XML 16 R1.htm IDEA: XBRL DOCUMENT v3.20.4
Document And Entity Information
 12 Months Ended
Dec. 31, 2020
shares
Document Information [Line Items]  
Entity Registrant Name Colliers International Group Inc.
Entity Central Index Key 0000913353
Trading Symbol cigi
Current Fiscal Year End Date --12-31
Entity Current Reporting Status Yes
Entity Emerging Growth Company false
Entity Interactive Data Current Yes
Document Type 40-F
Document Period End Date Dec. 31, 2020
Document Fiscal Year Focus 2020
Document Fiscal Period Focus FY
Amendment Flag false
Title of 12(b) Security Subordinate Voting Shares
Multiple Voting Shares [Member]  
Document Information [Line Items]  
Entity Common Stock, Shares Outstanding (in shares) 1,325,694
Subordinate Voting Shares [Member]  
Document Information [Line Items]  
Entity Common Stock, Shares Outstanding (in shares) 38,519,517