$CSGP
COSTAR GROUP, INC. Stock $csgp

$csgp Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000105735220000036 Filed on February 26, 2020

Income Statement

Concept	2019 Q4	2019 Q3	2019 Q2
Revenue	$374.7M	$352.8M	$343.8M
YoY Change	18.75%	15.48%	15.74%
Cost Of Revenue	$75.00M	$71.17M	$71.92M
YoY Change	9.89%	-1.25%	7.12%
Gross Profit	$299.7M	$281.6M	$271.8M
YoY Change	21.19%	20.64%	18.25%
Gross Profit Margin	79.99%	79.83%	79.08%
Selling, General & Admin	$151.8M	$147.1M	$161.4M
YoY Change	40.3%	14.7%	6.88%
% of Gross Profit	50.65%	52.23%	59.38%
Research & Development	$35.40M	$32.64M	$28.46M
YoY Change	38.28%	24.7%	8.31%
% of Gross Profit	11.81%	11.59%	10.47%
Depreciation & Amortization	$24.00M	$18.80M	$18.70M
YoY Change	21.83%	-7.84%	-9.22%
% of Gross Profit	8.01%	6.68%	6.88%
Operating Expenses	$198.7M	$187.4M	$197.0M
YoY Change	40.29%	15.12%	5.88%
Operating Profit	$101.0M	$94.27M	$74.80M
YoY Change	-4.42%	33.36%	70.88%
Interest Expense	$482.0K	$704.0K	$697.0K
YoY Change	-30.65%	-1.81%	-4.26%
% of Operating Profit	0.48%	0.75%	0.93%
Other Income/Expense, Net	-$300.0K	$240.0K	$538.0K
YoY Change	-57.14%	-20.0%
Pretax Income	$114.3M	$98.92M	$80.02M
YoY Change	4.32%	35.5%	75.1%
Income Tax	$26.38M	$20.30M	$16.77M
% Of Pretax Income	23.08%	20.53%	20.96%
Net Earnings	$87.93M	$72.79M	$63.25M
YoY Change	5.29%	23.88%	44.29%
Net Earnings / Revenue	23.46%	20.63%	18.4%
Basic Earnings Per Share	$2.42	$2.16	$1.74
Diluted Earnings Per Share	$2.39	$2.15	$1.73
COMMON SHARES
Basic Shares Outstanding	36.63M shares	36.33M shares	36.31M shares
Diluted Shares Outstanding		36.65M shares	36.63M shares

Balance Sheet

Concept	2019 Q4	2019 Q3	2019 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$1.071B	$1.390B	$1.298B
YoY Change	-2.7%	29.65%	34.31%
Cash & Equivalents	$1.071B	$1.390B	$1.298B
Short-Term Investments
Other Short-Term Assets	$36.20M	$23.80M	$20.40M
YoY Change	52.74%	-5.56%	-48.61%
Inventory
Prepaid Expenses
Receivables	$92.24M	$91.33M	$95.58M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$1.199B	$1.505B	$1.414B
YoY Change	-1.16%	27.6%	31.39%
LONG-TERM ASSETS
Property, Plant & Equipment	$107.5M	$108.0M	$84.52M
YoY Change	29.08%	31.8%	-0.15%
Goodwill	$1.882B	$1.617B	$1.618B
YoY Change	16.78%	4.36%	4.41%
Intangibles	$421.2M	$259.4M	$272.2M
YoY Change	45.79%	-9.27%	-9.16%
Long-Term Investments	$10.10M	$10.10M	$10.10M
YoY Change	0.0%	0.0%	0.0%
Other Assets	$104.0M	$96.20M	$96.30M
YoY Change	14.41%	11.73%	9.56%
Total Long-Term Assets	$2.655B	$2.211B	$2.207B
YoY Change	26.44%	9.01%	7.83%
TOTAL ASSETS
Total Short-Term Assets	$1.199B	$1.505B	$1.414B
Total Long-Term Assets	$2.655B	$2.211B	$2.207B
Total Assets	$3.854B	$3.715B	$3.621B
YoY Change	16.33%	15.84%	15.95%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$7.640M	$8.082M	$6.996M
YoY Change	20.75%	-20.09%	-25.53%
Accrued Expenses	$38.68M	$41.82M	$48.93M
YoY Change	29.71%	24.82%	31.03%
Deferred Revenue	$67.27M	$60.00M	$58.00M
YoY Change	30.73%	19.53%	25.16%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$207.1M	$198.0M	$197.3M
YoY Change	34.31%	29.04%	35.18%
LONG-TERM LIABILITIES
Long-Term Debt	$0.00	$0.00	$0.00
YoY Change
Other Long-Term Liabilities	$154.2M	$135.1M	$141.8M
YoY Change	130.15%	122.94%	124.37%
Total Long-Term Liabilities	$0.00	$135.1M	$141.8M
YoY Change	-100.0%	122.94%	124.37%
TOTAL LIABILITIES
Total Short-Term Liabilities	$207.1M	$198.0M	$197.3M
Total Long-Term Liabilities	$0.00	$135.1M	$141.8M
Total Liabilities	$448.4M	$416.2M	$416.5M
YoY Change	54.08%	49.23%	53.16%
SHAREHOLDERS EQUITY
Retained Earnings	$940.5M
YoY Change	53.31%
Common Stock	$366.0K
YoY Change	0.55%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$3.406B	$3.299B	$3.204B
YoY Change
Total Liabilities & Shareholders Equity	$3.854B	$3.715B	$3.621B
YoY Change	16.33%	15.84%	15.95%

Cashflow Statement

Concept	2019 Q4	2019 Q3	2019 Q2
OPERATING ACTIVITIES
Net Income	$87.93M	$72.79M	$63.25M
YoY Change	5.29%	23.88%	44.29%
Depreciation, Depletion And Amortization	$24.00M	$18.80M	$18.70M
YoY Change	21.83%	-7.84%	-9.22%
Cash From Operating Activities	$107.8M	$116.4M	$85.10M
YoY Change	-6.1%	14.79%	83.8%
INVESTING ACTIVITIES
Capital Expenditures	-$2.000M	-$29.80M	-$5.000M
YoY Change	-74.36%	405.08%	-31.51%
Acquisitions
YoY Change
Other Investing Activities	-$423.9M	$0.00	-$13.70M
YoY Change	441.38%
Cash From Investing Activities	-$425.9M	-$29.80M	-$18.70M
YoY Change	394.66%	396.67%	159.72%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-2.000M	5.500M	-1.100M
YoY Change	-433.33%	-46.6%	-67.65%
NET CHANGE
Cash From Operating Activities	107.8M	116.4M	85.10M
Cash From Investing Activities	-425.9M	-29.80M	-18.70M
Cash From Financing Activities	-2.000M	5.500M	-1.100M
Net Change In Cash	-320.1M	92.10M	65.30M
YoY Change	-1192.49%	-12.87%	82.91%
FREE CASH FLOW
Cash From Operating Activities	$107.8M	$116.4M	$85.10M
Capital Expenditures	-$2.000M	-$29.80M	-$5.000M
Free Cash Flow	$109.8M	$146.2M	$90.10M
YoY Change	-10.44%	36.25%	68.1%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2019	dei	Amendment Flag AmendmentFlag	false
CY2019	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2019	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2019	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
CY2018	us-gaap	Defined Contribution Plan Administrative Expenses DefinedContributionPlanAdministrativeExpenses	0	USD
CY2019	dei	Entity Central Index Key EntityCentralIndexKey	0001057352
CY2019	dei	Entity Registrant Name EntityRegistrantName	COSTAR GROUP INC
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	5709000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	5097000	USD
CY2018Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	60000000	shares
CY2018Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	36446000	shares
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	36668000	shares
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	36446000	shares
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	36668000	shares
CY2017	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0	USD
CY2017	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	0	USD
CY2017	us-gaap	Defined Contribution Plan Administrative Expenses DefinedContributionPlanAdministrativeExpenses	0	USD
CY2017	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Percent DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent	0.0400
CY2018	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Percent DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent	0.0400
CY2017	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	0	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	0	USD
CY2017	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2018	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2017	us-gaap	Impairment Of Intangible Assets Excluding Goodwill ImpairmentOfIntangibleAssetsExcludingGoodwill	0	USD
CY2018	us-gaap	Impairment Of Intangible Assets Excluding Goodwill ImpairmentOfIntangibleAssetsExcludingGoodwill	0	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	0	USD
CY2018Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2018Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2018Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2018	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	0	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period1 ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1	P3Y
CY2019	dei	Document Type DocumentType	10-K
CY2019	dei	Document Annual Report DocumentAnnualReport	true
CY2019	dei	Document Period End Date DocumentPeriodEndDate	2019-12-31
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity File Number EntityFileNumber	0-24531
CY2019	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2019	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	52-2091509
CY2019	dei	Entity Address Address Line1 EntityAddressAddressLine1	1331 L Street, NW
CY2019	dei	Entity Address City Or Town EntityAddressCityOrTown	Washington,
CY2019	dei	Entity Address State Or Province EntityAddressStateOrProvince	DC
CY2019	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	20005
CY2019	dei	City Area Code CityAreaCode	202)
CY2019	dei	Local Phone Number LocalPhoneNumber	346-6500
CY2019	dei	Security12b Title Security12bTitle	Common Stock ($0.01 par value)
CY2019	dei	Trading Symbol TradingSymbol	CSGP
CY2019	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2019	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2019	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2019	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2019	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2019	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2019	dei	Entity Small Business EntitySmallBusiness	false
CY2019	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2019	dei	Entity Shell Company EntityShellCompany	false
CY2019Q2	dei	Entity Public Float EntityPublicFloat	20000000000	USD
CY2020Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	36644734	shares
CY2016Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	6344000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	5690000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	5565000	USD
CY2017Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	6469000	USD
CY2017Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	6469000	USD
CY2018	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	6542000	USD
CY2018	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	7302000	USD
CY2018Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	5709000	USD
CY2018Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	5709000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	10978000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	11590000	USD
CY2019Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	5097000	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
CY2017	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	965230000	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
CY2017	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	220403000	USD
CY2019	us-gaap	Gross Profit GrossProfit	1110480000	USD
CY2018	us-gaap	Gross Profit GrossProfit	921899000	USD
CY2017	us-gaap	Gross Profit GrossProfit	744827000	USD
CY2019	us-gaap	Selling And Marketing Expense SellingAndMarketingExpense	408596000	USD
CY2018	us-gaap	Selling And Marketing Expense SellingAndMarketingExpense	359858000	USD
CY2017	us-gaap	Selling And Marketing Expense SellingAndMarketingExpense	318362000	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
CY2017	us-gaap	Research And Development Expense Software Excluding Acquired In Process Cost ResearchAndDevelopmentExpenseSoftwareExcludingAcquiredInProcessCost	88850000	USD
CY2019	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	178740000	USD
CY2018	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	156659000	USD
CY2017	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	146128000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	33995000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	30881000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	17671000	USD
CY2019	us-gaap	Operating Expenses OperatingExpenses	746933000	USD
CY2018	us-gaap	Operating Expenses OperatingExpenses	648335000	USD
CY2017	us-gaap	Operating Expenses OperatingExpenses	571011000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	363547000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	273564000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	173816000	USD
CY2019	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	30017000	USD
CY2018	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	13281000	USD
CY2017	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	4044000	USD
CY2019	us-gaap	Interest Expense InterestExpense	2615000	USD
CY2018	us-gaap	Interest Expense InterestExpense	2830000	USD
CY2017	us-gaap	Interest Expense InterestExpense	9014000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2017	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-3788000	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
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	165058000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	42363000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	122695000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	8.67
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.61
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.70
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	8.60
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.54
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.66
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
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33200000	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
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	33559000	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	122695000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	3103000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-2668000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	3901000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	0	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	118000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	3103000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-2668000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	4019000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	318066000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	235666000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	126714000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1070731000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1100416000	USD
CY2019Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	92240000	USD
CY2018Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	89192000	USD
CY2019Q4	us-gaap	Income Taxes Receivable Noncurrent IncomeTaxesReceivableNoncurrent	14908000	USD
CY2018Q4	us-gaap	Assets Assets	3312957000	USD
CY2019Q4	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	36194000	USD
CY2018Q4	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	23690000	USD
CY2019Q4	us-gaap	Assets Current AssetsCurrent	1199165000	USD
CY2018Q4	us-gaap	Assets Current AssetsCurrent	1213298000	USD
CY2019Q4	us-gaap	Long Term Investments LongTermInvestments	10070000	USD
CY2018Q4	us-gaap	Long Term Investments LongTermInvestments	10070000	USD
CY2019Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	5408000	USD
CY2018Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	7469000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	115084000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	107529000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	83303000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	1882020000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	1611535000	USD
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	421196000	USD
CY2018Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	288911000	USD
CY2019Q4	us-gaap	Deferred Costs DeferredCosts	89374000	USD
CY2018Q4	us-gaap	Deferred Costs DeferredCosts	76031000	USD
CY2019Q4	us-gaap	Deposits Assets Noncurrent DepositsAssetsNoncurrent	9232000	USD
CY2018Q4	us-gaap	Deposits Assets Noncurrent DepositsAssetsNoncurrent	7432000	USD
CY2018Q4	us-gaap	Income Taxes Receivable Noncurrent IncomeTaxesReceivableNoncurrent	14908000	USD
CY2019Q4	us-gaap	Assets Assets	3853986000	USD
CY2019Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	7640000	USD
CY2018Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	6327000	USD
CY2019Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	53087000	USD
CY2018Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	45588000	USD
CY2019Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	38680000	USD
CY2018Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	29821000	USD
CY2019Q4	csgp	Deferredgainonthesaleofbuildingcurrent Deferredgainonthesaleofbuildingcurrent	0	USD
CY2018Q4	csgp	Deferredgainonthesaleofbuildingcurrent Deferredgainonthesaleofbuildingcurrent	2523000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	10705000	USD
CY2018Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	14288000	USD
CY2019Q4	csgp	Deferred Rent Current DeferredRentCurrent	0	USD
CY2018Q4	csgp	Deferred Rent Current DeferredRentCurrent	4153000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	29670000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	67274000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	51459000	USD
CY2019Q4	us-gaap	Liabilities Current LiabilitiesCurrent	207056000	USD
CY2018Q4	us-gaap	Liabilities Current LiabilitiesCurrent	154159000	USD
CY2019Q4	us-gaap	Deferred Gain On Sale Of Property DeferredGainOnSaleOfProperty	0	USD
CY2018Q4	us-gaap	Deferred Gain On Sale Of Property DeferredGainOnSaleOfProperty	13669000	USD
CY2019Q4	csgp	Deferred Rent DeferredRent	0	USD
CY2018Q4	csgp	Deferred Rent DeferredRent	31944000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	87096000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	69857000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Noncurrent AccruedIncomeTaxesNoncurrent	20521000	USD
CY2018Q4	us-gaap	Accrued Income Taxes Noncurrent AccruedIncomeTaxesNoncurrent	17386000	USD
CY2019Q4	us-gaap	Other Long Term Debt Noncurrent OtherLongTermDebtNoncurrent	133720000	USD
CY2018Q4	us-gaap	Other Long Term Debt Noncurrent OtherLongTermDebtNoncurrent	4000000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	448393000	USD
CY2018Q4	us-gaap	Liabilities Liabilities	291015000	USD
CY2019Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2018Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2019Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2018Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	366000	USD
CY2018Q4	us-gaap	Common Stock Value CommonStockValue	364000	USD
CY2019Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	2473338000	USD
CY2018Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	2419812000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-8585000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-11688000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	940474000	USD
CY2018Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	613454000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3405593000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	3021942000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3853986000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3312957000	USD
CY2016Q4	us-gaap	Stockholders Equity StockholdersEquity	1654213000	USD
CY2017Q1	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	2162000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	122695000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	4019000	USD
CY2017	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	6797000	USD
CY2017	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2017	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	14902000	USD
CY2017	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	38921000	USD
CY2017	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	833911000	USD
CY2017	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	3434000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	2651250000	USD
CY2018Q1	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	54464000	USD
CY2018Q1	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1 StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	2705714000	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	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	122695000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	81165000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	77743000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	63643000	USD
CY2019	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	53421000	USD
CY2018	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	24327000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	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 Acquisitions StockIssuedDuringPeriodValueAcquisitions	36366000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	3021942000	USD
CY2019Q1	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	12057000	USD
CY2019Q1	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1 StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	3033999000	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	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	27577000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	51818000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	3491000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	7144000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3405593000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	48313000	USD
CY2017	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	0	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
CY2017	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	2303000	USD
CY2019	csgp	Non Cash Lease Expense NonCashLeaseExpense	22748000	USD
CY2018	csgp	Non Cash Lease Expense NonCashLeaseExpense	0	USD
CY2017	csgp	Non Cash Lease Expense NonCashLeaseExpense	0	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2017	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-3788000	USD
CY2019	us-gaap	Disposal Group Not Discontinued Operation Loss Gain On Write Down DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown	105000	USD
CY2018	us-gaap	Disposal Group Not Discontinued Operation Loss Gain On Write Down DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown	73000	USD
CY2017	us-gaap	Disposal Group Not Discontinued Operation Loss Gain On Write Down DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown	129000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	52255000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	41214000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	39030000	USD
CY2018	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	6542000	USD
CY2017	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	5690000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	5014000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	27819000	USD
CY2017	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	17524000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	14244000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	8220000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	3666000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2903000	USD
CY2019	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	10978000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	1651000	USD
CY2017	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	3672000	USD
CY2018	csgp	Increase Decrease In Lease Liability IncreaseDecreaseInLeaseLiability	0	USD
CY2017	csgp	Increase Decrease In Lease Liability IncreaseDecreaseInLeaseLiability	0	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
CY2019	csgp	Increase Decrease Deferred Commissions IncreaseDecreaseDeferredCommissions	-66688000	USD
CY2018	csgp	Increase Decrease Deferred Commissions IncreaseDecreaseDeferredCommissions	-53497000	USD
CY2017	csgp	Increase Decrease Deferred Commissions IncreaseDecreaseDeferredCommissions	0	USD
CY2019	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	0	USD
CY2018	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	1927000	USD
CY2017	us-gaap	Increase Decrease In Income Taxes Receivable IncreaseDecreaseInIncomeTaxesReceivable	12981000	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
CY2017	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	11525000	USD
CY2019	csgp	Increase Decrease In Lease Liability IncreaseDecreaseInLeaseLiability	-25442000	USD
CY2017	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	16937000	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
CY2017	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	6004000	USD
CY2019	csgp	Increase Decrease Lease Rightof Useand Other Assets IncreaseDecreaseLeaseRightofUseandOtherAssets	-648000	USD
CY2018	csgp	Increase Decrease Lease Rightof Useand Other Assets IncreaseDecreaseLeaseRightofUseandOtherAssets	212000	USD
CY2017	csgp	Increase Decrease Lease Rightof Useand Other Assets IncreaseDecreaseLeaseRightofUseandOtherAssets	39000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	457780000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	335458000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	234703000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	46197000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	29632000	USD
CY2017	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	24499000	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
CY2017	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	47768000	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
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-72267000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2017	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	345000000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
CY2017	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	3467000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	27577000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	24327000	USD
CY2017	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	14902000	USD
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2018	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	833911000	USD
CY2019	csgp	Proceeds From Exercise Of Stock Options And Espp ProceedsFromExerciseOfStockOptionsAndEspp	25080000	USD
CY2018	csgp	Proceeds From Exercise Of Stock Options And Espp ProceedsFromExerciseOfStockOptionsAndEspp	27071000	USD
CY2017	csgp	Proceeds From Exercise Of Stock Options And Espp ProceedsFromExerciseOfStockOptionsAndEspp	9888000	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
CY2017	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	0	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
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	480430000	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
CY2017	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1374000	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
CY2017	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	644240000	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
CY2016Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	567223000	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
CY2019	us-gaap	Interest Paid Net InterestPaidNet	1998000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	1421000	USD
CY2017	us-gaap	Interest Paid Net InterestPaidNet	6445000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	68935000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	35980000	USD
CY2017	us-gaap	Income Taxes Paid IncomeTaxesPaid	41283000	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
CY2017	us-gaap	Other Significant Noncash Transaction Value Of Consideration Given1 OtherSignificantNoncashTransactionValueOfConsiderationGiven1	0	USD
CY2019	csgp	Other Significant Noncash Transaction Amounts Owedfor Acquisitions OtherSignificantNoncashTransactionAmountsOwedforAcquisitions	1650000	USD
CY2018	csgp	Other Significant Noncash Transaction Amounts Owedfor Acquisitions OtherSignificantNoncashTransactionAmountsOwedforAcquisitions	1534000	USD
CY2017	csgp	Other Significant Noncash Transaction Amounts Owedfor Acquisitions OtherSignificantNoncashTransactionAmountsOwedforAcquisitions	0	USD
CY2019	us-gaap	Nature Of Operations NatureOfOperations	<div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">ORGANIZATION</span><span style="font-family:inherit;font-size:10pt;font-weight:bold;"> </span></div><div style="line-height:120%;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">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 </span><span style="font-family:inherit;font-size:10pt;"><span>one year</span></span><span style="font-family:inherit;font-size:10pt;">. The Company operates within </span><span style="font-family:inherit;font-size:10pt;"><span>two</span></span><span style="font-family:inherit;font-size:10pt;"> 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="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">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. See Note 4 to the accompanying Notes to the Consolidated Financial Statements for further discussion of this acquisition.</span></div>
CY2019	csgp	Subscription Based Licensing Agreement Minimum Term Years SubscriptionBasedLicensingAgreementMinimumTermYears	P1Y
CY2019	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	operating_segments
CY2019	us-gaap	Use Of Estimates UseOfEstimates	<div style="line-height:120%;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Use of Estimates</span></div><div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div>The preparation of financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, allowance for doubtful accounts, the useful lives and recoverability of long-lived and intangible assets, and goodwill; income taxes, the fair value of auction rate securities, 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.
CY2019	csgp	Subscription Based Licensing Agreement Minimum Term Years SubscriptionBasedLicensingAgreementMinimumTermYears	P1Y
CY2019	csgp	Deferred Sales Commission Amortization Period DeferredSalesCommissionAmortizationPeriod	P3Y
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	0	USD
CY2019	us-gaap	Advertising Expense AdvertisingExpense	164000000	USD
CY2018	us-gaap	Advertising Expense AdvertisingExpense	124000000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-7855000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-10958000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-730000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-730000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-8585000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-11688000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	0	USD
CY2017	us-gaap	Advertising Expense AdvertisingExpense	104000000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	52255000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	42718000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	39030000	USD
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Compensation Cost1 SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1	1500000	USD
CY2019	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	<div style="line-height:120%;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Concentration of Credit Risk and Financial Instruments</span></div><div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">The Company’s customer base creates a lack of dependence on any individual customer that mitigates the risk of nonpayment of the Company’s accounts receivable. No single customer accounted for more than </span><span style="font-family:inherit;font-size:10pt;">5%</span><span style="font-family:inherit;font-size:10pt;"> of the Company’s revenues for each of the years ended </span><span style="font-family:inherit;font-size:10pt;">December 31, 2019</span><span style="font-family:inherit;font-size:10pt;">, </span><span style="font-family:inherit;font-size:10pt;">2018</span><span style="font-family:inherit;font-size:10pt;">, and </span><span style="font-family:inherit;font-size:10pt;">2017</span><span style="font-family:inherit;font-size:10pt;">. The carrying amount of the accounts receivable approximates the net realizable value. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div>The Company holds cash at major financial institutions that often exceed Federal Deposit Insurance Corporation insured limits. The Company manages its credit risk associated with cash concentrations by concentrating its cash deposits in high quality financial institutions and by periodically evaluating the credit quality of the primary financial institutions holding such deposits. The carrying value of cash approximates fair value. Historically, the Company has not experienced any losses due to such cash concentrations.
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
CY2018Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	51459000	USD
CY2019	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	49937000	USD
CY2019	csgp	Contractwith Customer Liability New Deferrals Netof Amounts Recognizedin Current Period ContractwithCustomerLiabilityNewDeferralsNetofAmountsRecognizedinCurrentPeriod	68814000	USD
CY2019	csgp	Contractwith Customer Asset Effectsof Currency Translation ContractwithCustomerAssetEffectsofCurrencyTranslation	284000	USD
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	70620000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	67000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	3000000	USD
CY2019	csgp	Contractwith Customer Liability New Deferrals Business Acquisition ContractwithCustomerLiabilityNewDeferralsBusinessAcquisition	11000000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Gross ContractWithCustomerAssetGross	4000000	USD
CY2018Q4	us-gaap	Contract With Customer Asset Gross ContractWithCustomerAssetGross	2000000	USD
CY2019	csgp	Commissions Incurred CommissionsIncurred	87043000	USD
CY2018	csgp	Commissions Incurred CommissionsIncurred	72899000	USD
CY2019	csgp	Commissions Capitalizedinthe Current Period CommissionsCapitalizedintheCurrentPeriod	66688000	USD
CY2018	csgp	Commissions Capitalizedinthe Current Period CommissionsCapitalizedintheCurrentPeriod	53497000	USD
CY2019	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	53421000	USD
CY2018	us-gaap	Amortization Of Deferred Sales Commissions AmortizationOfDeferredSalesCommissions	48313000	USD
CY2019	us-gaap	Sales Commissions And Fees SalesCommissionsAndFees	73776000	USD
CY2018	us-gaap	Sales Commissions And Fees SalesCommissionsAndFees	67715000	USD
CY2019Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	257000000	USD
CY2019Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P5Y
CY2019	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1450954000	USD
CY2018	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1264696000	USD
CY2017	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1067742000	USD
CY2019	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	306755000	USD
CY2018	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	226305000	USD
CY2017	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	103000000	USD
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	8.45
CY2018	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	6.28
CY2017	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	3.09
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	8.37
CY2018	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	6.21
CY2017	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	3.06
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	10070000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	10070000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	0	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	10800000	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	10070000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	10800000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	0	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	730000	USD
CY2018Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	10070000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	10070000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	730000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	10070000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	730000	USD
CY2019Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	586831000	USD
CY2018Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	600637000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	27593000	USD
CY2018	us-gaap	Operating Lease Cost OperatingLeaseCost	28118000	USD
CY2017	us-gaap	Operating Lease Cost OperatingLeaseCost	25681000	USD
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	120153000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P5Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.040
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	30287000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	22629000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	34976000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	33760000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	30938000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	29663000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	23972000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	12233000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	165542000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	15719000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	149823000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	243290000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	193094000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	135761000	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	109791000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	107529000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	83303000	USD
CY2019	us-gaap	Depreciation Depreciation	26000000	USD
CY2018	us-gaap	Depreciation Depreciation	26000000	USD
CY2017	us-gaap	Depreciation Depreciation	26000000	USD
CY2017Q4	us-gaap	Goodwill Goodwill	1283457000	USD
CY2018	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	329938000	USD
CY2018	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	-1860000	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
CY2019Q4	us-gaap	Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount	166000000	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	421196000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	288911000	USD
CY2019	us-gaap	Adjustment For Amortization AdjustmentForAmortization	55000000	USD
CY2018	us-gaap	Adjustment For Amortization AdjustmentForAmortization	52000000	USD
CY2017	us-gaap	Adjustment For Amortization AdjustmentForAmortization	37000000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	72000000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	61000000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	51000000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	45000000	USD
CY2019Q4	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
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	0	USD
CY2019	us-gaap	Interest Expense Debt InterestExpenseDebt	3000000	USD
CY2018	us-gaap	Interest Expense Debt InterestExpenseDebt	3000000	USD
CY2017	us-gaap	Interest Expense Debt InterestExpenseDebt	9000000	USD
CY2019	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	900000	USD
CY2018	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	1000000	USD
CY2017	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	2000000	USD
CY2019Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	2000000	USD
CY2018Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	3000000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	41453000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	13422000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	53039000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	36167000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	5140000	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	3518000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	1305000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	708000	USD
CY2017	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	295000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	67766000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	42015000	USD
CY2017	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	45266000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	6881000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	6576000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-7917000	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
CY2017	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	4695000	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
CY2017	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	319000	USD
CY2019	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	8220000	USD
CY2018	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	3666000	USD
CY2017	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	-2903000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	42363000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	1312000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	1457000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	4297000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	4803000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	13877000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	10041000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	20555000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	26349000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves	4177000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsReserves	1773000	USD
CY2019Q4	csgp	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	36472000	USD
CY2018Q4	csgp	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Deferred Rent DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsDeferredRent	0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Deferred Rent DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsDeferredRent	5928000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Deferred Gain On Sale Leaseback Transaction DeferredTaxAssetsDeferredGainOnSaleLeasebackTransaction	0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Deferred Gain On Sale Leaseback Transaction DeferredTaxAssetsDeferredGainOnSaleLeasebackTransaction	4140000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	6341000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	6331000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	87031000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	60822000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	13553000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	14246000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	73478000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	46576000	USD
CY2019Q4	csgp	Deferred Tax Liabilities Accrued Commissions DeferredTaxLiabilitiesAccruedCommissions	22612000	USD
CY2018Q4	csgp	Deferred Tax Liabilities Accrued Commissions DeferredTaxLiabilitiesAccruedCommissions	19314000	USD
CY2019Q4	csgp	Deferred Tax Liabilities Lease Rightof Use Assets DeferredTaxLiabilitiesLeaseRightofUseAssets	30830000	USD
CY2018Q4	csgp	Deferred Tax Liabilities Lease Rightof Use Assets DeferredTaxLiabilitiesLeaseRightofUseAssets	0	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	1548000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Prepaid Expenses DeferredTaxLiabilitiesPrepaidExpenses	2204000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	8891000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	5367000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	91285000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	82079000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	155166000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	108964000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	81688000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	62388000	USD
CY2019	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-700000	USD
CY2018	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	1000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Foreign DeferredTaxAssetsOperatingLossCarryforwardsForeign	1100000	USD
CY2018	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	1000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	403000000	USD
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	1984000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	294000000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	167000000	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
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	2000000	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
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	57770000	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
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	4776000	USD
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	1515000	USD
CY2018	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-315000	USD
CY2017	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-3540000	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
CY2017	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	3624000	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-13000	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	141000	USD
CY2017	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-7340000	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
CY2017	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	20547000	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
CY2017	csgp	Effective Income Tax Rate Reconciliation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationExcessTaxBenefitAmount	7010000	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
CY2017	csgp	Effective Income Tax Rate Reconciliation Change In Tax Reserves Amount EffectiveIncomeTaxRateReconciliationChangeInTaxReservesAmount	12646000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	2529000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	2416000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	42363000	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
CY2017Q4	csgp	Realized Tax Benefits Related To Operating Loss Carryforward RealizedTaxBenefitsRelatedToOperatingLossCarryforward	7000000	USD
CY2016Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1843000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	12620000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	34000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	66000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	14363000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	9561000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	70000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	1482000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	22372000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3487000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	440000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	832000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25467000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	25000000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	22000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	200000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	200000	USD
CY2017	csgp	Income Tax Penaltiesand Interest Expense Reversal IncomeTaxPenaltiesandInterestExpenseReversal	100000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	600000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	400000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	200000	USD
CY2019	us-gaap	Proceeds From Legal Settlements ProceedsFromLegalSettlements	11000000	USD
CY2019	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	operating_segments
CY2019	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	444712000	USD
CY2018	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	351307000	USD
CY2017	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	237459000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	122695000	USD
CY2019	csgp	Amortization Of Intangible Assets Costof Revenue AmortizationOfIntangibleAssetsCostofRevenue	21357000	USD
CY2018	csgp	Amortization Of Intangible Assets Costof Revenue AmortizationOfIntangibleAssetsCostofRevenue	20586000	USD
CY2017	csgp	Amortization Of Intangible Assets Costof Revenue AmortizationOfIntangibleAssetsCostofRevenue	19707000	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
CY2017	csgp	Amortization Of Intangible Assets Net Of Adjustments AmortizationOfIntangibleAssetsNetOfAdjustments	17684000	USD
CY2019	us-gaap	Other Depreciation And Amortization OtherDepreciationAndAmortization	25813000	USD
CY2018	us-gaap	Other Depreciation And Amortization OtherDepreciationAndAmortization	26276000	USD
CY2017	us-gaap	Other Depreciation And Amortization OtherDepreciationAndAmortization	26252000	USD
CY2019	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	30017000	USD
CY2018	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	13281000	USD
CY2017	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	4044000	USD
CY2019	us-gaap	Interest Expense InterestExpense	2615000	USD
CY2018	us-gaap	Interest Expense InterestExpense	2830000	USD
CY2017	us-gaap	Interest Expense InterestExpense	9014000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2017	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-3788000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	75986000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	45681000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	42363000	USD
CY2019	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	444712000	USD
CY2018	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	351307000	USD
CY2017	csgp	Netincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortization Ebitda NetincomelossbeforeinterestandotherincomeexpenseincometaxesdepreciationandamortizationEBITDA	237459000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	107529000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	83303000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	1882020000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	1611535000	USD
CY2019Q4	us-gaap	Assets Assets	3853986000	USD
CY2018Q4	us-gaap	Assets Assets	3312957000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	448393000	USD
CY2018Q4	us-gaap	Liabilities Liabilities	291015000	USD
CY2019Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	2000000	shares
CY2019Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	60000000	shares
CY2019Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2017Q4	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	3300000	shares
CY2017Q4	us-gaap	Shares Issued Price Per Share SharesIssuedPricePerShare	260
CY2017Q4	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	834000000	USD
CY2017Q4	us-gaap	Payments For Underwriting Expense PaymentsForUnderwritingExpense	29000000	USD
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	390000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	36058000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33200000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	320000	shares
CY2018	us-gaap	Net Income Loss NetIncomeLoss	238334000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	122695000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	36310000	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	314963000	USD
CY2017	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	359000	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
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	33559000	shares
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	8.67
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.61
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.70
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	8.60
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.54
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.66
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
CY2017	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	126000	shares
CY2019Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Outstanding Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions	275658	shares
CY2019Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Outstanding Options Weighted Average Exercise Price Beginning Balance1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1	267.23
CY2019Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Exercisable Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions	147620	shares
CY2019Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options Weighted Average Exercise Price1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1	210.96
CY2019	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
CY2017	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	10000000	USD
CY2019	us-gaap	Defined Contribution Plan Administrative Expenses DefinedContributionPlanAdministrativeExpenses	0	USD
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 Revenue CostOfRevenue	71153000	USD
CY2019Q2	us-gaap	Cost Of Revenue CostOfRevenue	71918000	USD
CY2019Q3	us-gaap	Cost Of Revenue CostOfRevenue	71172000	USD
CY2019Q4	us-gaap	Cost Of Revenue CostOfRevenue	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	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	4945000	USD
CY2019Q2	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	5913000	USD
CY2019Q3	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	5358000	USD
CY2019Q4	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	13801000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	732000	USD
CY2018Q4	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	4607000	USD
CY2018Q1	us-gaap	Interest Expense InterestExpense	690000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	697000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	704000	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	482000	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
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	98923000	USD
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.33
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
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.42
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.73
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.15
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.39
CY2018Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	273718000	USD
CY2018Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	297018000	USD
CY2018Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	305525000	USD
CY2018Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	315571000	USD
CY2018Q1	us-gaap	Cost Of Revenue CostOfRevenue	62477000	USD
CY2018Q2	us-gaap	Cost Of Revenue CostOfRevenue	67136000	USD
CY2018Q3	us-gaap	Cost Of Revenue CostOfRevenue	72072000	USD
CY2018Q4	us-gaap	Cost Of Revenue CostOfRevenue	68248000	USD
CY2018Q1	us-gaap	Gross Profit GrossProfit	211241000	USD
CY2018Q2	us-gaap	Gross Profit GrossProfit	229882000	USD
CY2018Q3	us-gaap	Gross Profit GrossProfit	233453000	USD
CY2018Q4	us-gaap	Gross Profit GrossProfit	247323000	USD
CY2018Q1	us-gaap	Operating Expenses OperatingExpenses	157796000	USD
CY2018Q2	us-gaap	Operating Expenses OperatingExpenses	186108000	USD
CY2018Q3	us-gaap	Operating Expenses OperatingExpenses	162765000	USD
CY2018Q4	us-gaap	Operating Expenses OperatingExpenses	141666000	USD
CY2018Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	53445000	USD
CY2018Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	43774000	USD
CY2018Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	70688000	USD
CY2018Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	105657000	USD
CY2018Q1	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	2987000	USD
CY2018Q2	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	2652000	USD
CY2018Q3	us-gaap	Other Nonoperating Income OtherNonoperatingIncome	3035000	USD
CY2018Q2	us-gaap	Interest Expense InterestExpense	728000	USD
CY2018Q3	us-gaap	Interest Expense InterestExpense	717000	USD
CY2018Q4	us-gaap	Interest Expense InterestExpense	695000	USD
CY2018Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	55742000	USD
CY2018Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	45698000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	73006000	USD
CY2018Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	109569000	USD
CY2018Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3511000	USD
CY2018Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1863000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14247000	USD
CY2018Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26060000	USD
CY2018Q1	us-gaap	Net Income Loss NetIncomeLoss	52231000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	43835000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	58759000	USD
CY2018Q4	us-gaap	Net Income Loss NetIncomeLoss	83509000	USD
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.46
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.22
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.63
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.31
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.44
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.20
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.61
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.29

Files In Submission

Name	View Source	Status
0001057352-20-000036-index-headers.html	Edgar Link	pending
0001057352-20-000036-index.html	Edgar Link	pending
0001057352-20-000036.txt	Edgar Link	pending
0001057352-20-000036-xbrl.zip	Edgar Link	pending
csgp-20191231.xsd	Edgar Link	pending
csgp-20191231_cal.xml	Edgar Link	unprocessable
csgp-20191231_def.xml	Edgar Link	unprocessable
csgp-20191231_lab.xml	Edgar Link	unprocessable
csgp-20191231_pre.xml	Edgar Link	unprocessable
csgp-ex21120191231.htm	Edgar Link	pending
csgp-ex23120191231.htm	Edgar Link	pending
csgp-ex31120191231.htm	Edgar Link	pending
csgp-ex31220191231.htm	Edgar Link	pending
csgp-ex32120191231.htm	Edgar Link	pending
csgp-ex32220191231.htm	Edgar Link	pending
csgp-ex4220191231.htm	Edgar Link	pending
csgp-logoa01a19.jpg	Edgar Link	pending
csgp20191231-10k.htm	Edgar Link	pending
csgp20191231-10k_htm.xml	Edgar Link	completed
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
image001.jpg	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R11.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R62.htm	Edgar Link	pending
R63.htm	Edgar Link	pending
R64.htm	Edgar Link	pending
R65.htm	Edgar Link	pending
R66.htm	Edgar Link	pending
R67.htm	Edgar Link	pending
R68.htm	Edgar Link	pending
R69.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R70.htm	Edgar Link	pending
R71.htm	Edgar Link	pending
R72.htm	Edgar Link	pending
R73.htm	Edgar Link	pending
R74.htm	Edgar Link	pending
R75.htm	Edgar Link	pending
R76.htm	Edgar Link	pending
R77.htm	Edgar Link	pending
R78.htm	Edgar Link	pending
R79.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R80.htm	Edgar Link	pending
R81.htm	Edgar Link	pending
R82.htm	Edgar Link	pending
R83.htm	Edgar Link	pending
R84.htm	Edgar Link	pending
R85.htm	Edgar Link	pending
R86.htm	Edgar Link	pending
R87.htm	Edgar Link	pending
R88.htm	Edgar Link	pending
R89.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
R90.htm	Edgar Link	pending
R91.htm	Edgar Link	pending
R92.htm	Edgar Link	pending
R93.htm	Edgar Link	pending
R94.htm	Edgar Link	pending
R95.htm	Edgar Link	pending
R9999.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$CSGP
COSTAR GROUP, INC. Stock $csgp

2019 Q4 Form 10-K Financial Statement

#000105735220000036 Filed on February 26, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CSGP COSTAR GROUP, INC. Stock $csgp

2019 Q4 Form 10-K Financial Statement

#000105735220000036 Filed on February 26, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$CSGP
COSTAR GROUP, INC. Stock $csgp