Acquisition of Global Workplace Solutions (GWS) - Summary of Pro Forma Results Prepared for Comparative Purposes (Detail) - Global Workplace Solutions (GWS) [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Revenue	$ 12,972,810	$ 12,492,918
Operating income	902,612	734,571
Net income attributable to CBRE Group, Inc.	$ 581,807	$ 422,676
Basic income per share:
Net income per share attributable to CBRE Group, Inc.	$ 1.75	$ 1.28
Weighted average shares outstanding for basic income per share	332,616,301	330,620,206
Diluted income per share:
Net income per share attributable to CBRE Group, Inc.	$ 1.73	$ 1.26
Weighted average shares outstanding for diluted income per share	336,414,856	334,171,509