Segments - EBITDA Calculation by Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net income (loss) attributable to CBRE Group, Inc.	$ 204,277	$ 107,099	$ 105,464	$ 67,663	$ 114,646	$ 94,444	$ 69,902	$ 37,546	$ 484,503	$ 316,538	$ 315,555
Depreciation and amortization									265,101	190,390	169,645
Write-off of financing costs									23,087	56,295
Provision for income taxes									263,759	187,187	185,322
EBITDA									1,142,252	982,883	861,621
Non-amortizable intangible asset impairment										98,129	19,826
Depreciation and amortization									265,101	191,270	170,905
Americas [Member]
Segment Reporting Information [Line Items]
Net income (loss) attributable to CBRE Group, Inc.									387,302	539,373	267,313
Depreciation and amortization									149,214	116,564	82,841
Interest expense (income), net									15,959	85,230	120,075
Write-off of financing costs									23,087	56,295
Royalty and management service (income) expense									(13,411)	(295,154)	(32,214)
Provision for income taxes									163,408	100,883	140,634
EBITDA									725,559	603,191	578,649
EMEA [Member]
Segment Reporting Information [Line Items]
Net income (loss) attributable to CBRE Group, Inc.									13,383	(248,888)	9,846
Depreciation and amortization									64,628	20,496	14,198
Interest expense (income), net									50,344	2,060	(9,395)
Royalty and management service (income) expense									(5,210)	267,199	12,654
Provision for income taxes									35,279	30,400	7,170
EBITDA									158,424	71,267	54,299
Non-amortizable intangible asset impairment											19,826
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net income (loss) attributable to CBRE Group, Inc.									35,797	14,876	35,040
Depreciation and amortization									14,661	12,397	11,475
Interest expense (income), net									2,250	875	3,887
Royalty and management service (income) expense									13,876	23,184	15,388
Provision for income taxes									21,287	19,463	14,840
EBITDA									87,871	70,795	80,630
Global Investment Management [Member]
Segment Reporting Information [Line Items]
Net income (loss) attributable to CBRE Group, Inc.									7,530	(7,056)	(14,872)
Depreciation and amortization									32,802	36,194	51,290
Interest expense (income), net									33,896	37,286	43,697
Royalty and management service (income) expense									4,745	4,771	4,172
Provision for income taxes									17,289	24,809	11,805
EBITDA									96,262	194,609	96,359
Non-amortizable intangible asset impairment										98,129
Depreciation and amortization									32,802	36,670	51,557
Development Services [Member]
Segment Reporting Information [Line Items]
Net income (loss) attributable to CBRE Group, Inc.									40,491	18,233	18,228
Depreciation and amortization									3,796	4,739	9,841
Interest expense (income), net									3,353	6,639	10,738
Provision for income taxes									26,496	13,006	11,884
EBITDA									74,136	43,021	51,684
Depreciation and amortization									$ 3,796	$ 5,143	$ 10,834