Telford Acquisition - Summary of Pro Forma Results Prepared for Comparative Purposes (Detail) - Telford Homes Plc [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Revenue	$ 24,158,427	$ 21,803,506
Operating income	1,294,480	1,157,051
Net income attributable to CBRE Group, Inc.	$ 1,321,097	$ 1,121,469
Basic income per share:
Net income per share attributable to CBRE Group, Inc.	$ 3.93	$ 3.31
Weighted average shares outstanding for basic income per share	335,795,654	339,321,056
Diluted income per share:
Net income per share attributable to CBRE Group, Inc.	$ 3.88	$ 3.27
Weighted average shares outstanding for diluted income per share	340,522,871	343,122,741

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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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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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