Note 17 - Variable Interest Entities (Details Textual)	Dec. 31, 2023
Minimum [Member]
Limited Partner Equity Interest in Real Estate Portfolio	1.00%
Maximum [Member]
Limited Partner Equity Interest in Real Estate Portfolio	2.00%

The limited partner equity interest in real estate portfolio percent.

No definition available.

Name:	cigi_LimitedPartnerEquityInterestInRealEstatePortfolio
Namespace Prefix:	cigi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant