CoStar (CSGP) 10-K 23 Feb 22 2021 FY Annual report Financial data

Cover page

Cover page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Feb. 18, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	0-24531
Entity Registrant Name	CoStar Group, Inc.
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Small Business Entity	false
Emerging Growth	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Public Float			$ 28.7
Entity Common Stock, Shares Outstanding		394,987,704
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive proxy statement, which is expected to be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2021 are incorporated by reference into Part III of this Report.
Entity Central Index Key	0001057352
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Tysons, Virginia

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Income Statement [Abstract]
Revenues		$ 1,944,135	$ 1,659,019	$ 1,399,719
Cost of revenues		357,241	308,968	289,239
Gross profit		1,586,894	1,350,051	1,110,480
Operating expenses:
Selling and marketing (excluding customer base amortization)		622,007	535,778	408,596
Software development		201,022	162,916	125,602
General and administrative		256,711	299,698	178,740
Customer base amortization		74,817	62,457	33,995
Total operating expenses		1,154,557	1,060,849	746,933
Income from operations		432,337	289,202	363,547
Interest (expense) income, net		(31,621)	(17,395)	16,742
Other income (expense), net		3,252	(827)	10,660
Income before income taxes		403,968	270,980	390,949
Income tax expense		111,404	43,852	75,986
Net income		$ 292,564	$ 227,128	$ 314,963
Net income per share — basic (in dollars per share) | $ / shares	[1]	$ 0.75	$ 0.60	$ 0.87
Net income per share — diluted (in dollars per share) | $ / shares	[1]	$ 0.74	$ 0.59	$ 0.86
Weighted average outstanding shares — basic (in shares) | shares	[1]	392,210	380,726	363,096
Weighted average outstanding shares — diluted (in shares) | shares	[1]	394,160	383,266	366,301
[1]	Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 292,564	$ 227,128	$ 314,963
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustment	(4,869)	6,966	3,103
Unrealized gain on investments	0	189	0
Reclassification adjustment for realized loss on investments included in net income	0	541	0
Total other comprehensive (loss) income	(4,869)	7,696	3,103
Total comprehensive income	$ 287,695	$ 234,824	$ 318,066

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS $ in Thousands		Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Current assets:
Cash, cash equivalents and restricted cash		$ 3,827,126	$ 3,755,912
Accounts receivable		138,191	119,059
Less: Allowance for credit losses		(13,374)	(15,110)
Accounts receivable, net		124,817	103,949
Prepaid expenses and other current assets		36,182	28,651
Total current assets		3,988,125	3,888,512
Deferred income taxes, net		5,034	4,983
Lease right-of-use assets		100,680	108,740
Property and equipment, net		271,431	126,325
Goodwill		2,321,015	2,235,999
Intangible assets, net		435,662	426,745
Deferred commission costs, net		101,879	93,274
Deposits and other assets		21,762	15,856
Income tax receivable		11,283	14,986
Total assets		7,256,871	6,915,420
Current liabilities:
Accounts payable		22,244	15,732
Accrued wages and commissions		81,794	80,998
Accrued expenses		81,676	110,305
Income taxes payable		31,236	16,316
Lease liabilities		26,268	32,648
Deferred revenue		95,471	74,851
Total current liabilities		338,689	330,850
Long-term debt, net		987,944	986,715
Deferred income taxes, net		98,656	72,991
Income taxes payable		12,496	25,282
Lease and other long-term liabilities		107,414	124,223
Total liabilities		1,545,199	1,540,061
Stockholders’ equity:
Preferred stock, $0.01 par value; 2,000 shares authorized; zero outstanding		0	0
Common stock, $0.01 par value; 1.2 billion shares authorized; 394,936 and 394,285 issued and outstanding as of December 31, 2021 and 2020, respectively	[1]	3,946	3,943
Additional paid-in capital		4,253,318	4,204,703
Accumulated other comprehensive loss		(5,758)	(889)
Retained earnings		1,460,166	1,167,602
Total stockholders’ equity		5,711,672	5,375,359
Total liabilities and stockholders’ equity		$ 7,256,871	$ 6,915,420
[1]	Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021		Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01		$ 0.01
Preferred stock, shares authorized (in shares)	2,000,000		2,000,000
Preferred stock, shares outstanding (in shares)	0
Common stock, par or stated value per share (in dollars per share)	$ 0.01		$ 0.01
Common stock, shares authorized (in shares)	1,200,000,000		1,200,000,000
Common stock, shares issued, (in shares)	394,936,000	[1]	394,285,000
Common stock, shares outstanding (in shares)	394,936,000	[1]	394,285,000
[1]	Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock		Common StockCumulative Effect, Period of Adoption, Adjusted Balance		Additional Paid-in Capital	[1]	Additional Paid-in CapitalCumulative Effect, Period of Adoption, Adjusted Balance	[1]	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive LossCumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Retained EarningsCumulative Effect, Period of Adoption, Adjusted Balance
Balance (in shares) at Dec. 31, 2018	[1]				364,588,000		364,588,000
Balance at Dec. 31, 2018		$ 3,021,942	$ 12,057	$ 3,033,999	$ 3,646	[1]	$ 3,646	[1]	$ 2,416,530		$ 2,416,530		$ (11,688)	$ (11,688)	$ 613,454	$ 12,057	$ 625,511
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		314,963													314,963
Other comprehensive income (loss)		3,103											3,103
Exercise of stock options (in shares)	[1]				1,159,000
Exercise of stock options		18,652			$ 12	[1]			18,640
Restricted stock issued (in shares)	[1]				1,680,000
Restricted stock issued		0			$ 17	[1]			(17)
Restricted stock grants surrendered (in shares)	[1]				(757,000)
Restricted stock grants surrendered		(27,577)			$ (8)	[1]			(27,569)
Stock-based compensation expense		51,818							51,818
Management stock purchase plan		3,491							3,491
Employee stock purchase plan (in shares)	[1]				136,000
Employee stock purchase plan		7,144			$ 1	[1]			7,143
Balance (in shares) at Dec. 31, 2019	[1]				366,806,000
Balance at Dec. 31, 2019		3,405,593			$ 3,668	[1]			2,470,036				(8,585)		940,474
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		227,128													227,128
Other comprehensive income (loss)		7,696											7,696
Exercise of stock options (in shares)	[1]				953,000
Exercise of stock options		21,871			$ 10	[1]			21,861
Restricted stock issued (in shares)	[1]				1,012,000
Restricted stock issued		0			$ 10	[1]			(10)
Restricted stock grants surrendered (in shares)	[1]				(952,000)
Restricted stock grants surrendered		(38,866)			$ (9)	[1]			(38,857)
Stock-based compensation expense		$ 52,624							52,624
Employee stock purchase plan (in shares)		129,930			130,000	[1]
Employee stock purchase plan		$ 9,343			$ 1	[1]			9,342
Stock issued for equity offerings, net of transaction costs/Stock issued for acquisitions (in shares)	[1]				26,336,000
Stock issued for equity offerings, net of transaction costs/Stock issued for acquisitions		1,689,970			$ 263	[1]			1,689,707
Balance (in shares) at Dec. 31, 2020	[1]				394,285,000
Balance at Dec. 31, 2020		5,375,359			$ 3,943	[1]			4,204,703				(889)		1,167,602
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		292,564													292,564
Other comprehensive income (loss)		(4,869)											(4,869)
Exercise of stock options (in shares)	[1]				206,000
Exercise of stock options		6,341			$ 2	[1]			6,339
Restricted stock issued (in shares)	[1]				862,000
Restricted stock issued		1			$ 8	[1]			(7)
Restricted stock grants surrendered (in shares)	[1]				(569,000)
Restricted stock grants surrendered		(33,314)			$ (7)	[1]			(33,307)
Stock-based compensation expense		$ 62,585							62,585
Employee stock purchase plan (in shares)		152,047			152,000	[1]
Employee stock purchase plan		$ 13,005							13,005
Balance at Dec. 31, 2021		$ 5,711,672			$ 3,946	[1]			$ 4,253,318				$ (5,758)		$ 1,460,166
[1]	Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net income	$ 292,564	$ 227,128	$ 314,963
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	139,558	116,944	81,165
Amortization of deferred commissions costs	63,391	60,516	53,421
Amortization of senior notes discount and issuance costs	2,327	1,658	876
Non-cash lease expense	28,485	26,326	22,748
Stock-based compensation expense	63,709	53,450	52,255
Deferred income taxes, net	24,165	(11,530)	8,220
Credit loss expense	10,928	25,212	10,978
Other operating activities, net	(654)	288	105
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(29,630)	(36,118)	(5,014)
Prepaid expenses and other current assets	(14,873)	1,936	(14,244)
Deferred commissions	(72,038)	(64,355)	(66,688)
Accounts payable and other liabilities	(30,051)	100,846	17,751
Lease liabilities	(30,904)	(30,497)	(25,442)
Income taxes payable	5,860	10,352	(577)
Deferred revenue	17,396	2,188	7,911
Other assets	(502)	1,762	(648)
Net cash provided by operating activities	469,731	486,106	457,780
Investing activities:
Proceeds from sale and settlement of investments	0	10,259	0
Proceeds from sale of property and equipment and other assets	612	0	0
Purchase of Richmond assets and other intangibles	(123,764)	0	0
Purchases of property and equipment and other assets	(65,220)	(48,347)	(46,197)
Cash paid for acquisitions, net of cash acquired	(192,971)	(426,075)	(437,556)
Net cash used in investing activities	(381,343)	(464,163)	(483,753)
Financing activities:
Proceeds from long-term debt	0	1,744,210	0
Payments of long-term debt	0	(745,000)	0
Payments of debt issuance costs	0	(16,647)	0
Repurchase of restricted stock to satisfy tax withholding obligations	(33,314)	(38,867)	(27,577)
Proceeds from equity offering, net of transaction costs	0	1,689,971	0
Proceeds from exercise of stock options and employee stock purchase plan	18,046	30,280	25,080
Other financing activities	(411)	(1,650)	(1,657)
Net cash (used in) provided by financing activities	(15,679)	2,662,297	(4,154)
Effect of foreign currency exchange rates on cash and cash equivalents	(1,495)	941	442
Net increase (decrease) in cash and cash equivalents	71,214	2,685,181	(29,685)
Cash, cash equivalents and restricted cash at beginning of year	3,755,912	1,070,731	1,100,416
Cash, cash equivalents and restricted cash at end of year	3,827,126	3,755,912	1,070,731
Supplemental cash flow disclosures:
Interest paid	31,510	5,948	1,998
Income taxes paid	82,117	45,783	68,935
Supplemental non-cash investing and financing activities:
Consideration owed for acquisitions	60	793	1,650
Accrued capital expenditures and non-cash landlord incentives	$ 2,117	$ 2,364	$ 2,160

ORGANIZATION

ORGANIZATION	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	ORGANIZATION CoStar Group, Inc. (the “Company” or “CoStar”) provides information, analytics, online marketplace and auction services to the commercial real estate and related business community through its comprehensive, proprietary database of commercial real estate information and related tools. The Company provides online marketplaces for commercial real estate, apartment rentals, residential real estate, land for sale and businesses for sale, and its services are typically distributed to its clients under subscription-based agreements that typically renew automatically, a majority of which have a term of at least one year. The Company operates within two operating segments, North America, which includes the United States (“U.S.”) and Canada, and International, which primarily includes Europe, Asia-Pacific and Latin America. On June 24, 2020, the Company acquired Ten-X Holding Company, Inc. and its subsidiaries ("Ten-X"), which operate an online auction platform for commercial real estate. On October 26, 2020, the Company acquired Emporis GmbH, a Germany-based provider of international commercial real estate data and images. On December 22, 2020, the Company acquired Homesnap, Inc. (“Homesnap”), which operates an online mobile software platform for residential real estate agents and brokers. On May 24, 2021, the Company acquired Homes Group, LLC ("Homes.com"), a residential real estate advertising and marketing services company primarily operating through its property listing and marketing portal, Homes.com. On October 1, 2021, the Company acquired Comreal Info, a French société par actions simplifiée ("BureauxLocaux"), the owner and operator of BureauxLocaux, a leading commercial real estate digital marketplace in France. See Note 5 for further discussion of these acquisitions.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The 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. Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles (“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, 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, real estate agents and brokers and landlords, in each case, typically through a fixed monthly fee for its subscription-based services. Other subscription based-services include (i) real estate and lease management solutions to commercial customers, real estate investors and lenders, (ii) access to applications to manage workflow and advertising and marketing services for residential real estate agents through our acquisitions of Homes.com, which was acquired in May 2021, and Homesnap, which was acquired in December 2020, (iii) benchmarking and analytics for the hospitality industry and (iv) market research, portfolio and debt analysis, management and reporting capabilities. See Note 5 for further discussion of acquisitions. 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 derives revenues from transaction-based services including: (i) an online auction platform for commercial real estate through Ten-X, which was acquired in June 2020, (ii) providing online tenant applications, including background and credit checks, and rental payment processing and (iii) complementary services on an ad hoc basis for our (a) real estate and lease management solutions to commercial customers, real estate investors and lenders, (b) benchmarking and analytics for the hospitality industry and (c) other service offerings. 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 obligations. 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. Revenues from transaction-based services are recognized when the promised product or services are delivered, which, in the case of Ten-X auctions, is at the time of a successful closing for the sale of the property. 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 and costs related to advertising purchased on behalf of customers, 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 certain other intangible assets. Foreign Currency Translation 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 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. Gains and losses resulting from transactions denominated in a currency other than the functional currency of the entity are included in other income (expense), net in the consolidated statements of operations using the average exchange rates in effect during the period. The Company recognized a net foreign currency gain of $0.3 million and losses of $0.2 million and $0.6 million for the years ended December 31, 2021, 2020 and 2019, respectively, which are included in other income (expense), net on the consolidated statement of operations. Accumulated Other Comprehensive Loss The components of accumulated other comprehensive loss, net of tax were as follows (in thousands): As of December 31, 2021 2020 Foreign currency translation adjustment $ (5,758) $ (889) Total accumulated other comprehensive loss $ (5,758) $ (889) During the year ended December 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 other income (expense), net in the consolidated statement of operations. There were no amounts reclassified out of accumulated other comprehensive loss to the consolidated statements of operations for the years ended December 31, 2021 and December 31, 2019. Advertising Costs The Company expenses advertising costs as incurred. Advertising costs include digital marketing, television, radio, print and other media advertising. Advertising costs were $312 million, $270 million and $168 million for the years ended December 31, 2021, 2020 and 2019, respectively. 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. The Company has elected to record the global intangible low taxed income inclusion ("GILTI") under the current-period cost method. See Note 12 for further discussion of 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 Company's potentially dilutive securities include outstanding stock options, unvested stock-based awards which include restricted stock awards that vest over a specific service period, restricted stock awards with a performance and market condition, restricted stock units and awards of matching restricted stock units ("Matching RSUs") awarded under the Company's Management Stock Purchase Plan (the “MSPP”). Shares underlying unvested restricted stock awards that vest based on a performance and market condition 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 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 service period of the awards, net of an estimated forfeiture rate. For equity instruments that vest based on achievement of both a performance and market condition, stock-based compensation expense is recognized over the service period of the awards based on the expected achievement of the related performance conditions at the end of each reporting period. 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, restricted stock awards and restricted stock units issued under equity incentive plans, stock purchases under the Employee Stock Purchase Plan, Deferred Stock Units ("DSUs") and Matching RSUs awarded under the MSPP included in the Company’s statement of operations were as follows (in thousands): Year Ended December 31, 2021 2020 2019 Cost of revenues $ 11,165 $ 10,879 $ 9,273 Selling and marketing (excluding customer base amortization) 6,314 5,194 6,809 Software development 12,544 10,325 8,985 General and administrative 33,686 27,706 27,188 Total stock-based compensation expense (1) $ 63,709 $ 54,104 $ 52,255 __________________________ (1) Stock-based compensation expense for the year ended December 31, 2020 includes $0.7 million of expense related to the cash settlement of stock options in connection with the acquisition of Ten-X. See Note 5 for further discussion. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash, cash equivalents, and restricted cash consisted of the following as of December 31, 2021 and 2020 (in thousands): As of December 31, 2021 2020 Cash and cash equivalents $ 3,827,126 $ 3,693,813 Restricted cash: RentPath break fee held in escrow under the terms of the Asset Purchase Agreement — 58,750 Other restricted cash related to acquisitions — 3,349 Total restricted cash — 62,099 Cash, cash equivalents and restricted cash $ 3,827,126 $ 3,755,912 Concentration of Credit Risk and Financial Instruments The Company’s customer base creates a lack of dependence on any individual customer that mitigates the risk of nonpayment of the Company’s accounts receivable. No single customer accounted for more than 5% of the Company’s revenues for each of the years ended December 31, 2021, 2020 and 2019. The carrying amount of the accounts receivable approximates the net realizable value. The Company holds cash at major financial institutions that often exceed Federal Deposit Insurance Corporation insured limits. The Company manages its credit risk associated with cash concentrations by diversifying cash holdings across AAA rated Government and Treasury Money Market Funds and multiple high quality financial institutions, and by periodically evaluating the credit quality of the primary financial institutions holding such deposits. The carrying value of cash approximates fair value. Historically, the Company has not experienced any losses due to such cash concentrations. Allowance for Credit Losses The Company maintains 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 collectability by reviewing the duration of collection pursuits on its delinquent trade receivables and historical write off trends. Based on the Company’s experience, the customer's delinquency status, which is analyzed periodically, is the strongest indicator of the credit quality of the underlying trade receivables. 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 outstanding. Under the CECL impairment model, the Company develops and documents its allowance for credit losses on its trade receivables based on five 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 Portfolio Segment - The CoStar portfolio segment consists of two classes of trade receivables based on geographical location: North America and International. • Information Services Portfolio Segment - The Information Services portfolio segment consists of four classes of trade receivables: CoStar 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. • LoopNet Portfolio Segment - The LoopNet portfolio segment consists of one class of trade receivables. • Other Marketplaces Portfolio Segment - The Other Marketplaces portfolio segment consists of two classes of trade receivables: Ten-X and other marketplaces. The majority of Residential revenue is e-commerce based and does not result in accounts receivable. Residential accounts receivable and the related allowance for credit losses are not material. 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 the commencement of the arrangement, 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. Upon commencement, the initial 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 the new lease standard. 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. Property and Equipment, Net Property and equipment are stated at cost, net of accumulated depreciation and amortization. All repairs and maintenance costs are expensed as incurred. Costs related to acquisition of additional aircraft components or the replacement of existing aircraft components are capitalized and depreciated over the estimated useful life of the aircraft or the added or replaced component, whichever is less. Depreciation and amortization are calculated on a straight-line basis over the following estimated useful lives of the assets: Buildings Twenty thirty-nine Land Indefinite Aircrafts Ten twenty Furniture and office equipment Five ten Vehicles Five years Computer hardware and software Three five Leasehold improvements Shorter of lease terms or useful life Qualifying internal-use software costs incurred during the application development stage, which consist primarily of internal product development costs, outside services and purchased software license costs are capitalized and amortized over the estimated useful life of the asset. All other costs are expensed as incurred. In the fourth quarter of 2021, the Company began removing fully depreciated property and equipment from the cost and accumulated depreciation amounts disclosed. 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. Acquired technology and data, customer base assets, trade names and other intangible assets are related to the Company’s acquisitions. Acquired technology and data is amortized on a straight-line basis over periods ranging from one year to eight years. Acquired intangible assets characterized as customer base assets consist of acquired customer contracts and the related customer relationships and are amortized over periods ranging from five years to thirteen years. Acquired customer bases are amortized on an accelerated or straight-line basis depending on the expected economic benefit of the intangible asset. Acquired trade names and other intangible assets are amortized on a straight-line basis over periods ranging from one year to fifteen years. In the fourth quarter of 2021, the Company began removing fully amortized intangible assets from the cost and accumulated amortization amounts disclosed. Goodwill represents the future economic benefits arising from a business combination and is calculated as the excess of the purchase consideration paid in a business combination over the fair value of the net identifiable assets acquired. Goodwill is not amortized, but instead is assigned to each of the Company's reporting units and tested for impairment at least annually, on October 1, or more frequently if an event or other circumstance indicates that the fair value of a reporting unit may be below its carrying amount. 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, the Company then determines the fair value of each reporting unit. The estimate of the fair value of each reporting unit is based on a projected discounted cash flow model that includes significant assumptions and estimates including the discount rate, growth rate and future financial performance. Assumptions about the discount rate are based on a weighted average cost of capital for comparable companies. Assumptions about the growth rate and future financial performance of a reporting unit are based on the Company's forecasts, business plans, economic projections and anticipated future cash flows. 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. See Notes 5, 9 and 10 for further discussion of acquisitions, goodwill and intangible assets, respectively. 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 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 11 for further discussion of the Company's 2020 Credit Agreement and Senior Notes issuance. Business Combinations The Company allocates the purchase consideration to the tangible assets acquired, liabilities assumed and intangible assets acquired based on their estimated fair values. The purchase price is determined based on the fair value of the assets transferred, liabilities assumed 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. The Company applies significant assumptions, estimates and judgments in determining the fair value of assets acquired and liabilities assumed on the acquisition date, 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, 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, to determine their estimated amounts. 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 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 In the fourth quarter of 2021, the Company adopted ASU 2021-08, Business Combinations (Topic 805), Accounting for Contract Assets and Contract Liabilities from Contracts with Customers . This guidance requires contract assets and liabilities acquired or assumed in an acquisition be measured in accordance with the accounting framework for revenue from contracts with customers as if the Company had originated the acquired contract. This is an exception to the general requirement to measure assets acquired and liabilities assumed at their fair value on the acquisition date. The Company applied this revised guidance to all acquisitions in the year ended December 31, 2021. The application of this guidance to contract assets and contract liabilities acquired or assumed in connection with the Company's acquisitions for the year ended December 31, 2021 did not have a material impact on the Company's consolidated financial statements and related disclosures. Recent Accounting Pronouncements Not Yet Adopted On March 12, 2020, the Financial Accounting Standards Board issued ASU 2020-04, Reference Rate Reform (“ASC 848”): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. Accounting Standards Codification (“ASC”) 848 contains optional expedients and exceptions for applying GAAP to debt, contracts, hedging relationships and other transactions affected by reference rate reform. The provisions of ASC 848 must be applied to all contracts that are accounted for under a Topic, Subtopic or Industry Subtopic for all transactions other than derivatives, which may be applied at a hedging relationship level. This guidance is effective for fiscal years beginning after January 1, 2021, including interim periods within those fiscal years. The Company's 2020 Credit Agreement provides for a $750 million revolving credit facility and a letter of credit sublimit of $20 million, with interest rates benchmarked to LIBOR. As of December 31, 2021, no amounts were issued or drawn under this facility. The Company is currently evaluating the impact this guidance will have on its consolidated financial statements and related disclosures.

REVENUE FROM CONTRACTS WITH CUS

REVENUE FROM CONTRACTS WITH CUSTOMERS	12 Months Ended
	Dec. 31, 2021
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, hospitality industry, residential industry and related professionals. The revenues by operating segment and type of service consist of the following (in thousands): Year Ended December 31, 2021 2020 2019 North America International Total North America International Total North America International Total CoStar $ 686,948 $ 35,873 $ 722,821 $ 634,205 $ 30,530 $ 664,735 $ 590,222 $ 27,576 $ 617,798 Information services 113,723 27,932 141,655 104,117 25,953 130,070 76,950 11,496 88,446 Multifamily 678,680 — 678,680 598,555 — 598,555 490,631 — 490,631 LoopNet (1) 204,816 2,695 207,511 179,371 434 179,805 149,400 580 149,980 Residential (1) 74,583 — 74,583 — — — — — — Other Marketplaces (1) 118,885 — 118,885 85,854 — 85,854 52,864 — 52,864 Total revenues $ 1,877,635 $ 66,500 $ 1,944,135 $ 1,602,102 $ 56,917 $ 1,659,019 $ 1,360,067 $ 39,652 $ 1,399,719 (1) As of September 30, 2021, Commercial Property and Land revenue has been further disaggregated into LoopNet, Residential and Other Marketplaces. Prior period amounts have been adjusted to reflect this presentation. Deferred Revenue Changes in deferred revenue for the period were as follows (in thousands): Balance at December 31, 2020 (1) $ 77,363 Revenue recognized in the current period from the amounts in the beginning balance (74,578) New deferrals, net of amounts recognized in the current period 94,143 Effects of foreign currency (204) Balance at December 31, 2021 (2) $ 96,724 __________________________ (1) Deferred revenue was comprised of $74.9 million of current liabilities and $2.5 million of noncurrent liabilities classified within lease and other long-term liabilities on the Company’s consolidated balance sheet as of December 31, 2020. (2) Deferred revenue was comprised of $95.5 million of current liabilities and $1.2 million of noncurrent liabilities classified within lease and other long-term liabilities on the Company’s consolidated balance sheet as of December 31, 2021. This balance includes $2.2 million of net new deferrals recognized in connection with business acquisitions made in 2021. See Note 5 for further discussion of acquisitions. Contract Assets The Company had contract assets of $9 million as of December 31, 2021 and December 31, 2020, 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 consolidated balance sheets. Commissions Commissions expense is included in selling and marketing expense in the Company's consolidated statements of operations. The Company determined that no deferred commissions were impaired as of December 31, 2021 and December 31, 2020. Commissions expense activity for the years ended December 31, 2021, 2020 and 2019 was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Commissions incurred $ 117,391 $ 97,183 $ 87,043 Commissions capitalized in the current period (72,038) (64,355) (66,688) Amortization of deferred commissions costs 63,391 60,516 53,421 Total commissions expense $ 108,744 $ 93,344 $ 73,776 See Note 2 for the Company's policy on accounting for commissions. Unsatisfied Performance Obligations Remaining contract consideration for which revenue had not been recognized due to unsatisfied performance obligations was $315 million as of December 31, 2021.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	12 Months Ended
	Dec. 31, 2021
Credit Loss [Abstract]
ALLOWANCE FOR CREDIT LOSSES	4. 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): Year Ended December 31, 2021 CoStar Information services Multifamily LoopNet (3) Other Marketplaces (3) Total Beginning balance at December 31, 2020 $ 5,531 $ 2,739 $ 4,387 $ 1,667 $ 786 $ 15,110 Current-period provision (release) for expected credit losses (1), (2) 5,699 (392) 3,057 2,564 — 10,928 Write-offs charged against the allowance, net of recoveries and other (5,850) (527) (4,051) (2,263) 27 (12,664) Ending balance at December 31, 2021 $ 5,380 $ 1,820 $ 3,393 $ 1,968 $ 813 $ 13,374 ________________________ (1) Credit loss expense is included in general and administrative expenses on the consolidated statement of operations. (2) Credit loss expense related to contract assets was not material for the year ended December 31, 2021. (3) Amounts previously disclosed in the Commercial Property and Land portfolio segment have been further disaggregated into the LoopNet, Residential and Other Marketplaces portfolio segments. The majority of the Residential portfolio segment revenue is e-commerce based and does not result in accounts receivable. Year Ended December 31, 2020 CoStar Information services Multifamily LoopNet (3) Other Marketplaces (3) Total Beginning balance at December 31, 2019 $ 1,264 $ 624 $ 1,195 $ 576 $ 889 $ 4,548 Current-period provision for expected credit losses (1), (2) 11,622 2,649 7,644 3,213 84 25,212 Write-offs charged against the allowance, net of recoveries and other (7,355) (534) (4,452) (2,122) (187) (14,650) Ending balance at December 31, 2020 $ 5,531 $ 2,739 $ 4,387 $ 1,667 $ 786 $ 15,110 ________________________ (1) Credit loss expense is included in general and administrative expenses on the consolidated statement of operations. (2) Credit loss expense related to contract assets was not material for the year ended December 31, 2020. (3) Amounts previously disclosed in the Commercial Property and Land portfolio segment have been further disaggregated into the LoopNet, Residential and Other Marketplaces portfolio segments. The majority of the Residential portfolio segment revenue is e-commerce based and does not result in accounts receivable.

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [Abstract]
ACQUISITIONS	ACQUISITIONS BureauxLocaux On October 1, 2021, CoStar UK Limited, a wholly owned subsidiary of the Company, M.A.J.E. Marketing & Strategie and an individual entered into a Share Sale and Purchase Agreement pursuant to which the Company acquired all of the share capital interests in Comreal Info, a French société par actions simplifiée , the owner and operator of BureauxLocaux, a leading commercial real estate digital marketplace in France, for a base purchase price of €35 million ($41 million) in cash, subject to customary working capital and other post-closing adjustments which were settled in the fourth quarter of 2021. As part of the acquisition, the Company recorded goodwill and intangibles assets of $27 million and $18 million, respectively, in the Company's International operating segment. The net assets of BureauxLocaux were recorded at their estimated fair value. The purchase price allocation is preliminary, subject primarily to the Company's assessment of certain tax matters and contingencies. Homes.com On April 14, 2021, Landmark Media Enterprises, LLC (“Landmark”), Homes Group, LLC and CoStar Realty Information, Inc., a Delaware corporation and wholly owned subsidiary of the Company entered into a securities purchase agreement, pursuant to which the Company agreed to acquire all of the outstanding equity interests in Homes.com from Landmark for a purchase price of $150 million in cash, subject to customary working capital and other post-closing adjustments. The Company's acquisition of Homes.com closed on May 24, 2021. The securities purchase agreement required an initial payment of $148 million, net of estimated working capital adjustments, at the time of closing, with the remainder of the purchase price payable four months following the acquisition date, subject to offset for adjustments to the purchase price after final determination of closing net working capital. These amounts were settled in the third quarter of 2021 resulting in total consideration of $152 million. Homes.com is a residential real estate advertising and marketing services company primarily operating through its property listing and marketing portal, Homes.com. 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: Measurement Period Adjustments Updated Preliminary: May 24, 2021 Cash, cash equivalents and restricted cash $ — $ — $ — Accounts receivable 1,798 — 1,798 Lease right-of-use assets 371 — 371 Goodwill 88,132 342 88,474 Intangible assets 53,400 — 53,400 Deferred tax assets 11,171 93 11,264 Lease liabilities (371) — (371) Deferred revenue (1,086) (435) (1,521) Other assets and liabilities (1,240) — (1,240) Fair value of identifiable net assets acquired $ 152,175 $ — $ 152,175 The net assets of Homes.com 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. The purchase price allocation is preliminary, subject primarily to the Company's assessment of certain tax matters and contingencies. The estimated fair value of 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 profit margins. The following table summarizes the fair values of the identifiable intangible assets acquired in the Homes.com acquisition included in the Company's North America operating segment, their related estimated useful lives (in years) and their respective amortization methods (in thousands): Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 32,000 8 Accelerated Trade name 21,000 15 Straight-line Technology 400 2 Straight-line Total intangible assets $ 53,400 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 Homes.com 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 Homes.com operations; and (ii) any intangible assets that do not qualify for separate recognition, such as the assembled workforce. The $88 million of goodwill recorded as part of the acquisition is associated with the Company's North America operating segment, of which $20 million is expected to be deductible for income tax purposes. As of December 31, 2021, transaction costs associated with the Homes.com acquisition were not material. In addition, the Company paid $5 million into a cash escrow account for stay bonuses for certain Homes.com employees and recognized compensation expense for the stay bonus over the six month post-combination period. Upon acquisition, the Company assessed the probability Homes.com would be required to pay certain state tax liabilities and recorded an accrual of $7 million determined in accordance with the provisions of ASC 450, “Contingencies,” as the fair value was not determinable. Landmark has agreed to indemnify the Company for tax liabilities related to periods prior to the acquisition and an indemnification asset was established for $7 million in the purchase price allocation. Homesnap On December 22, 2020, pursuant to the Agreement and Plan of Merger, dated November 20, 2020, by and among CoStar Realty Information, Inc., a Delaware corporation and wholly owned subsidiary of the Company (“CRI”), Snapped Halo Merger Sub Corp., a Delaware corporation and wholly-owned subsidiary of CRI (“Merger Sub”), and Homesnap, Inc., a Delaware corporation, Merger Sub was merged with and into Homesnap (the “Homesnap Merger”), with Homesnap surviving the merger as a wholly-owned subsidiary of CRI. In connection with the Homesnap Merger, the Company acquired all of the issued and outstanding equity interests in Homesnap for a purchase price of $250 million in cash. Homesnap is an industry-leading online and mobile software platform that provides user-friendly applications to optimize residential real estate agent workflow and reinforce the agent-client relationship. Homesnap has relationships, data, software and tools for residential real estate professionals that are complementary to CoStar Group’s existing offerings. The acquisition of Homesnap enabled CoStar Group to enter the residential real estate market and expand the markets in which the Company competes. 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): Final: Cash, cash equivalents and restricted cash $ 10,225 Accounts receivable 662 Lease right-of-use assets 3,437 Goodwill 184,371 Intangible assets 67,000 Deferred tax assets, net (2,778) Lease liabilities (3,375) Deferred revenue (4,000) Other assets and liabilities (5,188) Fair value of identifiable net assets acquired $ 250,354 The net assets of Homesnap 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. The estimated fair value of 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 profit margins. The following table summarizes the fair values (in thousands) of the identifiable intangible assets included in the Company's North America operating segment, their related estimated useful lives (in years) and their respective amortization methods: Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 45,000 10 Accelerated Trade name 7,000 10 Straight-line Technology 15,000 6 Straight-line Total intangible assets $ 67,000 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 Homesnap 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 Homesnap's operations; and (ii) any intangible assets that do not qualify for separate recognition, such as the assembled workforce. The $184 million of goodwill recorded as part of the acquisition is associated with the Company's North America operating segment. Goodwill recognized is not deductible for income tax purposes. Transaction costs associated with the Homesnap acquisition were not material. Ten-X On June 24, 2020, pursuant to the Agreement and Plan of Merger, dated May 13, 2020, by and among CoStar Realty Information, Inc., a Delaware corporation and wholly owned subsidiary of the Company (“CRI”), Crescendo Sub, Inc., a Delaware corporation and wholly-owned subsidiary of CRI (“Merger Sub”), Ten-X Holding Company, Inc., a Delaware corporation ("Ten-X Holding"), and Thomas H. Lee Equity Fund VII L.P., a Delaware limited partnership, solely in its capacity as representative thereunder, Merger Sub was merged with and into Ten-X Holding (the “Merger”), with Ten-X Holding surviving the Merger as a wholly-owned subsidiary of CRI. In connection with the Merger, the Company acquired all of the issued and outstanding equity interests in Ten-X Holding and Ten-X Holding's subsidiaries for a purchase price of $188 million in cash. Ten-X operates an online auction platform for commercial real estate. The Ten-X acquisition is expected to enable the Company to create an end-to-end commercial real estate platform, combining LoopNet and the Company's online audience of buyers with Ten-X’s leadership in online auctions for performing and distressed assets. 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): Final: Cash and cash equivalents $ 3,290 Accounts receivable 131 Lease right-of-use assets 4,945 Goodwill 134,322 Intangible assets 58,000 Lease liabilities (4,945) Deferred tax liabilities, net (2,981) Other assets and liabilities (5,047) Fair value of identifiable net assets acquired $ 187,715 The net assets of Ten-X 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. The estimated fair value of 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 profit margins. The following table summarizes the fair values (in thousands) of the identifiable intangible assets included in the Company's North America operating segment, their related estimated useful lives (in years) and their respective amortization methods: Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 46,000 6 Accelerated Technology 11,000 5 Straight-line Other intangible assets 1,000 2 Straight-line Total intangible assets $ 58,000 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 Ten-X 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 Ten-X's operations; and (ii) any intangible assets that do not qualify for separate recognition, such as the assembled workforce. The $134 million of goodwill recorded as part of the acquisition is associated with the Company's North America operating segment. Goodwill recognized is not deductible for income tax purposes. The transaction costs associated with the Ten-X acquisition were not material. The Company paid $3 million in incentive compensation to Ten-X employees negotiated as part of the acquisition, and this expense was recognized in the post-combination period. Pro Forma Financial Information (unaudited) The unaudited pro forma financial information presented below summarizes the combined results of operations for the Company, Ten-X and Homesnap as though the companies were combined as of January 1, 2019, and the Company and Homes.com as though the companies were combined as of January 1, 2020. The impact of the October 2021 BureauxLocaux acquisition on the pro forma financial information was not material and therefore was not included. 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 acquisitions had taken place on January 1, 2019 for Ten-X and Homesnap and January 1, 2020 for Homes.com. The unaudited pro forma financial information for the years ended December 31, 2021, 2020 and 2019 combines the historical results of the Company, Ten-X, Homesnap and Homes.com for the periods prior to the respective acquisition dates, and the effects of the pro forma adjustments listed above. The unaudited pro forma financial information, in aggregate, was as follows (in thousands, except per share data): Year Ended 2021 2020 2019 Revenue $ 1,962,102 $ 1,758,612 $ 1,483,218 Net income $ 286,718 $ 197,994 $ 271,789 Net income per share - basic $ 0.74 $ 0.52 $ 0.75 Net income per share - diluted $ 0.73 $ 0.51 $ 0.74

INVESTMENTS AND FAIR VALUE MEAS

INVESTMENTS AND FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2021
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. The Company's financial assets comprise Level 1 cash equivalents with original maturities of three months or less in the amount of $3.0 billion and $3.4 billion as of December 31, 2021 and December 31, 2020, respectively. The Company had no Level 2 or Level 3 financial assets measured at fair value. The Company holds other financial instruments, including cash deposits, accounts receivable, accounts payable, accrued expenses and senior notes. The carrying value for such financial instruments, other than the Senior Notes, each approximated their fair values as of December 31, 2021 and December 31, 2020. The estimated fair value of the Company's outstanding Senior Notes using quoted prices from the over-the-counter markets, considered Level 2 inputs, was $1.0 billion as of December 31, 2021 and December 31, 2020.
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. The Company's financial assets comprise Level 1 cash equivalents with original maturities of three months or less in the amount of $3.0 billion and $3.4 billion as of December 31, 2021 and December 31, 2020, respectively. The Company had no Level 2 or Level 3 financial assets measured at fair value. The Company holds other financial instruments, including cash deposits, accounts receivable, accounts payable, accrued expenses and senior notes. The carrying value for such financial instruments, other than the Senior Notes, each approximated their fair values as of December 31, 2021 and December 31, 2020. The estimated fair value of the Company's outstanding Senior Notes using quoted prices from the over-the-counter markets, considered Level 2 inputs, was $1.0 billion as of December 31, 2021 and December 31, 2020.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2021
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 seven years. The leases contain various renewal and termination options. The period which 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 which 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 consolidated statements of operations were as follows (in thousands): Year Ended December 31, 2021 2020 2019 Operating lease costs: Cost of revenues $ 10,110 $ 11,632 $ 11,407 Software development 6,947 6,020 4,209 Selling and marketing (excluding customer base amortization) 11,911 10,356 8,678 General and administrative 5,911 4,827 3,299 Total operating lease costs $ 34,879 $ 32,835 $ 27,593 The impact of lease costs related to finance leases and short-term leases was not material for the years ended December 31, 2021, 2020 and 2019. Supplemental balance sheet information related to operating leases was as follows (in thousands): Year Ended December 31, Balance Balance Sheet Location 2021 2020 Operating lease liabilities $ 134,150 $ 148,975 Less: imputed interest (8,512) (10,998) Present value of lease liabilities 125,638 137,977 Less: current portion of lease liabilities Lease liabilities 26,268 32,648 Long-term lease liabilities Lease and other long-term liabilities $ 99,370 $ 105,329 Weighted-average remaining lease term in years 4.0 4.0 Weighted-average discount rate 3.1 % 3.6 % Balance sheet information related to finance leases was not material as of December 31, 2021 and December 31, 2020. Supplemental cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows used in operating leases $ 37,298 $ 37,006 $ 30,287 ROU assets obtained in exchange for lease obligations: Operating leases $ 34,247 $ 19,746 $ 22,629

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment consists of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ 75,634 $ 80,963 Furniture, office equipment and vehicles 47,540 68,587 Computer hardware and software 30,179 86,755 Aircrafts 68,670 28,561 Land 38,774 24,642 Buildings 96,496 2,970 Property and equipment, gross 357,293 292,478 Accumulated depreciation and amortization (85,862) (166,153) Property and equipment, net $ 271,431 $ 126,325 Depreciation expense for property and equipment was approximately $29 million, $29 million and $26 million, for the years ended December 31, 2021, 2020 and 2019, respectively. In 2021, the Company removed $107 million of property and equipment which was fully depreciated from property and equipment, gross and accumulated depreciation and amortization, which had no net impact on the Company's financial results.

GOODWILL

GOODWILL	12 Months Ended
	Dec. 31, 2021
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, 2019 $ 1,738,360 $ 143,660 $ 1,882,020 Acquisitions, including measurement period adjustments (1) 347,134 1,273 348,407 Effect of foreign currency translation — 5,572 5,572 Goodwill, December 31, 2020 2,085,494 150,505 2,235,999 Acquisitions, including measurement period adjustments (2) 60,352 27,441 87,793 Effect of foreign currency translation — (2,777) (2,777) Goodwill, December 31, 2021 $ 2,145,846 $ 175,169 $ 2,321,015 __________________________ (1) North America goodwill for the year ended December 31, 2020 includes goodwill recorded in connection with the acquisitions of Ten-X and Homesnap of $135.7 million and $211.1 million, respectively, as well as STR measurement period adjustments to goodwill of $0.3 million. International goodwill for the year ended December 31, 2020 includes goodwill recorded in connection with the acquisition of Emporis GmbH of $1.2 million and STR measurement period adjustments of $0.1 million. (2) North America goodwill for the year ended December 31, 2021 includes goodwill recorded in connection with the acquisition of Homes.com of $88.5 million, offset by measurement period adjustments of $1.4 million for Ten-X and $26.7 million for Homesnap recorded during the year ended December 31, 2021 primarily related to the measurement of the fair value of Homesnap customer relationships in the first quarter of 2021. International goodwill recorded in connection with the acquisition of BureauxLocaux was $27.4 million. See Note 5 for further discussion. Of the goodwill generated from acquisitions completed in 2021, $20 million is expected to be deductible for tax purposes. Goodwill generated from acquisitions completed in 2020 was not deductible for tax purposes. No impairments of the Company's goodwill were recognized during the years ended December 31, 2021, 2020 and 2019.

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2021
Intangible Assets, Net (Excluding Goodwill) [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS Intangible assets consist of the following (in thousands, except amortization period data): December 31, Weighted- Average 2021 2020 Acquired technology and data $ 41,979 $ 131,551 6 Accumulated amortization (15,333) (97,791) Acquired technology and data, net 26,646 33,760 Acquired customer base 569,666 545,643 10 Accumulated amortization (319,039) (296,758) Acquired customer base, net 250,627 248,885 Acquired trade names and other intangible assets 262,136 249,465 13 Accumulated amortization (103,747) (105,365) Acquired trade names and other intangible assets, net 158,389 144,100 Intangible assets, net $ 435,662 $ 426,745 Amortization expense for intangible assets was approximately $104 million, $88 million and $55 million for the years ended December 31, 2021, 2020 and 2019, respectively. In 2021, the Company removed $171 million of intangible assets that were fully amortized from the acquired intangible assets and accumulated amortization, which had no net impact on the Company's financial results. In the aggregate, the Company expects the future amortization expense for intangible assets existing as of December 31, 2021 to be approxi mately $87 million, $71 million, $59 million, $47 million and $39 million for the years e nding December 31, 2022, 2023, 2024, 2025 and 2026, respectively. Intangible assets are reviewed for impairment 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 years ended December 31, 2021, 2020 and 2019.

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT The table below presents the components of outstanding debt (in thousands): December 31, 2021 December 31, 2020 2.800% Senior Notes due July 15, 2030 $ 1,000,000 $ 1,000,000 2020 Credit Agreement, due July 1, 2025 — — Total face amount of long-term debt 1,000,000 1,000,000 Senior notes unamortized discount and issuance costs (12,056) (13,285) Long-term debt, net $ 987,944 $ 986,715 Senior Notes On July 1, 2020, the Company issued $1.0 billion aggregate principal amount of 2.800% Senior Notes due July 15, 2030 (the “Senior Notes”). The Senior Notes were sold to a group of financial institutions as initial purchasers who subsequently resold the Senior Notes to non-U.S. persons pursuant to Regulation S under the Securities Act of 1933, as amended (the “Securities Act”), and to persons reasonably believed to be qualified institutional buyers pursuant to Rule 144A under the Securities Act at a purchase price equal to 99.921% of their principal amount. Interest on the Senior Notes is payable semi-annually in arrears beginning on January 15, 2021. The Senior Notes may be redeemed in whole or in part by the Company (a) at any time prior to April 15, 2030 at a redemption price equal to 100% of the principal amount of the Senior Notes, plus the Applicable Premium (as calculated in accordance with the indenture governing the Senior Notes), and any accrued and unpaid interest, if any, on the principal amount of Senior Notes being redeemed to, but excluding, the redemption date, and (b) on or after April 15, 2030 at a redemption price equal to 100% of the principal amount of the Senior Notes, plus any accrued and unpaid interest, if any, on the principal amount of Senior Notes being redeemed to, but excluding, the redemption date. The Company’s obligations under the Senior Notes are guaranteed on a senior, unsecured basis by the Company’s domestic wholly owned subsidiaries and contain covenants, events of default and other customary provisions for which the Company was in compliance with as of December 31, 2021. Revolving Credit Facility On July 1, 2020, the Company also entered into a second amended and restated credit agreement (the "2020 Credit Agreement"), which amended and restated in its entirety the then-existing credit agreement originally entered into on April 1, 2014 and amended and restated on October 19, 2017 (the “2017 Credit Agreement”). The 2020 Credit Agreement provides for a $750 million revolving credit facility with a term of five years (maturing July 1, 2025) and a letter of credit sublimit of $20 million from a syndicate of financial institutions as lenders and issuing banks. A commitment fee of 0.25% to 0.30% per annum, depending on the Total Leverage Ratio (defined in 2020 Credit Agreement), is payable quarterly in arrears based on the unused revolving commitment. Subject to certain conditions, on no more than five occasions, the Company may request increases in the amount of revolving commitments and/or the establishment of term commitments under the 2020 Credit Agreement. Borrowings under the 2020 Credit Agreement will bear interest at a floating rate which can be, at the Company’s option, either (a) an alternate base rate plus an applicable rate ranging from 0.50% to 1.25% or (b) a LIBOR or EURIBOR (with a floor of 0.0%) for the specified interest period plus an applicable rate ranging from 1.50% to 2.25%, in each case depending on the Company's Total Leverage Ratio (as defined in the 2020 Credit Agreement). As LIBOR may not always be available to the Company as a base interest rate for borrowings under the credit facility, the 2020 Credit Agreement allows the Company and the administrative agent under the 2020 Credit Agreement to amend the 2020 Credit Agreement to replace LIBOR with one or more Secured Overnight Financing Rate (“SOFR”) based rates or another alternative benchmark rate. Funds drawn down on the revolving credit facility pursuant to the 2020 Credit Agreement may be used for working capital and other general corporate purposes of the Company and its restricted subsidiaries. The obligations under the 2020 Credit Agreement are guaranteed by each of the Company’s current and future direct or indirect wholly owned restricted domestic subsidiaries, other than certain excluded subsidiaries, in each case subject to certain exceptions, pursuant to guarantee agreements. The 2020 Credit Agreement includes covenants, including ones that, subject to certain exceptions, restrict the ability of the Company and its subsidiaries to (i) merge and consolidate with other companies, (ii) incur indebtedness, (iii) grant liens or security interests on assets, (iv) make investments, acquisitions, loans or advances, (v) pay dividends and (vi) sell or otherwise transfer assets. During any period of time that the Company has obtained and maintained a corporate investment grade rating from at least two designated rating agencies and no Event of Default is continuing, the Company will not be subject to certain of these covenants such as restrictions on the ability to incur indebtedness (such period, a “Covenant Suspension Period”). As of December 31, 2021, the Company is in a Covenant Suspension Period. The 2020 Credit Agreement also requires the Company to maintain a Total Leverage Ratio (as defined in the 2020 Credit Agreement) not exceeding 4.50 to 1.00. The Company was in compliance with the covenants in the 2020 Credit Agreement as of December 31, 2021. As of December 31, 2021, the Company had not drawn any amounts under this facility. The Company had $3.8 million and $4.9 million of deferred debt issuance costs as of December 31, 2021 and December 31, 2020, respectively, in connection with the 2020 Credit Agreement. These amounts are included in deposits and other assets on the Company's consolidated balance sheets. For the years ended December 31, 2021, 2020 and 2019 the Company recognized interest expense as follows (in thousands): Year Ended 2021 2020 2019 Interest on outstanding borrowings $ 28,000 $ 18,509 $ — Amortization of senior notes discount and issuance costs 2,327 1,658 874 Commitment fees and other 1,989 1,627 1,741 Total interest expense $ 32,316 $ 21,794 $ 2,615

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The components of the provision for income taxes attributable to operations consist of the following (in thousands): Year Ended December 31, 2021 2020 2019 Current: Federal $ 61,290 $ 43,461 $ 53,039 State 24,618 11,726 13,422 Foreign 1,331 195 1,305 Total current 87,239 55,382 67,766 Deferred: Federal 22,859 (9,599) 6,881 State 8,467 (926) 2,424 Foreign (7,161) (1,005) (1,085) Total deferred 24,165 (11,530) 8,220 Total provision for income taxes $ 111,404 $ 43,852 $ 75,986 The components of deferred tax assets and liabilities consist of the following (in thousands): December 31, 2021 2020 Deferred tax assets: Allowance for credit losses $ 3,601 $ 3,698 Accrued compensation 3,913 4,934 Stock compensation 18,956 15,289 Net operating losses 45,835 38,498 Accrued reserve and other 4,134 5,900 Lease liabilities 28,306 34,758 Research and development credits 5,812 6,059 Accrued transaction fees — 13,334 Total deferred tax assets, prior to valuation allowance 110,557 122,470 Valuation allowance (5,694) (11,170) Total deferred tax assets, net of valuation allowance 104,863 111,300 Deferred tax liabilities: Deferred commission costs, net (25,700) (23,691) Lease right-of-use assets (22,574) (27,168) Prepaid expenses (2,569) (2,384) Property and equipment, net (21,827) (13,078) Intangible assets, net (125,815) (112,987) Total deferred tax liabilities (198,485) (179,308) Net deferred tax assets (liabilities) $ (93,622) $ (68,008) For the years ended December 31, 2021 and 2020, the Company has not recognized deferred tax liabilities for temporary differences related to investments in foreign subsidiaries that were deemed permanently reinvested. Determination of the amount of unrecognized deferred income tax liabilities on these earnings is not practicable because such liability, if any, depends on certain circumstances existing if and when remittance occurs. A deferred tax liability will be recognized if and when the Company no longer plans to permanently reinvest these undistributed earnings. As of December 31, 2021 and 2020, a valuation allowance has been established for certain deferred tax assets due to the uncertainty of realization. The valuation allowance as of December 31, 2021 and 2020 includes an allowance for acquired net operating losses and foreign deferred tax assets. The Company established the valuation allowance because it is more likely than not that a portion of the deferred tax asset for certain items will not be realized based on the weight of available evidence. A valuation allowance was established for the foreign deferred tax assets due to the cumulative loss in recent years in those jurisdictions. The Company has not had sufficient taxable income historically to utilize the foreign deferred tax assets, and it is uncertain whether the Company will generate sufficient taxable income in the future to utilize the deferred tax assets. The Company has established a valuation allowance for certain acquired net operating losses where Section 382 limitations will impact the ability of the Company to utilize the net operating losses before they expire. The Company’s change in valuation allowance was a decrease of approximately $5.5 million for the year ended December 31, 2021 and a decrease of approximately $2.4 million for the year ended December 31, 2020. The decrease for the year ended December 31, 2021 is primarily due to an international restructuring. The decrease for the year ended December 31, 2020 is primarily due to the removal of the valuation allowance for the Washington, D.C. qualified high technology company tax credits which expired in 2020, partially offset by an increase in the valuation allowance for acquired net operating losses. The Company had U.S. income before income taxes of approximately $409 million, $291 million and $403 million for the years ended December 31, 2021, 2020 and 2019, respectively. The Company had foreign losses before income taxes of approximately $5 million, $20 million and $12 million for the years ended December 31, 2021, 2020 and 2019, respectively. The Company’s provision for income taxes resulted in effective tax rates that varied from the statutory federal income tax rate as follows (in thousands): Year Ended December 31, 2021 2020 2019 Expected federal income tax provision at statutory rate $ 84,833 $ 56,906 $ 82,099 State income taxes, net of federal benefit 21,012 11,409 14,884 (Decrease) in valuation allowance (4,995) (4,848) (693) Research credits (13,070) (14,322) (12,188) Excess tax benefit (10,933) (21,038) (15,282) Tax reserves (12,787) 4,762 3,135 Nondeductible compensation 10,369 5,949 1,777 International restructuring 34,854 — — Other adjustments 2,121 5,034 2,254 Income tax expense $ 111,404 $ 43,852 $ 75,986 The Company has net operating loss carryforwards for international income tax purposes of approximately $41 million which do not expire. The Company has federal net operating loss carryforwards of approximately $151 million which begin to expire in 2029, state net operating loss carryforwards with a tax value of approximately $5 million which begin to expire in 2029 and state income tax credit carryforwards with a tax value of approximately $6 million primarily relating to state research and development credits which do not expire. The Company realized a cash benefit relating to the use of its tax loss carryforwards of approximately $14 million, $5 million and $6 million in December 31, 2021, 2020 and 2019, respectively. The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands): Unrecognized tax benefit as of December 31, 2018 $ 22,372 Increase for current year tax positions 3,487 Increase for prior year tax positions 440 Expiration of the statute of limitation for assessment of taxes (832) Unrecognized tax benefit as of December 31, 2019 25,467 Increase for current year tax positions 4,213 Increase for prior year tax positions 452 Expiration of the statute of limitation for assessment of taxes (1,259) Unrecognized tax benefit as of December 31, 2020 28,873 Increase for current year tax positions 3,024 Decrease for prior year tax positions (5,353) Decrease for settlements with taxing authorities (9,924) Expiration of the statute of limitation for assessment of taxes (1,866) Unrecognized tax benefit as of December 31, 2021 $ 14,754 Approximately $15 million and $29 million of the unrecognized tax benefits as of December 31, 2021 and 2020, respectively, would favorably affect the annual effective tax rate if recognized in future periods. The increase for current year tax positions of $3 million, decrease for prior year tax positions of $5 million and decrease for settlements with taxing authorities of $10 million for the year ended December 31, 2021 are primarily attributable to research credits. The decrease for expiration of the statute of limitation of $2 million for the year ended December 31, 2021 is attributable to research credits and state apportionment reserves. The Company reversed $0.4 million and recognized $0.4 million and $0.2 million for interest and penalties in its consolidated statement of operations for the years ended December 31, 2021, 2020 and 2019 respectively. The Company had liabilities of $0.6 million, $1.0 million $0.6 million for interest and penalties in its consolidated balance sheets as of December 31, 2021, 2020 and 2019, respectively. The Company does not anticipate the amount of the unrecognized tax benefits will change significantly over the next twelve months. The Company is subject to taxation in the U.S. federal jurisdiction and various states and foreign jurisdictions. The Company’s federal income tax returns for tax years 2013 through 2016 and 2018 through 2020 remain open to examination. The Company is under Internal Revenue Service examination for tax years 2013, 2014 and 2016 related to the research and development credit. Most of the Company’s state income tax returns for tax years 2018 through 2020 remain open to examination. For states that have a four-year statute of limitations, the state income tax returns for tax years 2017 through 2020 remain open to examination. The Company’s U.K. income tax return for tax year 2020 remains open to examination. The Company believes that an adequate provision has been made for any adjustments that may result from tax examinations.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The following summarizes our significant contractual obligations, including related payments due by period, as of December 31, 2021 (in thousands): Year Ending December 31, Operating lease obligations Long-term debt principal payments Long-term debt principal interest payments 2022 $ 29,678 $ — $ 28,000 2023 36,477 — 28,000 2024 32,808 — 28,000 2025 16,051 — 28,000 2026 7,235 — 28,000 Thereafter 11,901 1,000,000 112,000 Total $ 134,150 $ 1,000,000 $ 252,000 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.

SEGMENT REPORTING

SEGMENT REPORTING	12 Months Ended
	Dec. 31, 2021
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 (expense) income, net, other income (expense), net, 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 EBITDA information by operating segment consists of the following (in thousands): Year Ended December 31, 2021 2020 2019 North America $ 557,125 $ 410,852 $ 451,699 International 7,856 (4,706) (6,987) Total EBITDA $ 564,981 $ 406,146 $ 444,712 The reconciliation of net income to EBITDA consists of the following (in thousands): Year Ended December 31, 2021 2020 2019 Net income $ 292,564 $ 227,128 $ 314,963 Amortization of acquired intangible assets in cost of revenues 28,809 25,675 21,357 Amortization of acquired intangible assets in operating expenses 74,817 62,457 33,995 Depreciation and other amortization 29,018 28,812 25,813 Interest expense (income), net 31,621 17,395 (16,742) Other (income) expense, net (3,252) 827 (10,660) Income tax expense 111,404 43,852 75,986 EBITDA $ 564,981 $ 406,146 $ 444,712 Summarized information by operating segment consists of the following (in thousands): December 31, 2021 2020 Property and equipment, net North America $ 269,792 $ 123,634 International 1,639 2,691 Total property and equipment, net $ 271,431 $ 126,325 Goodwill North America $ 2,145,846 $ 2,085,494 International 175,169 150,505 Total goodwill $ 2,321,015 $ 2,235,999 Assets North America $ 6,976,752 $ 6,674,974 International 280,119 240,446 Total assets $ 7,256,871 $ 6,915,420 Liabilities North America $ 1,502,497 $ 1,496,894 International 42,702 43,167 Total liabilities $ 1,545,199 $ 1,540,061

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDER'S EQUITY Preferred Stock The Company has 2 million shares of preferred stock, $0.01 par value, authorized for issuance as of December 31, 2021. The Board of Directors may issue the preferred stock from time to time as shares of one or more classes or series. Common Stock The Company has 1.2 billion shares of common stock, $0.01 par value, authorized for issuance. Dividends may be declared and paid on the common stock, subject in all cases to the rights and preferences of the holders of preferred stock and authorization by the Board of Directors. In the event of liquidation or winding up of the Company and after the payment of all preferential amounts required to be paid to the holders of any series of preferred stock, any remaining funds shall be distributed among the holders of the issued and outstanding common stock. Common Stock Split At the Company's 2021 Annual Meeting of Stockholders in June 2021, upon the recommendation of the Company's Board of Directors, the Company's stockholders approved the adoption of the Company's Fourth Amended and Restated Certificate of Incorporation, which increased the total number of shares of common stock that the Company is authorized to issue from 60 million to 1.2 billion. The Fourth Amended and Restated Certificate of Incorporation became effective on June 7, 2021. On June 7, 2021, the Board of Directors approved a ten-for-one stock split of the Company's outstanding shares of common stock to be effected in the form of a stock dividend. Each stockholder of record on June 17, 2021 received a dividend of nine additional shares of common stock for each then-held share, distributed after close of trading on June 25, 2021. The par value of the Company's common stock remained $0.01 per share. All applicable share and per-share amounts in the consolidated financial statements and the accompanying notes have been retroactively adjusted to reflect the impact of the stock split. Equity Offering On May 28, 2020, the Company completed a public equity offering of 26.3 million shares of common stock for $65.50 per share. Net proceeds from the public equity offering were approximately $1.7 billion, after deducting approximately $35 million of underwriting fees, commissions and other stock issuance costs. The Company intends to use the net proceeds from the sale of the securities to fund all or a portion of the costs of any strategic acquisitions it pursues in the future, to finance the growth of its business and for working capital and other general corporate purposes. General corporate purposes may include additions to working capital, capital expenditures, repayment of debt, investments in the Company’s subsidiaries and the repurchase, redemption or retirement of securities, including the Company’s common stock.

NET INCOME PER SHARE

NET INCOME PER SHARE	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHARE The following table sets forth the calculation of basic and diluted net income per share (in thousands except per share data): Year Ended December 31, 2021 2020 2019 Numerator: Net income $ 292,564 $ 227,128 $ 314,963 Denominator: Denominator for basic net income per share — weighted-average outstanding shares 392,210 380,726 363,096 Effect of dilutive securities: Stock options, restricted stock awards and restricted stock units 1,950 2,540 3,205 Denominator for diluted net income per share — weighted-average outstanding shares 394,160 383,266 366,301 Net income per share — basic (1) $ 0.75 $ 0.60 $ 0.87 Net income per share — diluted (1) $ 0.74 $ 0.59 $ 0.86 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. 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): Year Ended December 31, 2021 2020 2019 Performance-based restricted stock awards (1) 415 526 600 Anti-dilutive securities (1) 373 540 425 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
	Dec. 31, 2021
Compensation Related Costs [Abstract]
EMPLOYEE BENEFIT PLANS	EMPLOYEE BENEFIT PLANS Stock Incentive Plans In April 2007, the Company’s Board of Directors adopted the CoStar Group, Inc. 2007 Stock Incentive Plan (as amended, the “2007 Plan”), subject to stockholder approval, which was obtained on June 7, 2007. In April 2016, the Company’s Board of Directors adopted the CoStar Group, Inc. 2016 Stock Incentive Plan (as amended, the “2016 Plan”), subject to stockholder approval, which was obtained on June 9, 2016. All shares of common stock that were authorized for issuance under the 2007 Plan that, as of June 9, 2016, remained available for issuance under the 2007 Plan (excluding shares subject to outstanding awards) were rolled into the 2016 Plan and, as of that date, no shares of common stock were available for new awards under the 2007 Plan. The 2007 Plan continues to govern vested unexercised stock options issued prior to June 9, 2016. Upon the occurrence of a Change of Control, as defined in the 2007 Plan, all outstanding unexercisable options under the 2007 Plan immediately become exercisable. The 2016 Plan provides for the grant of stock options, restricted stock, restricted stock units and stock appreciation rights to officers, directors and employees of the Company and its subsidiaries. Stock options granted under the 2016 Plan may be non-qualified or may qualify as incentive stock options. Except in limited circumstances related to a merger or other acquisition, the exercise price for an option may not be less than the fair market value of the Company’s common stock on the date of grant. The vesting period for each grant of options, restricted stock, restricted stock units and stock appreciation rights under the 2016 Plan is determined by the Board of Directors or a committee thereof and is generally three At December 31, 2021, there was approximately $91 million of unrecognized compensation cost related to stock incentive plans, net of estimated forfeitures, which the Company expects to recognize over a weighted-average-period of 2.3 years. The income tax benefit realized from stock-based compensation was $2 million, $20 million and $17 million for the years ended December 31, 2021, 2020 and 2019, respectively. See Notes 2 and 12 for further discussion of stock-based compensation expense and income taxes, respectively. Stock Options Option activity was as follows: Number of Shares (1) Range of Exercise Price (1) Weighted- Average Exercise Price (1) Weighted- Aggregate Outstanding at December 31, 2018 3,442,760 $3.67 - $34.21 $ 21.23 7.03 $ 43,418 Granted 483,000 $39.82 $ 39.82 Exercised (1,169,180) $5.45 - $34.21 $ 15.95 Outstanding at December 31, 2019 2,756,580 $5.45 - $39.82 $ 26.72 6.98 $ 91,262 Granted 341,000 $66.65 $ 66.65 Exercised (953,130) $19.37 - $39.82 $ 22.95 Canceled or expired (121,350) $34.21 - $66.65 $ 44.31 Outstanding at December 31, 2020 2,023,100 $10.22 - $66.65 $ 34.18 6.99 $ 117,846 Granted 159,000 $91.98 $ 91.98 Exercised (206,000) $20.49 - $39.82 $ 30.78 Outstanding at December 31, 2021 1,976,100 $10.22 - $91.98 $ 39.18 6.24 $ 80,800 Exercisable at December 31, 2019 1,476,200 $10.22 - $34.21 $ 21.10 5.84 $ 57,180 Exercisable at December 31, 2020 1,228,060 $10.22 - $39.82 $ 24.68 6.18 $ 83,204 Exercisable at December 31, 2021 1,473,420 $10.22 - $66.65 $ 29.55 5.59 $ 72,905 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. The aggregate intrinsic value of outstanding options is calculated as the difference between (i) the closing price of the common stock at the end of the period and (ii) the exercise price of the underlying awards, multiplied by the number of outstanding options as of the end of the period that had an exercise price less than the closing price on that date. The aggregate intrinsic value of options exercised, determined as of the exercise date, was approximately $11 million, $49 million and $40 million for the years ended December 31, 2021, 2020 and 2019, respectively. The Company estimated the fair value of each option granted on the date of grant using the Black-Scholes option-pricing model, using the assumptions in the following table: Year Ended December 31, 2021 2020 2019 Dividend yield 0 % 0 % 0 % Expected volatility 30 % 26 % 27 % Risk-free interest rate 0.56 % 1.45 % 2.46 % Expected life (in years) 5 5 5 Weighted-average grant date fair value (1) $ 25.09 $ 17.21 $ 11.52 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. The expected dividend yield is determined based on the Company's past cash dividend history and anticipated future cash dividend payments. The Company has never declared nor paid any dividends on its common stock and does not anticipate paying any dividends on its common stock during the foreseeable future, but intends to retain any earnings for future growth of its business. Expected volatility is calculated based on historical volatility of the daily closing price of the Company's common stock over a period consistent with the expected life of the options granted. The risk-free interest rate is based on the U.S. Treasury rate with terms similar to the expected life of the options granted. The expected life for the options is determined based on multiple factors, including historical employee behavior patterns of exercising options and post-employment termination behavior as well as expected future employee option exercise patterns. The following table summarizes information regarding options outstanding at December 31, 2021: Options Outstanding Options Exercisable Range of Exercise Price (1) Number of Shares (1) Weighted-Average Remaining Contractual Life (in years) Weighted- Average Exercise Price (1) Number of Shares (1) Weighted- Average Exercise Price (1) $10.22 - $24.24 762,420 4.49 $ 18.94 762,420 $ 18.94 $24.25 - $48.82 742,680 6.65 $ 37.12 607,000 $ 36.52 $48.83 - $69.93 312,000 8.10 $ 66.65 104,000 $ 66.65 $69.94 - $91.98 159,000 9.13 $ 91.98 — $ — 1,976,100 6.24 $ 39.18 1,473,420 $ 29.55 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. Restricted Stock Awards The Compensation Committee of the Board of Directors of the Company historically approved grants of restricted common stock to employees and directors of the Company that vest over a specific service period and to executive officers that vest based on the achievement of certain performance conditions, primarily, the achievement of a three-year cumulative revenue goal established at the grant date. The grant of awards with performance conditions supports the Company’s goal of aligning executive incentives with long-term stockholder value and ensuring that executive officers have a continuing stake in the long-term success of the Company. The vesting of restricted common stock is subject to continuing employment requirements. Certain performance-based restricted common stock awards are also subject to a market condition such that the actual number of shares that vest at the end of the respective three-year period is determined based on the Company’s achievement of performance goals and an established Company specific TSR factor relative to the Russell 1000 Index over the same three-year performance period. At the end of the three-year performance period, if the performance condition is achieved at or above the pre-established threshold, the number of shares earned is further adjusted by a TSR payout percentage, which ranges between 80% and 120%, based on the Company’s TSR performance relative to that of the Russell 1000 Index over the respective three-year period. The Company estimates the fair value of its equity awards with both a performance and market condition on the date of grant using a Monte-Carlo simulation valuation model. This pricing model uses multiple simulations to evaluate the probability of achieving the market condition to calculate the fair value of the awards. Expense is only recorded for awards that are expected to vest, net of estimated forfeitures. The assumptions used to estimate the fair value of awards with both a performance and a market condition were as follows: Year Ended December 31, 2021 2020 2019 Dividend yield 0 % 0 % 0 % Expected volatility 42 % 27 % 27 % Risk-free interest rate 0.20 % 1.43 % 2.45 % Expected life (in years) 3 3 3 Weighted-average grant date fair value (1) $ 99.73 $ 72.69 $ 42.96 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. The expected dividend yield is determined based on the Company's past cash dividend history and anticipated future cash dividend payments. The Company has never declared nor paid any dividends on its common stock and does not anticipate paying any dividends on its common stock during the foreseeable future, but intends to retain any earnings for future growth of its business. Expected volatility is calculated based on historical volatility of the daily closing price of the common stock of the companies within the Russell 1000 Index over a period consistent with the expected life of the awards. The risk-free interest rate is based on the U.S. Treasury rate with terms similar to the expected life of the awards. The expected life is consistent with the performance measurement period of the awards. As of December 31, 2021, the Company determined that it was probable that at least the minimum performance goals associated with restricted stock awards with performance and market conditions granted during 2021, 2020 and 2019 would be met by their forfeiture dates. The Company recorded a total of approximately $8 million, $4 million and $8 million of stock-based compensation expense related to restricted stock awards with performance and market conditions for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, the Company expects to record an aggregate stock-based compensation expense of approximately $11 million for restricted stock awards with performance and market conditions over the periods 2022, 2023 and 2024. The following table presents unvested restricted stock awards activity for the year ended December 31, 2021: Restricted Stock Awards — without Market Condition Restricted Stock Awards — with Market Condition Number of Shares (1) Weighted-Average Grant Date Fair Value per Share (1) Number of Shares (1) Weighted-Average Grant Date Fair Value per Share (1) Unvested restricted stock awards at December 31, 2020 2,028,640 $ 52.17 724,800 $ 43.83 Granted 813,397 $ 80.64 192,000 $ 99.73 Vested (894,291) $ 43.77 (182,619) $ 38.02 Canceled (165,440) $ 64.07 (16,581) $ 38.02 Unvested restricted stock awards at December 31, 2021 1,782,306 $ 66.74 717,600 $ 67.40 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. Restricted Stock Units The following table presents unvested restricted stock units activity for the year ended December 31, 2021: Number of Units (1) Weighted-Average Grant Date Fair Value per Share (1) Unvested restricted stock units at December 31, 2020 8,640 $ 61.90 Granted 6,855 $ 78.00 Vested (2,650) $ 56.99 Canceled (360) $ 73.79 Unvested restricted stock units at December 31, 2021 12,485 $ 71.44 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. Management Stock Purchase Plan The Board of Directors adopted the Company’s Management Stock Purchase Plan in December 2017 with the intent of providing selected key employees of the Company and its subsidiaries, including the Company's executive officers, the opportunity to defer a portion of their cash incentive compensation and to align management and stockholder interests through awards of DSUs under the MSPP and awards of Matching RSUs issued under the Company 2016 Plan. Under this plan participants are permitted to elect to defer up to 100% of their annual incentive bonus or commissions earned during the year by submitting an irrevocable election in accordance with Section 409A of the Internal Revenue Code, as amended. On the date the incentive bonus or commission would otherwise be paid in cash (typically during the following calendar year), the Company awards the participant DSUs representing the number of shares of common stock with an aggregate fair market value on that date equal to the amount of compensation elected to be deferred under the MSPP. On the same date the DSUs are awarded, the participant receives a grant of Matching RSUs covering the number of shares of common stock equal up to 100% of the DSUs granted. The expense related to the DSUs is recognized on a straight-line basis during the period that the related incentive bonus or commission is earned. The Company granted 40,960 and 33,840 DSUs during the years 2021 and 2020, respectively. The expense related to the Matching RSUs is recognized over the four-year vesting period following the grant date. The following tables presents the Matching RSU activity for the year ended December 31, 2021: Number of Matching RSU Shares (1) Weighted-Average Grant Date Fair Value per Share (1) Unvested MSPP restricted stock units at December 31, 2020 93,170 $ 53.12 Granted 40,960 $ 83.79 Canceled (18,040) $ 61.36 Unvested MSPP restricted stock units at December 31, 2021 116,090 $ 62.66 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. Employee 401(k) Plan The Company maintains a 401(k) Plan (the “401(k)”) as a defined contribution retirement plan for all eligible employees. The 401(k) provides for tax-deferred contributions of employees’ salaries, limited to a maximum annual amount as established by the IRS. In addition to the traditional 401(k), effective January 1, 2015, eligible employees have the option of making an after-tax contribution to a Roth 401(k) plan or a combination of both. In 2021, 2020 and 2019, the Company matched 100% of employee contributions up to a maximum of 4% of total compensation. Amounts contributed to the 401(k) by the Company to match employee contributions for the years ended December 31, 2021, 2020 and 2019 were approximately $18 million, $15 million and $12 million, respectively. The Company had no administrative expenses in connection with the 401(k) plan for the years ended December 31, 2021, 2020 and 2019. Employee Pension Plan The Company maintains a Group Personal Pension Plan (the “Plan”) for all eligible employees in the Company’s U.K. offices. The Plan is a defined contribution plan. Employees are eligible to contribute a portion of their salaries, subject to a maximum annual amount as established by Her Majesty's Revenue and Customs. In 2021, 2020 and 2019, the Company's matching contribution was based on the percentage contributed by the employee, up to a maximum of 6% of total compensation. Amounts contributed to the Plan by the Company to match employee contributions for the years ended December 31, 2021, 2020 and 2019, were approximately $0.9 million, $0.9 million and $0.6 million, respectively. Registered Retirement Savings Plan As of January 1, 2015, the Company introduced a registered retirement savings plan (“RRSP”) for all eligible employees in the Company’s Canadian offices. In 2021, 2020 and 2019, the Company matched 100% of employee contributions up to a maximum of 4% of total compensation. Amounts contributed to the RRSP by the Company to match employee contributions were approximately $0.1 million for the years ended December 31, 2021, 2020 and 2019. Employee Stock Purchase Plan

Schedule II Valuation and Quali

Schedule II Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Schedule II – Valuation and Qualifying Accounts The table below details the activity of the allowance for doubtful accounts and sales credits (1) for the year ended December 31, 2019 (in thousands): Balance at Charged to Reductions Balance at Year ended December 31, 2019 (2) $ 5,709 $ 10,978 $ 11,590 $ 5,097 __________________________ (1) Additions to the allowance for doubtful accounts are charged to bad debt expense. Additions to the allowance for sales credits are charged against revenues. (2) 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. The adoption resulted in a $0.5 million reduction to the December 31, 2019 allowance for credit losses. See Note 4 for a description of changes in the allowance for credit losses for the years ended December 31, 2021 and 2020.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The 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.
Use of Estimates	Use of EstimatesThe preparation of financial statements in conformity with U.S. generally accepted accounting principles (“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, 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, real estate agents and brokers and landlords, in each case, typically through a fixed monthly fee for its subscription-based services. Other subscription based-services include (i) real estate and lease management solutions to commercial customers, real estate investors and lenders, (ii) access to applications to manage workflow and advertising and marketing services for residential real estate agents through our acquisitions of Homes.com, which was acquired in May 2021, and Homesnap, which was acquired in December 2020, (iii) benchmarking and analytics for the hospitality industry and (iv) market research, portfolio and debt analysis, management and reporting capabilities. See Note 5 for further discussion of acquisitions. 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 derives revenues from transaction-based services including: (i) an online auction platform for commercial real estate through Ten-X, which was acquired in June 2020, (ii) providing online tenant applications, including background and credit checks, and rental payment processing and (iii) complementary services on an ad hoc basis for our (a) real estate and lease management solutions to commercial customers, real estate investors and lenders, (b) benchmarking and analytics for the hospitality industry and (c) other service offerings. 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 obligations. 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. Revenues from transaction-based services are recognized when the promised product or services are delivered, which, in the case of Ten-X auctions, is at the time of a successful closing for the sale of the property. 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.
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 and costs related to advertising purchased on behalf of customers, 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 certain other intangible assets.
Foreign Currency Translation	Foreign Currency Translation 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 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
Advertising Costs	Advertising CostsThe Company expenses advertising costs as incurred. Advertising costs include digital marketing, television, radio, print and other media advertising.
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	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 Company's potentially dilutive securities include outstanding stock options, unvested stock-based awards which include restricted stock awards that vest over a specific service period, restricted stock awards with a performance and market condition, restricted stock units and awards of matching restricted stock units ("Matching RSUs") awarded under the Company's Management Stock Purchase Plan (the “MSPP”). Shares underlying unvested restricted stock awards that vest based on a performance and market condition 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
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 service period of the awards, net of an estimated forfeiture rate. For equity instruments that vest based on achievement of both a performance and market condition, stock-based compensation expense is recognized over the service period of the awards based on the expected achievement of the related performance conditions at the end of each reporting period. 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.
Cash and Cash Equivalents	Cash, Cash Equivalents and Restricted CashThe Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.
Concentration of Credit Risk	The Company’s customer base creates a lack of dependence on any individual customer that mitigates the risk of nonpayment of the Company’s accounts receivable.
Financial Instruments	The Company holds cash at major financial institutions that often exceed Federal Deposit Insurance Corporation insured limits. The Company manages its credit risk associated with cash concentrations by diversifying cash holdings across AAA rated Government and Treasury Money Market Funds and multiple high quality financial institutions, and by periodically evaluating the credit quality of the primary financial institutions holding such deposits. The carrying value of cash approximates fair value. Historically, the Company has not experienced any losses due to such cash concentrations.
Allowance for Credit Losses	Allowance for Credit Losses The Company maintains 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 collectability by reviewing the duration of collection pursuits on its delinquent trade receivables and historical write off trends. Based on the Company’s experience, the customer's delinquency status, which is analyzed periodically, is the strongest indicator of the credit quality of the underlying trade receivables. 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 outstanding. Under the CECL impairment model, the Company develops and documents its allowance for credit losses on its trade receivables based on five 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 Portfolio Segment - The CoStar portfolio segment consists of two classes of trade receivables based on geographical location: North America and International. • Information Services Portfolio Segment - The Information Services portfolio segment consists of four classes of trade receivables: CoStar 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. • LoopNet Portfolio Segment - The LoopNet portfolio segment consists of one class of trade receivables. • Other Marketplaces Portfolio Segment - The Other Marketplaces portfolio segment consists of two classes of trade receivables: Ten-X and other marketplaces. The majority of Residential revenue is e-commerce based and does not result in accounts receivable. Residential accounts receivable and the related allowance for credit losses are not material.
Leases	Leases The determination of whether an arrangement contains a lease and the classification of a lease, if applicable, is made at the commencement of the arrangement, 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. Upon commencement, the initial 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 the new lease standard. 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.
Property and Equipment, Net	Property and Equipment, NetProperty and equipment are stated at cost, net of accumulated depreciation and amortization. All repairs and maintenance costs are expensed as incurred. Costs related to acquisition of additional aircraft components or the replacement of existing aircraft components are capitalized and depreciated over the estimated useful life of the aircraft or the added or replaced component, whichever is less.Qualifying internal-use software costs incurred during the application development stage, which consist primarily of internal product development costs, outside services and purchased software license costs are capitalized and amortized over the estimated useful life of the asset. All other costs are expensed as incurred. In the fourth quarter of 2021, the Company began removing fully depreciated property and equipment from the cost and accumulated depreciation amounts disclosed.
Long-Lived Assets, Intangible Assets and Goodwill	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. Acquired technology and data, customer base assets, trade names and other intangible assets are related to the Company’s acquisitions. Acquired technology and data is amortized on a straight-line basis over periods ranging from one year to eight years. Acquired intangible assets characterized as customer base assets consist of acquired customer contracts and the related customer relationships and are amortized over periods ranging from five years to thirteen years. Acquired customer bases are amortized on an accelerated or straight-line basis depending on the expected economic benefit of the intangible asset. Acquired trade names and other intangible assets are amortized on a straight-line basis over periods ranging from one year to fifteen years. In the fourth quarter of 2021, the Company began removing fully amortized intangible assets from the cost and accumulated amortization amounts disclosed. Goodwill represents the future economic benefits arising from a business combination and is calculated as the excess of the purchase consideration paid in a business combination over the fair value of the net identifiable assets acquired. Goodwill is not amortized, but instead is assigned to each of the Company's reporting units and tested for impairment at least annually, on October 1, or more frequently if an event or other circumstance indicates that the fair value of a reporting unit may be below its carrying amount. 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, the Company then determines the fair value of each reporting unit. The estimate of the fair value of each reporting unit is based on a projected discounted cash flow model that includes significant assumptions and estimates including the discount rate, growth rate and future financial performance. Assumptions about the discount rate are based on a weighted average cost of capital for comparable companies. Assumptions about the growth rate and future financial performance of a reporting unit are based on the Company's forecasts, business plans, economic projections and anticipated future cash flows. 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 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 to the tangible assets acquired, liabilities assumed and intangible assets acquired based on their estimated fair values. The purchase price is determined based on the fair value of the assets transferred, liabilities assumed 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. The Company applies significant assumptions, estimates and judgments in determining the fair value of assets acquired and liabilities assumed on the acquisition date, 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, 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, to determine their estimated amounts. 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 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 In the fourth quarter of 2021, the Company adopted ASU 2021-08, Business Combinations (Topic 805), Accounting for Contract Assets and Contract Liabilities from Contracts with Customers . This guidance requires contract assets and liabilities acquired or assumed in an acquisition be measured in accordance with the accounting framework for revenue from contracts with customers as if the Company had originated the acquired contract. This is an exception to the general requirement to measure assets acquired and liabilities assumed at their fair value on the acquisition date. The Company applied this revised guidance to all acquisitions in the year ended December 31, 2021. The application of this guidance to contract assets and contract liabilities acquired or assumed in connection with the Company's acquisitions for the year ended December 31, 2021 did not have a material impact on the Company's consolidated financial statements and related disclosures. Recent Accounting Pronouncements Not Yet Adopted On March 12, 2020, the Financial Accounting Standards Board issued ASU 2020-04, Reference Rate Reform (“ASC 848”): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. Accounting Standards Codification (“ASC”) 848 contains optional expedients and exceptions for applying GAAP to debt, contracts, hedging relationships and other transactions affected by reference rate reform. The provisions of ASC 848 must be applied to all contracts that are accounted for under a Topic, Subtopic or Industry Subtopic for all transactions other than derivatives, which may be applied at a hedging relationship level. This guidance is effective for fiscal years beginning after January 1, 2021, including interim periods within those fiscal years. The Company's 2020 Credit Agreement provides for a $750 million revolving credit facility and a letter of credit sublimit of $20 million, with interest rates benchmarked to LIBOR. As of December 31, 2021, no amounts were issued or drawn under this facility. The Company is currently evaluating the impact this guidance will have on its consolidated financial statements and related disclosures.
Commitments and Contingencies	Currently, and from time to time, the Company is involved in litigation incidental to the conduct of its business. 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.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The components of accumulated other comprehensive loss, net of tax were as follows (in thousands): As of December 31, 2021 2020 Foreign currency translation adjustment $ (5,758) $ (889) Total accumulated other comprehensive loss $ (5,758) $ (889)
Schedule of Stock-Based Compensation Expense for Stock Options and Restricted Stock	Stock-based compensation expense for stock options, restricted stock awards and restricted stock units issued under equity incentive plans, stock purchases under the Employee Stock Purchase Plan, Deferred Stock Units ("DSUs") and Matching RSUs awarded under the MSPP included in the Company’s statement of operations were as follows (in thousands): Year Ended December 31, 2021 2020 2019 Cost of revenues $ 11,165 $ 10,879 $ 9,273 Selling and marketing (excluding customer base amortization) 6,314 5,194 6,809 Software development 12,544 10,325 8,985 General and administrative 33,686 27,706 27,188 Total stock-based compensation expense (1) $ 63,709 $ 54,104 $ 52,255 __________________________ (1) Stock-based compensation expense for the year ended December 31, 2020 includes $0.7 million of expense related to the cash settlement of stock options in connection with the acquisition of Ten-X. See Note 5 for further discussion.
Schedule of Cash and Cash Equivalents	Cash, cash equivalents, and restricted cash consisted of the following as of December 31, 2021 and 2020 (in thousands): As of December 31, 2021 2020 Cash and cash equivalents $ 3,827,126 $ 3,693,813 Restricted cash: RentPath break fee held in escrow under the terms of the Asset Purchase Agreement — 58,750 Other restricted cash related to acquisitions — 3,349 Total restricted cash — 62,099 Cash, cash equivalents and restricted cash $ 3,827,126 $ 3,755,912
Restrictions on Cash and Cash Equivalents	Cash, cash equivalents, and restricted cash consisted of the following as of December 31, 2021 and 2020 (in thousands): As of December 31, 2021 2020 Cash and cash equivalents $ 3,827,126 $ 3,693,813 Restricted cash: RentPath break fee held in escrow under the terms of the Asset Purchase Agreement — 58,750 Other restricted cash related to acquisitions — 3,349 Total restricted cash — 62,099 Cash, cash equivalents and restricted cash $ 3,827,126 $ 3,755,912
Schedule of Property and Equipment	Depreciation and amortization are calculated on a straight-line basis over the following estimated useful lives of the assets: Buildings Twenty thirty-nine Land Indefinite Aircrafts Ten twenty Furniture and office equipment Five ten Vehicles Five years Computer hardware and software Three five Leasehold improvements Shorter of lease terms or useful life Property and equipment consists of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ 75,634 $ 80,963 Furniture, office equipment and vehicles 47,540 68,587 Computer hardware and software 30,179 86,755 Aircrafts 68,670 28,561 Land 38,774 24,642 Buildings 96,496 2,970 Property and equipment, gross 357,293 292,478 Accumulated depreciation and amortization (85,862) (166,153) Property and equipment, net $ 271,431 $ 126,325

REVENUE FROM CONTRACTS WITH C_2

REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The Company provides information, analytics and online marketplaces to the commercial real estate industry, hospitality industry, residential industry and related professionals. The revenues by operating segment and type of service consist of the following (in thousands): Year Ended December 31, 2021 2020 2019 North America International Total North America International Total North America International Total CoStar $ 686,948 $ 35,873 $ 722,821 $ 634,205 $ 30,530 $ 664,735 $ 590,222 $ 27,576 $ 617,798 Information services 113,723 27,932 141,655 104,117 25,953 130,070 76,950 11,496 88,446 Multifamily 678,680 — 678,680 598,555 — 598,555 490,631 — 490,631 LoopNet (1) 204,816 2,695 207,511 179,371 434 179,805 149,400 580 149,980 Residential (1) 74,583 — 74,583 — — — — — — Other Marketplaces (1) 118,885 — 118,885 85,854 — 85,854 52,864 — 52,864 Total revenues $ 1,877,635 $ 66,500 $ 1,944,135 $ 1,602,102 $ 56,917 $ 1,659,019 $ 1,360,067 $ 39,652 $ 1,399,719 (1) As of September 30, 2021, Commercial Property and Land revenue has been further disaggregated into LoopNet, Residential and Other Marketplaces. Prior period amounts have been adjusted to reflect this presentation.
Contract With Customer, Asset and Liability	Changes in deferred revenue for the period were as follows (in thousands): Balance at December 31, 2020 (1) $ 77,363 Revenue recognized in the current period from the amounts in the beginning balance (74,578) New deferrals, net of amounts recognized in the current period 94,143 Effects of foreign currency (204) Balance at December 31, 2021 (2) $ 96,724 __________________________ (1) Deferred revenue was comprised of $74.9 million of current liabilities and $2.5 million of noncurrent liabilities classified within lease and other long-term liabilities on the Company’s consolidated balance sheet as of December 31, 2020. (2) Deferred revenue was comprised of $95.5 million of current liabilities and $1.2 million of noncurrent liabilities classified within lease and other long-term liabilities on the Company’s consolidated balance sheet as of December 31, 2021. This balance includes $2.2 million of net new deferrals recognized in connection with business acquisitions made in 2021. See Note 5 for further discussion of acquisitions.
Schedule of Commissions Expense	Commissions expense activity for the years ended December 31, 2021, 2020 and 2019 was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Commissions incurred $ 117,391 $ 97,183 $ 87,043 Commissions capitalized in the current period (72,038) (64,355) (66,688) Amortization of deferred commissions costs 63,391 60,516 53,421 Total commissions expense $ 108,744 $ 93,344 $ 73,776

ALLOWANCE FOR CREDIT LOSSES (Ta

ALLOWANCE FOR CREDIT LOSSES (Tables)	12 Months Ended
	Dec. 31, 2021
Credit Loss [Abstract]
Schedule of 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): Year Ended December 31, 2021 CoStar Information services Multifamily LoopNet (3) Other Marketplaces (3) Total Beginning balance at December 31, 2020 $ 5,531 $ 2,739 $ 4,387 $ 1,667 $ 786 $ 15,110 Current-period provision (release) for expected credit losses (1), (2) 5,699 (392) 3,057 2,564 — 10,928 Write-offs charged against the allowance, net of recoveries and other (5,850) (527) (4,051) (2,263) 27 (12,664) Ending balance at December 31, 2021 $ 5,380 $ 1,820 $ 3,393 $ 1,968 $ 813 $ 13,374 ________________________ (1) Credit loss expense is included in general and administrative expenses on the consolidated statement of operations. (2) Credit loss expense related to contract assets was not material for the year ended December 31, 2021. (3) Amounts previously disclosed in the Commercial Property and Land portfolio segment have been further disaggregated into the LoopNet, Residential and Other Marketplaces portfolio segments. The majority of the Residential portfolio segment revenue is e-commerce based and does not result in accounts receivable. Year Ended December 31, 2020 CoStar Information services Multifamily LoopNet (3) Other Marketplaces (3) Total Beginning balance at December 31, 2019 $ 1,264 $ 624 $ 1,195 $ 576 $ 889 $ 4,548 Current-period provision for expected credit losses (1), (2) 11,622 2,649 7,644 3,213 84 25,212 Write-offs charged against the allowance, net of recoveries and other (7,355) (534) (4,452) (2,122) (187) (14,650) Ending balance at December 31, 2020 $ 5,531 $ 2,739 $ 4,387 $ 1,667 $ 786 $ 15,110 ________________________ (1) Credit loss expense is included in general and administrative expenses on the consolidated statement of operations. (2) Credit loss expense related to contract assets was not material for the year ended December 31, 2020. (3) Amounts previously disclosed in the Commercial Property and Land portfolio segment have been further disaggregated into the LoopNet, Residential and Other Marketplaces portfolio segments. The majority of the Residential portfolio segment revenue is e-commerce based and does not result in accounts receivable.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [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: Measurement Period Adjustments Updated Preliminary: May 24, 2021 Cash, cash equivalents and restricted cash $ — $ — $ — Accounts receivable 1,798 — 1,798 Lease right-of-use assets 371 — 371 Goodwill 88,132 342 88,474 Intangible assets 53,400 — 53,400 Deferred tax assets 11,171 93 11,264 Lease liabilities (371) — (371) Deferred revenue (1,086) (435) (1,521) Other assets and liabilities (1,240) — (1,240) Fair value of identifiable net assets acquired $ 152,175 $ — $ 152,175 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): Final: Cash, cash equivalents and restricted cash $ 10,225 Accounts receivable 662 Lease right-of-use assets 3,437 Goodwill 184,371 Intangible assets 67,000 Deferred tax assets, net (2,778) Lease liabilities (3,375) Deferred revenue (4,000) Other assets and liabilities (5,188) Fair value of identifiable net assets acquired $ 250,354 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): Final: Cash and cash equivalents $ 3,290 Accounts receivable 131 Lease right-of-use assets 4,945 Goodwill 134,322 Intangible assets 58,000 Lease liabilities (4,945) Deferred tax liabilities, net (2,981) Other assets and liabilities (5,047) Fair value of identifiable net assets acquired $ 187,715
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	The following table summarizes the fair values of the identifiable intangible assets acquired in the Homes.com acquisition included in the Company's North America operating segment, their related estimated useful lives (in years) and their respective amortization methods (in thousands): Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 32,000 8 Accelerated Trade name 21,000 15 Straight-line Technology 400 2 Straight-line Total intangible assets $ 53,400 The following table summarizes the fair values (in thousands) of the identifiable intangible assets included in the Company's North America operating segment, their related estimated useful lives (in years) and their respective amortization methods: Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 45,000 10 Accelerated Trade name 7,000 10 Straight-line Technology 15,000 6 Straight-line Total intangible assets $ 67,000 The following table summarizes the fair values (in thousands) of the identifiable intangible assets included in the Company's North America operating segment, their related estimated useful lives (in years) and their respective amortization methods: Estimated Fair Value Estimated Useful Life Amortization Method Customer base $ 46,000 6 Accelerated Technology 11,000 5 Straight-line Other intangible assets 1,000 2 Straight-line Total intangible assets $ 58,000
Business Acquisition, Pro Forma Information	The unaudited pro forma financial information, in aggregate, was as follows (in thousands, except per share data): Year Ended 2021 2020 2019 Revenue $ 1,962,102 $ 1,758,612 $ 1,483,218 Net income $ 286,718 $ 197,994 $ 271,789 Net income per share - basic $ 0.74 $ 0.52 $ 0.75 Net income per share - diluted $ 0.73 $ 0.51 $ 0.74

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Components of Lease Expense	Lease costs related to the Company's operating leases included in the consolidated statements of operations were as follows (in thousands): Year Ended December 31, 2021 2020 2019 Operating lease costs: Cost of revenues $ 10,110 $ 11,632 $ 11,407 Software development 6,947 6,020 4,209 Selling and marketing (excluding customer base amortization) 11,911 10,356 8,678 General and administrative 5,911 4,827 3,299 Total operating lease costs $ 34,879 $ 32,835 $ 27,593
Supplemental Balance Sheet Information Related to Leases	Supplemental balance sheet information related to operating leases was as follows (in thousands): Year Ended December 31, Balance Balance Sheet Location 2021 2020 Operating lease liabilities $ 134,150 $ 148,975 Less: imputed interest (8,512) (10,998) Present value of lease liabilities 125,638 137,977 Less: current portion of lease liabilities Lease liabilities 26,268 32,648 Long-term lease liabilities Lease and other long-term liabilities $ 99,370 $ 105,329 Weighted-average remaining lease term in years 4.0 4.0 Weighted-average discount rate 3.1 % 3.6 %
Schedule of Supplemental Cash Flow Information for Leases	Supplemental cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows used in operating leases $ 37,298 $ 37,006 $ 30,287 ROU assets obtained in exchange for lease obligations: Operating leases $ 34,247 $ 19,746 $ 22,629

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Depreciation and amortization are calculated on a straight-line basis over the following estimated useful lives of the assets: Buildings Twenty thirty-nine Land Indefinite Aircrafts Ten twenty Furniture and office equipment Five ten Vehicles Five years Computer hardware and software Three five Leasehold improvements Shorter of lease terms or useful life Property and equipment consists of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ 75,634 $ 80,963 Furniture, office equipment and vehicles 47,540 68,587 Computer hardware and software 30,179 86,755 Aircrafts 68,670 28,561 Land 38,774 24,642 Buildings 96,496 2,970 Property and equipment, gross 357,293 292,478 Accumulated depreciation and amortization (85,862) (166,153) Property and equipment, net $ 271,431 $ 126,325

GOODWILL (Tables)

GOODWILL (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2019 $ 1,738,360 $ 143,660 $ 1,882,020 Acquisitions, including measurement period adjustments (1) 347,134 1,273 348,407 Effect of foreign currency translation — 5,572 5,572 Goodwill, December 31, 2020 2,085,494 150,505 2,235,999 Acquisitions, including measurement period adjustments (2) 60,352 27,441 87,793 Effect of foreign currency translation — (2,777) (2,777) Goodwill, December 31, 2021 $ 2,145,846 $ 175,169 $ 2,321,015 __________________________ (1) North America goodwill for the year ended December 31, 2020 includes goodwill recorded in connection with the acquisitions of Ten-X and Homesnap of $135.7 million and $211.1 million, respectively, as well as STR measurement period adjustments to goodwill of $0.3 million. International goodwill for the year ended December 31, 2020 includes goodwill recorded in connection with the acquisition of Emporis GmbH of $1.2 million and STR measurement period adjustments of $0.1 million. (2) North America goodwill for the year ended December 31, 2021 includes goodwill recorded in connection with the acquisition of Homes.com of $88.5 million, offset by measurement period adjustments of $1.4 million for Ten-X and $26.7 million for Homesnap recorded during the year ended December 31, 2021 primarily related to the measurement of the fair value of Homesnap customer relationships in the first quarter of 2021. International goodwill recorded in connection with the acquisition of BureauxLocaux was $27.4 million. See Note 5 for further discussion.

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2021
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): December 31, Weighted- Average 2021 2020 Acquired technology and data $ 41,979 $ 131,551 6 Accumulated amortization (15,333) (97,791) Acquired technology and data, net 26,646 33,760 Acquired customer base 569,666 545,643 10 Accumulated amortization (319,039) (296,758) Acquired customer base, net 250,627 248,885 Acquired trade names and other intangible assets 262,136 249,465 13 Accumulated amortization (103,747) (105,365) Acquired trade names and other intangible assets, net 158,389 144,100 Intangible assets, net $ 435,662 $ 426,745

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The table below presents the components of outstanding debt (in thousands): December 31, 2021 December 31, 2020 2.800% Senior Notes due July 15, 2030 $ 1,000,000 $ 1,000,000 2020 Credit Agreement, due July 1, 2025 — — Total face amount of long-term debt 1,000,000 1,000,000 Senior notes unamortized discount and issuance costs (12,056) (13,285) Long-term debt, net $ 987,944 $ 986,715
Schedule of Interest Expense	For the years ended December 31, 2021, 2020 and 2019 the Company recognized interest expense as follows (in thousands): Year Ended 2021 2020 2019 Interest on outstanding borrowings $ 28,000 $ 18,509 $ — Amortization of senior notes discount and issuance costs 2,327 1,658 874 Commitment fees and other 1,989 1,627 1,741 Total interest expense $ 32,316 $ 21,794 $ 2,615

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	The components of the provision for income taxes attributable to operations consist of the following (in thousands): Year Ended December 31, 2021 2020 2019 Current: Federal $ 61,290 $ 43,461 $ 53,039 State 24,618 11,726 13,422 Foreign 1,331 195 1,305 Total current 87,239 55,382 67,766 Deferred: Federal 22,859 (9,599) 6,881 State 8,467 (926) 2,424 Foreign (7,161) (1,005) (1,085) Total deferred 24,165 (11,530) 8,220 Total provision for income taxes $ 111,404 $ 43,852 $ 75,986
Schedule of Deferred Tax Assets and Liabilities	The components of deferred tax assets and liabilities consist of the following (in thousands): December 31, 2021 2020 Deferred tax assets: Allowance for credit losses $ 3,601 $ 3,698 Accrued compensation 3,913 4,934 Stock compensation 18,956 15,289 Net operating losses 45,835 38,498 Accrued reserve and other 4,134 5,900 Lease liabilities 28,306 34,758 Research and development credits 5,812 6,059 Accrued transaction fees — 13,334 Total deferred tax assets, prior to valuation allowance 110,557 122,470 Valuation allowance (5,694) (11,170) Total deferred tax assets, net of valuation allowance 104,863 111,300 Deferred tax liabilities: Deferred commission costs, net (25,700) (23,691) Lease right-of-use assets (22,574) (27,168) Prepaid expenses (2,569) (2,384) Property and equipment, net (21,827) (13,078) Intangible assets, net (125,815) (112,987) Total deferred tax liabilities (198,485) (179,308) Net deferred tax assets (liabilities) $ (93,622) $ (68,008)
Schedule of Effective Income Tax Rate Reconciliation	The Company’s provision for income taxes resulted in effective tax rates that varied from the statutory federal income tax rate as follows (in thousands): Year Ended December 31, 2021 2020 2019 Expected federal income tax provision at statutory rate $ 84,833 $ 56,906 $ 82,099 State income taxes, net of federal benefit 21,012 11,409 14,884 (Decrease) in valuation allowance (4,995) (4,848) (693) Research credits (13,070) (14,322) (12,188) Excess tax benefit (10,933) (21,038) (15,282) Tax reserves (12,787) 4,762 3,135 Nondeductible compensation 10,369 5,949 1,777 International restructuring 34,854 — — Other adjustments 2,121 5,034 2,254 Income tax expense $ 111,404 $ 43,852 $ 75,986
Schedule of Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands): Unrecognized tax benefit as of December 31, 2018 $ 22,372 Increase for current year tax positions 3,487 Increase for prior year tax positions 440 Expiration of the statute of limitation for assessment of taxes (832) Unrecognized tax benefit as of December 31, 2019 25,467 Increase for current year tax positions 4,213 Increase for prior year tax positions 452 Expiration of the statute of limitation for assessment of taxes (1,259) Unrecognized tax benefit as of December 31, 2020 28,873 Increase for current year tax positions 3,024 Decrease for prior year tax positions (5,353) Decrease for settlements with taxing authorities (9,924) Expiration of the statute of limitation for assessment of taxes (1,866) Unrecognized tax benefit as of December 31, 2021 $ 14,754

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Lessee, Operating Lease, Liability, Maturity	The following summarizes our significant contractual obligations, including related payments due by period, as of December 31, 2021 (in thousands): Year Ending December 31, Operating lease obligations Long-term debt principal payments Long-term debt principal interest payments 2022 $ 29,678 $ — $ 28,000 2023 36,477 — 28,000 2024 32,808 — 28,000 2025 16,051 — 28,000 2026 7,235 — 28,000 Thereafter 11,901 1,000,000 112,000 Total $ 134,150 $ 1,000,000 $ 252,000
Schedule of Maturities of Long-term Debt	The following summarizes our significant contractual obligations, including related payments due by period, as of December 31, 2021 (in thousands): Year Ending December 31, Operating lease obligations Long-term debt principal payments Long-term debt principal interest payments 2022 $ 29,678 $ — $ 28,000 2023 36,477 — 28,000 2024 32,808 — 28,000 2025 16,051 — 28,000 2026 7,235 — 28,000 Thereafter 11,901 1,000,000 112,000 Total $ 134,150 $ 1,000,000 $ 252,000

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Summarized EBITDA Information by Operating Segment	Summarized EBITDA information by operating segment consists of the following (in thousands): Year Ended December 31, 2021 2020 2019 North America $ 557,125 $ 410,852 $ 451,699 International 7,856 (4,706) (6,987) Total EBITDA $ 564,981 $ 406,146 $ 444,712
Reconciliation of Net Income to EBITDA	The reconciliation of net income to EBITDA consists of the following (in thousands): Year Ended December 31, 2021 2020 2019 Net income $ 292,564 $ 227,128 $ 314,963 Amortization of acquired intangible assets in cost of revenues 28,809 25,675 21,357 Amortization of acquired intangible assets in operating expenses 74,817 62,457 33,995 Depreciation and other amortization 29,018 28,812 25,813 Interest expense (income), net 31,621 17,395 (16,742) Other (income) expense, net (3,252) 827 (10,660) Income tax expense 111,404 43,852 75,986 EBITDA $ 564,981 $ 406,146 $ 444,712
Summarized Information by Operating Segment, Assets and Liabilities	Summarized information by operating segment consists of the following (in thousands): December 31, 2021 2020 Property and equipment, net North America $ 269,792 $ 123,634 International 1,639 2,691 Total property and equipment, net $ 271,431 $ 126,325 Goodwill North America $ 2,145,846 $ 2,085,494 International 175,169 150,505 Total goodwill $ 2,321,015 $ 2,235,999 Assets North America $ 6,976,752 $ 6,674,974 International 280,119 240,446 Total assets $ 7,256,871 $ 6,915,420 Liabilities North America $ 1,502,497 $ 1,496,894 International 42,702 43,167 Total liabilities $ 1,545,199 $ 1,540,061

NET INCOME PER SHARE (Tables)

NET INCOME PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
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): Year Ended December 31, 2021 2020 2019 Numerator: Net income $ 292,564 $ 227,128 $ 314,963 Denominator: Denominator for basic net income per share — weighted-average outstanding shares 392,210 380,726 363,096 Effect of dilutive securities: Stock options, restricted stock awards and restricted stock units 1,950 2,540 3,205 Denominator for diluted net income per share — weighted-average outstanding shares 394,160 383,266 366,301 Net income per share — basic (1) $ 0.75 $ 0.60 $ 0.87 Net income per share — diluted (1) $ 0.74 $ 0.59 $ 0.86 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.
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): Year Ended December 31, 2021 2020 2019 Performance-based restricted stock awards (1) 415 526 600 Anti-dilutive securities (1) 373 540 425 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2021
Compensation Related Costs [Abstract]
Schedule of Option Activity	Option activity was as follows: Number of Shares (1) Range of Exercise Price (1) Weighted- Average Exercise Price (1) Weighted- Aggregate Outstanding at December 31, 2018 3,442,760 $3.67 - $34.21 $ 21.23 7.03 $ 43,418 Granted 483,000 $39.82 $ 39.82 Exercised (1,169,180) $5.45 - $34.21 $ 15.95 Outstanding at December 31, 2019 2,756,580 $5.45 - $39.82 $ 26.72 6.98 $ 91,262 Granted 341,000 $66.65 $ 66.65 Exercised (953,130) $19.37 - $39.82 $ 22.95 Canceled or expired (121,350) $34.21 - $66.65 $ 44.31 Outstanding at December 31, 2020 2,023,100 $10.22 - $66.65 $ 34.18 6.99 $ 117,846 Granted 159,000 $91.98 $ 91.98 Exercised (206,000) $20.49 - $39.82 $ 30.78 Outstanding at December 31, 2021 1,976,100 $10.22 - $91.98 $ 39.18 6.24 $ 80,800 Exercisable at December 31, 2019 1,476,200 $10.22 - $34.21 $ 21.10 5.84 $ 57,180 Exercisable at December 31, 2020 1,228,060 $10.22 - $39.82 $ 24.68 6.18 $ 83,204 Exercisable at December 31, 2021 1,473,420 $10.22 - $66.65 $ 29.55 5.59 $ 72,905 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.
Fair Value Assumption for Options Granted	The Company estimated the fair value of each option granted on the date of grant using the Black-Scholes option-pricing model, using the assumptions in the following table: Year Ended December 31, 2021 2020 2019 Dividend yield 0 % 0 % 0 % Expected volatility 30 % 26 % 27 % Risk-free interest rate 0.56 % 1.45 % 2.46 % Expected life (in years) 5 5 5 Weighted-average grant date fair value (1) $ 25.09 $ 17.21 $ 11.52 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. Year Ended December 31, 2021 2020 2019 Dividend yield 0 % 0 % 0 % Expected volatility 42 % 27 % 27 % Risk-free interest rate 0.20 % 1.43 % 2.45 % Expected life (in years) 3 3 3 Weighted-average grant date fair value (1) $ 99.73 $ 72.69 $ 42.96 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.
Summarized Information Regarding Options Outstanding	The following table summarizes information regarding options outstanding at December 31, 2021: Options Outstanding Options Exercisable Range of Exercise Price (1) Number of Shares (1) Weighted-Average Remaining Contractual Life (in years) Weighted- Average Exercise Price (1) Number of Shares (1) Weighted- Average Exercise Price (1) $10.22 - $24.24 762,420 4.49 $ 18.94 762,420 $ 18.94 $24.25 - $48.82 742,680 6.65 $ 37.12 607,000 $ 36.52 $48.83 - $69.93 312,000 8.10 $ 66.65 104,000 $ 66.65 $69.94 - $91.98 159,000 9.13 $ 91.98 — $ — 1,976,100 6.24 $ 39.18 1,473,420 $ 29.55 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.
Unvested Restricted Stock Awards Activity	The following table presents unvested restricted stock awards activity for the year ended December 31, 2021: Restricted Stock Awards — without Market Condition Restricted Stock Awards — with Market Condition Number of Shares (1) Weighted-Average Grant Date Fair Value per Share (1) Number of Shares (1) Weighted-Average Grant Date Fair Value per Share (1) Unvested restricted stock awards at December 31, 2020 2,028,640 $ 52.17 724,800 $ 43.83 Granted 813,397 $ 80.64 192,000 $ 99.73 Vested (894,291) $ 43.77 (182,619) $ 38.02 Canceled (165,440) $ 64.07 (16,581) $ 38.02 Unvested restricted stock awards at December 31, 2021 1,782,306 $ 66.74 717,600 $ 67.40 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. The following table presents unvested restricted stock units activity for the year ended December 31, 2021: Number of Units (1) Weighted-Average Grant Date Fair Value per Share (1) Unvested restricted stock units at December 31, 2020 8,640 $ 61.90 Granted 6,855 $ 78.00 Vested (2,650) $ 56.99 Canceled (360) $ 73.79 Unvested restricted stock units at December 31, 2021 12,485 $ 71.44 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021. The following tables presents the Matching RSU activity for the year ended December 31, 2021: Number of Matching RSU Shares (1) Weighted-Average Grant Date Fair Value per Share (1) Unvested MSPP restricted stock units at December 31, 2020 93,170 $ 53.12 Granted 40,960 $ 83.79 Canceled (18,040) $ 61.36 Unvested MSPP restricted stock units at December 31, 2021 116,090 $ 62.66 (1) Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

ORGANIZATION (Details)

ORGANIZATION (Details)	12 Months Ended
	Dec. 31, 2021operating_segment
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) (Details)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Term of subscription-based license agreements	1 year
Amortization period of deferred sales commissions	3 years

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Foreign Currency Translation and Accumulated Other Comprehensive Loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Foreign currency transaction gain (loss), realized	$ 300,000	$ (200,000)	$ (600,000)
Accumulated Other Comprehensive Income (Loss) Net of Tax [Abstract]
Foreign currency translation adjustment	(5,758,000)	(889,000)
Total accumulated other comprehensive loss	(5,758,000)	(889,000)
Reclassification out of accumulated other comprehensive loss	0	$ 0
Reclassification from accumulated other comprehensive income, current period, net of tax	$ 500,000

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Advertising Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Advertising costs	$ 312	$ 270	$ 168

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Stock-Based Compensation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-Based Compensation Expense [Abstract]
Compensation expense	$ 63,709	$ 54,104	$ 52,255
Expense related to stock options settled	700
Cost of revenues
Stock-Based Compensation Expense [Abstract]
Compensation expense	11,165	10,879	9,273
Selling and marketing (excluding customer base amortization)
Stock-Based Compensation Expense [Abstract]
Compensation expense	6,314	5,194	6,809
Software development
Stock-Based Compensation Expense [Abstract]
Compensation expense	12,544	10,325	8,985
General and administrative
Stock-Based Compensation Expense [Abstract]
Compensation expense	$ 33,686	$ 27,706	$ 27,188

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Cash Reconciliation) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Reconciliation [Line Items]
Cash and cash equivalents	$ 3,827,126	$ 3,693,813
Restricted cash	0	62,099
Cash, cash equivalents and restricted cash	3,827,126	3,755,912	$ 1,070,731	$ 1,100,416
RentPath break fee held in escrow under the terms of the Asset Purchase Agreement
Cash Reconciliation [Line Items]
Restricted cash	0	58,750
Other restricted cash related to acquisitions
Cash Reconciliation [Line Items]
Restricted cash	$ 0	$ 3,349

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Allowance for Credit Losses) (Details)	Dec. 31, 2021numberOfReceivableportfolioSegment
Accounting Policies [Abstract]
Number of portfolio segments | portfolioSegment	5
Number of classes of trade receivables based on location	2
Number of trade receivables in information services portfolio	4
Number of trade receivables in multifamily portfolio	1

SUMMARY OF SIGNIFICANT ACCOU_10

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Property and Equipment) (Details)	12 Months Ended
	Dec. 31, 2021
Vehicles
Property, Plant and Equipment [Line Items]
Useful life	5 years
Minimum | Buildings
Property, Plant and Equipment [Line Items]
Useful life	20 years
Minimum | Aircrafts
Property, Plant and Equipment [Line Items]
Useful life	10 years
Minimum | Furniture and office equipment
Property, Plant and Equipment [Line Items]
Useful life	5 years
Minimum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Useful life	3 years
Maximum | Buildings
Property, Plant and Equipment [Line Items]
Useful life	39 years
Maximum | Aircrafts
Property, Plant and Equipment [Line Items]
Useful life	20 years
Maximum | Furniture and office equipment
Property, Plant and Equipment [Line Items]
Useful life	10 years
Maximum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Useful life	5 years

SUMMARY OF SIGNIFICANT ACCOU_11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Long-Lived Assets, Intangible Assets and Goodwill) (Details)	12 Months Ended
	Dec. 31, 2021
Acquired Technology | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	1 year
Acquired Technology | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	8 years
Acquired customer base | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	5 years
Acquired customer base | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	13 years
Trade name | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	1 year
Trade name | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	15 years

SUMMARY OF SIGNIFICANT ACCOU_12

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Recent Accounting Pronouncements) (Details) - 2020 Credit Agreement	Jul. 01, 2020USD ($)
Revolving Loans and Letters of Credit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revolving credit sub-facility for swing-line loans and issuances of letters of credit	$ 750,000,000
Letter of Credit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revolving credit sub-facility for swing-line loans and issuances of letters of credit	$ 20,000,000

REVENUE FROM CONTRACTS WITH C_3

REVENUE FROM CONTRACTS WITH CUSTOMERS (Disaggregated Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 1,944,135	$ 1,659,019	$ 1,399,719
CoStar
Disaggregation of Revenue [Line Items]
Revenues	722,821	664,735	617,798
Information services
Disaggregation of Revenue [Line Items]
Revenues	141,655	130,070	88,446
Multifamily
Disaggregation of Revenue [Line Items]
Revenues	678,680	598,555	490,631
LoopNet
Disaggregation of Revenue [Line Items]
Revenues	207,511	179,805	149,980
Residential
Disaggregation of Revenue [Line Items]
Revenues	74,583	0	0
Other Marketplaces
Disaggregation of Revenue [Line Items]
Revenues	118,885	85,854	52,864
North America
Disaggregation of Revenue [Line Items]
Revenues	1,877,635	1,602,102	1,360,067
North America | CoStar
Disaggregation of Revenue [Line Items]
Revenues	686,948	634,205	590,222
North America | Information services
Disaggregation of Revenue [Line Items]
Revenues	113,723	104,117	76,950
North America | Multifamily
Disaggregation of Revenue [Line Items]
Revenues	678,680	598,555	490,631
North America | LoopNet
Disaggregation of Revenue [Line Items]
Revenues	204,816	179,371	149,400
North America | Residential
Disaggregation of Revenue [Line Items]
Revenues	74,583	0	0
North America | Other Marketplaces
Disaggregation of Revenue [Line Items]
Revenues	118,885	85,854	52,864
International
Disaggregation of Revenue [Line Items]
Revenues	66,500	56,917	39,652
International | CoStar
Disaggregation of Revenue [Line Items]
Revenues	35,873	30,530	27,576
International | Information services
Disaggregation of Revenue [Line Items]
Revenues	27,932	25,953	11,496
International | Multifamily
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
International | LoopNet
Disaggregation of Revenue [Line Items]
Revenues	2,695	434	580
International | Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
International | Other Marketplaces
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0

REVENUE FROM CONTRACTS WITH C_4

REVENUE FROM CONTRACTS WITH CUSTOMERS (Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Change in Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 77,363
Revenue recognized in the current period from the amounts in the beginning balance	(74,578)
New deferrals, net of amounts recognized in the current period	94,143
Effects of foreign currency	(204)
Ending balance	96,724
Current liability	95,471	$ 74,851
Noncurrent liability	1,200	$ 2,500
New deferrals recognized in connection with business acquisitions made in 2021	$ (2,200)

REVENUE FROM CONTRACTS WITH C_5

REVENUE FROM CONTRACTS WITH CUSTOMERS (Contract Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract with customer, asset, gross	$ 9	$ 9

REVENUE FROM CONTRACTS WITH C_6

REVENUE FROM CONTRACTS WITH CUSTOMERS (Commissions) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred sales commissions of impaired	$ 0	$ 0
Commissions incurred	117,391,000	97,183,000	$ 87,043,000
Commissions capitalized in the current period	(72,038,000)	(64,355,000)	(66,688,000)
Amortization of deferred commissions costs	63,391,000	60,516,000	53,421,000
Total commissions expense	$ 108,744,000	$ 93,344,000	$ 73,776,000

REVENUE FROM CONTRACTS WITH C_7

REVENUE FROM CONTRACTS WITH CUSTOMERS (Unsatisfied Performance Obligations) (Details) $ in Millions	Dec. 31, 2021USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 315
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
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) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2020	$ 15,110	$ 4,548
Current-period provision (release) for expected credit losses	10,928	25,212
Write-offs charged against the allowance, net of recoveries and other	(12,664)	(14,650)
Ending balance at December 31, 2021	13,374	15,110
CoStar
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2020	5,531	1,264
Current-period provision (release) for expected credit losses	5,699	11,622
Write-offs charged against the allowance, net of recoveries and other	(5,850)	(7,355)
Ending balance at December 31, 2021	5,380	5,531
Information services
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2020	2,739	624
Current-period provision (release) for expected credit losses	(392)	2,649
Write-offs charged against the allowance, net of recoveries and other	(527)	(534)
Ending balance at December 31, 2021	1,820	2,739
Multifamily
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2020	4,387	1,195
Current-period provision (release) for expected credit losses	3,057	7,644
Write-offs charged against the allowance, net of recoveries and other	(4,051)	(4,452)
Ending balance at December 31, 2021	3,393	4,387
LoopNet
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2020	1,667	576
Current-period provision (release) for expected credit losses	2,564	3,213
Write-offs charged against the allowance, net of recoveries and other	(2,263)	(2,122)
Ending balance at December 31, 2021	1,968	1,667
Other Marketplaces
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at December 31, 2020	786	889
Current-period provision (release) for expected credit losses	0	84
Write-offs charged against the allowance, net of recoveries and other	27	(187)
Ending balance at December 31, 2021	$ 813	$ 786

ACQUISITIONS (Narrative) (Detai

ACQUISITIONS (Narrative) (Details) $ in Thousands, € in Millions	Oct. 01, 2021USD ($)	Oct. 01, 2021EUR (€)	May 24, 2021USD ($)	Apr. 14, 2021USD ($)	Dec. 22, 2020USD ($)	Jun. 24, 2020USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Business Acquisition [Line Items]
Goodwill							$ 2,321,015	$ 2,235,999	$ 2,321,015	$ 2,321,015	$ 2,235,999	$ 1,882,020
Goodwill, expected tax deductible amount							20,000		20,000	20,000
North America
Business Acquisition [Line Items]
Goodwill							2,145,846	2,085,494	2,145,846	2,145,846	2,085,494	$ 1,738,360
BureauxLocaux
Business Acquisition [Line Items]
Aggregate purchase price	$ 41,000	€ 35
Goodwill acquired							27,000
Intangible assets							18,000		18,000	18,000
Homes.com
Business Acquisition [Line Items]
Intangible assets			$ 53,400
Purchase price before adjustments			150,000
Purchase price, net of estimated working capital adjustments				$ 148,000
Purchase price due				4 months
Fair value of identifiable net assets acquired			152,175
Goodwill			88,474
Goodwill, expected tax deductible amount			20,000
Transaction costs							5,000		5,000	5,000
Accrual amount										7,000
Indemnification asset							7,000		7,000	7,000
Homes.com | North America
Business Acquisition [Line Items]
Goodwill acquired			$ 88,500
Homesnap
Business Acquisition [Line Items]
Aggregate purchase price					$ 250,000
Goodwill acquired					184,000
Intangible assets					67,000
Fair value of identifiable net assets acquired					250,354
Goodwill					$ 184,371
Homesnap | North America
Business Acquisition [Line Items]
Goodwill acquired											211,100
Ten-X
Business Acquisition [Line Items]
Aggregate purchase price						$ 188,000
Goodwill acquired						134,000
Intangible assets						58,000
Fair value of identifiable net assets acquired						187,715
Goodwill						$ 134,322
Transaction costs							$ 3,000		3,000	$ 3,000
Increase in revenue								32,000	14,000
Decrease in net income								$ 10,000	$ 23,000
Ten-X | North America
Business Acquisition [Line Items]
Goodwill acquired											$ 135,700

ACQUISITIONS (Schedule of Recog

ACQUISITIONS (Schedule of Recognized Identified Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	May 24, 2021	Dec. 31, 2020	Dec. 22, 2020	Jun. 24, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 2,321,015		$ 2,235,999			$ 1,882,020
Deferred tax liabilities, net	$ (2,200)
Homes.com
Business Acquisition [Line Items]
Cash, cash equivalents and restricted cash		$ 0
Accounts receivable		1,798
Lease right-of-use assets		371
Goodwill		88,474
Intangible assets		53,400
Deferred tax assets		11,264
Lease liabilities		(371)
Deferred revenue		(1,521)
Other assets and liabilities		(1,240)
Fair value of identifiable net assets acquired		152,175
Homes.com | Previously Reported
Business Acquisition [Line Items]
Cash, cash equivalents and restricted cash		0
Accounts receivable		1,798
Lease right-of-use assets		371
Goodwill		88,132
Intangible assets		53,400
Deferred tax assets		11,171
Lease liabilities		(371)
Deferred revenue		(1,086)
Other assets and liabilities		(1,240)
Fair value of identifiable net assets acquired		152,175
Homes.com | Revision of Prior Period, Adjustment
Business Acquisition [Line Items]
Goodwill		342
Deferred tax assets		93
Deferred revenue		435
Fair value of identifiable net assets acquired		$ 0
Homesnap
Business Acquisition [Line Items]
Cash, cash equivalents and restricted cash				$ 10,225
Accounts receivable				662
Lease right-of-use assets				3,437
Goodwill				184,371
Intangible assets				67,000
Deferred tax liabilities, net				(2,778)
Lease liabilities				(3,375)
Deferred revenue				(4,000)
Other assets and liabilities				(5,188)
Fair value of identifiable net assets acquired				$ 250,354
Ten-X
Business Acquisition [Line Items]
Cash, cash equivalents and restricted cash					$ 3,290
Accounts receivable					131
Lease right-of-use assets					4,945
Goodwill					134,322
Intangible assets					58,000
Deferred tax liabilities, net					(2,981)
Lease liabilities					(4,945)
Other assets and liabilities					(5,047)
Fair value of identifiable net assets acquired					$ 187,715

ACQUISITIONS (Intangible Assets

ACQUISITIONS (Intangible Assets Acquired) (Details) - USD ($) $ in Thousands	May 24, 2021	Dec. 22, 2020	Jun. 24, 2020
Homes.com
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 53,400
Homes.com | Customer base
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 32,000
Estimated Useful Life	8 years
Homes.com | Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 21,000
Estimated Useful Life	15 years
Homes.com | Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 400
Estimated Useful Life	2 years
Homesnap
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 67,000
Homesnap | Customer base
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 45,000
Estimated Useful Life		10 years
Homesnap | Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 7,000
Estimated Useful Life		10 years
Homesnap | Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 15,000
Estimated Useful Life		6 years
Ten-X
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value			$ 58,000
Ten-X | Customer base
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value			$ 46,000
Estimated Useful Life			6 years
Ten-X | Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value			$ 11,000
Estimated Useful Life			5 years
Ten-X | Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value			$ 1,000
Estimated Useful Life			2 years

ACQUISITIONS (Business Acquisit

ACQUISITIONS (Business Acquisition, Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Combination and Asset Acquisition [Abstract]
Revenue	$ 1,962,102	$ 1,758,612	$ 1,483,218
Net income	$ 286,718	$ 197,994	$ 271,789
Net income per share - basic (usd per share)	$ 0.74	$ 0.52	$ 0.75
Net income per share - diluted (usd per share)	$ 0.73	$ 0.51	$ 0.74

INVESTMENTS AND FAIR VALUE ME_2

INVESTMENTS AND FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Billions	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Inputs, Level 2
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Debt outstanding, fair value	$ 1	$ 1
Cash Equivalents | Fair Value, Inputs, Level 1
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 3	$ 3.4

LEASES (Narrative) (Details)

LEASES (Narrative) (Details)	Dec. 31, 2021
Minimum
Lessee, Lease, Description [Line Items]
Term of contract	1 year
Maximum
Lessee, Lease, Description [Line Items]
Term of contract	7 years

LEASES (Lease Cost) (Details)

LEASES (Lease Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease costs:	$ 34,879	$ 32,835	$ 27,593
Cost of revenues
Lessee, Lease, Description [Line Items]
Operating lease costs:	10,110	11,632	11,407
Software development
Lessee, Lease, Description [Line Items]
Operating lease costs:	6,947	6,020	4,209
Selling and marketing (excluding customer base amortization)
Lessee, Lease, Description [Line Items]
Operating lease costs:	11,911	10,356	8,678
General and administrative
Lessee, Lease, Description [Line Items]
Operating lease costs:	$ 5,911	$ 4,827	$ 3,299

LEASES (Supplemental Balance Sh

LEASES (Supplemental Balance Sheet Information Related to Leases) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases, Operating [Abstract]
Total	$ 134,150	$ 148,975
Less: imputed interest	(8,512)	(10,998)
Present value of lease liabilities	125,638	137,977
Lease liabilities	26,268	32,648
Long-term lease liabilities	$ 99,370	$ 105,329
Weighted-average remaining lease term in years	4 years	4 years
Weighted-average discount rate	3.10%	3.60%
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Lease and other long-term liabilities	Lease and other long-term liabilities

LEASES (Supplemental Cash Flow

LEASES (Supplemental Cash Flow Information Related to Leases) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases	$ 37,298	$ 37,006	$ 30,287
ROU assets obtained in exchange for lease obligations:
Operating leases	$ 34,247	$ 19,746	$ 22,629

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 357,293	$ 357,293	$ 292,478
Accumulated depreciation and amortization	(85,862)	(85,862)	(166,153)
Property and equipment, net	271,431	271,431	126,325
Depreciation expense for property and equipment		29,000	29,000	$ 26,000
Depreciated assets written-off	107,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	75,634	75,634	80,963
Furniture, office equipment and vehicles
Property, Plant and Equipment [Line Items]
Property and equipment, gross	47,540	47,540	68,587
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	30,179	30,179	86,755
Aircrafts
Property, Plant and Equipment [Line Items]
Property and equipment, gross	68,670	68,670	28,561
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	38,774	38,774	24,642
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 96,496	$ 96,496	$ 2,970

GOODWILL (Goodwill by Segment)

GOODWILL (Goodwill by Segment) (Details) - USD ($) $ in Thousands	Oct. 01, 2021	Dec. 22, 2020	Jun. 24, 2020	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill, beginning balance					$ 2,235,999	$ 1,882,020
Acquisitions, including measurement period adjustments					87,793	348,407
Effect of foreign currency translation					(2,777)	5,572
Goodwill, ending balance				$ 2,321,015	2,321,015	2,235,999
Ten-X
Goodwill [Roll Forward]
Goodwill, ending balance			$ 134,322
Goodwill acquired			$ 134,000
Homesnap
Goodwill [Roll Forward]
Goodwill, ending balance		$ 184,371
Goodwill acquired		$ 184,000
BureauxLocaux
Goodwill [Roll Forward]
Goodwill acquired				27,000
North America
Goodwill [Roll Forward]
Goodwill, beginning balance					2,085,494	1,738,360
Acquisitions, including measurement period adjustments					60,352	347,134
Effect of foreign currency translation					0	0
Goodwill, ending balance				2,145,846	2,145,846	2,085,494
North America | Ten-X
Goodwill [Roll Forward]
Goodwill acquired						135,700
Goodwill increase (decrease)					1,400
North America | Homesnap
Goodwill [Roll Forward]
Goodwill acquired						211,100
Goodwill increase (decrease)					26,700
North America | Ten-X, Homesnap and STR
Goodwill [Roll Forward]
Goodwill increase (decrease)						300
International
Goodwill [Roll Forward]
Goodwill, beginning balance					150,505	143,660
Acquisitions, including measurement period adjustments					27,441	1,273
Effect of foreign currency translation					(2,777)	5,572
Goodwill, ending balance				$ 175,169	$ 175,169	150,505
International | Emporis
Goodwill [Roll Forward]
Goodwill acquired						1,200
International | STR
Goodwill [Roll Forward]
Goodwill increase (decrease)						$ 100
International | BureauxLocaux
Goodwill [Roll Forward]
Goodwill acquired	$ 27,400

GOODWILL (Narrative) (Details)

GOODWILL (Narrative) (Details) - USD ($)	Dec. 22, 2020	Jun. 24, 2020	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	May 24, 2021
Goodwill [Line Items]
Goodwill, expected tax deductible amount			$ 20,000,000	$ 20,000,000
Goodwill, impairment				$ 0	$ 0	$ 0
BureauxLocaux
Goodwill [Line Items]
Goodwill acquired			$ 27,000,000
Homes.com
Goodwill [Line Items]
Goodwill, expected tax deductible amount							$ 20,000,000
Homesnap
Goodwill [Line Items]
Goodwill acquired	$ 184,000,000
Ten-X
Goodwill [Line Items]
Goodwill acquired		$ 134,000,000

INTANGIBLE ASSETS (Details)

INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	$ 435,662	$ 426,745
Acquired technology and data
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	41,979	131,551
Accumulated amortization	(15,333)	(97,791)
Finite-lived intangible assets, net	$ 26,646	33,760
Weighted- Average Amortization Period (in years)	6 years
Acquired customer base
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 569,666	545,643
Accumulated amortization	(319,039)	(296,758)
Finite-lived intangible assets, net	$ 250,627	248,885
Weighted- Average Amortization Period (in years)	10 years
Acquired trade names and other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 262,136	249,465
Accumulated amortization	(103,747)	(105,365)
Finite-lived intangible assets, net	$ 158,389	$ 144,100
Weighted- Average Amortization Period (in years)	13 years

INTANGIBLE ASSETS (Narrative) (

INTANGIBLE ASSETS (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 104,000,000	$ 88,000,000	$ 55,000,000
Indefinite-lived intangible assets, written off	171,000,000
Impairment of intangible assets	0	$ 0	$ 0
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization expense for 2021	87,000,000
Amortization expense for 2022	71,000,000
Amortization expense for 2023	59,000,000
Amortization expense for 2024	47,000,000
Amortization expense for 2025	$ 39,000,000

LONG-TERM DEBT (Schedule of Deb

LONG-TERM DEBT (Schedule of Debt) (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Jul. 01, 2020
Debt Instrument [Line Items]
Total face amount of long-term debt	$ 1,000,000,000	$ 1,000,000,000
Senior notes unamortized discount and issuance costs	(12,056,000)	(13,285,000)
Long-term debt, net	987,944,000	986,715,000
2.800% Senior Notes
Debt Instrument [Line Items]
Stated interest rate			2.80%
Total face amount of long-term debt	$ 1,000,000,000	$ 1,000,000,000	$ 1,000,000,000

LONG-TERM DEBT (Narrative) (Det

LONG-TERM DEBT (Narrative) (Details)	Jul. 01, 2020USD ($)occasion	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Total face amount of long-term debt		$ 1,000,000,000	$ 1,000,000,000
Number of Allowable Increase Requests | occasion	5
2.800% Senior Notes
Debt Instrument [Line Items]
Total face amount of long-term debt	$ 1,000,000,000	1,000,000,000	1,000,000,000
Stated interest rate	2.80%
Discounted rate par value	99.921%
Redemption price rate	100.00%
2020 Credit Agreement
Debt Instrument [Line Items]
Total face amount of long-term debt		$ 0	0
Total leverage ratio		4.50
2020 Credit Agreement | Other Assets
Debt Instrument [Line Items]
Debt issuance costs, net		$ 3,800,000	$ 4,900,000
2020 Credit Agreement | Revolving Loans and Letters of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 750,000,000
Term of credit facility	5 years
2020 Credit Agreement | Revolving Loans and Letters of Credit | Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.25%
2020 Credit Agreement | Revolving Loans and Letters of Credit | Maximum
Debt Instrument [Line Items]
Commitment fee percentage	0.30%
2020 Credit Agreement | Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 20,000,000
2020 Credit Agreement | Letter of Credit | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread	0.00%
2020 Credit Agreement | Letter of Credit | Minimum | Alternate Base Rate
Debt Instrument [Line Items]
Basis spread	0.50%
2020 Credit Agreement | Letter of Credit | Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread	1.50%
2020 Credit Agreement | Letter of Credit | Maximum | Alternate Base Rate
Debt Instrument [Line Items]
Basis spread	1.25%
2020 Credit Agreement | Letter of Credit | Maximum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread	2.25%

LONG-TERM DEBT (Interest) (Deta

LONG-TERM DEBT (Interest) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total interest expense	$ 32,316	$ 21,794	$ 2,615
Amortization of debt issuance costs	2,327	1,658	874
Commitment fees and other	1,989	1,627	1,741
Borrowings
Debt Instrument [Line Items]
Total interest expense	$ 28,000	$ 18,509	$ 0

INCOME TAXES (Components for Pr

INCOME TAXES (Components for Provision for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ 61,290	$ 43,461	$ 53,039
State	24,618	11,726	13,422
Foreign	1,331	195	1,305
Total current	87,239	55,382	67,766
Deferred:
Federal	22,859	(9,599)	6,881
State	8,467	(926)	2,424
Foreign	(7,161)	(1,005)	(1,085)
Total deferred	24,165	(11,530)	8,220
Income tax expense	$ 111,404	$ 43,852	$ 75,986

INCOME TAXES (Components of Def

INCOME TAXES (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Allowance for credit losses	$ 3,601	$ 3,698
Accrued compensation	3,913	4,934
Stock compensation	18,956	15,289
Net operating losses	45,835	38,498
Accrued reserve and other	4,134	5,900
Lease liabilities	28,306	34,758
Research and development credits	5,812	6,059
Deferred Tax Assets, Accrued Transaction Fees	0	13,334
Total deferred tax assets, prior to valuation allowance	110,557	122,470
Valuation allowance	(5,694)	(11,170)
Total deferred tax assets, net of valuation allowance	104,863	111,300
Deferred tax liabilities:
Deferred commission costs, net	(25,700)	(23,691)
Lease right-of-use assets	(22,574)	(27,168)
Prepaid expenses	(2,569)	(2,384)
Property and equipment, net	(21,827)	(13,078)
Intangible assets, net	(125,815)	(112,987)
Total deferred tax liabilities	(198,485)	(179,308)
Net deferred tax assets (liabilities)	$ (93,622)	$ (68,008)

INCOME TAXES (Narrative) (Detai

INCOME TAXES (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Decrease in valuation allowance	$ 5,500	$ 2,400
Income from U.S. sources	409,000	291,000	$ 403,000
Income from foreign sources	5,000	20,000	12,000
Cash tax benefits resulting in net operating loss carryforward	14,000	5,000	6,000
Unrecognized tax benefits that would favorably affect the annual effective tax rate if recognized in future periods	15,000	29,000
Increase for current year tax positions	3,024	4,213	3,487
Decrease for prior year tax positions	5,353
Decrease for settlements with taxing authorities	9,924
Expiration of the statute of limitation for assessment of taxes	1,866	1,259	832
Income tax penalties and interest expense (reversal)	(400)	400	200
Interest and penalties accrued on income taxes	600	$ 1,000	$ 600
Foreign Country
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	41,000
Domestic Country
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	151,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	5,000
Income tax credit carryforward	$ 6,000

INCOME TAXES (Reconciliation of

INCOME TAXES (Reconciliation of Provision for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective tax rate reconciliation [Abstract]
Expected federal income tax provision at statutory rate	$ 84,833	$ 56,906	$ 82,099
State income taxes, net of federal benefit	21,012	11,409	14,884
(Decrease) in valuation allowance	(4,995)	(4,848)	(693)
Research credits	(13,070)	(14,322)	(12,188)
Excess tax benefit	(10,933)	(21,038)	(15,282)
Tax reserves	(12,787)	4,762	3,135
Nondeductible compensation	10,369	5,949	1,777
International restructuring	34,854	0	0
Other adjustments	2,121	5,034	2,254
Income tax expense	$ 111,404	$ 43,852	$ 75,986

INCOME TAXES (Unrecognized Tax

INCOME TAXES (Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits beginning balance	$ 28,873	$ 25,467	$ 22,372
Increase for current year tax positions	3,024	4,213	3,487
Increase for prior year tax positions		452	440
Decrease for prior year tax positions	(5,353)
Decrease for settlements with taxing authorities	(9,924)
Expiration of the statute of limitation for assessment of taxes	(1,866)	(1,259)	(832)
Unrecognized tax benefits ending balance	$ 14,754	$ 28,873	$ 25,467

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating lease obligations
2022	$ 29,678
2023	36,477
2024	32,808
2025	16,051
2026	7,235
Thereafter	11,901
Total	134,150	$ 148,975
Long-term debt principal payments
2022	0
2023	0
2024	0
2025	0
2026	0
Thereafter	1,000,000
Total	1,000,000
Long-term debt principal interest payments
2022	28,000
2023	28,000
2024	28,000
2025	28,000
2026	28,000
Thereafter	112,000
Total	$ 252,000

SEGMENT REPORTING (Narrative) (

SEGMENT REPORTING (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021operating_segment
Segment Reporting [Abstract]
Number of operating segments	2

SEGMENT REPORTING (EBITDA) (Det

SEGMENT REPORTING (EBITDA) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total EBITDA	$ 564,981	$ 406,146	$ 444,712
Operating Segments | North America
Segment Reporting Information [Line Items]
Total EBITDA	557,125	410,852	451,699
Operating Segments | International
Segment Reporting Information [Line Items]
Total EBITDA	$ 7,856	$ (4,706)	$ (6,987)

SEGMENT REPORTING (Reconciliati

SEGMENT REPORTING (Reconciliation of Net Income (Loss) to EBITDA) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting [Abstract]
Net income	$ 292,564	$ 227,128	$ 314,963
Amortization of acquired intangible assets in cost of revenues	28,809	25,675	21,357
Amortization of acquired intangible assets in operating expenses	74,817	62,457	33,995
Depreciation and other amortization	29,018	28,812	25,813
Interest expense (income), net	31,621	17,395	(16,742)
Other income (expense), net	(3,252)	827	(10,660)
Income tax expense	111,404	43,852	75,986
EBITDA	$ 564,981	$ 406,146	$ 444,712

SEGMENT REPORTING (Summarized I

SEGMENT REPORTING (Summarized Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Property and equipment, net	$ 271,431	$ 126,325
Goodwill	2,321,015	2,235,999	$ 1,882,020
Total assets	7,256,871	6,915,420
Total liabilities	1,545,199	1,540,061
North America
Segment Reporting Information [Line Items]
Goodwill	2,145,846	2,085,494	1,738,360
International
Segment Reporting Information [Line Items]
Goodwill	175,169	150,505	$ 143,660
Operating Segments | North America
Segment Reporting Information [Line Items]
Property and equipment, net	269,792	123,634
Goodwill	2,145,846	2,085,494
Total assets	6,976,752	6,674,974
Total liabilities	1,502,497	1,496,894
Operating Segments | International
Segment Reporting Information [Line Items]
Property and equipment, net	1,639	2,691
Goodwill	175,169	150,505
Total assets	280,119	240,446
Total liabilities	$ 42,702	$ 43,167

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details) $ / shares in Units, $ in Millions	Jun. 07, 2021$ / sharesshares	May 28, 2020USD ($)$ / sharesshares	Dec. 31, 2021$ / sharesshares	Jun. 17, 2021shares	Jun. 06, 2021shares	Dec. 31, 2020$ / sharesshares
Preferred stock
Preferred stock authorized for issuance (in shares)			2,000,000			2,000,000
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01			$ 0.01
Common stock
Common stock authorized for issuance (in shares)			1,200,000,000			1,200,000,000
Common stock, par or stated value per share (in dollars per share) | $ / shares	$ 0.01		$ 0.01			$ 0.01
Subsidiary, Sale of Stock [Line Items]
Common stock authorized for issuance (in shares)			1,200,000,000			1,200,000,000
Conversion ratio	10
Dividends common stock, shares (in shares)				9
Common stock, par or stated value per share (in dollars per share) | $ / shares	$ 0.01		$ 0.01			$ 0.01
Board of Directors
Common stock
Common stock authorized for issuance (in shares)	1,200,000,000				60,000,000
Subsidiary, Sale of Stock [Line Items]
Common stock authorized for issuance (in shares)	1,200,000,000				60,000,000
Public Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)		26,300,000
Sale of stock, price per share (usd per share) | $ / shares		$ 65.50
Consideration received on transaction | $		$ 1,700
Payments of stock issuance costs | $		$ 35

NET INCOME PER SHARE (Details)

NET INCOME PER SHARE (Details) $ / shares in Units, shares in Thousands, $ in Thousands		Jun. 07, 2021	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Numerator:
Net income | $			$ 292,564	$ 227,128	$ 314,963
Denominator:
Denominator for basic net income per share — weighted-average outstanding shares	[1]		392,210	380,726	363,096
Effect of dilutive securities:
Stock options, restricted stock awards and restricted stock units (in shares)			1,950	2,540	3,205
Denominator for diluted net income per share — weighted-average outstanding shares (in shares)	[1]		394,160	383,266	366,301
Net income per share — basic (in dollars per share) | $ / shares	[1]		$ 0.75	$ 0.60	$ 0.87
Net income per share — diluted (in dollars per share) | $ / shares	[1]		$ 0.74	$ 0.59	$ 0.86
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)			373	540	425
Conversion ratio		10
Performance-based restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)			415	526	600
[1]	Prior period amounts have been retroactively adjusted to reflect the ten-for-one stock split effected in the form of a stock dividend in June 2021.

EMPLOYEE BENEFIT PLANS (Stock I

EMPLOYEE BENEFIT PLANS (Stock Incentive Plans - Narrative) (Details) $ in Thousands	Jun. 07, 2021	Dec. 31, 2021USD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)	Jun. 09, 2016shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio	10
Tax benefit from stock-based compensation		$ 2,000	$ 20,000	$ 17,000
Compensation expense		$ 63,709	54,104	52,255
CoStar Group, Inc. 2007 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant under the plan (in shares) | shares					0
CoStar Group, Inc. 2016 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant under the plan (in shares) | shares		15,300,000
Shares of common stock authorized for issuance under the plan (in shares) | shares		22,700,000
CoStar Group, Inc. 2016 Stock Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of options and restricted stock grants		3 years
CoStar Group, Inc. 2016 Stock Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of options and restricted stock grants		4 years
Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of options and restricted stock grants		1 year
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost expected to be recognized in future years		$ 91,000
Weighted-average-period expected to recognize the unrecognized compensation cost (in years)		2 years 3 months 18 days
Aggregate intrinsic value of options exercised		$ 11,000	49,000	40,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of options and restricted stock grants		3 years
Performance service period		3 years
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement, award vesting rights, percentage		80.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement, award vesting rights, percentage		120.00%
Performance-based RSAs - with Market Condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost expected to be recognized in future years		$ 11,000
Compensation expense		$ 8,000	$ 4,000	$ 8,000
Granted (in shares) | shares		192,000
DSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred stock unit, granted percentage		100.00%
Granted (in shares) | shares		40,960	33,840

EMPLOYEE BENEFIT PLANS (Stock O

EMPLOYEE BENEFIT PLANS (Stock Option Activity) (Details) $ / shares in Units, $ in Thousands	Jun. 07, 2021	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Conversion ratio	10
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period (in shares) | shares		2,023,100	2,756,580	3,442,760
Granted (in shares) | shares		159,000	341,000	483,000
Exercised (in shares) | shares		(206,000)	(953,130)	(1,169,180)
Canceled or expired (in shares) | shares			(121,350)
Outstanding at end of period (in shares) | shares		1,976,100	2,023,100	2,756,580	3,442,760
Exercisable at end of period (in shares) | shares		1,473,420	1,228,060	1,476,200
Share Based Compensation Exercisable Range [Abstract]
Granted (dollars per share)		$ 91.98	$ 66.65	$ 39.82
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding at beginning of period (in dollars per share)		34.18	26.72	21.23
Granted (in dollars per share)		91.98	66.65	39.82
Exercised (in dollars per share)		30.78	22.95	15.95
Canceled or expired (in dollars per share)			44.31
Outstanding at end of period (in dollars per share)		39.18	34.18	26.72	$ 21.23
Exercisable at end of period (in dollars per share)		$ 29.55	$ 24.68	$ 21.10
Weighted average remaining contract life, outstanding		6 years 2 months 26 days	6 years 11 months 26 days	6 years 11 months 23 days	7 years 10 days
Weighted average remaining contract life, outstanding, exercisable		5 years 7 months 2 days	6 years 2 months 4 days	5 years 10 months 2 days
Aggregate intrinsic value of options outstanding at end of period | $		$ 80,800	$ 117,846	$ 91,262	$ 43,418
Aggregate intrinsic value of options exercisable at end of period | $		$ 72,905	$ 83,204	$ 57,180
Minimum
Share Based Compensation Exercisable Range [Abstract]
Exercised (dollars per share)		$ 20.49
Outstanding (dollars per share)		10.22
Minimum | Stock Options
Share Based Compensation Exercisable Range [Abstract]
Outstanding (dollars per share)		10.22	$ 5.45	$ 3.67
Exercised (dollars per share)			19.37		$ 5.45
Canceled or expired (dollars per share)			34.21
Outstanding (dollars per share)			10.22	5.45	3.67
Exercisable at end of period (dollars per share)		10.22	10.22	10.22
Maximum | Stock Options
Share Based Compensation Exercisable Range [Abstract]
Outstanding (dollars per share)		66.65	39.82	34.21
Exercised (dollars per share)		39.82	39.82		34.21
Canceled or expired (dollars per share)			66.65
Outstanding (dollars per share)		91.98	66.65	39.82	$ 34.21
Exercisable at end of period (dollars per share)		$ 66.65	$ 39.82	$ 34.21

EMPLOYEE BENEFIT PLANS (Assumpt

EMPLOYEE BENEFIT PLANS (Assumptions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	30.00%	26.00%	27.00%
Risk-free interest rate	0.56%	1.45%	2.46%
Expected life (in years)	5 years	5 years	5 years
Weighted-average grant date fair value (in dollars per share)	$ 25.09	$ 17.21	$ 11.52
Performance-based RSAs - with Market Condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	42.00%	27.00%	27.00%
Risk-free interest rate	0.20%	1.43%	2.45%
Expected life (in years)	3 years	3 years	3 years
Weighted-average grant date fair value (in dollars per share)	$ 99.73	$ 72.69	$ 42.96

EMPLOYEE BENEFIT PLANS (Informa

EMPLOYEE BENEFIT PLANS (Information Regarding Stock Options) (Details)	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Options Outstanding
Number of shares (in shares) | shares	1,976,100
Weighted-average remaining contractual life (in years)	6 years 2 months 26 days
Weighted- average exercise price (in dollars per share)	$ 39.18
Options Exercisable
Number of shares (in shares) | shares	1,473,420
Weighted-average exercise price (in dollars per share)	$ 29.55
24.24
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise price, minimum, (in dollars per share)	10.22
Range of exercise price, maximum, (in dollars per share)	$ 24.24
Options Outstanding
Number of shares (in shares) | shares	762,420
Weighted-average remaining contractual life (in years)	4 years 5 months 26 days
Weighted- average exercise price (in dollars per share)	$ 18.94
Options Exercisable
Number of shares (in shares) | shares	762,420
Weighted-average exercise price (in dollars per share)	$ 18.94
48.82
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise price, minimum, (in dollars per share)	24.25
Range of exercise price, maximum, (in dollars per share)	$ 48.82
Options Outstanding
Number of shares (in shares) | shares	742,680
Weighted-average remaining contractual life (in years)	6 years 7 months 24 days
Weighted- average exercise price (in dollars per share)	$ 37.12
Options Exercisable
Number of shares (in shares) | shares	607,000
Weighted-average exercise price (in dollars per share)	$ 36.52
69.93
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise price, minimum, (in dollars per share)	48.83
Range of exercise price, maximum, (in dollars per share)	$ 69.93
Options Outstanding
Number of shares (in shares) | shares	312,000
Weighted-average remaining contractual life (in years)	8 years 1 month 6 days
Weighted- average exercise price (in dollars per share)	$ 66.65
Options Exercisable
Number of shares (in shares) | shares	104,000
Weighted-average exercise price (in dollars per share)	$ 66.65
91.98
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise price, minimum, (in dollars per share)	69.94
Range of exercise price, maximum, (in dollars per share)	$ 91.98
Options Outstanding
Number of shares (in shares) | shares	159,000
Weighted-average remaining contractual life (in years)	9 years 1 month 17 days
Weighted- average exercise price (in dollars per share)	$ 91.98
Options Exercisable
Number of shares (in shares) | shares	0
Weighted-average exercise price (in dollars per share)	$ 0

EMPLOYEE BENEFIT PLANS (Restric

EMPLOYEE BENEFIT PLANS (Restrictive Stock Award Activity) (Details)	Jun. 07, 2021	Dec. 31, 2021$ / sharesshares
Weighted-Average Grant Date Fair Value per Share(1)
Conversion ratio	10
Performance Based RSAs Without Market Condition
Number of Shares(1)
Unvested restricted stock at beginning of period (in shares) | shares		2,028,640
Granted (in shares) | shares		813,397
Vested (in shares) | shares		(894,291)
Canceled (in shares) | shares		(165,440)
Unvested restricted stock at end of period (in shares) | shares		1,782,306
Weighted-Average Grant Date Fair Value per Share(1)
Unvested restricted stock at beginning of period (in dollars per share) | $ / shares		$ 52.17
Granted (in dollars per share) | $ / shares		80.64
Vested (in dollars per share) | $ / shares		43.77
Canceled (in dollars per share) | $ / shares		64.07
Unvested restricted stock at end of period (in dollars per share) | $ / shares		$ 66.74
Performance-based RSAs - with Market Condition
Number of Shares(1)
Unvested restricted stock at beginning of period (in shares) | shares		724,800
Granted (in shares) | shares		192,000
Vested (in shares) | shares		(182,619)
Canceled (in shares) | shares		(16,581)
Unvested restricted stock at end of period (in shares) | shares		717,600
Weighted-Average Grant Date Fair Value per Share(1)
Unvested restricted stock at beginning of period (in dollars per share) | $ / shares		$ 43.83
Granted (in dollars per share) | $ / shares		99.73
Vested (in dollars per share) | $ / shares		38.02
Canceled (in dollars per share) | $ / shares		38.02
Unvested restricted stock at end of period (in dollars per share) | $ / shares		$ 67.40

EMPLOYEE BENEFIT PLANS (Restr_2

EMPLOYEE BENEFIT PLANS (Restrictive Stock Units) (Details)	Jun. 07, 2021	Dec. 31, 2021$ / sharesshares	Dec. 31, 2020$ / sharesshares
Weighted-Average Grant Date Fair Value per Share(1)
Conversion ratio	10
Restricted Stock Units (RSUs)
Number of Shares(1)
Unvested restricted stock at beginning of period (in shares) | shares		8,640
Granted (in shares) | shares		6,855
Vested (in shares) | shares		(2,650)
Canceled (in shares) | shares		(360)
Unvested restricted stock at end of period (in shares) | shares		12,485	8,640
Weighted-Average Grant Date Fair Value per Share(1)
Unvested restricted stock at beginning of period (in dollars per share) | $ / shares			$ 61.90
Granted (in dollars per share) | $ / shares		$ 78
Vested (in dollars per share) | $ / shares		56.99
Canceled (in dollars per share) | $ / shares		73.79
Unvested restricted stock at end of period (in dollars per share) | $ / shares		$ 71.44

EMPLOYEE BENEFIT PLANS (MSU and

EMPLOYEE BENEFIT PLANS (MSU and DSU Activity) (Details)	Jun. 07, 2021	Dec. 31, 2021$ / sharesshares
Weighted-Average Grant Date Fair Value per Share(1)
Conversion ratio	10
MSPP RSUs
Number of Matching RSU Shares(1)
Unvested restricted stock at beginning of period (in shares) | shares		93,170
Granted (in shares) | shares		40,960
Canceled (in shares) | shares		(18,040)
Unvested restricted stock at end of period (in shares) | shares		116,090
Weighted-Average Grant Date Fair Value per Share(1)
Unvested restricted stock at beginning of period (in dollars per share) | $ / shares		$ 53.12
Granted (in dollars per share) | $ / shares		83.79
Canceled (in dollars per share) | $ / shares		61.36
Unvested restricted stock at end of period (in dollars per share) | $ / shares		$ 62.66

EMPLOYEE BENEFIT PLANS (Employe

EMPLOYEE BENEFIT PLANS (Employee 401(k) Plan, Employee Pension Plan, Registered Retirement Savings Plan and Employee Stock Purchase Plan) (Details) - USD ($)	Jun. 02, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Maximum percentage of employee total compensation matched by employer (in hundredths)		100.00%	100.00%	100.00%
Maximum annual employee contribution		4.00%	4.00%	4.00%
Company match to employee contributions		$ 18,000,000	$ 15,000,000	$ 12,000,000
Administrative expense		$ 0	$ 0	$ 0
Percentage of purchase price of company's common stock to the market price		90.00%
Increase in shares of common stock issued pursuant to stock plan (in shares)	1,000,000
Shares available, employee stock purchase plan (in shares)		1,233,863	385,910
Shares of company's common stock purchased during the period (in shares)		152,047	129,930
Registered Retirement Savings Plan
Defined Contribution Plan Disclosure [Line Items]
Maximum percentage of employee total compensation matched by employer (in hundredths)		100.00%	100.00%	100.00%
Maximum annual employee contribution		4.00%	4.00%	4.00%
Company match to employee contributions		$ 100,000	$ 100,000	$ 100,000
Foreign Plan | Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Maximum percentage of employee total compensation matched by employer (in hundredths)		6.00%	6.00%	6.00%
Company match to employee contributions		$ 900,000	$ 900,000	$ 600,000

Schedule II Valuation and Qua_2

Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 5,097	$ 5,709
Charged to expense		10,978
Write-offs, net of recoveries		11,590
Balance at end of year		$ 5,097
Revision of Prior Period, Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reduction to allowance for credit loss, adjustment	$ 500