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v3.22.0.1

Note 1 - Description of the Business (Details Textual) | Dec. 31, 2021
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Number of Countries in which Entity Operates | 37
Number of Geographic Regions in which Entity Operates | 4
Colliers and Its Affiliates and Franchisees [Member] |
Number of Countries in which Entity Operates | 64

X
- Definition The number of geographic regions in which the entity operates as of the balance sheet date. + References No definition available. + Details
Name: | cigi_NumberOfGeographicRegionsInWhichEntityOperates
Namespace Prefix: | cigi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of countries in which the entity operates as of balance sheet date. + References No definition available. + Details
Name: | us-gaap_NumberOfCountriesInWhichEntityOperates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=cigi_ColliersAndItsAffiliatesAndFranchiseesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |