CoStar (CSGP) 10-Q 29 Apr 20 2020 Q1 Quarterly report Financial data

Cover page

Cover page - shares	3 Months Ended
	Mar. 31, 2020	Apr. 24, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2020
Entity File Number	0-24531
Entity Registrant Name	COSTAR GROUP, INC.
Entity Central Index Key	0001057352
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2091509
Entity Address, Address Line One	1331 L Street, NW
Entity Address, City or Town	Washington,
Entity Address, State or Province	DC
Entity Address, Postal Zip Code	20005
City Area Code	(202)
Local Phone Number	346-6500
Title of 12(b) Security	Common Stock ($0.01 par value)
Trading Symbol	CSGP
Security Exchange Name	NASDAQ
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		36,726,443

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenues	$ 391,847	$ 328,425
Cost of revenues	78,909	71,153
Gross profit	312,938	257,272
Operating expenses:
Selling and marketing (excluding customer base amortization)	125,107	88,094
Software development	41,610	27,928
General and administrative	58,873	40,076
Customer base amortization	11,484	7,682
Total operating expenses	237,074	163,780
Income from operations	75,864	93,492
Interest and other income	4,518	4,945
Interest and other expense	(2,026)	(732)
Income before income taxes	78,356	97,705
Income tax expense	5,563	12,536
Net income	$ 72,793	$ 85,169
Net income per share-basic (in dollars per share)	$ 2	$ 2.35
Net income per share-diluted (in dollars per share)	$ 1.98	$ 2.33
Weighted average outstanding shares-basic (in shares)	36,471	36,237
Weighted average outstanding shares-diluted (in shares)	36,776	36,567

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 72,793	$ 85,169
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustment	(12,949)	380
Unrealized gain on investments	189	0
Reclassification adjustment for realized loss on investments included in net income	541	0
Total other comprehensive (loss) income	(12,219)	380
Total comprehensive income	$ 60,574	$ 85,549

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash, cash equivalents and restricted cash	$ 1,927,923	$ 1,070,731
Accounts receivable	120,559	96,788
Less: Allowance for credit losses	(8,311)	(4,548)
Accounts receivable	112,248	92,240
Prepaid expenses and other current assets	30,219	36,194
Total current assets	2,070,390	1,199,165
Long-term investments	0	10,070
Deferred income taxes, net	4,762	5,408
Property and equipment, net	106,409	107,529
Lease right-of-use assets	112,811	115,084
Goodwill	1,873,987	1,882,020
Intangible assets, net	400,689	421,196
Deferred commission costs, net	91,000	89,374
Deposits and other assets	9,743	9,232
Income tax receivable	14,806	14,908
Total assets	4,684,597	3,853,986
Current liabilities:
Accounts payable	22,486	7,640
Accrued wages and commissions	49,302	53,087
Accrued expenses	40,310	38,680
Income taxes payable	12,183	10,705
Lease liabilities	27,681	29,670
Deferred revenue	84,717	67,274
Total current liabilities	236,679	207,056
Long-term debt	745,000	0
Deferred income taxes, net	88,799	87,096
Income taxes payable	20,611	20,521
Lease and other long-term liabilities	130,697	133,720
Total liabilities	1,221,786	448,393
Total stockholders’ equity	3,462,811	3,405,593
Total liabilities and stockholders’ equity	$ 4,684,597	$ 3,853,986

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Balance at January 1, 2019	$ 3,033,999	$ 364	$ 2,419,812	$ (11,688)	$ 625,511
Balance (in shares) at Dec. 31, 2018		36,446
Beginning balance at Dec. 31, 2018	3,021,942	$ 364	2,419,812	(11,688)	613,454
Net income	85,169				85,169
Other comprehensive income (loss)	380			380
Exercise of stock options (in shares)		79
Exercise of stock options	10,638	$ 1	10,637
Restricted stock grants (in shares)		132
Restricted stock grants	0	$ 1	(1)
Restricted stock grants surrendered (in shares)		(43)
Restricted stock grants surrendered	(18,679)		(18,679)
Stock-based compensation expense	12,034		12,034
Management stock purchase plan	3,491		3,491
Employee stock purchase plan (in shares)		4
Employee stock purchase plan	1,582	$ 0	1,582
Balance (in shares) at Mar. 31, 2019		36,618
Ending balance at Mar. 31, 2019	3,128,614	$ 366	2,428,876	(11,308)	710,680
Balance (in shares) at Dec. 31, 2019		36,668
Beginning balance at Dec. 31, 2019	3,405,593	$ 366	2,473,338	(8,585)	940,474
Net income	72,793				72,793
Other comprehensive income (loss)	(12,219)			(12,219)
Exercise of stock options (in shares)		41
Exercise of stock options	9,233	$ 1	9,232
Restricted stock grants (in shares)		83
Restricted stock grants	0	$ 1	(1)
Restricted stock grants surrendered (in shares)		(56)
Restricted stock grants surrendered	(30,145)	$ (1)	(30,144)
Stock-based compensation expense	15,006		15,006
Employee stock purchase plan (in shares)		4
Employee stock purchase plan	2,550	$ 0	2,550
Balance (in shares) at Mar. 31, 2020		36,740
Ending balance at Mar. 31, 2020	$ 3,462,811	$ 367	$ 2,469,981	$ (20,804)	$ 1,013,267

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net income	$ 72,793	$ 85,169
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	24,256	19,659
Amortization of deferred commissions costs	14,747	12,407
Amortization of debt issuance costs	292	219
Realized loss on investments	541
Non-cash lease expense	6,261
Stock-based compensation expense	15,180	12,029
Deferred income taxes, net	2,825	3,702
Credit loss expense	6,183	2,185
Changes in operating assets and liabilities:
Accounts receivable	(26,613)	(5,835)
Income taxes payable	1,624	8,311
Prepaid expenses and other current assets	1,838	206
Deferred commissions	(16,523)	(13,729)
Other assets	1,215	(59)
Accounts payable and other liabilities	15,564	15,068
Lease liabilities	(6,967)
Deferred revenue	18,248	8,708
Net cash provided by operating activities	131,464	148,494
Investing activities:
Proceeds from sale and settlement of investments	10,259	0
Purchases of property and equipment and other assets	(7,133)	(9,429)
Cash paid for acquisitions, net of cash acquired	432	0
Net cash provided by (used in) investing activities	2,694	(9,429)
Financing activities:
Proceeds from long-term debt	745,000	0
Repurchase of restricted stock to satisfy tax withholding obligations	(30,144)	(18,679)
Proceeds from exercise of stock options and employee stock purchase plan	10,295	12,061
Net cash provided by (used in) financing activities	725,151	(6,618)
Effect of foreign currency exchange rates on cash and cash equivalents	(2,117)	(46)
Net increase in cash, cash equivalents and restricted cash	857,192	132,401
Cash, cash equivalents and restricted cash at the beginning of period	1,070,731	1,100,416
Cash, cash equivalents and restricted cash at the end of period	1,927,923	1,232,817
Supplemental cash flow disclosures:
Interest paid	499	519
Income taxes paid	$ 1,111	$ 521

ORGANIZATION

ORGANIZATION	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	ORGANIZATION CoStar Group, Inc. (the “Company” or “CoStar”) provides information, analytics and online marketplace services to the commercial real estate and related business community through its comprehensive, proprietary database of commercial real estate information. The Company provides online marketplaces for commercial real estate, apartment rentals, lands for sale and businesses for sale, and its services are typically distributed to its clients under subscription-based license agreements that renew automatically, a majority of which have a term of at least one year . The Company operates within two

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Accounting policies are consistent for each operating segment. Interim Financial Statements The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information. In the opinion of the Company’s management, the financial statements reflect all adjustments, consisting only of a normal recurring nature, necessary to present fairly the Company’s financial position at March 31, 2020 and December 31, 2019 , the results of its operations for the three months ended March 31, 2020 and 2019 , its comprehensive income for the three months ended March 31, 2020 and 2019 , its changes in stockholders' equity for the three months ended March 31, 2020 and 2019 , and its cash flows for the three months ended March 31, 2020 and 2019 . Certain notes and other information have been condensed or omitted from the interim financial statements presented in this Quarterly Report on Form 10-Q. Therefore, these financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 . Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, allowance for credit losses, the useful lives and recoverability of long-lived and intangible assets, and goodwill, income taxes, accounting for business combinations, stock-based compensation, estimating the Company's incremental borrowing rate for its leases, and contingencies, among others. The Company bases these estimates on historical and anticipated results, trends and various other assumptions that it believes are reasonable, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses. Actual results could differ from these estimates. Revenue Recognition The Company derives revenues primarily by (i) providing access to its proprietary database of commercial real estate information and (ii) providing online marketplaces for professional property management companies, property owners, brokers and landlords, in each case typically through a fixed monthly fee for its subscription-based services. The Company's subscription-based services consist primarily of information, analytics and online marketplace services offered over the Internet to commercial real estate industry and related professionals. Subscription contract rates are based on the number of sites, number of users, organization size, the client’s business focus, geography, the number and types of services to which a client subscribes, the number of properties a client advertises and the prominence and placement of a client's advertised properties in the search results. The Company’s subscription-based license agreements typically renew automatically, and a majority have a term of at least one year . The Company also provides (i) market research, portfolio and debt analysis, management and reporting capabilities and (ii) real estate and lease management solutions, including lease administration and abstraction services, to commercial customers, real estate investors, and lenders via the Company’s other service offerings, as well as (iii) benchmarking and analytics for the hospitality industry through STR, LLC (formerly known as STR, Inc.) and STR Global, Ltd. (together with STR, LLC, referred to as “STR”), which were acquired in the fourth quarter of 2019. The Company analyzes contracts to determine the appropriate revenue recognition using the following steps: (i) identification of contracts with customers, (ii) identification of distinct performance obligations in the contract, (iii) determination of contract transaction price, (iv) allocation of contract transaction price to the performance obligations, and (v) determination of revenue recognition based on timing of satisfaction of the performance obligation(s). The Company recognizes revenues upon the satisfaction of its performance obligation(s) (upon transfer of control of promised services to its customers) in an amount that reflects the consideration to which it expects to be entitled to in exchange for those services. Revenues from subscription-based services are recognized on a straight-line basis over the term of the agreement. In limited circumstances, the Company's contracts with customers include promises to transfer multiple services, such as contracts for its subscription-based services and professional services. For these contracts, the Company accounts for individual performance obligations separately if they are distinct, which involves the determination of the standalone selling price for each distinct performance obligation. Deferred revenue results from amounts billed in advance to customers or cash received from customers in advance of the Company's fulfillment of its performance obligation(s) and is recognized as those obligations are satisfied. Contract assets represent a conditional right to consideration for satisfied performance obligations that become a receivable when the conditions are satisfied. Contract assets are generated when contractual billing schedules differ from revenue recognition timing. Certain sales commissions are considered incremental and recoverable costs of obtaining a contract with a customer. Sales commissions incurred for obtaining new contracts are deferred and then amortized as selling and marketing expenses on a straight-line basis over a period of benefit that the Company has determined to be three years . The three-year amortization period was determined based on several factors, including the nature of the technology and proprietary data underlying the services being purchased, customer contract renewal rates and industry competition. Certain commission costs are not capitalized as they do not represent incremental costs of obtaining a contract. See Note 3 for further discussion of the Company's revenue recognition. Cost of Revenues Cost of revenues principally consists of salaries, benefits, bonuses and stock-based compensation expenses and other indirect costs for the Company's researchers who collect and analyze the commercial real estate data that is the basis for the Company's information, analytics and online marketplaces and for employees that support these products. Additionally, cost of revenues includes the cost of data from third-party data sources, credit card and other transaction fees relating to processing customer transactions, which are expensed as incurred, and the amortization of acquired trade names, technology and other intangible assets. Advertising Costs The Company expenses advertising costs as incurred. Advertising costs include digital marketing, television, company-sponsored events, print and other media advertising. Advertising costs were approximately $53 million and $33 million for the three months ended March 31, 2020 and 2019 , respectively. Foreign Currency The Company’s reporting currency is the U.S. dollar. The functional currency for the majority of its operations is the local currency, with the exception of certain international locations of STR for which the functional currency is the British Pound. Assets and liabilities denominated in a foreign currency are translated into U.S. dollars using the exchange rates in effect as of the balance sheet date. Gains and losses resulting from translation are included in accumulated other comprehensive loss. Currency g ains and losses on the translation of intercompany loans made to foreign subsidiaries that are of a long-term investment nature are also included in accumulated other comprehensive loss. Net gains or losses resulting from transactions denominated in a currency other than the functional currency of the entity are included in interest and other income (expense) in the condensed consolidated statements of operations using the average exchange rates in effect during the period. For the three months ended March 31, 2020 , the Company recognized net foreign currency gains of $1.4 million included in interest and other income (expense) on the condensed consolidated statements of operations. There were no material gains or losses from these transactions for the three months ended March 31, 2019 . Accumulated Other Comprehensive Loss The components of accumulated other comprehensive loss were as follows (in thousands): March 31, December 31, Foreign currency translation adjustment $ (20,804 ) $ (7,855 ) Net unrealized loss on investments, net of tax — (730 ) Total accumulated other comprehensive loss $ (20,804 ) $ (8,585 ) During the three months ended March 31, 2020 , the Company sold its long-term variable debt instruments with an auction reset feature, referred to as auction rate securities ("ARS") and reclassified out of accumulated other comprehensive loss a realized loss of $0.5 million to earnings which is included in interest and other income expense in the condensed consolidated statements of operations. There were no amounts reclassified out of accumulated other comprehensive loss to the condensed consolidated statements of operations for the three months ended March 31, 2019 . See Note 6 for additional information regarding investments. Income Taxes Deferred income taxes result from temporary differences between the tax basis of assets and liabilities and the basis reported in the Company’s consolidated financial statements. Deferred tax liabilities and assets are determined based on the difference between the financial statement and the tax basis of assets and liabilities using enacted rates in effect during the year in which the Company expects differences to reverse. Valuation allowances are provided against assets, including net operating losses, if the Company determines it is more likely than not that some portion or all of an asset may not be realized. Interest and penalties related to income tax matters are recognized in income tax expense. See Note 11 for additional information regarding income taxes. Net Income Per Share Net income per share is computed by dividing net income by the weighted-average number of common shares outstanding during the period on a basic and diluted basis. The following table sets forth the calculation of basic and diluted net income per share (in thousands, except per share data): Three Months Ended Numerator: 2020 2019 Net income $ 72,793 $ 85,169 Denominator: Denominator for basic net income per share — weighted-average outstanding shares 36,471 36,237 Effect of dilutive securities: Stock options, restricted stock awards and restricted stock units 305 330 Denominator for diluted net income per share — weighted-average outstanding shares 36,776 36,567 Net income per share — basic $ 2.00 $ 2.35 Net income per share — diluted $ 1.98 $ 2.33 The Company’s potentially dilutive securities include outstanding stock options and unvested stock-based awards which include restricted stock awards that vest over a specific service period, restricted stock awards that vest based on achievement of a performance condition, restricted stock awards with a performance and a market condition, restricted stock units and matching restricted stock units awarded under the Company's Management Stock Purchase Plan. Shares underlying unvested restricted stock awards that vest based on performance and market conditions that have not been achieved as of the end of the period are not included in the computation of basic or diluted earnings per share. Diluted net income per share considers the impact of potentially dilutive securities except when the inclusion of the potentially dilutive securities would have an anti-dilutive effect. The following table summarizes the shares underlying the unvested performance-based restricted stock and anti-dilutive securities excluded from the basic and diluted earnings per share calculations (in thousands): Three Months Ended 2020 2019 Performance-based restricted stock awards 84 89 Anti-dilutive securities 96 141 Stock-Based Compensation Equity instruments issued in exchange for services performed by officers, employees, and directors of the Company are accounted for using a fair-value based method and the fair value of such equity instruments is recognized as expense in the consolidated statements of operations. For stock-based awards that vest over a specific service period, compensation expense is measured based on the fair value of the awards at the grant date, and is recognized on a straight-line basis over the vesting period of the awards, net of an estimated forfeiture rate. For equity instruments that vest based on achievement of a performance condition, stock-based compensation expense is recognized based on the expected achievement of the related performance conditions at the end of each reporting period over the vesting period of the awards. If the Company's initial estimates of the achievement of the performance conditions change, the related stock-based compensation expense and timing may fluctuate from period to period based on those estimates. If the performance conditions are not met, no stock-based compensation expense will be recognized, and any previously recognized stock-based compensation expense will be reversed. For awards with both a performance and a market condition, the Company estimates the fair value of each equity instrument granted on the date of grant using a Monte-Carlo simulation model. This pricing model uses multiple simulations to evaluate the probability of achieving the market condition to calculate the fair value of the awards. Stock-based compensation expense for stock options and restricted stock awards issued under equity incentive plans and stock purchases under the Employee Stock Purchase Plan included in the Company’s results of operations were as follows (in thousands): Three Months Ended 2020 2019 Cost of revenues $ 2,472 $ 2,058 Selling and marketing (excluding customer base amortization) 2,024 1,638 Software development 2,528 2,056 General and administrative 8,156 6,277 Total stock-based compensation expense $ 15,180 $ 12,029 Allowance for Credit Losses On January 1, 2020 , the Company adopted Accounting Standards Updates ("ASU") 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ; ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses ; ASU 2019-04, Codification Improvements to Financial Instruments - Credit Losses (Topic 326) ; ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument ; ASU 2019-11, Codification Improvements to Financial Instruments - Credit Losses (Topic 326) and ASU 2020-02, Financial Instruments-Credit Losses (Topic 326) and Leases (Topic 842) , later codified as Accounting Standards Codification ("ASC") 326 ("ASC 326"), using the modified retrospective transition approach. Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the Securities and Exchange Commission on February 26, 2020, for further details of the Company’s policy prior to the adoption of ASC 326. As of January 1, 2020 , the Company maintained an allowance for credit losses to cover its current expected credit losses ("CECL") on its trade receivables and contract assets arising from the failure of customers to make contractual payments. The Company estimates credit losses expected over the life of its trade receivables and contract assets based on historical information combined with current conditions that may affect a customer’s ability to pay and reasonable and supportable forecasts. While the Company uses various credit quality metrics, it primarily monitors collectibility by reviewing the duration of collection pursuits on its delinquent trade receivables. Based on the Company’s experience, the customer's delinquency status is the strongest indicator of the credit quality of the underlying trade receivables, which is analyzed monthly. In most instances, the Company’s policy is to write-off trade receivables when they are deemed uncollectible. A majority of the Company's trade receivables are less than 365 days. Under the CECL impairment model, the Company develops and documents its allowance for credit losses on its trade receivables based on four portfolio segments. The determination of portfolio segments is based primarily on the qualitative consideration of the nature of the Company’s business operations and the characteristics of the underlying trade receivables, as follows: • CoStar Suite Portfolio Segment - The CoStar Suite portfolio segment consists of two classes of trade receivables based on geographical location: CoStar Suite, North America and CoStar Suite, International. • Information Services Portfolio Segment - The information services portfolio segment consists of four classes of trade receivables: Real Estate Manager; information services, North America; STR, US; and STR, International. • Multifamily Portfolio Segment - The multifamily portfolio segment consists of one class of trade receivables. • Commercial property and land Portfolio Segment - The commercial property and land portfolio segment consists of two classes of trade receivables: LoopNet and other commercial property and land online marketplaces. See Note 4 for further discussion of the Company’s accounting for allowance for credit losses. Leases The determination of whether an arrangement contains a lease and the classification of a lease, if applicable, is made at lease commencement, at which time the Company also measures and recognizes a right-of-use ("ROU") asset, representing the Company’s right to use the underlying asset, and a lease liability, representing the Company’s obligation to make lease payments under the terms of the arrangement. For the purposes of recognizing ROU assets and lease liabilities associated with the Company’s leases, the Company has elected the practical expedient to not recognize a ROU asset or lease liability for short-term leases, which are leases with a term of twelve months or less. The lease term is defined as the noncancelable portion of the lease term, plus any periods covered by an option to extend the lease if it is reasonably certain that that the option will be exercised. In determining the amount of lease payments used in measuring ROU assets and lease liabilities, the Company has elected the practical expedient not to separate non-lease components from lease components for all classes of underlying assets. Consideration deemed part of the lease payments used to measure ROU assets and lease liabilities generally includes fixed payments and variable payments based on either an index or a rate, offset by lease incentives. The ROU asset also includes any lease prepayments. ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The rates implicit within the Company's leases are generally not determinable. Therefore, the Company's incremental borrowing rate is used to determine the present value of lease payments. The determination of the Company’s incremental borrowing rate requires judgment and is determined at lease commencement, or as of January 1, 2019 for operating leases in existence upon adoption of ASC 842 . The incremental borrowing rate is subsequently reassessed upon a modification to the lease arrangement. Lease costs related to the Company's operating leases are generally recognized as a single ratable lease cost over the lease term. See Note 7 for further discussion of the Company’s accounting for leases. Long-Lived Assets, Intangible Assets and Goodwill Long-lived assets, such as property and equipment, and purchased intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset exceeds its estimated undiscounted future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. Goodwill is tested annually for impairment by each reporting unit on October 1 of each year or more frequently if an event or other circumstance indicates that we may not recover the carrying value of the asset. The Company may first assess qualitative factors to evaluate whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount or elect to bypass such assessment. If it is determined that it is more likely than not that the fair value of a reporting unit is less than its carrying value, or the Company elects to bypass such assessment, the Company then determines the fair value of each reporting unit. The fair value of each reporting unit is compared to the carrying amount of the reporting unit. If the carrying value of the reporting unit exceeds the fair value, then an impairment loss is recognized for the difference. Debt Issuance Costs Costs incurred in connection with the issuance of long-term debt are deferred and amortized as interest expense over the term of the related debt using the effective interest method for term debt and on a straight-line basis for revolving debt. The Company made a policy election to classify deferred issuance costs on the revolving credit facility as a long-term asset on its condensed consolidated balance sheets. Upon a refinancing or amendment, previously capitalized debt issuance costs are expensed and included in loss on extinguishment of debt if the Company determines that there has been a substantial modification of the related debt. If the Company determines that there has not been a substantial modification of the related debt, any previously capitalized debt issuance costs are amortized as interest expense over the term of the new debt instrument. See Note 10 for additional information regarding the Company's revolving credit facility. Business Combinations The Company allocates the purchase consideration related to business combinations to the identifiable tangible and intangible assets acquired, and liabilities assumed based on their estimated fair values. The purchase consideration is determined based on the fair value of the assets transferred, liabilities incurred and equity interests issued, after considering any transactions that are separate from the business combination. The excess of the fair value of purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets and contingent liabilities. Significant estimates in valuing certain intangible assets include, but are not limited to, future expected cash flows from acquired customer bases, acquired technology and acquired trade names and other intangible assets, useful lives, royalty rates and discount rates. Any adjustments to provisional amounts that are identified during the measurement period are recorded in the reporting period in which the adjustment amounts are determined. Upon the conclusion of the measurement period, any subsequent adjustments are recorded to earnings. For a given acquisition, the Company may identify certain pre-acquisition contingencies as of the acquisition date and may extend its review and evaluation of these pre-acquisition contingencies throughout the measurement period in order to obtain sufficient information to assess whether the Company includes these contingencies as a part of the fair value estimates of assets acquired and liabilities assumed and, if so, determine their estimated fair value. If the Company cannot reasonably determine the fair value of a pre-acquisition contingency (non-income tax related) by the end of the measurement period, which is generally the case given the nature of such matters, the Company will recognize an asset or a liability for such pre-acquisition contingency if: (i) it is probable that an asset existed or a liability had been assumed at the acquisition date and (ii) the amount of the asset or liability can be reasonably estimated. Subsequent to the measurement period, changes in the Company's estimates of such contingencies will affect earnings and could have a material effect on its results of operations and financial position. In addition, uncertain tax positions and tax related valuation allowances assumed in connection with a business combination are initially estimated as of the acquisition date. The Company reevaluates these items based upon facts and circumstances that existed as of the acquisition date with any adjustments to its preliminary estimates being recorded to goodwill, provided that the Company is within the measurement period. Subsequent to the measurement period, changes to these uncertain tax positions and tax related valuation allowances will affect the Company's provision for income taxes in its condensed consolidated statements of operations and comprehensive income and could have a material impact on its results of operations and financial position. Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements On January 1, 2020, the Company adopted ASU 2019-12, Simplifying the Accounting for Income Taxes on a prospective basis. The amounts related to the reclassification of franchise taxes from income from operations to income tax expense for the three months ended March 31, 2020 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures. On January 1, 2020, the Company adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract on a prospective basis. ASU 2018-15 requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to defer and recognize as an asset. The adoption did not have a material impact on the Company's condensed consolidated financial statements and related disclosures. On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments using the modified retrospective method. This accounting standard replaced the prior incurred loss accounting model with a current expected credit loss approach. As of January 1, 2020, no cumulative transition adjustment was recorded to the beginning balance of retained earnings, as the adoption did not result in a higher allowance for credit losses under the CECL impairment model. The adoption did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

REVENUE FROM CONTRACTS WITH CUS

REVENUE FROM CONTRACTS WITH CUSTOMERS	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
REVENUE FROM CONTRACTS WITH CUSTOMERS	REVENUE FROM CONTRACTS WITH CUSTOMERS Disaggregated Revenue The Company provides information, analytics and online marketplaces to the commercial real estate industry and related professionals. The revenues by operating segment and type of service consist of the following (in thousands): Three Months Ended March 31, 2020 2019 North America International Total North America International Total Information and analytics CoStar Suite $ 157,335 $ 7,621 $ 164,956 $ 140,973 $ 6,728 $ 147,701 Information services 25,690 6,692 32,382 16,591 2,259 18,850 Online marketplaces Multifamily 137,460 — 137,460 114,268 — 114,268 Commercial property and land 56,962 87 57,049 47,405 201 47,606 Total revenues $ 377,447 $ 14,400 $ 391,847 $ 319,237 $ 9,188 $ 328,425 Deferred Revenue Changes in deferred revenue for the period were as follows (in thousands): Balance at December 31, 2019 $ 70,620 Revenue recognized in the current period from the amounts in the beginning balance (38,354 ) New deferrals, net of amounts recognized in the current period 56,602 Effects of foreign currency (824 ) Balance at March 31, 2020 (1) $ 88,044 __________________________ (1) Deferred revenue is comprised of $85 million of current liabilities and $3 million of noncurrent liabilities classified within lease and other long-term liabilities on the Company’s condensed consolidated balance sheet as of March 31, 2020 . Contract Assets The Company had contract assets of $5 million and $4 million as of March 31, 2020 and December 31, 2019 , respectively, which are generated when contractual billing schedules differ from revenue recognition timing. Contract assets represent a conditional right to consideration for satisfied performance obligations that becomes a receivable when the conditions are satisfied. Current contract assets are included in prepaid expenses and other current assets, and non-current contract assets are included in deposits and other assets on the Company's condensed consolidated balance sheets. The Company recognized revenue of $1 million from contract assets for the three months ended March 31, 2020 . Commissions Commissi ons expense is included in selling and marketing expense in the Company's condensed consolidated statements of operations. Commis sions expense activity for the three months ended March 31, 2020 and 2019 was as follows (in thousands). The Company determined that no deferred commissions were impaired as of March 31, 2020 : Three Months Ended 2020 2019 Commissions incurred $ 22,437 $ 18,551 Commissions capitalized in the current period (16,523 ) (13,729 ) Amortization of deferred commissions costs 14,747 12,407 Total commissions expense $ 20,661 $ 17,229 Unsatisfied Performance Obligations Remaining contract consideration for which revenue has not been recognized due to unsatisfied performance obligations was approximately $249 million at March 31, 2020 , which the Company expects to recognize over the next five years . This amount does not include contract consideration for contracts with a duration of one year or less.

ALLOWANCE FOR CREDIT LOSSES

ALLOWANCE FOR CREDIT LOSSES	3 Months Ended
	Mar. 31, 2020
Credit Loss [Abstract]
ALLOWANCE FOR CREDIT LOSSES	ALLOWANCE FOR CREDIT LOSSES The following table details the activity related to the allowance for credit losses for trade receivables by portfolio segment (in thousands): Three Months Ended March 31, 2020 CoStar Suite Information services Multifamily Commercial property and land Total Beginning balance at December 31, 2019 $ 1,264 $ 624 $ 1,195 $ 1,465 $ 4,548 Current-period provision for expected credit losses (1), (2) 2,634 1,247 1,403 899 6,183 Write-offs charged against the allowance, net of recoveries and other (1,372 ) — (565 ) (483 ) (2,420 ) Ending balance at March 31, 2020 $ 2,526 $ 1,871 $ 2,033 $ 1,881 $ 8,311 __________________________ (1) Credit loss expense is included in general and administrative expenses on the condensed consolidated statement of operations. (2)

ACQUISITIONS

ACQUISITIONS	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
ACQUISITIONS	. ACQUISITIONS RentPath On February 11, 2020, RentPath Holdings, Inc. (“RentPath”), certain direct or indirect wholly-owned subsidiaries of RentPath (together with RentPath, the “Sellers”), and, solely for the purposes set forth therein, CSGP Holdings, LLC (“CSGP”), an indirect wholly owned subsidiary of the Company ("Buyer") entered into an asset purchase agreement (the “Asset Purchase Agreement”) dated as of February 12, 2020. Pursuant to the Asset Purchase Agreement, and subject to the terms and conditions set forth therein, CSGP agreed to acquire for $588 million in cash all of the equity interests of RentPath, as reorganized following an internal restructuring of the Sellers (“Reorganized RentPath") pursuant to and under the joint chapter 11 plan of reorganization of the Sellers and certain of their affiliates to be filed in the U.S. Bankruptcy Court for the District of Delaware. Under the terms of the Asset Purchase Agreement, the Company agreed to guarantee the full and timely performance of CSGP’s obligations under the Asset Purchase Agreement. The completion of the transaction is subject to customary conditions, including the expiration or termination of any applicable waiting period under applicable antitrust laws and bankruptcy court approvals. As required by the purchase agreement, the Company paid a $59 million break fee into a cash escrow account. In the event the agreement is terminated under specified circumstances in which certain antitrust approvals are not obtained, or a governmental order related to antitrust or competition matters prohibits the consummation of the transaction, this amount is not refundable to the Company. As the transaction had not closed as of March 31, 2020 , the break fee is recorded as restricted cash within cash, cash equivalents and restricted cash on the Company's condensed consolidated balance sheets. STR, LLC and STR Global Ltd. On Octo ber 22, 2019, the Company acquired all of the issued and outstanding equity interests of STR for a purchase price of $435 million . STR is a global provider of benchmarking and analytics for the hospitality industry. The combination of STR's and CoStar's offerings is expected to allow for the creation of valuable new and improved tools for industry participants. The Company applied the acquisition method to account for the STR transaction, which requires that assets acquired and liabilities assumed be recorded at their fair values as of the acquisition date. The following table summarizes the amounts recorded for acquired assets and assumed liabilities recorded at their fair values as of the acquisition date (in thousands): Preliminary: October 22, 2019 Measurement Period Adjustments Updated Preliminary: October 22, 2019 Cash and cash equivalents $ 11,710 $ (90 ) $ 11,620 Accounts receivable 8,067 8,067 Lease right-of-use assets 7,306 7,306 Goodwill 261,436 432 261,868 Intangible assets 178,000 178,000 Lease liabilities (7,306 ) (7,306 ) Deferred revenue (10,966 ) (10,966 ) Deferred tax liabilities (7,980 ) (7,980 ) Other assets and liabilities (4,815 ) (4,815 ) Fair value of identifiable net assets acquired $ 435,452 $ 342 $ 435,794 The net assets of STR were recorded at their estimated fair values. In valuing the acquired assets and assumed liabilities, fair value estimates were based primarily on future expected cash flows, market rate assumptions for contractual obligations and appropriate discount rates. Measurement period adjustments primarily relate to the determination of working capital as of the acquisition date. The purchase price allocation is preliminary, subject to the completion of the Company's assessment of certain tax matters. The customer base assets incorporated significant assumptions that had a material impact on the estimated fair value, such as discount rates, projected revenue growth rates, customer attrition rates and projected profit margins. The following table summarizes the fair values (in thousands) of the identifiable intangible assets included in each of the Company's operating segments, their related estimated useful lives (in years) and their respective amortization methods: North America International Estimated Fair Value Estimated Useful Life Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 97,000 13 $ 42,000 10 Accelerated Trade name 24,000 15 Straight-line Other intangible assets 10,000 5 5,000 5 Straight-line Total intangible assets $ 131,000 $ 47,000 Goodwill is calculated as the excess of the consideration transferred over the net assets recognized and represents the future economic benefits arising from other assets acquired that could not be individually identified and separately recognized. Specifically, the goodwill recorded as part of the STR acquisition includes but is not limited to: (i) the expected synergies and other benefits that the Company believes will result from combining its operations with STR's operations; and (ii) any intangible assets that do not qualify for separate recognition, such as the assembled workforce. Goodwill recorded in connection with this acquisition is not amortized, but is subject to an annual impairment test. Of the $262 million of goodwill recorded as part of the acquisition, $159 million and $103 million are associated with the Company's North America and International operating segments, respectively. The goodwill recognized in the North America operating segment is expected to be deductible for income tax purposes in future periods. As part of the STR acquisition, the Company incurred $2 million of transaction costs. Additionally, the Company paid $15 million into a cash escrow account for deferred compensation for certain STR employees, to be paid to active employees after a defined one year period following the acquisition or when earlier terminated by the Company without cause or by the employee for good reason. In the event some or all of those employees are not entitled to their retention bonus, the funds will be remitted to the seller. The Company is recognizing compensation expense for the deferred compensation over the one-year post-combination period. Off Campus Partners, LLC Acquisition On June 12, 2019, the Company acquired Off Campus Partners, LLC ("OCP"), a provider of student housing marketplace content and technology to U.S. universities for $16 million . The purchase agreement required an initial payment of $14 million , net of cash acquired, at the time of closing, with the remainder of the purchase price payable one year following the acquisition date, subject to offset for indemnification claims or adjustments to the purchase price after final determination of closing net working capital. As part of the acquisition, the Company recorded goodwill and intangibles assets of $8 million and $9 million , respectively. The net assets of OCP were recorded at their estimated fair value. The estimated fair values are preliminary, subject to the Company's assessment of certain tax matters. Measurement period adjustments recognized in 2019 were not material. Pro Forma Financial Information The unaudited pro forma financial information presented below summarizes the combined results of operations for the Company and STR as though the companies were combined as of January 1, 2018. The unaudited pro forma financial information for all periods presented includes amortization charges from acquired intangible assets, retention compensation, as referenced above, and the related tax effects, along with certain other accounting effects, but excludes the impacts of any expected operational synergies. The unaudited pro forma financial information as presented below is for informational purposes only and is not necessarily indicative of the results of operations that would have been achieved if the acquisition had taken place on January 1, 2018. The unaudited pro forma financial information for the three months ended March 31, 2019 combine the historical results of the Company and STR for the periods prior to the acquisition date, and the effects of the pro forma adjustments listed above. The unaudited pro forma financial information, in the aggregate, was as follows (in thousands, except per share data): Three Months Ended March 31, 2019 Revenue $ 340,180 Net income $ 79,423 Net income per share - basic $ 2.19 Net income per share - diluted $ 2.17

INVESTMENTS AND FAIR VALUE MEAS

INVESTMENTS AND FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2020
Investments And Fair Value Disclosures [Abstract]
INVESTMENTS AND FAIR VALUE MEASUREMENTS	INVESTMENTS AND FAIR VALUE MEASUREMENTS Fair value is defined as the price that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. There is a three-tier fair value hierarchy, which categorizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs for which little or no market data exists, therefore requiring an entity to develop its own assumptions. As of March 31, 2020 , the Company's financial assets comprise Level 1 cash equivalents with original maturities of three months or less in the amount of $586 million . As of March 31, 2020 , the Company had no Level 2 or Level 3 financial assets measured at fair value. During the first quarter of 2020 , the Company sold its ARS investments for $10.3 million and recognized a realized loss of $0.5 million for the three months ended March 31, 2020 included in interest and other expense on the Company's condensed consolidated statements of operations. The following table represents the Company's investments in marketable securities and fair value measurements by investment category reported as cash equivalents and investments as of December 31, 2019 (in thousands): December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Level 1 Level 2 Level 3 Cash equivalents $ 576,761 $ — $ — $ 576,761 $ 576,761 $ — $ — Auction rate securities 10,800 — (730 ) 10,070 — — 10,070 Total cash equivalents and long-term investments $ 587,561 $ — $ (730 ) $ 586,831 $ 576,761 $ — $ 10,070 The Company’s Level 3 assets consisted of ARS, whose underlying assets were primarily student loan securities supported by guarantees from the Federal Family Education Loan Program of the U.S. Department of Education. As of December 31, 2019 , these investments were in an unrealized loss position for a period of twelve months or greater. The unrealized losses were generated primarily from changes in interest rates and ARS that failed to settle at auction due to adverse conditions in the global credit markets. The losses were considered temporary, as the contractual terms of these investments do not permit the issuer to settle the security at a price less than the amortized cost of the investment. The Company had no realized gains or losses on its investments during the year ended December 31, 2019 . The carrying value of cash equivalents, accounts receivable, accounts payable and accrued expenses approximates fair value as of March 31, 2020 and December 31, 2019 .
INVESTMENTS AND FAIR VALUE MEASUREMENTS	INVESTMENTS AND FAIR VALUE MEASUREMENTS Fair value is defined as the price that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. There is a three-tier fair value hierarchy, which categorizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs for which little or no market data exists, therefore requiring an entity to develop its own assumptions. As of March 31, 2020 , the Company's financial assets comprise Level 1 cash equivalents with original maturities of three months or less in the amount of $586 million . As of March 31, 2020 , the Company had no Level 2 or Level 3 financial assets measured at fair value. During the first quarter of 2020 , the Company sold its ARS investments for $10.3 million and recognized a realized loss of $0.5 million for the three months ended March 31, 2020 included in interest and other expense on the Company's condensed consolidated statements of operations. The following table represents the Company's investments in marketable securities and fair value measurements by investment category reported as cash equivalents and investments as of December 31, 2019 (in thousands): December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Level 1 Level 2 Level 3 Cash equivalents $ 576,761 $ — $ — $ 576,761 $ 576,761 $ — $ — Auction rate securities 10,800 — (730 ) 10,070 — — 10,070 Total cash equivalents and long-term investments $ 587,561 $ — $ (730 ) $ 586,831 $ 576,761 $ — $ 10,070 The Company’s Level 3 assets consisted of ARS, whose underlying assets were primarily student loan securities supported by guarantees from the Federal Family Education Loan Program of the U.S. Department of Education. As of December 31, 2019 , these investments were in an unrealized loss position for a period of twelve months or greater. The unrealized losses were generated primarily from changes in interest rates and ARS that failed to settle at auction due to adverse conditions in the global credit markets. The losses were considered temporary, as the contractual terms of these investments do not permit the issuer to settle the security at a price less than the amortized cost of the investment. The Company had no realized gains or losses on its investments during the year ended December 31, 2019 . The carrying value of cash equivalents, accounts receivable, accounts payable and accrued expenses approximates fair value as of March 31, 2020 and December 31, 2019 .

LEASES

LEASES	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
LEASES	LEASES The Company has operating leases for its office facilities, data centers and certain vehicles, as well as finance leases for office equipment. The Company's leases have remaining terms of less than one year to nine years . The leases contain various renewal and termination options. The period that is subject to an option to extend the lease is included in the lease term if it is reasonably certain that the option will be exercised. The period that is subject to an option to terminate the lease is included if it is reasonably certain that the option will not be exercised. Lease costs related to the Company's operating leases included in the condensed consolidated statements of operations were as follows (in thousands): Three Months Ended Operating lease costs: 2020 2019 Cost of revenues $ 2,894 $ 3,238 Software development 1,396 952 Selling and marketing (excluding customer base amortization) 2,539 2,191 General and administrative 1,174 292 Total operating lease costs $ 8,003 $ 6,673 The impact of lease costs related to finance leases and short-term leases was not material for the three months ended March 31, 2020 . Supplemental balance sheet information related to operating leases was as follows (in thousands): Balance Balance Sheet Location March 31, 2020 December 31, 2019 Long-term lease liabilities Lease and other long-term liabilities $ 116,785 $ 120,153 Weighted-average remaining lease term in years 4.8 5.0 Weighted-average discount rate 3.9 % 4.0 % Balance sheet information related to finance leases was not material as of March 31, 2020 . Supplemental cash flow information related to leases was as follows (in thousands): Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: 2020 2019 Operating cash flows used in operating leases $ 8,709 $ 7,716 ROU assets obtained in exchange for lease obligations: Operating leases $ 5,080 $ 170 Maturities of operating lease liabilities at March 31, 2020 were as follows (in thousands): 2020 (1) $ 26,214 2021 32,115 2022 31,915 2023 30,674 2024 25,040 Thereafter 12,981 Total lease payments 158,939 Less imputed interest (14,473 ) Present value of lease liabilities $ 144,466 __________________________ (1) Represents the nine months ending December 31, 2020

GOODWILL

GOODWILL	3 Months Ended
	Mar. 31, 2020
Goodwill [Abstract]
GOODWILL	GOODWILL The changes in the carrying amount of goodwill by operating segment consist of the following (in thousands): North America International Total Goodwill, December 31, 2018 $ 1,573,088 $ 38,447 $ 1,611,535 Acquisitions, including measurement period adjustments 165,272 102,532 267,804 Effect of foreign currency translation — 2,681 2,681 Goodwill, December 31, 2019 1,738,360 143,660 1,882,020 Acquisitions, including measurement period adjustments 319 113 432 Effect of foreign currency translation (8,465 ) (8,465 ) Goodwill, March 31, 2020 $ 1,738,679 $ 135,308 $ 1,873,987 The Company recorded goodwill of approximately $262 million in connection with the October 22, 2019 acquisition of STR and approximately $8 million in connection with the June 2019 acquisition of OCP. In connection with the acquisition of Cozy, during 2019, the Company recorded a measurement period adjustment which resulted in a $1 million reduction to the initial amount of goodwill of approximately $53 million . No impairments of the Company's goodwill were recognized during the three months ended March 31, 2020 and 2019.

INTANGIBLE ASSETS

INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2020
Intangible Assets, Net (Excluding Goodwill) [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS Intangible assets consist of the following (in thousands, except amortization period data): March 31, December 31, Weighted- Average Amortization Period (in years) Acquired technology and data $ 104,933 $ 105,168 5 Accumulated amortization (91,929 ) (90,542 ) Acquired technology and data, net 13,004 14,626 Acquired customer base 484,131 487,532 11 Accumulated amortization (243,803 ) (233,202 ) Acquired customer base, net 240,328 254,330 Acquired trade names and other intangible assets 237,821 236,358 12 Accumulated amortization (90,464 ) (84,118 ) Acquired trade names and other intangible assets, net 147,357 152,240 Intangible assets, net $ 400,689 $ 421,196 Intangible assets are reviewed for impairment at least annually and more frequently whenever events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. No impairments of the Company's intangible assets were recognized during the three months ended March 31, 2020 and 2019.

LONG-TERM DEBT

LONG-TERM DEBT	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT On October 19, 2017, the Company entered into an amended and restated credit agreement (the "2017 Credit Agreement"), which amended and restated in its entirety the then-existing credit agreement dated April 1, 2014 (the "2014 Credit Agreement"). The 2017 Credit Agreement, through a syndicate of financial institutions as lenders and issuing banks, provides for a $750 million revolving credit facility with a term of five years , of which up to $20 million is available for the issuance of letters of credit. On March 25, 2020 , the Company borrowed $745 million under the revolving credit facility. At March 31, 2020 , $4.8 million of the revolving credit facility remained available. The Company expects to use the proceeds of the borrowing to fund the pending acquisition of RentPath Holdings, Inc., as well as other potential strategic acquisitions, and for other working capital and general corporate purposes. The Company had an irrevocable standby letter of credit outstanding totaling $0.2 million as of March 31, 2020 and December 31, 2019 , which is required to secure its San Francisco office lease. The letter of credit was established in 2014 and automatically renews annually through January 31, 2025. The loans under the 2017 Credit Agreement bear interest, at the Company’s option, of either (i) during any interest period selected by the Company, at the London interbank offered rate for deposits in U.S. dollars with a maturity comparable to such interest period, adjusted for statutory reserves (“LIBOR”), plus an initial spread of 1.25% per annum, subject to adjustment based on the Company’s First Lien Secured Leverage Ratio (as defined in the 2017 Credit Agreement) or (ii) at the greatest of (x) the prime rate from time to time announced by JPMorgan Chase Bank, N.A., (y) the New York Federal Reserve Bank rate, plus ½ of 1% and (z) LIBOR for a one-month interest period plus 1.00% , plus an initial spread of 0.25% per annum, subject to adjustment based on the Company’s First Lien Secured Leverage Ratio. If an event of default occurs under the 2017 Credit Agreement, the interest rate on overdue amounts will increase by 2.00% per annum. The obligations under the 2017 Credit Agreement are guaranteed by all material subsidiaries of the Company and are secured by a lien on substantially all of the assets of the Company and its material subsidiaries, in each case subject to certain exceptions, pursuant to security and guarantee agreements. LIBOR may not always be available to the Company as a base interest rate for borrowings under the credit facility. The transition away from LIBOR is anticipated to begin in 2021, though it may become unavailable as a base interest rate earlier. The Company may need or seek to negotiate with its lenders for an alternative rate. The Company may not be able to agree with its lenders on a replacement reference rate that is as favorable as LIBOR, which may increase the Company's capital costs. The 2017 Credit Agreement requires the Company to maintain (i) a First Lien Secured Leverage Ratio not exceeding 3.50 to 1.00 and (ii) after the incurrence of additional indebtedness under certain specified exceptions in the 2017 Credit Agreement, a Total Leverage Ratio (as defined in the 2017 Credit Agreement) not exceeding 4.50 to 1.00. The 2017 Credit Agreement also includes other covenants, including ones that, subject to certain exceptions, restrict the ability of the Company and its subsidiaries to (i) incur additional indebtedness, (ii) create, incur, assume or permit to exist any liens, (iii) enter into mergers, consolidations or similar transactions, (iv) make investments and acquisitions, (v) make certain dispositions of assets, (vi) make dividends, distributions and prepayments of certain indebtedness, and (vii) enter into certain transactions with affiliates. The Company was in compliance with the covenants in the 2017 Credit Agreement as of March 31, 2020 . The Company had $745 million debt outstanding at March 31, 2020 with a weighted average interest rate of 2.2% and no debt outstanding at December 31, 2019 . Borrowings under the revolving credit facility are recorded on the Company's condensed consolidated balance sheets as long-term debt and are due in October 2022. For the three months ended March 31, 2020 , the Company recognized interest expense of $1.2 million , including interest on outstanding borrowings of $0.3 million , amortization of debt issuance costs of $0.3 million , and commitment fees of $0.6 million on its revolving credit facility. For the three months ended March 31, 2019 , the Company recognized interest expense of $0.7 million , including amortization of debt issuance costs of $0.2 million and commitment fees of $0.5 million on its revolving credit facility. The Company had $2 million of deferred debt issuance costs included in deposits and other assets on the Company's condensed consolidated balance sheets as of March 31, 2020 and December 31, 2019 .

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The income tax provision reflects an effective tax rate of approximately 7% and 13% for the three months ended March 31, 2020 and 2019 , respectively. The decrease in the effective tax rate was primarily due to lower income before income taxes for the three months ended March 31, 2020 , as well as an increase in excess tax benefits. The amounts for other discrete items for the three months ended March 31, 2020 and 2019 were consistent. On March 27, 2020, President Trump signed into law the Coronavirus Aid, Relief and Economic Security Act (the "CARES Act"). The CARES Act did not have a material impact on the Company's condensed financial statements for the three months ended March 31, 2020

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The Company leases office facilities under various non-cancelable operating leases. The leases contain various renewal options. See Note 7 for further discussion of the Company's operating lease commitments. Currently, and from time to time, the Company is involved in litigation incidental to the conduct of its business. In accordance with GAAP, the Company records a provision for a liability when it is both probable that a liability has been incurred and the amount can be reasonably estimated. While it is reasonably possible that an unfavorable outcome may occur as a result of one or more of the Company’s current litigation matters, at this time management has concluded that the resolutions of these matters are not expected to have a material effect on the Company's consolidated financial position, future results of operations or liquidity. Legal defense costs are expensed as incurred.

SEGMENT REPORTING

SEGMENT REPORTING	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
SEGMENT REPORTING	SEGMENT REPORTING Segment Information The Company manages its business geographically in two operating segments, with the primary areas of measurement and decision-making being North America, which includes the U.S. and Canada, and International, which primarily includes Europe, Asia-Pacific and Latin America. Management relies on an internal management reporting process that provides revenue and operating segment net income before interest and other income (expense), loss on debt extinguishment, income taxes, depreciation and amortization (“EBITDA”). Management believes that operating segment EBITDA is an appropriate measure for evaluating the operational performance of the Company’s operating segments. EBITDA is used by management to internally measure operating and management performance and to evaluate the performance of the business. However, this measure should be considered in addition to, not as a substitute for or superior to, income from operations or other measures of financial performance prepared in accordance with GAAP. Summarized information by operating segment consists of the following (in thousands): Three Months Ended 2020 2019 EBITDA North America $ 102,413 $ 115,268 International (2,293 ) (2,117 ) Total EBITDA $ 100,120 $ 113,151 The reconciliation of net income to EBITDA consists of the following (in thousands): Three Months Ended 2020 2019 Net income $ 72,793 $ 85,169 Amortization of acquired intangible assets in cost of revenues 6,005 5,513 Amortization of acquired intangible assets in operating expenses 11,484 7,682 Depreciation and other amortization 6,767 6,464 Interest and other income (4,518 ) (4,945 ) Interest and other expense 2,026 732 Income tax expense 5,563 12,536 EBITDA $ 100,120 $ 113,151 Summarized information by operating segment consists of the following (in thousands): March 31, December 31, Property and equipment, net: North America $ 102,843 $ 103,383 International 3,566 4,146 Total property and equipment, net $ 106,409 $ 107,529 Goodwill: North America $ 1,738,679 $ 1,738,360 International 135,308 143,660 Total goodwill $ 1,873,987 $ 1,882,020 Assets: North America $ 4,462,340 $ 3,615,258 International 222,257 238,728 Total assets $ 4,684,597 $ 3,853,986 Liabilities: North America $ 1,176,504 $ 402,759 International 45,282 45,634 Total liabilities $ 1,221,786 $ 448,393

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS A novel strain of coronavirus known as "COVID-19" was first identified in Wuhan, China in December 2019, and was subsequently declared a pandemic by the World Health Organization on March 11, 2020. COVID-19 has surfaced in nearly all regions around the world and resulted in travel restrictions and business slowdowns or shutdowns in affected areas. The full impact of the COVID-19 pandemic is unknown and rapidly evolving. The COVID-19 pandemic did not materially affect the Company's condensed consolidated financial statements for the three months ended March 31, 2020 . As the extent and duration of the impacts from COVID-19 remain unclear, the Company’s estimates and assumptions may evolve as conditions change. Actual results could differ significantly from those estimates. Certain estimates and assumptions that affect the Company's financial statements take into account historical and forward-looking factors that the Company believes are reasonable, including assumptions as to the potential impacts arising from COVID-19. Such estimates and assumptions affect, among other things, the Company’s goodwill, long-lived asset and indefinite-lived intangible asset valuation, allowance for credit losses and share based compensation. COVID-19 is discussed in more detail throughout “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, allowance for credit losses, the useful lives and recoverability of long-lived and intangible assets, and goodwill, income taxes, accounting for business combinations, stock-based compensation, estimating the Company's incremental borrowing rate for its leases, and contingencies, among others. The Company bases these estimates on historical and anticipated results, trends and various other assumptions that it believes are reasonable, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses. Actual results could differ from these estimates.
Revenue Recognition	Revenue Recognition The Company derives revenues primarily by (i) providing access to its proprietary database of commercial real estate information and (ii) providing online marketplaces for professional property management companies, property owners, brokers and landlords, in each case typically through a fixed monthly fee for its subscription-based services. The Company's subscription-based services consist primarily of information, analytics and online marketplace services offered over the Internet to commercial real estate industry and related professionals. Subscription contract rates are based on the number of sites, number of users, organization size, the client’s business focus, geography, the number and types of services to which a client subscribes, the number of properties a client advertises and the prominence and placement of a client's advertised properties in the search results. The Company’s subscription-based license agreements typically renew automatically, and a majority have a term of at least one year . The Company also provides (i) market research, portfolio and debt analysis, management and reporting capabilities and (ii) real estate and lease management solutions, including lease administration and abstraction services, to commercial customers, real estate investors, and lenders via the Company’s other service offerings, as well as (iii) benchmarking and analytics for the hospitality industry through STR, LLC (formerly known as STR, Inc.) and STR Global, Ltd. (together with STR, LLC, referred to as “STR”), which were acquired in the fourth quarter of 2019. The Company analyzes contracts to determine the appropriate revenue recognition using the following steps: (i) identification of contracts with customers, (ii) identification of distinct performance obligations in the contract, (iii) determination of contract transaction price, (iv) allocation of contract transaction price to the performance obligations, and (v) determination of revenue recognition based on timing of satisfaction of the performance obligation(s). The Company recognizes revenues upon the satisfaction of its performance obligation(s) (upon transfer of control of promised services to its customers) in an amount that reflects the consideration to which it expects to be entitled to in exchange for those services. Revenues from subscription-based services are recognized on a straight-line basis over the term of the agreement. In limited circumstances, the Company's contracts with customers include promises to transfer multiple services, such as contracts for its subscription-based services and professional services. For these contracts, the Company accounts for individual performance obligations separately if they are distinct, which involves the determination of the standalone selling price for each distinct performance obligation. Deferred revenue results from amounts billed in advance to customers or cash received from customers in advance of the Company's fulfillment of its performance obligation(s) and is recognized as those obligations are satisfied. Contract assets represent a conditional right to consideration for satisfied performance obligations that become a receivable when the conditions are satisfied. Contract assets are generated when contractual billing schedules differ from revenue recognition timing. Certain sales commissions are considered incremental and recoverable costs of obtaining a contract with a customer. Sales commissions incurred for obtaining new contracts are deferred and then amortized as selling and marketing expenses on a straight-line basis over a period of benefit that the Company has determined to be three years . The three-year amortization period was determined based on several factors, including the nature of the technology and proprietary data underlying the services being purchased, customer contract renewal rates and industry competition. Certain commission costs are not capitalized as they do not represent incremental costs of obtaining a contract. See Note 3 for further discussion of the Company's revenue recognition.
Cost of Revenues	Cost of Revenues Cost of revenues principally consists of salaries, benefits, bonuses and stock-based compensation expenses and other indirect costs for the Company's researchers who collect and analyze the commercial real estate data that is the basis for the Company's information, analytics and online marketplaces and for employees that support these products. Additionally, cost of revenues includes the cost of data from third-party data sources, credit card and other transaction fees relating to processing customer transactions, which are expensed as incurred, and the amortization of acquired trade names, technology and other intangible assets.
Advertising Costs	Advertising Costs
Foreign Currency	Foreign Currency The Company’s reporting currency is the U.S. dollar. The functional currency for the majority of its operations is the local currency, with the exception of certain international locations of STR for which the functional currency is the British Pound. Assets and liabilities denominated in a foreign currency are translated into U.S. dollars using the exchange rates in effect as of the balance sheet date. Gains and losses resulting from translation are included in accumulated other comprehensive loss. Currency g ains and losses on the translation of intercompany loans made to foreign subsidiaries that are of a long-term investment nature are also included
Income Taxes	Income Taxes Deferred income taxes result from temporary differences between the tax basis of assets and liabilities and the basis reported in the Company’s consolidated financial statements. Deferred tax liabilities and assets are determined based on the difference between the financial statement and the tax basis of assets and liabilities using enacted rates in effect during the year in which the Company expects differences to reverse. Valuation allowances are provided against assets, including net operating losses, if the Company determines it is more likely than not that some portion or all of an asset may not be realized. Interest and penalties related to income tax matters are recognized in income tax expense.
Net Income Per Share	The Company’s potentially dilutive securities include outstanding stock options and unvested stock-based awards which include restricted stock awards that vest over a specific service period, restricted stock awards that vest based on achievement of a performance condition, restricted stock awards with a performance and a market condition, restricted stock units and matching restricted stock units awarded under the Company's Management Stock Purchase Plan. Shares underlying unvested restricted stock awards that vest based on performance and market conditions that have not been achieved as of the end of the period are not included in the computation of basic or diluted earnings per share. Diluted net income per share considers the impact of potentially dilutive securities except when the inclusion of the potentially dilutive securities would have an anti-dilutive effect. Net Income Per Share Net income per share is computed by dividing net income by the weighted-average number of common shares outstanding during the period on a basic and diluted basis.
Stock-Based Compensation	Stock-Based Compensation Equity instruments issued in exchange for services performed by officers, employees, and directors of the Company are accounted for using a fair-value based method and the fair value of such equity instruments is recognized as expense in the consolidated statements of operations. For stock-based awards that vest over a specific service period, compensation expense is measured based on the fair value of the awards at the grant date, and is recognized on a straight-line basis over the vesting period of the awards, net of an estimated forfeiture rate. For equity instruments that vest based on achievement of a performance condition, stock-based compensation expense is recognized based on the expected achievement of the related performance conditions at the end of each reporting period over the vesting period of the awards. If the Company's initial estimates of the achievement of the performance conditions change, the related stock-based compensation expense and timing may fluctuate from period to period based on those estimates. If the performance conditions are not met, no stock-based compensation expense will be recognized, and any previously recognized stock-based compensation expense will be reversed. For awards with both a performance and a market condition, the Company estimates the fair value of each equity instrument granted on the date of grant using a Monte-Carlo simulation model. This pricing model uses multiple simulations to evaluate the probability of achieving the market condition to calculate the fair value of the awards.
Allowance for Credit Losses	Allowance for Credit Losses On January 1, 2020 , the Company adopted Accounting Standards Updates ("ASU") 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ; ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses ; ASU 2019-04, Codification Improvements to Financial Instruments - Credit Losses (Topic 326) ; ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument ; ASU 2019-11, Codification Improvements to Financial Instruments - Credit Losses (Topic 326) and ASU 2020-02, Financial Instruments-Credit Losses (Topic 326) and Leases (Topic 842) , later codified as Accounting Standards Codification ("ASC") 326 ("ASC 326"), using the modified retrospective transition approach. Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the Securities and Exchange Commission on February 26, 2020, for further details of the Company’s policy prior to the adoption of ASC 326. As of January 1, 2020 , the Company maintained an allowance for credit losses to cover its current expected credit losses ("CECL") on its trade receivables and contract assets arising from the failure of customers to make contractual payments. The Company estimates credit losses expected over the life of its trade receivables and contract assets based on historical information combined with current conditions that may affect a customer’s ability to pay and reasonable and supportable forecasts. While the Company uses various credit quality metrics, it primarily monitors collectibility by reviewing the duration of collection pursuits on its delinquent trade receivables. Based on the Company’s experience, the customer's delinquency status is the strongest indicator of the credit quality of the underlying trade receivables, which is analyzed monthly. In most instances, the Company’s policy is to write-off trade receivables when they are deemed uncollectible. A majority of the Company's trade receivables are less than 365 days. Under the CECL impairment model, the Company develops and documents its allowance for credit losses on its trade receivables based on four portfolio segments. The determination of portfolio segments is based primarily on the qualitative consideration of the nature of the Company’s business operations and the characteristics of the underlying trade receivables, as follows: • CoStar Suite Portfolio Segment - The CoStar Suite portfolio segment consists of two classes of trade receivables based on geographical location: CoStar Suite, North America and CoStar Suite, International. • Information Services Portfolio Segment - The information services portfolio segment consists of four classes of trade receivables: Real Estate Manager; information services, North America; STR, US; and STR, International. • Multifamily Portfolio Segment - The multifamily portfolio segment consists of one class of trade receivables. • Commercial property and land Portfolio Segment - The commercial property and land portfolio segment consists of two classes of trade receivables: LoopNet and other commercial property and land online marketplaces.
Leases	Leases The determination of whether an arrangement contains a lease and the classification of a lease, if applicable, is made at lease commencement, at which time the Company also measures and recognizes a right-of-use ("ROU") asset, representing the Company’s right to use the underlying asset, and a lease liability, representing the Company’s obligation to make lease payments under the terms of the arrangement. For the purposes of recognizing ROU assets and lease liabilities associated with the Company’s leases, the Company has elected the practical expedient to not recognize a ROU asset or lease liability for short-term leases, which are leases with a term of twelve months or less. The lease term is defined as the noncancelable portion of the lease term, plus any periods covered by an option to extend the lease if it is reasonably certain that that the option will be exercised. In determining the amount of lease payments used in measuring ROU assets and lease liabilities, the Company has elected the practical expedient not to separate non-lease components from lease components for all classes of underlying assets. Consideration deemed part of the lease payments used to measure ROU assets and lease liabilities generally includes fixed payments and variable payments based on either an index or a rate, offset by lease incentives. The ROU asset also includes any lease prepayments. ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The rates implicit within the Company's leases are generally not determinable. Therefore, the Company's incremental borrowing rate is used to determine the present value of lease payments. The determination of the Company’s incremental borrowing rate requires judgment and is determined at lease commencement, or as of January 1, 2019 for operating leases in existence upon adoption of ASC 842 . The incremental borrowing rate is subsequently reassessed upon a modification to the lease arrangement. Lease costs related to the Company's operating leases are generally recognized as a single ratable lease cost over the lease term.
Long-Lived Assets, Intangible Assets	Long-lived assets, such as property and equipment, and purchased intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset exceeds its estimated undiscounted future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset.
Goodwill	Goodwill is tested annually for impairment by each reporting unit on October 1 of each year or more frequently if an event or other circumstance indicates that we may not recover the carrying value of the asset. The Company may first assess qualitative factors to evaluate whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount or elect to bypass such assessment. If it is determined that it is more likely than not that the fair value of a reporting unit is less than its carrying value, or the Company elects to bypass such assessment, the Company then determines the fair value of each reporting unit. The fair value of each reporting unit is compared to the carrying amount of the reporting unit. If the carrying value of the reporting unit exceeds the fair value, then an impairment loss is recognized for the difference.
Debt Issuance Costs	Debt Issuance Costs Costs incurred in connection with the issuance of long-term debt are deferred and amortized as interest expense over the term of the related debt using the effective interest method for term debt and on a straight-line basis for revolving debt. The Company made a policy election to classify deferred issuance costs on the revolving credit facility as a long-term asset on its condensed consolidated balance sheets. Upon a refinancing or amendment, previously capitalized debt issuance costs are expensed and included in loss on extinguishment of debt if the Company determines that there has been a substantial modification of the related debt. If the Company determines that there has not been a substantial modification of the related debt, any previously capitalized debt issuance costs are amortized as interest expense over the term of the new debt instrument.
Business Combinations	Business Combinations The Company allocates the purchase consideration related to business combinations to the identifiable tangible and intangible assets acquired, and liabilities assumed based on their estimated fair values. The purchase consideration is determined based on the fair value of the assets transferred, liabilities incurred and equity interests issued, after considering any transactions that are separate from the business combination. The excess of the fair value of purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets and contingent liabilities. Significant estimates in valuing certain intangible assets include, but are not limited to, future expected cash flows from acquired customer bases, acquired technology and acquired trade names and other intangible assets, useful lives, royalty rates and discount rates. Any adjustments to provisional amounts that are identified during the measurement period are recorded in the reporting period in which the adjustment amounts are determined. Upon the conclusion of the measurement period, any subsequent adjustments are recorded to earnings. For a given acquisition, the Company may identify certain pre-acquisition contingencies as of the acquisition date and may extend its review and evaluation of these pre-acquisition contingencies throughout the measurement period in order to obtain sufficient information to assess whether the Company includes these contingencies as a part of the fair value estimates of assets acquired and liabilities assumed and, if so, determine their estimated fair value. If the Company cannot reasonably determine the fair value of a pre-acquisition contingency (non-income tax related) by the end of the measurement period, which is generally the case given the nature of such matters, the Company will recognize an asset or a liability for such pre-acquisition contingency if: (i) it is probable that an asset existed or a liability had been assumed at the acquisition date and (ii) the amount of the asset or liability can be reasonably estimated. Subsequent to the measurement period, changes in the Company's estimates of such contingencies will affect earnings and could have a material effect on its results of operations and financial position. In addition, uncertain tax positions and tax related valuation allowances assumed in connection with a business combination are initially estimated as of the acquisition date. The Company reevaluates these items based upon facts and circumstances that existed as of the acquisition date with any adjustments to its preliminary estimates being recorded to goodwill, provided that the Company is within the measurement period. Subsequent to the measurement period, changes to these uncertain tax positions and tax related valuation allowances will affect the Company's provision for income taxes in its condensed consolidated statements of operations and comprehensive income and could have a material impact on its results of operations and financial position.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements On January 1, 2020, the Company adopted ASU 2019-12, Simplifying the Accounting for Income Taxes on a prospective basis. The amounts related to the reclassification of franchise taxes from income from operations to income tax expense for the three months ended March 31, 2020 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures. On January 1, 2020, the Company adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract on a prospective basis. ASU 2018-15 requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to defer and recognize as an asset. The adoption did not have a material impact on the Company's condensed consolidated financial statements and related disclosures. On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments using the modified retrospective method. This accounting standard replaced the prior incurred loss accounting model with a current expected credit loss approach. As of January 1, 2020, no cumulative transition adjustment was recorded to the beginning balance of retained earnings, as the adoption did not result in a higher allowance for credit losses under the CECL impairment model. The adoption did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Schedule of accumulated other comprehensive loss	The components of accumulated other comprehensive loss were as follows (in thousands): March 31, December 31, Foreign currency translation adjustment $ (20,804 ) $ (7,855 ) Net unrealized loss on investments, net of tax — (730 ) Total accumulated other comprehensive loss $ (20,804 ) $ (8,585 )
Calculation of basic and diluted net income (loss) per share	The following table sets forth the calculation of basic and diluted net income per share (in thousands, except per share data): Three Months Ended Numerator: 2020 2019 Net income $ 72,793 $ 85,169 Denominator: Denominator for basic net income per share — weighted-average outstanding shares 36,471 36,237 Effect of dilutive securities: Stock options, restricted stock awards and restricted stock units 305 330 Denominator for diluted net income per share — weighted-average outstanding shares 36,776 36,567 Net income per share — basic $ 2.00 $ 2.35 Net income per share — diluted $ 1.98 $ 2.33
Schedule of anti-dilutive securities excluded from computation of earnings per share	The following table summarizes the shares underlying the unvested performance-based restricted stock and anti-dilutive securities excluded from the basic and diluted earnings per share calculations (in thousands): Three Months Ended 2020 2019 Performance-based restricted stock awards 84 89 Anti-dilutive securities 96 141
Stock-based compensation expense for stock options and restricted stock	Stock-based compensation expense for stock options and restricted stock awards issued under equity incentive plans and stock purchases under the Employee Stock Purchase Plan included in the Company’s results of operations were as follows (in thousands): Three Months Ended 2020 2019 Cost of revenues $ 2,472 $ 2,058 Selling and marketing (excluding customer base amortization) 2,024 1,638 Software development 2,528 2,056 General and administrative 8,156 6,277 Total stock-based compensation expense $ 15,180 $ 12,029

REVENUE FROM CONTRACTS WITH C_2

REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The Company provides information, analytics and online marketplaces to the commercial real estate industry and related professionals. The revenues by operating segment and type of service consist of the following (in thousands): Three Months Ended March 31, 2020 2019 North America International Total North America International Total Information and analytics CoStar Suite $ 157,335 $ 7,621 $ 164,956 $ 140,973 $ 6,728 $ 147,701 Information services 25,690 6,692 32,382 16,591 2,259 18,850 Online marketplaces Multifamily 137,460 — 137,460 114,268 — 114,268 Commercial property and land 56,962 87 57,049 47,405 201 47,606 Total revenues $ 377,447 $ 14,400 $ 391,847 $ 319,237 $ 9,188 $ 328,425
Contract with Customer, Asset and Liability	Changes in deferred revenue for the period were as follows (in thousands): Balance at December 31, 2019 $ 70,620 Revenue recognized in the current period from the amounts in the beginning balance (38,354 ) New deferrals, net of amounts recognized in the current period 56,602 Effects of foreign currency (824 ) Balance at March 31, 2020 (1) $ 88,044 __________________________ (1) Deferred revenue is comprised of $85 million of current liabilities and $3 million of noncurrent liabilities classified within lease and other long-term liabilities on the Company’s condensed consolidated balance sheet as of March 31, 2020 .
Schedule of Commissions Expense	Commis sions expense activity for the three months ended March 31, 2020 and 2019 was as follows (in thousands). The Company determined that no deferred commissions were impaired as of March 31, 2020 : Three Months Ended 2020 2019 Commissions incurred $ 22,437 $ 18,551 Commissions capitalized in the current period (16,523 ) (13,729 ) Amortization of deferred commissions costs 14,747 12,407 Total commissions expense $ 20,661 $ 17,229

ALLOWANCE FOR CREDIT LOSSES (Ta

ALLOWANCE FOR CREDIT LOSSES (Tables)	3 Months Ended
	Mar. 31, 2020
Credit Loss [Abstract]
Financing Receivable, Allowance for Credit Loss	The following table details the activity related to the allowance for credit losses for trade receivables by portfolio segment (in thousands): Three Months Ended March 31, 2020 CoStar Suite Information services Multifamily Commercial property and land Total Beginning balance at December 31, 2019 $ 1,264 $ 624 $ 1,195 $ 1,465 $ 4,548 Current-period provision for expected credit losses (1), (2) 2,634 1,247 1,403 899 6,183 Write-offs charged against the allowance, net of recoveries and other (1,372 ) — (565 ) (483 ) (2,420 ) Ending balance at March 31, 2020 $ 2,526 $ 1,871 $ 2,033 $ 1,881 $ 8,311 __________________________ (1) Credit loss expense is included in general and administrative expenses on the condensed consolidated statement of operations. (2)

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the amounts recorded for acquired assets and assumed liabilities recorded at their fair values as of the acquisition date (in thousands): Preliminary: October 22, 2019 Measurement Period Adjustments Updated Preliminary: October 22, 2019 Cash and cash equivalents $ 11,710 $ (90 ) $ 11,620 Accounts receivable 8,067 8,067 Lease right-of-use assets 7,306 7,306 Goodwill 261,436 432 261,868 Intangible assets 178,000 178,000 Lease liabilities (7,306 ) (7,306 ) Deferred revenue (10,966 ) (10,966 ) Deferred tax liabilities (7,980 ) (7,980 ) Other assets and liabilities (4,815 ) (4,815 ) Fair value of identifiable net assets acquired $ 435,452 $ 342 $ 435,794
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	The following table summarizes the fair values (in thousands) of the identifiable intangible assets included in each of the Company's operating segments, their related estimated useful lives (in years) and their respective amortization methods: North America International Estimated Fair Value Estimated Useful Life Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 97,000 13 $ 42,000 10 Accelerated Trade name 24,000 15 Straight-line Other intangible assets 10,000 5 5,000 5 Straight-line Total intangible assets $ 131,000 $ 47,000
Business Acquisition, Pro Forma Information	The unaudited pro forma financial information, in the aggregate, was as follows (in thousands, except per share data): Three Months Ended March 31, 2019 Revenue $ 340,180 Net income $ 79,423 Net income per share - basic $ 2.19 Net income per share - diluted $ 2.17

INVESTMENTS AND FAIR VALUE ME_2

INVESTMENTS AND FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2020
Investments And Fair Value Disclosures [Abstract]
Schedule of available for sale securities reconciliation	The following table represents the Company's investments in marketable securities and fair value measurements by investment category reported as cash equivalents and investments as of December 31, 2019 (in thousands): December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Level 1 Level 2 Level 3 Cash equivalents $ 576,761 $ — $ — $ 576,761 $ 576,761 $ — $ — Auction rate securities 10,800 — (730 ) 10,070 — — 10,070 Total cash equivalents and long-term investments $ 587,561 $ — $ (730 ) $ 586,831 $ 576,761 $ — $ 10,070
Summary of fair value hierarchy for its financial assets and liabilities measured at fair value on a recurring basis	The following table represents the Company's investments in marketable securities and fair value measurements by investment category reported as cash equivalents and investments as of December 31, 2019 (in thousands): December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Level 1 Level 2 Level 3 Cash equivalents $ 576,761 $ — $ — $ 576,761 $ 576,761 $ — $ — Auction rate securities 10,800 — (730 ) 10,070 — — 10,070 Total cash equivalents and long-term investments $ 587,561 $ — $ (730 ) $ 586,831 $ 576,761 $ — $ 10,070

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Components of lease expense	Lease costs related to the Company's operating leases included in the condensed consolidated statements of operations were as follows (in thousands): Three Months Ended Operating lease costs: 2020 2019 Cost of revenues $ 2,894 $ 3,238 Software development 1,396 952 Selling and marketing (excluding customer base amortization) 2,539 2,191 General and administrative 1,174 292 Total operating lease costs $ 8,003 $ 6,673
Supplemental Balance Sheet Information Related to Leases	Supplemental balance sheet information related to operating leases was as follows (in thousands): Balance Balance Sheet Location March 31, 2020 December 31, 2019 Long-term lease liabilities Lease and other long-term liabilities $ 116,785 $ 120,153 Weighted-average remaining lease term in years 4.8 5.0 Weighted-average discount rate 3.9 % 4.0 %
Schedule of Supplemental Cash Flow Information for Leases	Supplemental cash flow information related to leases was as follows (in thousands): Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: 2020 2019 Operating cash flows used in operating leases $ 8,709 $ 7,716 ROU assets obtained in exchange for lease obligations: Operating leases $ 5,080 $ 170
Lessee, Operating Lease, Liability, Maturity	Maturities of operating lease liabilities at March 31, 2020 were as follows (in thousands): 2020 (1) $ 26,214 2021 32,115 2022 31,915 2023 30,674 2024 25,040 Thereafter 12,981 Total lease payments 158,939 Less imputed interest (14,473 ) Present value of lease liabilities $ 144,466 __________________________ (1) Represents the nine months ending December 31, 2020

GOODWILL (Tables)

GOODWILL (Tables)	3 Months Ended
	Mar. 31, 2020
Goodwill [Abstract]
Schedule of goodwill	The changes in the carrying amount of goodwill by operating segment consist of the following (in thousands): North America International Total Goodwill, December 31, 2018 $ 1,573,088 $ 38,447 $ 1,611,535 Acquisitions, including measurement period adjustments 165,272 102,532 267,804 Effect of foreign currency translation — 2,681 2,681 Goodwill, December 31, 2019 1,738,360 143,660 1,882,020 Acquisitions, including measurement period adjustments 319 113 432 Effect of foreign currency translation (8,465 ) (8,465 ) Goodwill, March 31, 2020 $ 1,738,679 $ 135,308 $ 1,873,987

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2020
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Schedule of acquired finite-lived intangible assets by major class	Intangible assets consist of the following (in thousands, except amortization period data): March 31, December 31, Weighted- Average Amortization Period (in years) Acquired technology and data $ 104,933 $ 105,168 5 Accumulated amortization (91,929 ) (90,542 ) Acquired technology and data, net 13,004 14,626 Acquired customer base 484,131 487,532 11 Accumulated amortization (243,803 ) (233,202 ) Acquired customer base, net 240,328 254,330 Acquired trade names and other intangible assets 237,821 236,358 12 Accumulated amortization (90,464 ) (84,118 ) Acquired trade names and other intangible assets, net 147,357 152,240 Intangible assets, net $ 400,689 $ 421,196

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Summarized information by operating segment	Summarized information by operating segment consists of the following (in thousands): Three Months Ended 2020 2019 EBITDA North America $ 102,413 $ 115,268 International (2,293 ) (2,117 ) Total EBITDA $ 100,120 $ 113,151
Reconciliation of net income to EBITDA	The reconciliation of net income to EBITDA consists of the following (in thousands): Three Months Ended 2020 2019 Net income $ 72,793 $ 85,169 Amortization of acquired intangible assets in cost of revenues 6,005 5,513 Amortization of acquired intangible assets in operating expenses 11,484 7,682 Depreciation and other amortization 6,767 6,464 Interest and other income (4,518 ) (4,945 ) Interest and other expense 2,026 732 Income tax expense 5,563 12,536 EBITDA $ 100,120 $ 113,151
Summarized information by operating segment, assets and liabilities	Summarized information by operating segment consists of the following (in thousands): March 31, December 31, Property and equipment, net: North America $ 102,843 $ 103,383 International 3,566 4,146 Total property and equipment, net $ 106,409 $ 107,529 Goodwill: North America $ 1,738,679 $ 1,738,360 International 135,308 143,660 Total goodwill $ 1,873,987 $ 1,882,020 Assets: North America $ 4,462,340 $ 3,615,258 International 222,257 238,728 Total assets $ 4,684,597 $ 3,853,986 Liabilities: North America $ 1,176,504 $ 402,759 International 45,282 45,634 Total liabilities $ 1,221,786 $ 448,393

ORGANIZATION (Details)

ORGANIZATION (Details)	3 Months Ended
	Mar. 31, 2020operating_segments
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Term of subscription-based license agreements	1 year
Number of business segments	2

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES , REVENUE RECOGNITION AND ADVERTISING COSTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounting Policies [Abstract]
Term of subscription-based license agreements	1 year
Deferred sales commission, amortization period	3 years
Advertising expense	$ 53	$ 33

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES , FOREIGN CURRENCY AND ACCUMULATED OTHER COMPREHENSIVE LOSS, NET OF TAX (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Accounting Policies [Abstract]
Unrealized foreign currency transaction gains	$ 1,400,000
Material gains or losses from foreign currency transactions	0	$ 0
Accumulated Other Comprehensive Loss Net of Tax [Abstract]
Foreign currency translation adjustment	(20,804,000)		$ (7,855,000)
Net unrealized loss on investments, net of tax	0		(730,000)
Total accumulated other comprehensive loss	$ (20,804,000)		$ (8,585,000)
Reclassification out of accumulated other comprehensive loss		$ 0

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES , NET INCOME PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 72,793	$ 85,169
Denominator:
Denominator for basic net income per share - weighted-average outstanding shares (in shares)	36,471	36,237
Effect of dilutive securities:
Stock options and restricted stock awards (in shares)	305	330
Denominator for diluted net income per share — weighted average outstanding shares (in shares)	36,776	36,567
Net income per share - basic (in dollars per share)	$ 2	$ 2.35
Net income per share - diluted (in dollars per share)	$ 1.98	$ 2.33
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	96	141
Performance Based Restricted Stock Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	84	89

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES , STOCK BASED COMPENSATION EXPENSE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	$ 15,180	$ 12,029
Cost of Revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	2,472	2,058
Selling and Marketing (excluding customer base amortization) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	2,024	1,638
Software Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	2,528	2,056
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	$ 8,156	$ 6,277

REVENUE FROM CONTRACTS WITH C_3

REVENUE FROM CONTRACTS WITH CUSTOMERS , DISAGGREGATED REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 391,847	$ 328,425
Information And Analytics [Member] | CoStar Suite [Member]
Disaggregation of Revenue [Line Items]
Revenues	164,956	147,701
Information And Analytics [Member] | Information services [Member]
Disaggregation of Revenue [Line Items]
Revenues	32,382	18,850
Online Marketplaces [Member] | Multifamily Online Marketplace [Member]
Disaggregation of Revenue [Line Items]
Revenues	137,460	114,268
Online Marketplaces [Member] | Commercial property and land [Member]
Disaggregation of Revenue [Line Items]
Revenues	57,049	47,606
North America [Member]
Disaggregation of Revenue [Line Items]
Revenues	377,447	319,237
North America [Member] | Information And Analytics [Member] | CoStar Suite [Member]
Disaggregation of Revenue [Line Items]
Revenues	157,335	140,973
North America [Member] | Information And Analytics [Member] | Information services [Member]
Disaggregation of Revenue [Line Items]
Revenues	25,690	16,591
North America [Member] | Online Marketplaces [Member] | Multifamily Online Marketplace [Member]
Disaggregation of Revenue [Line Items]
Revenues	137,460	114,268
North America [Member] | Online Marketplaces [Member] | Commercial property and land [Member]
Disaggregation of Revenue [Line Items]
Revenues	56,962	47,405
International [Member]
Disaggregation of Revenue [Line Items]
Revenues	14,400	9,188
International [Member] | Information And Analytics [Member] | CoStar Suite [Member]
Disaggregation of Revenue [Line Items]
Revenues	7,621	6,728
International [Member] | Information And Analytics [Member] | Information services [Member]
Disaggregation of Revenue [Line Items]
Revenues	6,692	2,259
International [Member] | Online Marketplaces [Member] | Multifamily Online Marketplace [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0
International [Member] | Online Marketplaces [Member] | Commercial property and land [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 87	$ 201

REVENUE FROM CONTRACTS WITH C_4

REVENUE FROM CONTRACTS WITH CUSTOMERS , CONTRACT ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Change in Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 70,620
Revenue recognized in the current period from the amounts in the beginning balance	(38,354)
New deferrals, net of amounts recognized in the current period	56,602
Effects of foreign currency	(824)
Ending balance	88,044
Current liability	84,717	$ 67,274
Noncurrent liability	$ 3,000

REVENUE FROM CONTRACTS WITH C_5

REVENUE FROM CONTRACTS WITH CUSTOMERS , CONTRACT ASSETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract with customer, asset, gross	$ 5	$ 4
Revenue recognized	$ 1

REVENUE FROM CONTRACTS WITH C_6

REVENUE FROM CONTRACTS WITH CUSTOMERS , COMMISSIONS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Commissions incurred	$ 22,437	$ 18,551
Commissions capitalized in the current period	(16,523)	(13,729)
Amortization of deferred commissions costs	14,747	12,407
Total commissions expense	$ 20,661	$ 17,229

REVENUE FROM CONTRACTS WITH C_7

REVENUE FROM CONTRACTS WITH CUSTOMERS , UNSATISFIED PERFORMANCE OBLIGATIONS (Details) $ in Millions	Mar. 31, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, remaining performance obligation	$ 249
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	5 years

ALLOWANCE FOR CREDIT LOSSES (De

ALLOWANCE FOR CREDIT LOSSES (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2019	$ 4,548
Current-period provision for expected credit losses	6,183
Write-offs charged against the allowance, net of recoveries and other	(2,420)
Ending balance at March 31, 2020	8,311
CoStar Suite [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2019	1,264
Current-period provision for expected credit losses	2,634
Write-offs charged against the allowance, net of recoveries and other	(1,372)
Ending balance at March 31, 2020	2,526
Information services [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2019	624
Current-period provision for expected credit losses	1,247
Write-offs charged against the allowance, net of recoveries and other	0
Ending balance at March 31, 2020	1,871
Multifamily [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2019	1,195
Current-period provision for expected credit losses	1,403
Write-offs charged against the allowance, net of recoveries and other	(565)
Ending balance at March 31, 2020	2,033
Commercial property and land [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2019	1,465
Current-period provision for expected credit losses	899
Write-offs charged against the allowance, net of recoveries and other	(483)
Ending balance at March 31, 2020	$ 1,881

ACQUISITIONS (Details)

ACQUISITIONS (Details) - USD ($)	Feb. 11, 2020	Oct. 22, 2019	Jun. 12, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill				$ 1,873,987,000		$ 1,882,020,000	$ 1,611,535,000
Cash paid for acquisitions, net of cash acquired				432,000	$ 0
Goodwill acquired				432,000		$ 267,804,000
RentPath [Member]
Business Acquisition [Line Items]
Aggregate purchase price	$ 588,000,000
Restricted cash				$ 59,000,000
STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Aggregate purchase price		$ 435,000,000
Goodwill		261,868,000
Transaction costs		2,000,000
Employee retention bonus		$ 15,000,000
Requisite service period		1 year
Off Campus Partners [Member]
Business Acquisition [Line Items]
Cash paid for acquisitions, net of cash acquired			$ 16,000,000
Initial payments to acquire businesses, net of cash acquired			14,000,000
Goodwill acquired			8,000,000
Finite-lived intangible assets acquired			$ 9,000,000
North America [Member] | STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Goodwill		$ 159,000,000
Finite-lived intangible assets acquired		131,000
International [Member] | STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Goodwill		103,000,000
Finite-lived intangible assets acquired		$ 47,000

ACQUISITIONS , SCHEDULE OF IDEN

ACQUISITIONS , SCHEDULE OF IDENTIFIED ASSETS AND LIABILITIES ASSUMED (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Oct. 22, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,873,987	$ 1,882,020		$ 1,611,535
STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Cash and cash equivalents			$ 11,620
Accounts receivable			8,067
Lease right-of-use assets			7,306
Goodwill			261,868
Intangible assets			178,000
Lease liabilities			(7,306)
Deferred revenue			(10,966)
Deferred tax liabilities			(7,980)
Other assets and liabilities			(4,815)
Fair value of identifiable net assets acquired			435,794
Previously Reported [Member] | STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Cash and cash equivalents			11,710
Accounts receivable			8,067
Lease right-of-use assets			7,306
Goodwill			261,436
Intangible assets			178,000
Lease liabilities			(7,306)
Deferred revenue			(10,966)
Deferred tax liabilities			(7,980)
Other assets and liabilities			(4,815)
Fair value of identifiable net assets acquired			435,452
Restatement Adjustment [Member] | STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Cash and cash equivalents			(90)
Accounts receivable
Lease right-of-use assets
Goodwill			432
Intangible assets
Lease liabilities
Deferred revenue
Deferred tax liabilities
Other assets and liabilities
Fair value of identifiable net assets acquired			$ 342

ACQUISITIONS , FINITE LIVED ASS

ACQUISITIONS , FINITE LIVED ASSETS (Details) - STR Inc and STR Global Ltd [Member]	Oct. 22, 2019USD ($)
North America [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 131,000
North America [Member] | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 97,000
Estimated Useful Life	13 years
North America [Member] | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 24,000
Estimated Useful Life	15 years
North America [Member] | Other Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 10,000
Estimated Useful Life	5 years
International [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 47,000
International [Member] | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 42,000
Estimated Useful Life	10 years
International [Member] | Other Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 5,000
Estimated Useful Life	5 years

ACQUISITIONS , SCHEDULE OF PRO

ACQUISITIONS , SCHEDULE OF PRO FORMA INFORMATION (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)$ / shares
Business Combinations [Abstract]
Revenue | $	$ 340,180
Net income | $	$ 79,423
Net income per share - basic (usd per share) | $ / shares	$ 2.19
Net income per share - diluted (usd per share) | $ / shares	$ 2.17

INVESTMENTS AND FAIR VALUE ME_3

INVESTMENTS AND FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from sale of investments	$ 10,300,000
Reclassification out of accumulated other comprehensive loss		$ 0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure			$ 576,761,000
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	586,000,000		576,761,000
Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reclassification out of accumulated other comprehensive loss	$ 500,000
Auction Rate Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure			$ 0

INVESTMENTS AND FAIR VALUE ME_4

INVESTMENTS AND FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investments And Fair Value Disclosures [Line Items]
Amortized Cost		$ 587,561
Gross Unrealized Gains		0
Gross Unrealized Losses		(730)
Fair Value		586,831
Cash Equivalents [Member]
Investments And Fair Value Disclosures [Line Items]
Amortized Cost		576,761
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		576,761
Auction Rate Securities [Member]
Investments And Fair Value Disclosures [Line Items]
Amortized Cost		10,800
Gross Unrealized Gains		0
Gross Unrealized Losses		(730)
Fair Value		10,070
Fair Value, Inputs, Level 1 [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure		576,761
Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure	$ 586,000	576,761
Fair Value, Inputs, Level 1 [Member] | Auction Rate Securities [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure		0
Fair Value, Inputs, Level 2 [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure		0
Fair Value, Inputs, Level 2 [Member] | Auction Rate Securities [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure		0
Fair Value, Inputs, Level 3 [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure		10,070
Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]
Investments And Fair Value Disclosures [Line Items]
Assets, fair value disclosure		$ 10,070

LEASES (Narrative) (Details)

LEASES (Narrative) (Details)	Mar. 31, 2020
Minimum [Member]
Lessee, Lease, Description [Line Items]
Term of contract	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Term of contract	9 years

LEASES (Lease Cost) (Details)

LEASES (Lease Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 8,003	$ 6,673
Cost of Revenues [Member]
Lessee, Lease, Description [Line Items]
Total operating lease costs	2,894	3,238
Software Development [Member]
Lessee, Lease, Description [Line Items]
Total operating lease costs	1,396	952
Selling and Marketing [Member]
Lessee, Lease, Description [Line Items]
Total operating lease costs	2,539	2,191
General and Administrative [Member]
Lessee, Lease, Description [Line Items]
Total operating lease costs	$ 1,174	$ 292

LEASES (Supplemental Balance Sh

LEASES (Supplemental Balance Sheet Information Related to Leases) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Operating leases
Long-term lease liabilities	$ 116,785	$ 120,153,000
Weighted-average remaining lease term in years	4 years 9 months 18 days	5 years
Weighted-average discount rate	3.90%	4.00%

LEASES (Supplemental Cash Flow

LEASES (Supplemental Cash Flow Information Related to Leases) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases		$ 7,716
ROU assets obtained in exchange for lease obligations:
Operating leases	$ 5,080	$ 170

LEASES (Maturities of Operating

LEASES (Maturities of Operating Lease Liabilities) (Details) $ in Thousands	Mar. 31, 2020USD ($)
Leases [Abstract]
2020(1)	$ 26,214
2021	32,115
2022	31,915
2023	30,674
2024	25,040
Thereafter	12,981
Total lease payments	158,939
Less imputed interest	(14,473)
Present value of lease liabilities	$ 144,466

GOODWILL (Details)

GOODWILL (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 1,882,020	$ 1,611,535
Acquisitions, including measurement period adjustments	432	267,804
Effect of foreign currency translation	(8,465)	2,681
Goodwill, ending balance	1,873,987	1,882,020
North America [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	1,738,360	1,573,088
Acquisitions, including measurement period adjustments	319	165,272
Effect of foreign currency translation		0
Goodwill, ending balance	1,738,679	1,738,360
International [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	143,660	38,447
Acquisitions, including measurement period adjustments	113	102,532
Effect of foreign currency translation	(8,465)	2,681
Goodwill, ending balance	$ 135,308	$ 143,660

GOODWILL (Narrative) (Details)

GOODWILL (Narrative) (Details) - USD ($)	Jun. 12, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Oct. 22, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill		$ 1,873,987,000		$ 1,882,020,000		$ 1,611,535,000
Goodwill acquired		432,000		267,804,000
Goodwill, impairment loss		$ 0	$ 0
STR Inc and STR Global Ltd [Member]
Business Acquisition [Line Items]
Goodwill					$ 261,868,000
Off Campus Partners [Member]
Business Acquisition [Line Items]
Goodwill acquired	$ 8,000,000
Cozy Services Ltd [Member]
Business Acquisition [Line Items]
Goodwill				53,000,000
Goodwill acquired				$ 1,000,000

INTANGIBLE ASSETS (Details)

INTANGIBLE ASSETS (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	$ 400,689,000		$ 421,196,000
Impairment of intangible assets, finite-lived	0	$ 0
Acquired database technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	104,933,000		105,168,000
Finite-lived intangible assets, accumulated amortization	(91,929,000)		(90,542,000)
Finite-lived intangible assets, net	$ 13,004,000		14,626,000
Weighted-average amortization period	5 years
Acquired customer base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 484,131,000		487,532,000
Finite-lived intangible assets, accumulated amortization	(243,803,000)		(233,202,000)
Finite-lived intangible assets, net	$ 240,328,000		254,330,000
Weighted-average amortization period	11 years
Acquired trade names and other intangible assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 237,821,000		236,358,000
Finite-lived intangible assets, accumulated amortization	(90,464,000)		(84,118,000)
Finite-lived intangible assets, net	$ 147,357,000		$ 152,240,000
Weighted-average amortization period	12 years

LONG-TERM DEBT (Details)

LONG-TERM DEBT (Details) - USD ($)	Oct. 19, 2017	Mar. 31, 2020	Mar. 31, 2019	Mar. 25, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest expense, debt		$ 1,200,000	$ 700,000
Amortization of debt issuance costs		300,000	200,000
Commitment fee		600,000	$ 500,000
Capitalized debt issuance costs		2,000,000
Borrowings [Member]
Debt Instrument [Line Items]
Interest expense, debt		300,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, amount outstanding		$ 745,000,000		$ 745,000,000	$ 0
Debt, Weighted Average Interest Rate		2.20%
Revolving Credit Facility [Member] | 2017 Credit Agreement [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 750,000,000
Term of loan	5 years
Covenant compliance, secured leverage ratio	3.50
Covenant compliance, total leverage ratio	4.50
Letter of Credit [Member]
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 20,000,000
Long-term debt		200,000
Line of credit facility, amount outstanding					$ 200,000
Letter of Credit [Member] | 2017 Credit Agreement [Member]
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 4,800,000
Interest rate, increase (decrease)	2.00%
Letter of Credit [Member] | 2017 Credit Agreement [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on federal funds rate (in percent)	1.00%
Letter of Credit [Member] | 2017 Credit Agreement [Member] | Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis spread on federal funds rate (in percent)	0.50%
Initial Basis Spread [Member] | Letter of Credit [Member] | 2017 Credit Agreement [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on federal funds rate (in percent)	1.25%
Initial Basis Spread One Month LIBOR [Member] | Letter of Credit [Member] | 2017 Credit Agreement [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on federal funds rate (in percent)	0.25%

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Effective income tax rate	7.00%	13.00%

SEGMENT REPORTING (Details)

SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)operating_segments	Mar. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Number of business segments | operating_segments	2
Reconciliation of EBITDA to net income (loss) [Abstract]
Net income	$ 72,793	$ 85,169
Amortization of acquired intangible assets in cost of revenues	6,005	5,513
Amortization of acquired intangible assets in operating expenses	11,484	7,682
Depreciation and other amortization	6,767	6,464
Interest and other income	(4,518)	(4,945)
Interest and other expense	2,026	732
Income tax expense	5,563	12,536
EBITDA	100,120	113,151
North America [Member]
Reconciliation of EBITDA to net income (loss) [Abstract]
EBITDA	102,413	115,268
International [Member]
Reconciliation of EBITDA to net income (loss) [Abstract]
EBITDA	$ (2,293)	$ (2,117)

SEGMENT REPORTING, ASSETS AND L

SEGMENT REPORTING, ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Property and equipment, net	$ 106,409	$ 107,529
Goodwill	1,873,987	1,882,020	$ 1,611,535
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	4,684,597	3,853,986
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	1,221,786	448,393
North America [Member]
Segment Reporting Information [Line Items]
Goodwill	1,738,679	1,738,360	1,573,088
International [Member]
Segment Reporting Information [Line Items]
Goodwill	135,308	143,660	$ 38,447
Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	102,843	103,383
Goodwill	1,738,679	1,738,360
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	4,462,340	3,615,258
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	1,176,504	402,759
Operating Segments [Member] | International [Member]
Segment Reporting Information [Line Items]
Property and equipment, net	3,566	4,146
Goodwill	135,308	143,660
Reconciliation of operating segment assets to total assets [Abstract]
Total assets	222,257	238,728
Reconciliation of operating segment liabilities to total liabilities [Abstract]
Total liabilities	$ 45,282	$ 45,634

Uncategorized Items - csgp-0331

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 12,057,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 12,057,000