Additional line of credit.

No definition available.

Name:	cbre_AdditionalLineOfCredit
Namespace Prefix:	cbre_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility, Maximum Number Of Additional Borrowings Within 12 Consecutive Months

+ References

No definition available.

+ Details

Name:	cbre_LineOfCreditFacilityMaximumNumberOfAdditionalBorrowingsWithin12ConsecutiveMonths
Namespace Prefix:	cbre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the minimum amount for the debt instrument's basis spread over the variable interest rate on a debt instrument.

+ References

No definition available.

+ Details

Name:	cbre_LineOfCreditLondonInterBankOfferRateFloor
Namespace Prefix:	cbre_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LinesOfCreditCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_ShortTermDebtLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying value as of the balance sheet date of the outstanding short-term borrowings under a revolving line of credit used by mortgage bankers to finance the origination or purchase of loans.

+ References

+ Details

Name:	us-gaap_WarehouseAgreementBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cbre_JPMorganMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cbre_FannieMaeASAPProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cbre_TDBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cbre_BankOfAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=cbre_SublimitBorrowingAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cbre_MUFGUnionBankNAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

Warehouse Receivables & Warehouse Lines of Credit - Summary of Warehouse Lines of Credit in Place (Detail)	3 Months Ended
	Mar. 31, 2021 USD ($)	Jan. 18, 2021 USD ($)	Dec. 31, 2020 USD ($)	Nov. 02, 2020 USD ($)	Oct. 19, 2020 USD ($)	Sep. 22, 2020 USD ($)	Sep. 21, 2020 USD ($)	Aug. 04, 2020 USD ($)	Jul. 01, 2020 USD ($)	Jun. 10, 2020 USD ($)	Jun. 28, 2019 USD ($) borrowing
Short-term Debt [Line Items]
Carrying Value	$ 675,473,000		$ 1,383,964,000
Warehouse Agreement Borrowings
Short-term Debt [Line Items]
Maximum Facility Size	3,000,000,000		3,500,000,000
Carrying Value	675,473,000		1,383,964,000
Warehouse Agreement Borrowings \| JP Morgan \| Pricing at daily floating rate LIBOR plus 1.30%, maturing October 19, 2020
Short-term Debt [Line Items]
Maximum Facility Size	985,000,000	$ 985,000,000.0	1,585,000,000		$ 1,585,000,000.0
Carrying Value	$ 370,054,000		561,726,000
Line of credit over LIBOR rate	1.60%
Warehouse Agreement Borrowings \| JP Morgan \| Pricing at daily floating rate LIBOR plus 2.75%, maturing October 19, 2020
Short-term Debt [Line Items]
Maximum Facility Size	$ 15,000,000		15,000,000
Carrying Value	$ 899,000		0
Line of credit over LIBOR rate	2.75%
Warehouse Agreement Borrowings \| Fannie Mae ASAP Program \| Pricing at daily one-month LIBOR plus 1.35%, with a LIBOR floor of 0.35%, Cancelable anytime
Short-term Debt [Line Items]
Maximum Facility Size	$ 650,000,000		450,000,000
Carrying Value	$ 85,530,000		132,692,000
Line of credit over LIBOR rate	1.45%
Line of credit, LIBOR floor rate	0.25%
Warehouse Agreement Borrowings \| TD Bank \| Pricing at daily floating rate LIBOR plus 1.15%, maturing June 30, 2021
Short-term Debt [Line Items]
Maximum Facility Size	$ 800,000,000		800,000,000						$ 400,000,000.0
Carrying Value	$ 94,164,000		401,849,000
Line of credit over LIBOR rate	1.15%
Revolving credit facility							$ 400,000,000.0
Warehouse Agreement Borrowings \| Bank of America (BofA) \| LIBOR daily floating rate plus 1.50% on general facility and LIBOR daily floating rate plus 1.75% on separate sublimit borrowing, maturing on May 26, 2021
Short-term Debt [Line Items]
Maximum Facility Size	$ 350,000,000		350,000,000							$ 350,000,000.0
Carrying Value	89,949,000		175,862,000
Warehouse Agreement Borrowings \| Bank of America (BofA) \| LIBOR daily floating rate plus 1.50% on general facility and LIBOR daily floating rate plus 1.75% on separate sublimit borrowing, maturing on May 26, 2021 \| Sublimit Borrowing Agreement
Short-term Debt [Line Items]
Maximum Facility Size										$ 100,000,000.0
Warehouse Agreement Borrowings \| MUFG Union Bank, N.A. (Union Bank) \| Pricing at daily floating rate LIBOR plus 1.20%, maturing June 28, 2020
Short-term Debt [Line Items]
Maximum Facility Size	200,000,000		300,000,000	$ 650,000,000.0							$ 200,000,000.0
Carrying Value	$ 34,877,000		$ 111,835,000
Line of credit over LIBOR rate	1.50%
Line of credit, LIBOR floor rate	0.25%
Additional line of credit								$ 100,000,000.0			$ 150,000,000.0
Maximum number of additional borrowings within 12 consecutive months \| borrowing											3
Warehouse Agreement Borrowings \| MUFG Union Bank, N.A. (Union Bank) \| Pricing at daily floating rate LIBOR plus 1.20%, maturing June 28, 2020 \| Maximum
Short-term Debt [Line Items]
Revolving credit facility						$ 100,000,000.0