REVENUE FROM CONTRACTS WITH CUSTOMERS - Changes in Deferred Revenue (Details) $ in Millions	9 Months Ended
Sep. 30, 2024 USD ($)
Change in Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 104.3
Revenues recognized in the current period from the amounts in the beginning balance	(100.9)
New deferrals, net of amounts recognized in the current period	109.1
Effects of foreign currency	1.2
Ending balance	$ 113.7

Change in Contract with Customer, Liability [Roll Forward]

No definition available.

Name:	csgp_ChangeinContractwithCustomerLiabilityRollForward
Namespace Prefix:	csgp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract with Customer, Asset, Effects of Currency Translation

+ References

No definition available.

+ Details

Name:	csgp_ContractwithCustomerAssetEffectsofCurrencyTranslation
Namespace Prefix:	csgp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Contract with Customer, Liability, New Deferrals, Net of Amounts Recognized in Current Period

+ References

No definition available.

+ Details

Name:	csgp_ContractwithCustomerLiabilityNewDeferralsNetofAmountsRecognizedinCurrentPeriod
Namespace Prefix:	csgp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

+ Details

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

+ Details

Name:	us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration