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	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue	$ 5,111,434	$ 4,439,571	$ 9,785,386	$ 8,490,537
Cost of services	3,958,748	3,409,540	7,578,709	6,556,017
Operating, administrative and other	826,282	712,615	1,558,517	1,319,241
Operating income	225,316	228,328	438,925	433,539
Income before provision for income taxes	299,950	272,895	496,239	465,640
Provision for income taxes	70,319	69,887	116,483	123,706
Net income	229,631	203,008	379,756	341,934
Net income attributable to CBRE Group, Inc.	$ 228,667	$ 201,777	$ 378,955	$ 338,797
Basic income per share attributable to CBRE Group, Inc. shareholders	$ 0.67	$ 0.60	$ 1.12	$ 1.01
Diluted income per share attributable to CBRE Group, Inc. shareholders	$ 0.67	$ 0.59	$ 1.10	$ 1.00
As Reported [Member] \| ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue		$ 3,342,215		$ 6,323,419
Cost of services		2,318,562		4,405,641
Operating, administrative and other		712,374		1,318,605
Operating income		222,191		417,433
Income before provision for income taxes		266,758		449,534
Provision for income taxes		68,362		119,635
Net income		198,396		329,899
Net income attributable to CBRE Group, Inc.		$ 197,165		$ 326,762
Basic income per share attributable to CBRE Group, Inc. shareholders		$ 0.59		$ 0.97
Diluted income per share attributable to CBRE Group, Inc. shareholders		$ 0.58		$ 0.96
Adoption of New Revenue Recognition Guidance [Member] \| ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Revenue		$ 1,097,356		$ 2,167,118
Cost of services		1,090,978		2,150,376
Operating, administrative and other		241		636
Operating income		6,137		16,106
Income before provision for income taxes		6,137		16,106
Provision for income taxes		1,525		4,071
Net income		4,612		12,035
Net income attributable to CBRE Group, Inc.		$ 4,612		$ 12,035
Basic income per share attributable to CBRE Group, Inc. shareholders		$ 0.01		$ 0.04
Diluted income per share attributable to CBRE Group, Inc. shareholders		$ 0.01		$ 0.04

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

3 Months Ended

6 Months Ended

Jun. 30, 2018

Jun. 30, 2017

Jun. 30, 2018

Jun. 30, 2017

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

Revenue

$ 5,111,434

$ 4,439,571

$ 9,785,386

$ 8,490,537