Name:	cigi_AssetsHeldforsaleNotPartOfDisposalGroupNoncurrentTotal
Namespace Prefix:	cigi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of liabilities held-for-sale, not part of disposal group.

No definition available.

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

The amount of liabilities held-for-sale, not part of disposal group,classified as current.

No definition available.

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

The amount of liabilities held-for-sale, not part of disposal group, classified as noncurrent.

No definition available.

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

Amount of assets held-for-sale that are not part of a disposal group.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482309/360-10-15-4

Name:	us-gaap_AssetsHeldForSaleNotPartOfDisposalGroup
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of assets held-for-sale that are not part of a disposal group, expected to be sold within a year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481372/852-10-55-10

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482309/360-10-15-4

Name:	us-gaap_AssetsHeldForSaleNotPartOfDisposalGroupCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of investment in land and building held for sale. Excludes real estate considered inventory.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1