New Accounting Pronouncements - Schedule of Adoption of New Revenue Recognition Guidance on Financial Statement - Consolidated Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue	$ 21,340,088	$ 18,628,787	$ 17,369,108
Cost of services	16,449,212	14,305,099	13,420,911
Operating, administrative and other	3,365,773	2,858,720	2,780,301
Operating income	1,087,989	1,078,682	816,831
Income before provision for income taxes	1,379,006	1,171,333	882,070
Provision for income taxes	313,058	467,757	296,900
Net income	1,065,948	703,576	585,170
Net income attributable to CBRE Group, Inc.	$ 1,063,219	$ 697,109	$ 573,079
Basic income per share attributable to CBRE Group, Inc. shareholders	$ 3.13	$ 2.06	$ 1.71
Diluted income per share attributable to CBRE Group, Inc. shareholders	$ 3.10	$ 2.05	$ 1.69
As Reported [Member] \| ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue		$ 14,209,608	$ 13,071,589
Cost of services		9,893,226	9,123,727
Operating, administrative and other		2,858,654	2,781,310
Operating income		1,071,442	815,487
Income before provision for income taxes		1,164,093	880,726
Provision for income taxes		466,147	296,662
Net income		697,946	584,064
Net income attributable to CBRE Group, Inc.		$ 691,479	$ 571,973
Basic income per share attributable to CBRE Group, Inc. shareholders		$ 2.05	$ 1.71
Diluted income per share attributable to CBRE Group, Inc. shareholders		$ 2.03	$ 1.69
Adoption of New Revenue Recognition Guidance [Member] \| ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue		$ 4,419,179	$ 4,297,519
Cost of services		4,411,873	4,297,184
Operating, administrative and other		66	(1,009)
Operating income		7,240	1,344
Income before provision for income taxes		7,240	1,344
Provision for income taxes		1,610	238
Net income		5,630	1,106
Net income attributable to CBRE Group, Inc.		$ 5,630	$ 1,106
Basic income per share attributable to CBRE Group, Inc. shareholders		$ 0.01
Diluted income per share attributable to CBRE Group, Inc. shareholders		$ 0.02

New Accounting Pronouncements - Schedule of Adoption of New Revenue Recognition Guidance on Financial Statement - Consolidated Statements of Operations (Details) - USD ($)
$ / shares in Units, $ in Thousands

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

New Accounting Pronouncements Or Change In Accounting Principle [Line Items]

Revenue

$ 21,340,088

$ 18,628,787

$ 17,369,108

Cost of services

16,449,212

14,305,099