Note 8 - Leases (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($)
Lessee, Operating Lease, Lease Not yet Commenced	$ 60,460
Minimum [Member]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract (Year)	5 years
Minimum [Member] \| Premise Leases [Member]
Lessee, Operating Lease, Term of Contract (Year)	1 year
Minimum [Member] \| Equipment Leases [Member]
Lessee, Lease, Term of Contract (Year)	1 year
Maximum [Member]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract (Year)	15 years
Maximum [Member] \| Premise Leases [Member]
Lessee, Operating Lease, Term of Contract (Year)	15 years
Maximum [Member] \| Equipment Leases [Member]
Lessee, Lease, Term of Contract (Year)	3 years

The term of contract for leases held by the lessee.

No definition available.

Name:	cigi_LesseeLeaseTermOfContract
Namespace Prefix:	cigi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of operating lease for lessee, lease not yet commenced.

+ References

No definition available.

+ Details

Name:	cigi_LesseeOperatingLeaseLeaseNotYetCommenced
Namespace Prefix:	cigi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Term of lessee's operating lease not yet commenced, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseContractualTermAxis=cigi_PremiseLeasesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseContractualTermAxis=cigi_EquipmentLeasesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: