	$ 17.64	$ 18.89
Unrecognized compensation costs	$ 17,600,000		$ 17,600,000
Unrecognized compensation costs, period for recognition			2 years 6 months
Employee Stock Option | Monthly Basis First Year Member
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			35.00%
Employee Stock Option | Monthly Basis Second Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			40.00%
Employee Stock Option | Monthly Basis Third Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			25.00%
Employee Stock Option | End of year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			25.00%
Employee Stock Option | First year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			10.00%
Employee Stock Option | Second year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			20.00%
Employee Stock Option | Third year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			30.00%
Employee Stock Option | Fourth year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			40.00%
Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Number of vesting schedules | schedule			3
Unrecognized compensation costs	$ 251,100,000		$ 251,100,000
Unrecognized compensation costs, period for recognition			2 years 8 months 12 days
RSUs | End of year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			25.00%
RSUs | First year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			10.00%
RSUs | Second year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			20.00%
RSUs | Third year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			30.00%
RSUs | Fourth year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			40.00%
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in USD per share) | $ / shares			$ 26.12	$ 36.42
Subscription rate of eligible compensation	15.00%		15.00%
Purchase price, percentage of fair market value			85.00%
Number of shares purchased (in shares) | shares	0	0	288,529	195,987
Stock-based compensation	$ 700,000	$ 700,000	$ 2,000,000	$ 2,000,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance goal stock price at which Performance Restricted Stock Unit awards would vest (usd per share) | $ / shares	$ 45.3125		$ 45.3125
July 31, 2017 Share Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount							$ 200,000,000
Stock repurchased, amount				$ 72,000,000
Stock repurchased and retired during period (in shares) | shares				1,752,895
November 27, 2018 Share Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount	$ 500,000,000		$ 500,000,000		$ 250,000,000	$ 250,000,000
Stock repurchased, amount			$ 475,000,000
Stock repurchased and retired during period (in shares) | shares			13,994,909

STOCKHOLDERS' EQUITY (Schedul_2

STOCKHOLDERS' EQUITY (Schedule of Stock Option Activity) (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Number of Shares
Outstanding, beginning balance (in shares) | shares	6,818,682
Granted (in shares) | shares	662,150
Exercised (in shares) | shares	(399,320)
Canceled (in shares) | shares	(339,301)
Outstanding, ending balance (in shares) | shares	6,742,211	6,818,682
Options vested and exercisable (in shares) | shares	5,683,209
Weighted-Average Exercise Price
Outstanding, beginning balance (in USD per share) | $ / shares	$ 24.54
Granted (in USD per share) | $ / shares	36.06
Exercised (in USD per share) | $ / shares	20.74
Canceled (in USD per share) | $ / shares	40.88
Outstanding, ending balance (in USD per share) | $ / shares	25.11	$ 24.54
Options vested and exercisable (in USD per share) | $ / shares	$ 22.78
Weighted- Average Remaining Contractual Term
Outstanding, Weighted-Average Remaining Contractual Term (in years)	4 years 4 months 9 days	5 years 1 month 9 days
Options vested and exercisable, Weighted-Average Remaining Contractual Term (in years)	3 years 7 months 2 days
Aggregate Intrinsic Value
Outstanding, Aggregate Intrinsic Value | $	$ 81,195	$ 88,983
Options vested and exercisable, Aggregate Intrinsic Value | $	$ 80,712

STOCKHOLDERS' EQUITY (Schedul_3

STOCKHOLDERS' EQUITY (Schedule of Restricted Stock Units Activity) (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Number of Shares
Unvested, beginning balance (in shares)	6,563,863
Granted (in shares)	4,361,791
Released (in shares)	(2,469,190)
Canceled (in shares)	(1,462,739)
Unvested, ending balance (in shares)	6,993,725
Weighted-Average Grant Date Fair Value
Unvested, beginning balance (in USD per share) | $ / shares	$ 38.67
Granted (in USD per share) | $ / shares	35.06
Released (in USD per share) | $ / shares	35.97
Canceled (in USD per share) | $ / shares	37.99
Unvested, ending balance (in USD per share) | $ / shares	$ 37.51
Shares withheld for taxes (in shares)	959,046

STOCKHOLDERS' EQUITY (Schedul_4

STOCKHOLDERS' EQUITY (Schedule of Stock-Based Compensation Expense) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation recorded to income before income taxes	$ 29,236	$ 29,194	$ 91,006	$ 85,732
Benefit from income taxes	(7,661)	(167)	(23,766)	(476)
Total stock-based compensation recorded to net income	21,575	29,027	67,240	85,256
Capitalized stock-based compensation expense	2,600	1,900	7,600	5,900
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation recorded to income before income taxes	1,054	1,162	3,415	3,345
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation recorded to income before income taxes	7,683	7,941	23,143	23,514
Product development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation recorded to income before income taxes	15,250	14,536	46,572	41,878
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation recorded to income before income taxes	$ 5,249	$ 5,555	$ 17,876	$ 16,995
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Number of shares purchased (in shares)	0	0	288,529	195,987
Weighted average grant date fair value (in USD per share)			$ 26.12	$ 36.42
Total stock-based compensation recorded to income before income taxes	$ 700	$ 700	$ 2,000	$ 2,000

OTHER INCOME, NET (Details)

OTHER INCOME, NET (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Income and Expenses [Abstract]
Interest Income (Expense), Nonoperating, Net	$ 2,830	$ 3,705	$ 10,946	$ 9,606
Transaction gain (loss) on foreign exchange	(20)	75	93	89
Other non-operating income, net	253	141	606	255
Other income, net	$ 3,063	$ 3,921	$ 11,645	$ 9,950

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income tax provision (benefit)	$ 2,552	$ (684)	$ 5,781	$ (281)
Income tax provision due to U.S. federal and state income taxes and foreign income taxes			5,500	1,200
Net discrete tax benefit			300	$ 1,500
Unrecognized tax benefits	38,600		38,600
Unrecognized tax benefits that would not impact the effective tax rate	16,300		16,300
Earnings of foreign subsidiaries to be reinvested indefinitely	$ 3,500		$ 3,500

NET INCOME PER SHARE (Schedule

NET INCOME PER SHARE (Schedule of Basic and Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share Reconciliation [Line Items]
Net income	$ 10,061	$ 14,986	$ 23,729	$ 23,404
Basic net income per share:
Weighted-average common shares outstanding (in shares)	70,773	84,008	75,975	83,865
Basic net income per share attributable to common stockholders (in USD per share)	$ 0.14	$ 0.18	$ 0.31	$ 0.28
Diluted net income per share:
Weighted-average common shares outstanding (in shares)	70,773	84,008	75,975	83,865
Number of shares used in diluted calculation (in shares)	73,712	88,724	79,315	89,271
Diluted net income per share attributable to common stockholders (in USD per share)	$ 0.14	$ 0.17	$ 0.30	$ 0.26
Stock options
Diluted net income per share:
Incremental common shares (in shares)	2,345	3,011	2,429	3,096
Restricted stock units
Diluted net income per share:
Incremental common shares (in shares)	478	1,656	870	2,240
Employee stock purchase program
Diluted net income per share:
Incremental common shares (in shares)	116	49	41	70

NET INCOME PER SHARE (Schedul_2

NET INCOME PER SHARE (Schedule of Anti-Dilutive Employee Stock Awards) (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive awards (in shares)	2,718	1,694	2,629	1,681
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive awards (in shares)	2,718	591	2,530	106

INFORMATION ABOUT REVENUE AND_3

INFORMATION ABOUT REVENUE AND GEOGRAPHIC AREAS (Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	$ 262,474	$ 241,096	$ 745,371	$ 699,033
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	258,820	237,597	735,169	689,096
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	3,654	3,499	10,202	9,937
Advertising
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	253,098	232,502	717,973	672,712
Transactions
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	3,074	3,042	9,528	10,402
Other services
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	$ 6,302	$ 5,552	$ 17,870	$ 15,919

INFORMATION ABOUT REVENUE AND_4

INFORMATION ABOUT REVENUE AND GEOGRAPHIC AREAS (Long-Lived Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 113,935	$ 114,800
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	112,700	112,984
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 1,235	$ 1,816