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Employee Benefit Plans - Additional Information (Detail) |  |  |  | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 15, 2017 shares | Dec. 01, 2017 shares | May 19, 2017 USD ($) shares | Dec. 31, 2018 USD ($) Pension_Plan shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Defined benefit plan |  |  |  | $ 363,600,000 | $ 286,500,000 | $ 248,100,000
Plan name |  |  |  | CBRE 401(k) Plan |  |
Defined Contribution Plan, Sponsor Location [Extensible List] |  |  |  | us-gaap:DomesticPlanMember |  |
Company contribution percent per year employed |  |  |  | 20.00% |  |
Percent of annual compensation match percentage |  |  |  |  | 50.00% | 50.00%
Percent of annual compensation to be matched |  |  |  |  | 6.00% | 6.00%
Defined benefit plan, annual compensation expense maximum |  |  |  |  | $ 150,000 | $ 150,000
Defined contribution plan, expenses recognized |  |  |  | $ 46,300,000 | 38,800,000 | $ 44,300,000
Percent of 401(k) that can be invested in common stock |  |  |  | 25.00% |  |
Number of share held as investment under 401(k) Plan | shares |  |  |  | 1,300,000 |  |
Defined Benefit Plan, Type [Extensible List] |  |  |  | us-gaap:PensionPlansDefinedBenefitMember |  |
Defined Benefit Plan, Sponsor Location [Extensible List] |  |  |  | us-gaap:ForeignPlanMember |  |
Number of contributory defined benefit pension plans in the United Kingdom | Pension_Plan |  |  |  | 2 |  |
Fair value of plan assets |  |  |  | $ 274,400,000 | 333,500,000 |
Benefit obligation |  |  |  | 387,400,000 | 455,600,000 |
Funded status |  |  |  | 113,000,000 | 122,100,000 |
Unamortized actuarial loss |  |  |  | $ 192,700,000 | $ 194,300,000 |
Annual Base Salary of Less than $100,000 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Percent of annual compensation match percentage |  |  |  | 67.00% |  |
Percent of annual compensation to be matched |  |  |  | 6.00% |  |
Defined benefit plan, annual compensation expense maximum |  |  |  | $ 100,000 |  |
Annual Base Salary of $100,000 or Up to $150,000 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Percent of annual compensation match percentage |  |  |  | 50.00% |  |
Percent of annual compensation to be matched |  |  |  | 6.00% |  |
Defined benefit plan, annual compensation expense minimum |  |  |  | $ 100,000,000 |  |
Defined benefit plan, annual compensation expense maximum |  |  |  | $ 150,000 |  |
Time Based Vesting [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Vesting period |  |  |  | 4 years |  |
Time-vesting awards, portion to be vested per year |  |  |  | 25.00% |  |
Restricted Stock Units [Member] | Time Based Vesting [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for future grant | shares |  |  |  | 1,332,085 | 1,466,986 | 1,436,310
Restricted Stock Units [Member] | Time Based Vesting [Member] | Senior Brokers [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Vesting period | 3 years |  |  |  |  |
Granted, Shares / Units | shares | 127,160 |  |  |  |  |
Restricted Stock Units [Member] | Performance Based Vesting [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for future grant | shares |  |  |  | 1,014,269 | 1,458,033 | 60,098
Non-Vested Stock Awards [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Granted, Shares / Units | shares |  |  |  | 2,023,266 | 5,152,082 | 1,496,408
Stock options, compensation expense |  |  |  | $ 128,200,000 | $ 93,100,000 | $ 63,500,000
Stock options, unrecognized estimated compensation cost |  |  |  | $ 197,300,000 |  |
Weighted average period of recognition |  |  |  | 3 years 3 months 18 days |  |
Maximum [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Employee subscription rate |  |  |  | 75.00% |  |
Minimum [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Employee subscription rate |  |  |  | 1.00% |  |
2017 Equity Incentive Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Unissued common stock available for issuance | shares |  |  | 0 |  |  |
Equity incentive plan termination date |  |  |  | Mar. 03, 2027 |  |
Maximum number of share to be granted per person | shares |  |  | 3,300,000 |  |  |
Maximum amount of share to be granted per person |  |  | $ 5,000,000 |  |  |
2017 Equity Incentive Plan [Member] | Stock Options [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for future grant | shares |  |  |  | 3,632,717 |  |
2017 Equity Incentive Plan [Member] | Restricted Stock Units [Member] | Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of trading days required for purposes of measuring shareholder return based on average closing price of common stock immediately preceding grant date |  | 60 days |  |  |  |
2017 Equity Incentive Plan [Member] | Restricted Stock Units [Member] | Time Based Vesting [Member] | Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Sharebased compensation arrangement by sharebased payment percentage of target restricted stock unit |  | 33.30% |  |  |  |
2017 Equity Incentive Plan [Member] | Restricted Stock Units [Member] | Total Shareholder Return [Member] | Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Equity incentive plan termination date |  | Dec. 01, 2023 |  |  |  |
Sharebased compensation arrangement by sharebased payment percentage of target restricted stock unit |  | 33.30% |  |  |  |
Share-based compensation arrangement by share-based payment award, measurement period |  | 6 years |  |  |  |
2017 Equity Incentive Plan [Member] | Restricted Stock Units [Member] | EPS [Member] | Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Equity incentive plan termination date |  | Dec. 31, 2023 |  |  |  |
Sharebased compensation arrangement by sharebased payment percentage of target restricted stock unit |  | 33.30% |  |  |  |
Share-based compensation arrangement by share-based payment award, measurement period |  | 6 years |  |  |  |
2017 Equity Incentive Plan [Member] | Maximum [Member] | Employee Stock Options And Stock Appreciation Rights [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Term of equity incentive and stock option plans |  |  | 10 years |  |  |
2017 Equity Incentive Plan [Member] | Maximum [Member] | Restricted Stock Units [Member] | Time Based Vesting [Member] | Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for future grant | shares |  | 939,605 |  | 35,031 |  |
2017 Equity Incentive Plan [Member] | Maximum [Member] | Restricted Stock Units [Member] | Performance Based Vesting [Member] | Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for future grant | shares |  | 3,288,618 |  | 122,610 |  |
2017 Equity Incentive Plan [Member] | Minimum [Member] | Time Based Vesting [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Vesting period |  |  | 3 years |  |  |
2012 Equity Incentive Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares available for future grant | shares |  |  |  | 3,255,964 |  |
Class A Common Stock [Member] | 2017 Equity Incentive Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares reserved for future issuance | shares |  |  | 10,000,000 |  |  |

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- Definition Date the equity-based award expires, in CCYY-MM-DD format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The highest quantity of shares an employee can purchase under the plan per period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting of share-based compensation awards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.D.2) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 + Details
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