Note 7 - Acquisition-related Items (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Contingent Consideration Compensation Expense	$ 50,646	$ 50,169
The 2023 Acquisitions [Member]
Contingent Consideration Compensation Expense	$ 2,853

Represents information about the contingent consideration compensation expense.

No definition available.

Name:	cigi_ContingentConsiderationCompensationExpense
Namespace Prefix:	cigi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration