J&J Worldwide Services Acquisition - Schedule of Pro Forma Results Prepared for Comparative Purposes (Details) - J&J Worldwide Services - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Business Acquisition [Line Items]
Revenue	$ 8,391	$ 7,830	$ 16,398	$ 15,355
Operating income	247	295	461	308
Net income attributable to CBRE Group, Inc.	$ 131	$ 187	$ 262	$ 279
Basic income per share:
Net income per share attributable to CBRE Group, Inc. (in USD per share)	$ 0.43	$ 0.60	$ 0.85	$ 0.90
Weighted average shares outstanding for basic income per share (in shares)	306,745,116	310,857,203	306,276,871	310,662,324
Diluted income per share:
Net income per share attributable to CBRE Group, Inc. (in USD per share)	$ 0.42	$ 0.59	$ 0.85	$ 0.89
Weighted average shares outstanding for diluted income per share (in shares)	308,035,211	314,282,247	308,269,040	314,821,615

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Business Acquisition Pro Forma Earnings Per Share Diluted [Abstract]

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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.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
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-Topic 805
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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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The weighted average number of shares or units and dilutive common stock or unit equivalents outstanding in the calculation of proforma diluted earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

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