Note 7 - Acquisition-related Items (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Contingent Consideration Compensation Expense	$ 50,169	$ 5,292
The 2022 Acquisitions [Member]
Contingent Consideration Compensation Expense	$ 41,765

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