Revenue Recognition (Policies)	9 Months Ended
Sep. 30, 2016
Revenue Recognition [Abstract]
Transactions commissions	We recognize transaction commissions related to leasing services and capital markets services as revenue when we provide the related services, unless future contingencies exist.
Advisory and management fees	We recognize advisory and management fees related to property and facility management services, valuation services, corporate property services, consulting services and investment management in the period in which we perform the related services.
Incentive fees	We recognize incentive fees in the period earned, based on the performance of funds' investments, contractual benchmarks and other contractual formulas. If future contingencies exist, we defer recognition of the related revenue until the respective contingencies have been satisfied.
Project and development management and construction management fees	We recognize project and development management and construction management fees by applying the percentage of completion method of accounting.
Gross and net accounting	We account for the majority of our service contracts on a net basis. The presentation of expenses pursuant to these arrangements under either a gross or net basis has no impact on operating income, net income or cash flows. Contracts accounted for on a gross basis resulted in certain costs reflected in both revenue and operating expenses (gross contract costs) of $258.0 million and $214.0 million for the three months ended September 30, 2016 and 2015, respectively, and $735.5 million and $580.0 million for the nine months ended September 30, 2016 and 2015, respectively.

Revenue Recognition (Policies)

9 Months Ended

Sep. 30, 2016

We recognize transaction commissions related to leasing services and capital markets services as revenue when we provide the related services, unless future contingencies exist.

Advisory and management fees

We recognize advisory and management fees related to property and facility management services, valuation services, corporate property services, consulting services and investment management in the period in which we perform the related services.

Incentive fees

We recognize incentive fees in the period earned, based on the performance of funds' investments, contractual benchmarks and other contractual formulas. If future contingencies exist, we defer recognition of the related revenue until the respective contingencies have been satisfied.

Project and development management and construction management fees

We recognize project and development management and construction management fees by applying the percentage of completion method of accounting.

Gross and net accounting

We account for the majority of our service contracts on a net basis. The presentation of expenses pursuant to these arrangements under either a gross or net basis has no impact on operating income, net income or cash flows.

Contracts accounted for on a gross basis resulted in certain costs reflected in both revenue and operating expenses (gross contract costs) of $258.0 million and $214.0 million for the three months ended September 30, 2016 and 2015, respectively, and $735.5 million and $580.0 million for the nine months ended September 30, 2016 and 2015, respectively.

- Definition

Disclosure of accounting policy for revenue recognition for long-term construction-type contracts accounted for using the percentage-of-completion method. The disclosure would generally be expected to include the method or methods of measuring extent of progress toward completion. If the entity departs from using the percentage-of-completion method for a single contract or a group of contracts for which reasonably dependable estimates cannot be made, such a departure from the basic policy is disclosed. The disclosure may also describe the accounting for significant changes in estimate.

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