Acquisitions - Summary of Pro Forma Results Prepared for Comparative Purposes (Details) - Turner & Townsend - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Revenue	$ 28,546	$ 24,716
Operating income	1,706	944
Net income attributable to CBRE Group, Inc.	$ 1,873	$ 705
Basic income per share:
Net income per share attributable to CBRE Group, Inc. (in USD per share)	$ 5.59	$ 2.10
Weighted average shares outstanding for basic income per share (in shares)	335,232,840	335,196,296
Diluted income per share:
Net income per share attributable to CBRE Group, Inc. (in USD per share)	$ 5.51	$ 2.08
Weighted average shares outstanding for diluted income per share (in shares)	339,717,401	338,392,210

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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
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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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