Debt Instrument Maturity Date Year

No definition available.

Name:	cbg_DebtInstrumentMaturityDateYear
Namespace Prefix:	cbg_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cbg_FivePercentSeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cbg_FourPointEightSevenFiveSeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cbg_FivePointTwoFivePercentSeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cbg_WarehouseLineOfCreditOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_WarehouseAgreementBorrowingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt and Short-Term Borrowings - Schedule of Long-Term Debt and Short-Term Borrowings (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 13, 2015	Dec. 12, 2014	Sep. 26, 2014
Senior secured term loans [Member]
Debt Instrument [Line Items]
Maturity date of debt, end	Dec. 31, 2022	Dec. 31, 2022
Senior secured term loans [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	1.77%	1.77%
Senior secured term loans [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	2.51%	2.51%
5.00% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	5.00%	5.00%
5.00% Senior Notes [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	5.00%	5.00%
Due date of debt instrument	2023	2023
4.875% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	4.875%	4.875%	4.875%	4.875%
4.875% Senior Notes [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	4.875%	4.875%		4.875%
Due date of debt instrument	2026	2026
5.25% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	5.25%	5.25%			5.25%	5.25%
5.25% Senior Notes [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	5.25%	5.25%
Due date of debt instrument	2025	2025
Pricing at daily one-month LIBOR plus 1.45%, maturing February 28, 2017 [Member] \| Warehouse Agreement Borrowings [Member]
Debt Instrument [Line Items]
Due date of debt instrument	2018	2018
Pricing at daily one-month LIBOR plus 1.45%, maturing February 28, 2017 [Member] \| Warehouse Agreement Borrowings [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	1.70%	1.70%
Pricing at daily one-month LIBOR plus 1.45%, maturing February 28, 2017 [Member] \| Warehouse Agreement Borrowings [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest rate of long-term debt	4.31%	4.31%