$CSGP
COSTAR GROUP, INC. Stock $csgp

$csgp Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-K Financial Statement

#000105735221000032 Filed on February 24, 2021

Income Statement

Concept	2020 Q4	2020	2019 Q4
Revenue	$444.4M	$1.659B	$374.7M
YoY Change	18.59%	18.53%	18.75%
Cost Of Revenue	$78.15M	$309.0M	$75.00M
YoY Change	4.21%	6.82%	9.89%
Gross Profit	$366.2M	$1.350B	$299.7M
YoY Change	22.19%	21.57%	21.19%
Gross Profit Margin	82.41%	81.38%	79.99%
Selling, General & Admin	$253.3M	$835.5M	$151.8M
YoY Change	66.86%	42.25%	40.3%
% of Gross Profit	69.16%	61.88%	50.65%
Research & Development	$40.00M	$162.9M	$35.40M
YoY Change	12.99%	29.71%	38.28%
% of Gross Profit	10.92%	12.07%	11.81%
Depreciation & Amortization	$33.00M	$116.9M	$24.00M
YoY Change	37.5%	44.08%	21.83%
% of Gross Profit	9.01%	8.66%	8.01%
Operating Expenses	$311.0M	$1.061B	$198.7M
YoY Change	56.5%	42.03%	40.29%
Operating Profit	$55.21M	$289.2M	$101.0M
YoY Change	-45.33%	-20.45%	-4.42%
Interest Expense	-$7.900M	-$17.40M	$482.0K
YoY Change	-1739.0%	-765.2%	-30.65%
% of Operating Profit	-14.31%	-6.01%	0.48%
Other Income/Expense, Net	-$900.0K	-$827.0K	-$300.0K
YoY Change	200.0%	-107.76%	-57.14%
Pretax Income	$46.44M	$271.0M	$114.3M
YoY Change	-59.37%	-30.69%	4.32%
Income Tax	$10.65M	$43.85M	$26.38M
% Of Pretax Income	22.94%	16.18%	23.08%
Net Earnings	$35.79M	$227.1M	$87.93M
YoY Change	-59.3%	-27.89%	5.29%
Net Earnings / Revenue	8.05%	13.69%	23.46%
Basic Earnings Per Share	$0.91	$0.60	$2.42
Diluted Earnings Per Share	$0.91	$0.59	$2.39
COMMON SHARES
Basic Shares Outstanding	39.42M shares	380.7M shares	36.63M shares
Diluted Shares Outstanding		383.3M shares

Balance Sheet

Concept	2020 Q4	2020	2019 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$3.756B	$3.756B	$1.071B
YoY Change	250.79%	250.79%	-2.7%
Cash & Equivalents	$3.694B	$3.756B	$1.071B
Short-Term Investments
Other Short-Term Assets	$28.70M	$28.70M	$36.20M
YoY Change	-20.72%	-20.72%	52.74%
Inventory
Prepaid Expenses
Receivables	$103.9M	$103.9M	$92.24M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$3.889B	$3.889B	$1.199B
YoY Change	224.27%	224.26%	-1.16%
LONG-TERM ASSETS
Property, Plant & Equipment	$126.3M	$235.1M	$107.5M
YoY Change	17.48%	5.62%	29.08%
Goodwill	$2.236B		$1.882B
YoY Change	18.81%		16.78%
Intangibles	$426.7M		$421.2M
YoY Change	1.32%		45.79%
Long-Term Investments	$0.00	$0.00	$10.10M
YoY Change	-100.0%	-100.0%	0.0%
Other Assets	$114.1M	$114.1M	$104.0M
YoY Change	9.71%	9.71%	14.41%
Total Long-Term Assets	$3.027B	$3.027B	$2.655B
YoY Change	14.02%	14.02%	26.44%
TOTAL ASSETS
Total Short-Term Assets	$3.889B	$3.889B	$1.199B
Total Long-Term Assets	$3.027B	$3.027B	$2.655B
Total Assets	$6.915B	$6.915B	$3.854B
YoY Change	79.44%	79.43%	16.33%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$15.73M	$15.70M	$7.640M
YoY Change	105.92%	106.58%	20.75%
Accrued Expenses	$110.3M	$224.0M	$38.68M
YoY Change	185.17%	84.51%	29.71%
Deferred Revenue	$74.90M		$67.27M
YoY Change	11.34%		30.73%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$330.9M	$330.9M	$207.1M
YoY Change	59.79%	59.78%	34.31%
LONG-TERM LIABILITIES
Long-Term Debt	$986.7M	$986.7M	$0.00
YoY Change
Other Long-Term Liabilities	$149.5M	$149.5M	$154.2M
YoY Change	-3.05%	-3.05%	130.15%
Total Long-Term Liabilities	$986.7M	$1.136B	$0.00
YoY Change		636.84%	-100.0%
TOTAL LIABILITIES
Total Short-Term Liabilities	$330.9M	$330.9M	$207.1M
Total Long-Term Liabilities	$986.7M	$1.136B	$0.00
Total Liabilities	$1.540B	$1.540B	$448.4M
YoY Change	243.46%	243.47%	54.08%
SHAREHOLDERS EQUITY
Retained Earnings	$1.168B		$940.5M
YoY Change	24.15%		53.31%
Common Stock	$3.943M		$366.0K
YoY Change	977.32%		0.55%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$5.375B	$5.375B	$3.406B
YoY Change
Total Liabilities & Shareholders Equity	$6.915B	$6.915B	$3.854B
YoY Change	79.44%	79.43%	16.33%

Cashflow Statement

Concept	2020 Q4	2020	2019 Q4
OPERATING ACTIVITIES
Net Income	$35.79M	$227.1M	$87.93M
YoY Change	-59.3%	-27.89%	5.29%
Depreciation, Depletion And Amortization	$33.00M	$116.9M	$24.00M
YoY Change	37.5%	44.08%	21.83%
Cash From Operating Activities	$130.8M	$486.1M	$107.8M
YoY Change	21.34%	6.19%	-6.1%
INVESTING ACTIVITIES
Capital Expenditures	-$6.200M	$0.00	-$2.000M
YoY Change	210.0%		-74.36%
Acquisitions		$426.1M
YoY Change		-2.62%
Other Investing Activities	-$234.1M	-$415.8M	-$423.9M
YoY Change	-44.77%	-4.98%	441.38%
Cash From Investing Activities	-$240.3M	-$464.2M	-$425.9M
YoY Change	-43.58%	-4.05%	394.66%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net		$1.690B
YoY Change
Debt Paid & Issued, Net		$745.0M
YoY Change
Cash From Financing Activities	-3.600M	$2.662B	-2.000M
YoY Change	80.0%	-64189.96%	-433.33%
NET CHANGE
Cash From Operating Activities	130.8M	$486.1M	107.8M
Cash From Investing Activities	-240.3M	-$464.2M	-425.9M
Cash From Financing Activities	-3.600M	$2.662B	-2.000M
Net Change In Cash	-113.1M	$2.685B	-320.1M
YoY Change	-64.67%	-9145.58%	-1192.49%
FREE CASH FLOW
Cash From Operating Activities	$130.8M	$486.1M	$107.8M
Capital Expenditures	-$6.200M	$0.00	-$2.000M
Free Cash Flow	$137.0M	$486.1M	$109.8M
YoY Change	24.77%	6.19%	-10.44%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0001057352
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2019Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2019Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2019Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	60000000	shares
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	60000000	shares
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	39414000	shares
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	36668000	shares
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	39414000	shares
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	36668000	shares
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList	us-gaap:OtherLongTermDebtNoncurrent
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList	us-gaap:OtherLongTermDebtNoncurrent
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	0-24531
CY2020	dei	Entity Registrant Name EntityRegistrantName	CoStar Group, Inc.
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	52-2091509
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	1331 L Street, NW
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Washington,
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	DC
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	20005
CY2020	dei	City Area Code CityAreaCode	202)
CY2020	dei	Local Phone Number LocalPhoneNumber	346-6500
CY2020	dei	Security12b Title Security12bTitle	Common Stock ($0.01 par value)
CY2020	dei	Trading Symbol TradingSymbol	CSGP
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2020	dei	Entity Small Business EntitySmallBusiness	false
CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2020	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2020	dei	Entity Shell Company EntityShellCompany	false
CY2020Q2	dei	Entity Public Float EntityPublicFloat	24600000000	USD
CY2021Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	39410441	shares
CY2018Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	6469000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	6542000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	7302000	USD
CY2019Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	5709000	USD
CY2019Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	5709000	USD
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CY2020	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	11590000	USD
CY2020Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	5097000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1659019000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1399719000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1191832000	USD
CY2020	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	308968000	USD
CY2019	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	289239000	USD
CY2018	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	269933000	USD
CY2020	us-gaap	Gross Profit GrossProfit	1350051000	USD
CY2019	us-gaap	Gross Profit GrossProfit	1110480000	USD
CY2018	us-gaap	Gross Profit GrossProfit	921899000	USD
CY2020	us-gaap	Selling And Marketing Expense SellingAndMarketingExpense	535778000	USD
CY2019	us-gaap	Selling And Marketing Expense SellingAndMarketingExpense	408596000	USD
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CY2020	us-gaap	Research And Development Expense Software Excluding Acquired In Process Cost ResearchAndDevelopmentExpenseSoftwareExcludingAcquiredInProcessCost	162916000	USD
CY2019	us-gaap	Research And Development Expense Software Excluding Acquired In Process Cost ResearchAndDevelopmentExpenseSoftwareExcludingAcquiredInProcessCost	125602000	USD
CY2018	us-gaap	Research And Development Expense Software Excluding Acquired In Process Cost ResearchAndDevelopmentExpenseSoftwareExcludingAcquiredInProcessCost	100937000	USD
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CY2019	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	178740000	USD
CY2018	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	156659000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	62457000	USD
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CY2020	us-gaap	Operating Expenses OperatingExpenses	1060849000	USD
CY2018	us-gaap	Operating Expenses OperatingExpenses	648335000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	289202000	USD
CY2019	us-gaap	Operating Expenses OperatingExpenses	746933000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	363547000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	273564000	USD
CY2020	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	-17395000	USD
CY2019	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	16742000	USD
CY2018	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	10539000	USD
CY2020	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	827000	USD
CY2019	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-10660000	USD
CY2018	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	88000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	270980000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	390949000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	284015000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	43852000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
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CY2019Q4	us-gaap	Assets Assets	3853986000	USD
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CY2019Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	7640000	USD
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CY2019Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	53087000	USD
CY2020Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	110305000	USD
CY2019Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	38680000	USD
CY2020Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	16316000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	10705000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	32648000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	29670000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	74851000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	67274000	USD
CY2020Q4	us-gaap	Liabilities Current LiabilitiesCurrent	330850000	USD
CY2019Q4	us-gaap	Liabilities Current LiabilitiesCurrent	207056000	USD
CY2020Q4	us-gaap	Deferred Gain On Sale Of Property DeferredGainOnSaleOfProperty	986715000	USD
CY2019Q4	us-gaap	Deferred Gain On Sale Of Property DeferredGainOnSaleOfProperty	0	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	72991000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	87096000	USD
CY2020Q4	us-gaap	Accrued Income Taxes Noncurrent AccruedIncomeTaxesNoncurrent	25282000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Noncurrent AccruedIncomeTaxesNoncurrent	20521000	USD
CY2020Q4	us-gaap	Other Long Term Debt Noncurrent OtherLongTermDebtNoncurrent	124223000	USD
CY2019Q4	us-gaap	Other Long Term Debt Noncurrent OtherLongTermDebtNoncurrent	133720000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	1540061000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	448393000	USD
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2020Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2019Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	60000000	shares
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	39414000	shares
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	36668000	shares
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	394000	USD
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	366000	USD
CY2020Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	4208252000	USD
CY2019Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	2473338000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-889000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-8585000	USD
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1167602000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	940474000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	5375359000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3405593000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	6915420000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3853986000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	2651250000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	7144000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-2668000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	21993000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2018	csgp	Adjustments To Additional Paid In Capital Restricted Stock Surrendered AdjustmentsToAdditionalPaidInCapitalRestrictedStockSurrendered	24327000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	40889000	USD
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	5641000	USD
CY2018	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	36366000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	3021942000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	3103000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	18652000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2019	csgp	Adjustments To Additional Paid In Capital Restricted Stock Surrendered AdjustmentsToAdditionalPaidInCapitalRestrictedStockSurrendered	27577000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	51818000	USD
CY2019	csgp	Apic Share Based Payment Arrangement Management Plan APICShareBasedPaymentArrangementManagementPlan	3491000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3405593000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	7696000	USD
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	21871000	USD
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2020	csgp	Adjustments To Additional Paid In Capital Restricted Stock Surrendered AdjustmentsToAdditionalPaidInCapitalRestrictedStockSurrendered	38867000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	52624000	USD
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	9343000	USD
CY2020	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	1689971000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	5375359000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2020	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	116944000	USD
CY2019	csgp	Non Cash Lease Expense NonCashLeaseExpense	22748000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	81165000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	77743000	USD
CY2020	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	60516000	USD
CY2019	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	53421000	USD
CY2018	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	48313000	USD
CY2020	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	1658000	USD
CY2019	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	876000	USD
CY2018	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	876000	USD
CY2020	csgp	Non Cash Lease Expense NonCashLeaseExpense	26326000	USD
CY2018	csgp	Non Cash Lease Expense NonCashLeaseExpense	0	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	53450000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	52255000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	41214000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-11530000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	8220000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	3666000	USD
CY2020	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	25212000	USD
CY2019	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	10978000	USD
CY2018	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	6542000	USD
CY2020	us-gaap	Other Operating Activities Cash Flow Statement OtherOperatingActivitiesCashFlowStatement	288000	USD
CY2019	us-gaap	Other Operating Activities Cash Flow Statement OtherOperatingActivitiesCashFlowStatement	105000	USD
CY2018	us-gaap	Other Operating Activities Cash Flow Statement OtherOperatingActivitiesCashFlowStatement	73000	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	36118000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	5014000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	27819000	USD
CY2020	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	-1936000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	14244000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	1651000	USD
CY2020	csgp	Increase Decrease Deferred Commissions IncreaseDecreaseDeferredCommissions	-64355000	USD
CY2019	csgp	Increase Decrease Deferred Commissions IncreaseDecreaseDeferredCommissions	-66688000	USD
CY2018	csgp	Increase Decrease Deferred Commissions IncreaseDecreaseDeferredCommissions	-53497000	USD
CY2020	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	100846000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	17751000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-14132000	USD
CY2020	csgp	Increase Decrease In Lease Liability IncreaseDecreaseInLeaseLiability	-30497000	USD
CY2019	csgp	Increase Decrease In Lease Liability IncreaseDecreaseInLeaseLiability	-25442000	USD
CY2018	csgp	Increase Decrease In Lease Liability IncreaseDecreaseInLeaseLiability	0	USD
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	10352000	USD
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-577000	USD
CY2018	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	9632000	USD
CY2020	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	2188000	USD
CY2019	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	7911000	USD
CY2018	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	7879000	USD
CY2020	csgp	Increase Decrease Lease Rightof Useand Other Assets IncreaseDecreaseLeaseRightofUseandOtherAssets	1762000	USD
CY2019	csgp	Increase Decrease Lease Rightof Useand Other Assets IncreaseDecreaseLeaseRightofUseandOtherAssets	-648000	USD
CY2018	csgp	Increase Decrease Lease Rightof Useand Other Assets IncreaseDecreaseLeaseRightofUseandOtherAssets	-1715000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	486106000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	457780000	USD
CY2020	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	48347000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	335458000	USD
CY2020	us-gaap	Proceeds From Sale Maturity And Collections Of Investments ProceedsFromSaleMaturityAndCollectionsOfInvestments	10259000	USD
CY2019	us-gaap	Proceeds From Sale Maturity And Collections Of Investments ProceedsFromSaleMaturityAndCollectionsOfInvestments	0	USD
CY2018	us-gaap	Proceeds From Sale Maturity And Collections Of Investments ProceedsFromSaleMaturityAndCollectionsOfInvestments	0	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	46197000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	29632000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	426075000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	437556000	USD
CY2018	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	418369000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-464163000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-483753000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-448001000	USD
CY2020	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	1744210000	USD
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2018	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	27577000	USD
CY2018	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2020	csgp	Proceeds From Exercise Of Stock Options And Espp ProceedsFromExerciseOfStockOptionsAndEspp	30280000	USD
CY2019	csgp	Proceeds From Exercise Of Stock Options And Espp ProceedsFromExerciseOfStockOptionsAndEspp	25080000	USD
CY2020	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	745000000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2020	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	16647000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	38867000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	24327000	USD
CY2020	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	1689971000	USD
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2018	csgp	Proceeds From Exercise Of Stock Options And Espp ProceedsFromExerciseOfStockOptionsAndEspp	27071000	USD
CY2020	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1650000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1100416000	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1657000	USD
CY2018	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	0	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2662297000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-4154000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2744000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	941000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	442000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-1248000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	2685181000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-29685000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-111047000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1070731000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1100416000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1211463000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	3755912000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1070731000	USD
CY2020	csgp	Other Significant Noncash Transaction Amounts Owedfor Acquisitions OtherSignificantNoncashTransactionAmountsOwedforAcquisitions	793000	USD
CY2019	csgp	Other Significant Noncash Transaction Amounts Owedfor Acquisitions OtherSignificantNoncashTransactionAmountsOwedforAcquisitions	1650000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	5948000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	1998000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	1421000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	45783000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	68935000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	35980000	USD
CY2020	us-gaap	Other Significant Noncash Transaction Value Of Consideration Given1 OtherSignificantNoncashTransactionValueOfConsiderationGiven1	0	USD
CY2019	us-gaap	Other Significant Noncash Transaction Value Of Consideration Given1 OtherSignificantNoncashTransactionValueOfConsiderationGiven1	0	USD
CY2018	us-gaap	Other Significant Noncash Transaction Value Of Consideration Given1 OtherSignificantNoncashTransactionValueOfConsiderationGiven1	36366000	USD
CY2018	csgp	Other Significant Noncash Transaction Amounts Owedfor Acquisitions OtherSignificantNoncashTransactionAmountsOwedforAcquisitions	1534000	USD
CY2020	us-gaap	Nature Of Operations NatureOfOperations	ORGANIZATION <div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">CoStar Group, Inc. (the “Company” or “CoStar”) provides information, analytics and online marketplace services to the commercial real estate and related business community through its comprehensive, proprietary database of commercial real estate information. The Company provides online marketplaces for commercial real estate, apartment rentals, lands for-sale and businesses for-sale, and its services are typically distributed to its clients under subscription-based license agreements that renew automatically, a majority of which have a term of at least one year. The Company operates within two operating segments, North America, which includes the United States (“U.S.”) and Canada, and International, which primarily includes Europe, Asia-Pacific and Latin America. </span></div><div style="text-align:justify;text-indent:18pt"><span><br/></span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On October 22, 2019, the Company acquired STR, Inc. and STR Global, Ltd. (together with STR, Inc., referred to as "STR"). STR provides benchmarking and analytics for the hospitality industry. 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. See Notes 5 and 9 to the accompanying Notes to the Consolidated Financial Statements for further discussion of these acquisitions.</span></div>
CY2020	csgp	Subscription Based Licensing Agreement Minimum Term Years SubscriptionBasedLicensingAgreementMinimumTermYears	P1Y
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	operating_segments
CY2020	us-gaap	Use Of Estimates UseOfEstimates	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 doubtful accounts, the useful lives and recoverability of long-lived and intangible assets, and goodwill; income taxes, accounting for business combinations, stock-based compensation, estimating the Company's incremental borrowing rate for its leases, and contingencies, among others. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that it believes are reasonable, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses. Actual results could differ from these estimates.
CY2020	csgp	Subscription Based Licensing Agreement Minimum Term Years SubscriptionBasedLicensingAgreementMinimumTermYears	P1Y
CY2020	csgp	Deferred Sales Commission Amortization Period DeferredSalesCommissionAmortizationPeriod	P3Y
CY2020	csgp	Deferred Sales Commission Amortization Period DeferredSalesCommissionAmortizationPeriod	P3Y
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	200000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	600000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	100000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-889000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-7855000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	0	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-730000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-889000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-8585000	USD
CY2020	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-500000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	0	USD
CY2020	us-gaap	Advertising Expense AdvertisingExpense	270000000	USD
CY2019	us-gaap	Advertising Expense AdvertisingExpense	168000000	USD
CY2018	us-gaap	Advertising Expense AdvertisingExpense	125000000	USD
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	54104000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	52255000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	42718000	USD
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Compensation Cost1 SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1	700000	USD
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Compensation Cost1 SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1	1500000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	3693813000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1070731000	USD
CY2020Q4	us-gaap	Restricted Cash RestrictedCash	62099000	USD
CY2019Q4	us-gaap	Restricted Cash RestrictedCash	0	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	3755912000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1070731000	USD
CY2020	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	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.
CY2020Q4	csgp	Number Of Portfolio Segments NumberOfPortfolioSegments	4	portfolioSegment
CY2020Q4	csgp	Number Of Classes Of Trade Receivables Based On Location NumberOfClassesOfTradeReceivablesBasedOnLocation	2	numberOfReceivable
CY2020Q4	csgp	Number Of Trade Receivables In Information Services Portfolio NumberOfTradeReceivablesInInformationServicesPortfolio	4	numberOfReceivable
CY2020Q4	csgp	Number Of Trade Receivables In Multifamily Portfolio NumberOfTradeReceivablesInMultifamilyPortfolio	1	numberOfReceivable
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1659019000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1399719000	USD
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	70620000	USD
CY2020	csgp	Contractwith Customer Liability Prior Period Amounts Recognized ContractwithCustomerLiabilityPriorPeriodAmountsRecognized	66140000	USD
CY2020	csgp	Contractwith Customer Liability New Deferrals Netof Amounts Recognizedin Current Period ContractwithCustomerLiabilityNewDeferralsNetofAmountsRecognizedinCurrentPeriod	72328000	USD
CY2020	csgp	Contractwith Customer Asset Effectsof Currency Translation ContractwithCustomerAssetEffectsofCurrencyTranslation	555000	USD
CY2020Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	77363000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	74900000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	2500000	USD
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deferred Tax Liabilities BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities	4000000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Gross ContractWithCustomerAssetGross	9000000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Gross ContractWithCustomerAssetGross	4000000	USD
CY2020	csgp	Contractwith Customer Asset Revenue Recognized ContractwithCustomerAssetRevenueRecognized	5000000	USD
CY2020	csgp	Commissions Incurred CommissionsIncurred	97183000	USD
CY2019	csgp	Commissions Incurred CommissionsIncurred	87043000	USD
CY2020	csgp	Commissions Capitalizedinthe Current Period CommissionsCapitalizedintheCurrentPeriod	64355000	USD
CY2019	csgp	Commissions Capitalizedinthe Current Period CommissionsCapitalizedintheCurrentPeriod	66688000	USD
CY2020	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	60516000	USD
CY2019	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	53421000	USD
CY2020	us-gaap	Sales Commissions And Fees SalesCommissionsAndFees	93344000	USD
CY2019	us-gaap	Sales Commissions And Fees SalesCommissionsAndFees	73776000	USD
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	268000000	USD
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P5Y
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	4548000	USD
CY2020	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	25212000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	14650000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	15110000	USD
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deferred Tax Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets	7502000	USD
CY2020	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1719552000	USD
CY2019	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1534452000	USD
CY2018	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1264696000	USD
CY2020	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	216245000	USD
CY2019	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	265843000	USD
CY2018	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	223830000	USD
CY2020	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	5.68
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	7.32
CY2018	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	6.21
CY2020	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	5.64
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	7.26
CY2018	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	6.14
CY2020	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	10300000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	587561000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	0	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	730000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	586831000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	32835000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	27593000	USD
CY2018	us-gaap	Operating Lease Cost OperatingLeaseCost	28118000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	148975000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	165542000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	10998000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	15719000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	137977000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	149823000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	32648000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	29670000	USD
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	105329000	USD
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	120153000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P4Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P5Y
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.036
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.040
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	22629000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	37006000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	30287000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	19746000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	292478000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	243290000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	166153000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	135761000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	126325000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	107529000	USD
CY2020	us-gaap	Depreciation Depreciation	29000000	USD
CY2019	us-gaap	Depreciation Depreciation	26000000	USD
CY2018	us-gaap	Depreciation Depreciation	26000000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	1611535000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	267804000	USD
CY2019	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	2681000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	1882020000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	348407000	USD
CY2020	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	5572000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	2235999000	USD
CY2018	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	426745000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	421196000	USD
CY2020	us-gaap	Adjustment For Amortization AdjustmentForAmortization	88000000	USD
CY2019	us-gaap	Adjustment For Amortization AdjustmentForAmortization	55000000	USD
CY2018	us-gaap	Adjustment For Amortization AdjustmentForAmortization	52000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	89000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	70000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	58000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	48000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	39000000	USD
CY2019	us-gaap	Impairment Of Intangible Assets Excluding Goodwill ImpairmentOfIntangibleAssetsExcludingGoodwill	0	USD
CY2020	us-gaap	Impairment Of Intangible Assets Excluding Goodwill ImpairmentOfIntangibleAssetsExcludingGoodwill	0	USD
CY2018	us-gaap	Impairment Of Intangible Assets Excluding Goodwill ImpairmentOfIntangibleAssetsExcludingGoodwill	0	USD
CY2020Q4	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	1000000000	USD
CY2019Q4	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	0	USD
CY2020Q4	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	13285000	USD
CY2019Q4	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet		USD
CY2020Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	986715000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	0	USD
CY2020	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	1658000	USD
CY2019	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	874000	USD
CY2018	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	950000	USD
CY2020	us-gaap	Line Of Credit Facility Commitment Fee Amount LineOfCreditFacilityCommitmentFeeAmount	1627000	USD
CY2019	us-gaap	Line Of Credit Facility Commitment Fee Amount LineOfCreditFacilityCommitmentFeeAmount	1741000	USD
CY2018	us-gaap	Line Of Credit Facility Commitment Fee Amount LineOfCreditFacilityCommitmentFeeAmount	1880000	USD
CY2020	us-gaap	Interest Expense Debt InterestExpenseDebt	21794000	USD
CY2019	us-gaap	Interest Expense Debt InterestExpenseDebt	2615000	USD
CY2018	us-gaap	Interest Expense Debt InterestExpenseDebt	2830000	USD
CY2020Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	4900000	USD
CY2019Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	2500000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	43461000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	53039000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	36167000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	11726000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	13422000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	6881000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	5140000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	195000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	1305000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	708000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	55382000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	67766000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	42015000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-9599000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	6576000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-926000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	2424000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-2582000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-1005000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-1085000	USD
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-328000	USD
CY2020	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	-11530000	USD
CY2019	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	8220000	USD
CY2018	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	3666000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	4934000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	4297000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	15289000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	43852000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	3698000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	1312000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	13877000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	38498000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	20555000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves	5900000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves	4177000	USD
CY2020Q4	csgp	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	34758000	USD
CY2019Q4	csgp	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	36472000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	6059000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	6341000	USD
CY2020Q4	csgp	Deferred Tax Assets Accrued Transaction Fees DeferredTaxAssetsAccruedTransactionFees	13334000	USD
CY2019Q4	csgp	Deferred Tax Assets Accrued Transaction Fees DeferredTaxAssetsAccruedTransactionFees	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	122470000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	87031000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	11170000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	13553000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	111300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	73478000	USD
CY2020Q4	csgp	Deferred Tax Liabilities Accrued Commissions DeferredTaxLiabilitiesAccruedCommissions	23691000	USD
CY2019Q4	csgp	Deferred Tax Liabilities Accrued Commissions DeferredTaxLiabilitiesAccruedCommissions	22612000	USD
CY2020Q4	csgp	Deferred Tax Liabilities Lease Rightof Use Assets DeferredTaxLiabilitiesLeaseRightofUseAssets	27168000	USD
CY2019Q4	csgp	Deferred Tax Liabilities Lease Rightof Use Assets DeferredTaxLiabilitiesLeaseRightofUseAssets	30830000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	2384000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	1548000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	13078000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	179308000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	155166000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	8891000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	112987000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	91285000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	68008000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	81688000	USD
CY2020	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-2400000	USD
CY2019	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-700000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	291000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	403000000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	294000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	20000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	12000000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	10000000	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	56906000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	82099000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	59643000	USD
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	11409000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	14884000	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	10312000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-4848000	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-693000	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	1214000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	14322000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	12188000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	15373000	USD
CY2020	csgp	Effective Income Tax Rate Reconciliation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationExcessTaxBenefitAmount	21038000	USD
CY2019	csgp	Effective Income Tax Rate Reconciliation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationExcessTaxBenefitAmount	15282000	USD
CY2018	csgp	Effective Income Tax Rate Reconciliation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationExcessTaxBenefitAmount	14227000	USD
CY2020	csgp	Effective Income Tax Rate Reconciliation Change In Tax Reserves Amount EffectiveIncomeTaxRateReconciliationChangeInTaxReservesAmount	4762000	USD
CY2019	csgp	Effective Income Tax Rate Reconciliation Change In Tax Reserves Amount EffectiveIncomeTaxRateReconciliationChangeInTaxReservesAmount	3135000	USD
CY2018	csgp	Effective Income Tax Rate Reconciliation Change In Tax Reserves Amount EffectiveIncomeTaxRateReconciliationChangeInTaxReservesAmount	1870000	USD
CY2020	csgp	Effective Income Tax Rate Reconciliation Nondeductible Expense Compensation Amount EffectiveIncomeTaxRateReconciliationNondeductibleExpenseCompensationAmount	5949000	USD
CY2019	csgp	Effective Income Tax Rate Reconciliation Nondeductible Expense Compensation Amount EffectiveIncomeTaxRateReconciliationNondeductibleExpenseCompensationAmount	1777000	USD
CY2018	csgp	Effective Income Tax Rate Reconciliation Nondeductible Expense Compensation Amount EffectiveIncomeTaxRateReconciliationNondeductibleExpenseCompensationAmount	949000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	5034000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	2254000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	1293000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	43852000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2020Q4	csgp	Realized Tax Benefits Related To Operating Loss Carryforward RealizedTaxBenefitsRelatedToOperatingLossCarryforward	5000000	USD
CY2019Q4	csgp	Realized Tax Benefits Related To Operating Loss Carryforward RealizedTaxBenefitsRelatedToOperatingLossCarryforward	6000000	USD
CY2018Q4	csgp	Realized Tax Benefits Related To Operating Loss Carryforward RealizedTaxBenefitsRelatedToOperatingLossCarryforward	6000000	USD
CY2016Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	14363000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	9561000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	70000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	1482000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	22372000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3487000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	440000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	832000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25467000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	4213000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	452000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	1259000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	28873000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	29000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	600000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	25000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	400000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	200000	USD
CY2018	csgp	Income Tax Penaltiesand Interest Expense Reversal IncomeTaxPenaltiesandInterestExpenseReversal	200000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	1000000.0	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	400000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	37013000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments Year One LongTermDebtMaturityInterestPaymentsYearOne	29089000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	35257000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	0	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments Year Two LongTermDebtMaturityInterestPaymentsYearTwo	28000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	34470000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	0	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments Year Three LongTermDebtMaturityInterestPaymentsYearThree	28000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	28343000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments Year Four LongTermDebtMaturityInterestPaymentsYearFour	28000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	10544000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	0	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments Year Five LongTermDebtMaturityInterestPaymentsYearFive	28000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	3348000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	1000000000	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments After Year Five LongTermDebtMaturityInterestPaymentsAfterYearFive	140000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	148975000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	1000000000	USD
CY2020Q4	csgp	Long Term Debt Maturity Interest Payments LongTermDebtMaturityInterestPayments	281089000	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	operating_segments
CY2020	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	406146000	USD
CY2020	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	406146000	USD
CY2019	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	444712000	USD
CY2018	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	351307000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2020	csgp	Amortization Of Intangible Assets Costof Revenue AmortizationOfIntangibleAssetsCostofRevenue	25675000	USD
CY2019	csgp	Amortization Of Intangible Assets Costof Revenue AmortizationOfIntangibleAssetsCostofRevenue	21357000	USD
CY2018	csgp	Amortization Of Intangible Assets Costof Revenue AmortizationOfIntangibleAssetsCostofRevenue	20586000	USD
CY2020	csgp	Amortization Of Intangible Assets Net Of Adjustments AmortizationOfIntangibleAssetsNetOfAdjustments	62457000	USD
CY2019	csgp	Amortization Of Intangible Assets Net Of Adjustments AmortizationOfIntangibleAssetsNetOfAdjustments	33995000	USD
CY2018	csgp	Amortization Of Intangible Assets Net Of Adjustments AmortizationOfIntangibleAssetsNetOfAdjustments	30881000	USD
CY2020	us-gaap	Other Depreciation And Amortization OtherDepreciationAndAmortization	28812000	USD
CY2019	us-gaap	Other Depreciation And Amortization OtherDepreciationAndAmortization	25813000	USD
CY2018	us-gaap	Other Depreciation And Amortization OtherDepreciationAndAmortization	26276000	USD
CY2020	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	-17395000	USD
CY2019	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	16742000	USD
CY2018	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	10539000	USD
CY2020	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	827000	USD
CY2019	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-10660000	USD
CY2018	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	88000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	43852000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2020	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	406146000	USD
CY2020	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	406146000	USD
CY2019	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	444712000	USD
CY2018	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	351307000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	126325000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	107529000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	2235999000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	1882020000	USD
CY2020Q4	us-gaap	Assets Assets	6915420000	USD
CY2019Q4	us-gaap	Assets Assets	3853986000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	1540061000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	448393000	USD
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	60000000	shares
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2020	us-gaap	Net Income Loss NetIncomeLoss	227128000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	38073000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	36310000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	36058000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	253000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	320000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	390000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	38326000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	38326000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	36630000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	36448000	shares
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.97
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	8.67
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.61
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.93
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	8.60
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.54
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	54000	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	42000	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	100000	shares
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	20000000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	17000000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	17000000	USD
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	156.24
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	63861000	USD
CY2018	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	342.13
CY2018	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	125.16
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	261.20
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	212.28
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	43418000	USD
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	398.15
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	159.52
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	267.23
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	91262000	USD
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	666.52
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	229.46
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	443.05
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	341.78
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	117846000	USD
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	165.31
CY2018Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	31895000	USD
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	210.96
CY2019Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	57180000	USD
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	246.76
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	83204000	USD
CY2020Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Outstanding Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions	202310	shares
CY2020Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Outstanding Options Weighted Average Exercise Price Beginning Balance1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1	341.78
CY2020Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Exercisable Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions	122806	shares
CY2020Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options Weighted Average Exercise Price1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1	246.76
CY2019	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	1
CY2020	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	1
CY2018	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	1
CY2019	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Percent DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent	0.04
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	12000000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	12000000	USD
CY2018	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Percent DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent	0.04
CY2020	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Percent DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent	0.04
CY2020	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	15000000	USD
CY2020	us-gaap	Defined Contribution Plan Administrative Expenses DefinedContributionPlanAdministrativeExpenses	0	USD
CY2019	us-gaap	Defined Contribution Plan Administrative Expenses DefinedContributionPlanAdministrativeExpenses	0	USD
CY2018	us-gaap	Defined Contribution Plan Administrative Expenses DefinedContributionPlanAdministrativeExpenses	0	USD
CY2020Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	391847000	USD
CY2020Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	397159000	USD
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	425620000	USD
CY2020Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	444393000	USD
CY2020Q1	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	78909000	USD
CY2020Q2	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	74040000	USD
CY2020Q3	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	77865000	USD
CY2020Q4	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	78154000	USD
CY2020Q1	us-gaap	Gross Profit GrossProfit	312938000	USD
CY2020Q2	us-gaap	Gross Profit GrossProfit	323119000	USD
CY2020Q3	us-gaap	Gross Profit GrossProfit	347755000	USD
CY2020Q4	us-gaap	Gross Profit GrossProfit	366239000	USD
CY2020Q1	us-gaap	Operating Expenses OperatingExpenses	237074000	USD
CY2020Q2	us-gaap	Operating Expenses OperatingExpenses	241800000	USD
CY2020Q3	us-gaap	Operating Expenses OperatingExpenses	270946000	USD
CY2020Q4	us-gaap	Operating Expenses OperatingExpenses	311029000	USD
CY2020Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	75864000	USD
CY2020Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	81319000	USD
CY2020Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	76809000	USD
CY2020Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	55210000	USD
CY2020Q1	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	1651000	USD
CY2020Q2	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	-3596000	USD
CY2020Q3	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	-7537000	USD
CY2020Q4	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	-7913000	USD
CY2020Q1	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-841000	USD
CY2020Q2	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	474000	USD
CY2020Q3	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	338000	USD
CY2020Q4	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	856000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	78356000	USD
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	77249000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	68934000	USD
CY2020Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	46441000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	5563000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16889000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10748000	USD
CY2020Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10652000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	72793000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	60360000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	58186000	USD
CY2020Q4	us-gaap	Net Income Loss NetIncomeLoss	35789000	USD
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.00
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.61
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.49
CY2020Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.91
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.98
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.60
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.48
CY2020Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.91
CY2019Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	328425000	USD
CY2019Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	343760000	USD
CY2019Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	352808000	USD
CY2019Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	374726000	USD
CY2019Q1	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	71153000	USD
CY2019Q2	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	71918000	USD
CY2019Q3	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	71172000	USD
CY2019Q4	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	74996000	USD
CY2019Q1	us-gaap	Gross Profit GrossProfit	257272000	USD
CY2019Q2	us-gaap	Gross Profit GrossProfit	271842000	USD
CY2019Q3	us-gaap	Gross Profit GrossProfit	281636000	USD
CY2019Q4	us-gaap	Gross Profit GrossProfit	299730000	USD
CY2019Q1	us-gaap	Operating Expenses OperatingExpenses	163780000	USD
CY2019Q2	us-gaap	Operating Expenses OperatingExpenses	197042000	USD
CY2019Q3	us-gaap	Operating Expenses OperatingExpenses	187367000	USD
CY2019Q4	us-gaap	Operating Expenses OperatingExpenses	198744000	USD
CY2019Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	93492000	USD
CY2019Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	74800000	USD
CY2019Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	94269000	USD
CY2019Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	100986000	USD
CY2019Q1	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	4212000	USD
CY2019Q2	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	4677000	USD
CY2019Q3	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	4414000	USD
CY2019Q4	csgp	Interest And Other Income Net InterestAndOtherIncomeNet	3439000	USD
CY2019Q1	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-1000	USD
CY2019Q2	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-539000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	98923000	USD
CY2019Q3	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-240000	USD
CY2019Q4	csgp	Interest And Other Expense Net InterestAndOtherExpenseNet	-9880000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	97705000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	80016000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	114305000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12536000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16768000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	20304000	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26378000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	85169000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	63248000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	78619000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	87927000	USD
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.35
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.74
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.16
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.15
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.39
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.42
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.33
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.73

Files In Submission

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0001057352-21-000032-index-headers.html	Edgar Link	pending
0001057352-21-000032-index.html	Edgar Link	pending
0001057352-21-000032.txt	Edgar Link	pending
0001057352-21-000032-xbrl.zip	Edgar Link	pending
csgp-20201231.htm	Edgar Link	pending
csgp-20201231.xsd	Edgar Link	pending
csgp-20201231_cal.xml	Edgar Link	unprocessable
csgp-20201231_def.xml	Edgar Link	unprocessable
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csgp-20201231_htm.xml	Edgar Link	completed
csgp-20201231_lab.xml	Edgar Link	unprocessable
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Financial_Report.xlsx	Edgar Link	pending
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$CSGP
COSTAR GROUP, INC. Stock $csgp

2020 Q4 Form 10-K Financial Statement

#000105735221000032 Filed on February 24, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CSGP COSTAR GROUP, INC. Stock $csgp

2020 Q4 Form 10-K Financial Statement

#000105735221000032 Filed on February 24, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CSGP
COSTAR GROUP, INC. Stock $csgp