Earnings Per Share Information - Computation of Basic and Diluted Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Computation of basic income per share attributable to CBRE Group, Inc.shareholders:
Net income attributable to CBRE Group, Inc. shareholders	$ 180,043	$ 149,123	$ 125,029	$ 92,937	$ 204,277	$ 107,099	$ 105,464	$ 67,663	$ 547,132	$ 484,503	$ 316,538
Weighted average shares outstanding for basic income per share	333,783,269	332,684,487	331,999,935	331,976,907	331,875,303	330,419,006	330,133,061	330,035,445	332,616,301	330,620,206	328,110,004
Basic income per share attributable to CBRE Group, Inc. shareholders	$ 0.54	$ 0.45	$ 0.38	$ 0.28	$ 0.62	$ 0.32	$ 0.32	$ 0.21	$ 1.64	$ 1.47	$ 0.96
Computation of diluted income per share attributable to CBRE Group, Inc. shareholders:
Net income attributable to CBRE Group, Inc. shareholders	$ 180,043	$ 149,123	$ 125,029	$ 92,937	$ 204,277	$ 107,099	$ 105,464	$ 67,663	$ 547,132	$ 484,503	$ 316,538
Weighted average shares outstanding for basic income per share	333,783,269	332,684,487	331,999,935	331,976,907	331,875,303	330,419,006	330,133,061	330,035,445	332,616,301	330,620,206	328,110,004
Dilutive effect of contingently issuable shares									3,620,194	3,154,589	2,942,919
Dilutive effect of stock options									178,361	396,714	709,931
Weighted average shares outstanding for diluted income per share	337,223,824	336,561,877	336,154,524	335,698,590	335,106,838	334,293,046	333,918,620	333,349,519	336,414,856	334,171,509	331,762,854
Diluted income per share attributable to CBRE Group, Inc. shareholders	$ 0.53	$ 0.44	$ 0.37	$ 0.28	$ 0.61	$ 0.32	$ 0.32	$ 0.20	$ 1.63	$ 1.45	$ 0.95