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v3.19.3.a.u2

Nature of Operations - Additional Information (Detail) - Minimum [Member] | 12 Months Ended
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Dec. 31, 2019 Employee Office
Schedule Of Description Of Business [Line Items] |
Number of offices | Office | 530
Number of employees | Employee | 100,000

X
- Definition The approximate number of offices in which the entity operates worldwide. + References No definition available. + Details
Name: | cbre_NumberOfOffices
Namespace Prefix: | cbre_
Data Type: | xbrli:positiveIntegerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule Of Description Of Business [Line Items] + References No definition available. + Details
Name: | cbre_ScheduleOfDescriptionOfBusinessLineItems
Namespace Prefix: | cbre_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of persons employed by the Entity + References No definition available. + Details
Name: | dei_EntityNumberOfEmployees
Namespace Prefix: | dei_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |