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	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Business Acquisition [Line Items]
Revenue	$ 9,036	$ 7,986	$ 25,434	$ 23,341
Operating income	373	272	833	581
Net income attributable to CBRE Group, Inc.	$ 229	$ 190	$ 490	$ 469
Basic income per share:
Net income per share attributable to CBRE Group, Inc. (in USD per share)	$ 0.75	$ 0.62	$ 1.60	$ 1.51
Weighted average shares outstanding for basic income per share (in shares)	306,253,811	307,854,518	306,269,264	309,716,456
Diluted income per share:
Net income per share attributable to CBRE Group, Inc. (in USD per share)	$ 0.74	$ 0.61	$ 1.59	$ 1.49
Weighted average shares outstanding for diluted income per share (in shares)	308,305,013	312,221,133	308,281,111	313,944,855

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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
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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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