| Summary of Significant Accounting Policies Summary of SIgnificant Accounting Policies (Policies) | 12 Months Ended |
| Dec. 31, 2020 |
| Accounting Policies [Abstract] | |
| Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block] | Principles of Consolidation Our Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted in the United States of America ("U.S. GAAP") and include the accounts of JLL and its majority-owned and controlled subsidiaries. Intercompany balances and transactions have been eliminated. Investments in real estate ventures over which we exercise significant influence, but do not control, are accounted for either at fair value or under the equity method. When applying principles of consolidation, we begin by determining whether an investee entity is a variable interest entity ("VIE") or a voting interest entity. U.S. GAAP draws a distinction between voting interest entities, which are embodied by common and traditional corporate and certain partnership structures, and VIEs, broadly defined as entities for which control is achieved through means other than voting rights. For voting interest entities, the interest holder with control through majority ownership and majority voting rights consolidates the entity. For VIEs, determination of the "primary beneficiary" dictates the accounting treatment. We identify the primary beneficiary of a VIE as the enterprise having both (i) the power to direct the activities of the VIE that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses or receive benefits of the VIE that could potentially be significant to the VIE. We perform the primary beneficiary analysis as of the inception of our investment and upon the occurrence of a reconsideration event. When we determine we are the primary beneficiary of a VIE, we consolidate the VIE; when we determine we are not the primary beneficiary of the VIE, we account for our investment in the VIE at fair value or under the equity method, based upon an election made at the time of investment. Our determination of the appropriate accounting method to apply for unconsolidated investments is based on the level of influence we have in the underlying entity. When we have an asset advisory contract with a real estate limited partnership in which we also hold an ownership interest, the combination of our limited partner interest and the advisory agreement generally provides us with significant influence over such real estate limited partnership. Accordingly, we account for such investments either at fair value or under the equity method. We eliminate transactions with such subsidiaries to the extent of our ownership in such subsidiaries. For less-than-wholly-owned consolidated subsidiaries, noncontrolling interest is the portion of equity not attributable, directly or indirectly, to JLL. We evaluate whether noncontrolling interests possess any redemption features outside of our control. If such features exist, the noncontrolling interests are presented outside of permanent equity on the Consolidated Balance Sheets within Redeemable noncontrolling interest. Redeemable noncontrolling interests are adjusted to the greater of their fair value or carrying value as of each balance sheet date through a charge to Additional paid-in capital, if necessary. If classification and presentation outside of permanent equity is not considered necessary, noncontrolling interests are presented as a component of permanent equity on the Consolidated Balance Sheets. We report revenues, expenses and net income (loss) from less-than-wholly-owned consolidated subsidiaries at the consolidated amounts, including both the amounts attributable to the Company and noncontrolling interests; the income or loss attributable to the noncontrolling interest holders is reflected in Net income attributable to noncontrolling interest on the Consolidated Statements of Comprehensive Income. Changes in amounts attributable to non-redeemable noncontrolling interests are reflected in the Consolidated Statements of Changes in Equity. Changes in amounts attributable to redeemable noncontrolling interests are presented in the following table. (in millions) Redeemable noncontrolling interests as of December 31, 2017 $ 3.8 Acquisition of redeemable noncontrolling interest (1) (3.8) Redeemable noncontrolling interests as of December 31, 2018 — Business acquisition (2) 8.4 Net income 0.2 Redeemable noncontrolling interests as of December 31, 2019 8.6 Net loss (0.3) Distribution to redeemable noncontrolling interest (0.5) Redeemable noncontrolling interests as of December 31, 2020 $ 7.8 (1) Reflects our redemption of a portion of the redeemable noncontrolling interest related to our Tenzing AB acquisition and includes $2.3 million, representing the difference between the redemption value and the carrying value of the acquired interest in 2018. (2) Reflects the ownership interests retained by the seller associated with our 2019 acquisition of Latitude Real Estate Investors. |
| Use of Estimates, Policy [Policy Text Block] | Use of Estimates The preparation of the Consolidated Financial Statements in conformity with U.S. GAAP requires us to make estimates and assumptions about future events that affect reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of revenue and expenses during the reporting periods. Such estimates include the value and allocation of purchase consideration, valuation of accounts receivable, Reimbursable receivables, Warehouse receivables, Investments in real estate ventures, Goodwill, intangible assets, derivative financial instruments, other long-lived assets, earn-out liabilities, legal contingencies, assumptions used in the calculation of income taxes, incentive compensation, self-insurance program liabilities, and retirement and other post-employment benefits, among others. These estimates and assumptions are based on management's best estimate and judgment. We evaluate these estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, which we believe to be reasonable under the circumstances. We adjust such estimates and assumptions when facts and circumstances dictate. Market factors, such as illiquid credit markets, volatile equity markets and foreign currency exchange rate fluctuations can increase the uncertainty in such estimates and assumptions. Because future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in those estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods. Although actual amounts may differ from such estimated amounts, we believe such differences are not likely to be material. |
| Advisory, Consulting and Other [Policy Text Block] | Advisory, Consulting and Other includes a variety of different service offerings, whereby our performance obligation is to provide services as specified in the contract. Occasionally, our entitlement to consideration is predicated on the occurrence of an event such as the delivery of a report for which client acceptance is required. However, except for event-driven point-in-time transactions, the majority of services provided within this service line are delivered over time due to the continuous transfer of control to our clients. |
| Management and Investment Advisory Fees, Policy [Policy Text Block] | LaSalle provides real estate investment management services to clients and generally earns consideration in the form of advisory fees, transaction fees and incentive fees. Typically, our performance obligation is to manage clients’ capital for a specified period of time and is delivered as a series of daily performance obligations over time. Revenue recognition for transaction and incentive fees is generally constrained until all contingencies have cleared due to the possibility of a significant reversal until completion of the events necessary to realize the associated consideration. Substantially all incentive fees recognized as revenue were previously constrained. |
| Revenue [Policy Text Block] | Revenue Recognition We earn revenue from the following: • Leasing; • Capital Markets; • Property & Facility Management; • Project & Development Services; • Advisory, Consulting and Other; and • LaSalle. Leasing Leasing revenue is earned from brokerage commissions as we represent tenants and/or landlords in connection with real estate leases. Our performance obligation is to facilitate the execution of a lease agreement, which is satisfied at a point in time, upon lease execution. Generally, we are either entitled to the full consideration upon lease execution or in part upon lease execution with the remainder upon the occurrence of a future event outside of our control (e.g. tenant occupancy, lease commencement, or rent commencement). The majority of the events that preclude our entitlement to the full consideration upon lease execution are considered to be “normal course of business” and, therefore, do not result in a constraint upon the recognition of revenue. In the infrequent instance our fee entitlement in a contract with a customer is predicated on the occurrence of a future event(s) uncertain of occurring, we constrain the recognition of revenue until the uncertainty is resolved or the future event occurs. Generally, less than 5% of our Leasing revenue recognized in a period had previously been constrained. Capital Markets Capital Markets provides brokerage and other services for capital transactions, such as real estate sales or loan originations and refinancings. Our performance obligation is to facilitate the execution of capital transactions, and we are generally entitled to the full consideration at the point in time upon which our performance obligation is satisfied, at which time we recognize revenue. Our mortgage banking and servicing operations - such as activities related to mortgage servicing rights ("MSR" or "MSRs"), loan origination fees and servicing income - are excluded from the scope of Accounting Standards Codification ("ASC") Topic 606, Revenue from Contracts with Customers, ("ASC Topic 606"). Such out-of-scope revenue was included entirely within Americas Capital Markets and is presented below. Year Ended December 31, (in millions) 2020 2019 2018 Revenue excluded from scope of ASC Topic 606 $ 305.3 204.6 135.8 Property & Facility Management Property Management provides on-site day-to-day real estate management services for owners of office, industrial, retail, multifamily residential and various other types of properties, representing a series of daily performance obligations delivered over time. Pricing is generally in the form of a monthly management fee based upon property-level cash receipts, square footage under management or some other variable metric. Although we are principal in limited situations, we generally act as agent on behalf of our Property Management clients in relation to third-party vendors and subcontractors engaged to deliver operational services to our clients' properties. In these situations, we arrange, but do not control, the services provided by third-party vendors and subcontractors prior to the transfer of the services to the client. As a result, the costs incurred on behalf of clients, along with the corresponding revenue, are presented net on our Consolidated Statements of Comprehensive Income. Facility Management primarily provides comprehensive, on-site day-to-day real estate management services to corporations and institutions across a broad range of industries that outsource the management of the real estate they occupy, representing a series of daily performance obligations delivered over time. Pricing generally includes a management fee and, in many instances, an incentive fee or other form of variable consideration. Although we may act as agent on behalf of our clients with respect to certain mandates, we generally act as principal for our Facility Management contracts with respect to third-party vendors and subcontractors engaged to deliver operational services to our clients' facilities. In these situations, we control the services provided by such third-party vendors and subcontractors prior to the transfer of the services to the client. As a result, the costs incurred on behalf of our clients, along with the corresponding reimbursement revenue, are presented gross on our Consolidated Statements of Comprehensive Income. Project & Development Services Project & Development Services provides short-term construction-related services ranging from general contracting to project management for owners and occupiers of real estate. Depending on the terms of our engagement, our performance obligation is either to arrange for the completion of a project or to assume responsibility for completing a project on behalf of a client. Our obligations to clients are satisfied over time due to the continuous transfer of control of the underlying asset. Therefore, we recognize revenue over time, generally using input measures (e.g. to-date costs incurred relative to total estimated costs at completion). Typically, we are entitled to consideration at distinct milestones over the term of an engagement. For certain contracts where we assume responsibility for completing a project, we control the services provided by third-party vendors and subcontractors prior to transfer of the assets to the client. In these situations, the costs incurred on behalf of clients, along with the associated reimbursement revenue are presented gross on our Consolidated Statements of Comprehensive Income. For situations in which we act as agent on behalf of clients, costs incurred and the associated revenue are presented net on our Consolidated Statements of Comprehensive Income. Advisory, Consulting and Other Advisory, Consulting and Other includes a variety of different service offerings, whereby our performance obligation is to provide services as specified in the contract. Occasionally, our entitlement to consideration is predicated on the occurrence of an event such as the delivery of a report for which client acceptance is required. However, except for event-driven point-in-time transactions, the majority of services provided within this service line are delivered over time due to the continuous transfer of control to our clients. LaSalle LaSalle provides real estate investment management services to clients and generally earns consideration in the form of advisory fees, transaction fees and incentive fees. Typically, our performance obligation is to manage clients’ capital for a specified period of time and is delivered as a series of daily performance obligations over time. Revenue recognition for transaction and incentive fees is generally constrained until all contingencies have cleared due to the possibility of a significant reversal until completion of the events necessary to realize the associated consideration. Substantially all incentive fees recognized as revenue were previously constrained. Contract Costs Expenses, primarily employee commissions, incurred on leasing and capital markets transactions represent substantially all our incremental costs to obtain revenue contracts. We apply the applicable practical expedient offered by ASC Topic 606 when the amortization period is one year or less and, therefore, recognize these costs as an operating expense as they are incurred. We also incur costs to fulfill revenue contracts, primarily related to transition costs incurred prior to delivering Property & Facility Management services. These costs are not expensed as incurred but are deferred and amortized as an operating expense over the expected life of the contract in accordance with the transfer of related services. These deferred costs are assessed periodically for impairment. Contract Assets and Liabilities Contract assets include amounts recognized as revenue for which we are not yet entitled to payment for reasons other than the passage of time, but that do not constrain revenue recognition. We include Contract assets in our reserving process and assess the risk of loss similar to our methodology for Trade receivables, since Contract assets are reclassified to Trade receivables when we become entitled to payment. Accordingly, a reserve is applied upon recognition of the contract asset. Contract liabilities include advance payments we have received which relate to performance obligations we have not yet satisfied. Our contract assets, net of allowance, are included in Short-term contract assets and Other assets and our contract liabilities are included in Short-term contract liabilities and deferred income on our Consolidated Balance Sheets. The majority of contract liabilities are recognized as revenue within 90 days. Detail of our contract assets and liabilities is presented below. (in millions) December 31, 2020 December 31, 2019 Contract assets, gross $ 347.8 419.3 Allowance for contract assets (2.1) n/a Contract assets, net $ 345.7 419.3 Contract liabilities $ 111.0 87.7 Deferred Income Deferred income includes payments received from customers for which we have satisfied our performance obligations but are not yet able to recognize the related revenue because of contractual requirements. Remaining Performance Obligations Remaining performance obligations represent the aggregate transaction price for contracts where our performance obligations have not yet been satisfied. As of December 31, 2020, the aggregate amount of transaction price allocated to remaining performance obligations represented approximately 5% of our total revenue. In accordance with ASC Topic 606, excluded from the aforementioned remaining performance obligations are (i) amounts attributable to contracts expected to be completed within 12 months and (ii) variable consideration for services performed as a series of daily performance obligations, such as property and facility management contracts and LaSalle advisory contracts. Contracts within these businesses represent a significant portion of our contracts with customers not expected to be completed within 12 months. |
| Cash and Cash Equivalents, Policy [Policy Text Block] | Cash and Cash Equivalents We consider all highly-liquid investments purchased with maturities of less than three months to be cash equivalents. The carrying amount of cash equivalents approximates fair value due to the short-term maturity of these investments. |
| Accounts Receivable [Policy Text Block] | Financing Receivables We account for Trade receivables, Notes and other receivables, Long-term receivables, Reimbursable receivables, and Warehouse receivables as financing receivables. Trade Receivables Pursuant to contractual arrangements, Trade receivables, net of allowances include unbilled amounts of $460.1 million and $586.6 million as of December 31, 2020 and 2019, respectively. We estimate an allowance to provide for uncollectible accounts receivable, which is applied upon recognition of the receivable. We base this estimate on historical experience combined with a review of the receivable aging, current and expected economic conditions, and client credit quality. Our estimate also includes specifically identified amounts for which payment has become unlikely. As trade receivables are due within one year, changes to economic conditions are not expected to have a significant impact on our estimate of expected credit losses. However, we will monitor economic conditions on a quarterly basis to determine if any adjustments are deemed necessary. After all collection efforts have been exhausted by management, the outstanding balance considered not collectible is written off against the allowance. The following table details the changes in the allowance for uncollectible receivables. (in millions) 2020 2019 2018 Allowance as of January 1, (1) $ 71.7 52.0 51.3 Charged to income 24.3 30.8 18.8 Write-off of uncollectible receivables (29.5) (13.8) (13.9) Impact of exchange rate movements and other — (0.9) (4.2) Allowance as of December 31, $ 66.5 68.1 52.0 (1) January 1, 2020 includes $3.6 million adjustment due to adoption of ASC Topic 326. Refer to the "New Accounting Standards" section below for further detail. |
| Notes and Other Recievables and Long-Term Receivables [Policy Text Block] | Notes and Other Receivables and Long-Term Receivables We make ongoing assessments of the collectability of outstanding Notes and other receivables and Long-term receivables, considering both objective and subjective factors such as the aging profile of outstanding balances, the contractual terms of repayment, and credit quality. Aspects of credit quality considered in our assessments of collectability include historical experience, current and expected economic conditions, and our broader business relationship with the obligor. We record an allowance against the outstanding balance when our assessments determine payment has become unlikely. After all collection efforts have been exhausted by management, the outstanding balance is written off against the reserve. Historically, credit quality deterioration to the point of impairment or non-performance in our Notes and other receivables and Long-term receivables has been limited and has not had a material impact on the Consolidated Financial Statements. |
| Reimbursable Receivables [Policy Text Block] | Reimbursable Receivables We recognize Reimbursable receivables for costs incurred on behalf of clients, primarily while performing Property & Facility Management services. These costs include direct reimbursements, primarily payroll and third-party vendor and subcontractor costs. We record an allowance based on specific identification of an uncollectible reimbursable receivable, considering current and future economic conditions as well as client credit quality. Historically, we have not experienced any material collection issues and, as such, have not applied a formulaic reserve to these receivables. Reimbursable receivables relate to our Reimbursable payables, which are typically satisfied on a pay-when-paid basis. |
| Warehouse Receivables and Facilities [Policy Text Block] | Warehouse Receivables We classify Warehouse receivables as held-for-sale as they represent originated mortgage loans for which we have simultaneously executed commitments to sell to a third-party investor, primarily the Federal Home Loan Mortgage Corporation ( Freddie Mac ), the Federal National Mortgage Association ( Fannie Mae ), and the Government National Mortgage Association ( Ginnie Mae ). These loans (also referred to as "Warehouse receivables") are funded directly to borrowers by our warehouse facilities and are generally repaid within a 45-day period after origination when the third-party investor buys the loan(s); upon surrender of control over each loan, we account for the transfer as a sale. Warehouse receivables are measured and reported at fair value in accordance with our entity-wide election of the fair value option. As such, increases or decreases in the fair value of loans are recognized as Revenue on the Consolidated Statements of Comprehensive Income. Historically, we have not experienced credit quality deterioration or uncollectible balances with respect to our Warehouse receivables. We generally retain certain servicing rights upon sale of the mortgage loan (refer to the Mortgage Servicing Rights section below). We typically retain no exposure for credit losses on loans subsequent to sale, except for loans under Fannie Mae's Delegated Underwriting and Servicing ("DUS") program. See the following section, Financial Guarantees, as well as Note 13, Commitments and Contingencies, for additional information on the risk of loss retained related to DUS program loans. Contractually specified servicing fees related to sold warehouse receivables were $80.0 million, $63.0 million and $49.6 million for the years ended December 31, 2020, 2019, and 2018, respectively, and are included in Revenue on the Consolidated Statements of Comprehensive Income. |
| Financial Guarantees [Policy Text Block] | Financial Guarantees Certain loans we originate and sell under the Fannie Mae DUS program retain a percentage of the risk of loss. This loss-sharing aspect of the program represents an off-balance sheet credit exposure, and we have established a contingent reserve ("loan loss guarantee reserve") for this risk in accordance with ASC Topic 326. To estimate the reserve, we use a model that analyzes historical losses, current and expected economic conditions, and reasonable and supportable forecasts. The model also considers specific details of the underlying property used as collateral, such as occupancy and financial performance. The loan loss guarantee reserve is calculated on an individual loan level. As of December 31, 2020, the loan loss guarantee reserve was $36.7 million and was included within Other liabilities on the Consolidated Balance Sheets. This balance reflected a notable increase from our opening balance (included in the New Accounting Standards section below) as a result of incorporating into our model, economic conditions and projections related to the COVID-19 pandemic. For all DUS program loans with loss-sharing obligations, we record a non-contingent liability equal to the estimated fair value of the guarantee obligations undertaken upon sale of the loan, which reduces our gain on sale of the loan. Subsequently, this liability is amortized over the estimated life of the loan and recognized as Revenue on the Consolidated Statements of Comprehensive Income. The loss-sharing guarantee obligation (in accordance with ASC Topic 460, Guarantees ) is separate from the loan loss guarantee reserve discussed above. As of December 31, 2020 and 2019, loss-sharing guarantee obligations were $22.1 million and $20.6 million, respectively, and are included in Other liabilities on the Consolidated Balance Sheets. See Note 13, Commitments and Contingencies, for further information on the DUS program. |
| Mortgage Servicing Rights [Policy Text Block] | Mortgage Servicing Rights We generally retain certain servicing rights in connection with the origination and sale of Warehouse receivables. We initially record MSRs based on the fair value of these rights on the date the loans are sold, which could result in net gains which we recognize as Revenue on the Consolidated Statements of Comprehensive Income. As of December 31, 2020 and 2019, we had $424.3 million and $376.4 million, respectively, of MSRs carried at the lower of amortized cost or fair value in Identified intangibles on the Consolidated Balance Sheets. We amortize servicing rights over the estimated period net servicing income is projected to be received. In addition, we evaluate MSR intangible assets for impairment on a quarterly basis, or more frequently if circumstances or events indicate a change in fair value. Other than write-offs due to prepayments of sold Warehouse receivables for which we retained the servicing rights (generally only during the last six months of loan term given the punitive contractual terms of any earlier prepayment), there have been no significant instances of impairment during the three-year period ended December 31, 2020. However, an increase in loan prepayment activity or deterioration in the credit quality of borrowers could result in a decrease to our MSR balance. MSRs do not actively trade in an open market with readily available observable prices; therefore, if necessary, the fair value of these rights are determined in part based on certain assumptions and judgments that are unobservable within the fair value hierarchy, including the estimation of the present value of future cash flows to be realized from servicing the underlying mortgages. T he estimated fair value of MSRs was $459.6 million and $423.7 million as of December 31, 2020 and 2019, respectively. See Note 4, Business Combinations, Goodwill and Other Intangible Assets for additional information on MSRs. |
| Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] | Restricted Cash Restricted cash primarily consists of cash amounts set aside to satisfy legal or contractual requirements arising in the normal course of business. We are restricted in our ability to withdraw these funds other than for their specified use. Restricted cash was included in Prepaid and other current assets on the Consolidated Balance Sheets. |
| Property, Plant and Equipment, Policy [Policy Text Block] | Property and Equipment We record property and equipment at cost and depreciate these assets over their relevant useful lives. We capitalize certain direct costs relating to internal-use software when incurred during the application development phase. We evaluate property and equipment for impairment whenever events or circumstances indicate the carrying value of an asset group may not be recoverable. We record an impairment loss to the extent the carrying value exceeds the estimated fair value. We did not recognize any significant impairment losses related to property and equipment during the three years ended December 31, 2020. We calculate depreciation on property and equipment for financial reporting purposes using the straight-line method based on the estimated useful lives of our assets. Depreciation expense related to property and equipment for the years ended December 31, 2020, 2019 and 2018 was $169.3 million, $157.6 million, and $156.5 million, respectively. The following table shows the gross value of major asset categories and the standard depreciable lives, as of December 31, 2020, for each of these asset categories. December 31, ($ in millions) 2020 2019 Depreciable Life Furniture, fixtures and equipment $ 127.9 115.4 3 to 13 years Computer equipment and software 829.8 752.9 3 to 10 years Leasehold improvements 352.4 308.6 1 to 10 years Other (1) 160.0 185.7 2 to 30 years Total 1,470.1 1,362.6 Less: Accumulated depreciation 806.2 660.7 Net property and equipment $ 663.9 701.9 (1) Other includes certain assets, such as land, which are not depreciated. |
| Goodwill and Intangible Assets, Policy [Policy Text Block] | Business Combinations, Goodwill and Other Intangible Assets We have historically grown, in part, through a series of acquisitions. Consistent with the services nature of the majority of businesses we have acquired, we have recognized significant goodwill and intangible assets resulting from these acquisitions. Intangible assets are initially recorded at their respective acquisition date fair values and amortized on a straight-line basis over their estimated useful lives. They primarily represent customer relationships, management contracts and customer backlogs acquired as part of our acquisitions. We evaluate goodwill for impairment at least annually. We define our four reporting units as the three geographic regions of RES (i) Americas, (ii) Europe, Middle East and Africa ("EMEA") and (iii) Asia Pacific; and (iv) LaSalle. We have considered qualitative and quantitative factors while performing our annual impairment test of goodwill (as of July 1, 2020) and determined it is not more-likely-than-not that the fair value of our Americas, Asia Pacific, and LaSalle reporting units are less than their carrying values. In performing our assessments of all reporting units, we primarily considered (i) macroeconomic and industry trends, (ii) our overall financial performance, and nature of the key drivers thereof, during the year at both the reporting unit and consolidated reporting levels, (iii) near and longer-term forecasts of operating income and cash flows generated by our reporting units in relation to the carrying values of the net assets of each reporting unit, and (iv) our market capitalization in relation to the aggregate carrying value of our net assets. With respect to our EMEA reporting unit, we performed Step 1 of the goodwill impairment analysis during our 2020 annual impairment test, which indicated the estimated fair value exceeded the carrying value by over 20%. In performing Step 1, we relied on the discounted cash flow (“DCF”) method, an income approach, in determining the estimated fair value. Our DCF analysis relied on significant judgments and assumptions in determining the inputs, specifically, forecasted revenue growth, forecasted profitability margin, and the discount rate used to present value the estimated future cash flows. In addition to our annual impairment evaluation, we evaluated whether events or circumstances have occurred in the period subsequent to our annual impairment testing and determined it is not more-likely-than-not that the fair value of all our reporting units are less than their respective carrying values. It is possible our determination that goodwill for a reporting unit is not impaired could change in the future if current economic or other conditions deteriorate. We will continue to monitor the relationship between our market capitalization and carrying value, as well as the ability of our reporting units to deliver current and projected earnings and cash flows sufficient to support the carrying values of the net assets of their respective businesses. We evaluate our Identified intangibles for impairment annually or more frequently if other events or circumstances indicate the carrying value may be impaired. See Note 4, Business Combinations, Goodwill and Other Intangible Assets, for additional information on business combinations, goodwill and other intangible assets. |
| Equity Method Investments [Policy Text Block] | Investments in Real Estate Ventures We invest in certain ventures that primarily own and operate commercial real estate on a global basis across a wide array of sectors including retail, residential and office. Historically, these investments have primarily been co-investments in funds our LaSalle business establishes in the ordinary course of business for its clients. These investments take the form of equity ownership interests generally ranging from less than 1% to 10% of the respective ventures and, based upon investment-specific objectives, have generally included five to nine-year investment periods. Typically, our investments in real estate ventures are not redeemable until the earlier of the disposition of the underlying real estate investments or the end of the fund's life. When in place, such restrictions are a result of our role beyond that of a passive investor, which generally means an advisory or management responsibility on behalf of the other investors who are typically clients of our LaSalle business. We primarily account for these investments at fair value utilizing information provided by investees, however, as further discussed below, we report certain of our investments under the equity method. In addition to our LaSalle investments, we invest, primarily through the JLL Spark Global Venture funds, in property technology funds and early-stage companies to improve our strategic position within the real estate technology landscape. We generally account for these investments at fair value. The fair value of these investments was $69.9 million and $42.9 million as of December 31, 2020, and 2019, respectively. For limited partnerships in which we are a general partner, the entities are generally well-capitalized and grant the limited partners substantive participating rights, such as the right to replace the general partner without cause, to dissolve or liquidate the partnership, to approve the sale or refinancing of the principal partnership assets, or to approve the acquisition of principal partnership assets. We account for such general partner interests at fair value or under the equity method. For limited partnerships in which we are a limited partner, management has concluded we do not have a controlling interest in these limited partnerships. When we have an asset advisory contract with the limited partnership, the combination of our limited partner interest and the advisory agreement generally provides us with significant influence over the real estate limited partnership venture. Accordingly, we account for such investments at fair value or under the equity method. See "Principles of Consolidation" above for additional discussion of the accounting for our co-investments. For investments in real estate ventures reported at fair value, we maintain an investment account that is increased or decreased each reporting period by the difference between the fair value of the investment and the carrying value as of the balance sheet date. These fair value adjustments are reflected as gains or losses on the Consolidated Statements of Comprehensive Income within Equity earnings. The fair value of these investments as of the balance sheet date is generally determined using NAV per share (or its equivalent), an unobservable input in the fair value hierarchy, provided by the investee. For investments in real estate ventures accounted for under the equity method, we maintain an investment account that is (i) increased by contributions made and by our share of net income earned by the real estate ventures, and (ii) decreased by distributions received and by our share of net losses realized by the real estate ventures. Our share of each real estate venture's net income or loss, including gains and losses from capital transactions, is reflected on the Consolidated Statements of Comprehensive Income as Equity earnings. We evaluate our investments in real estate ventures accounted for under the equity method for other-than-temporary impairment on a quarterly basis, or as events or changes in circumstances warrant such an evaluation. Our evaluations consider the existence of impairment indicators in the underlying real estate assets that compose the majority of our investments. We base such evaluations, in regard to both the investment and the investment’s underlying asset levels, on regular updates to future cash flow models, our share of co-investment cash flows, and factors such as operational performance, market conditions, major tenancy matters, legal and environmental concerns, and our ability and intent to hold each investment. If an investment is considered other-than-temporarily impaired, we record the excess of the carrying value over the estimated fair value as an impairment charge. Impairment charges to write down the carrying value of the real estate assets underlying our investments are generally based on the result of discounted cash flow models that primarily rely upon unobservable inputs to determine fair value. We recognize our proportionate share of such impairment within Equity earnings on the Consolidated Statements of Comprehensive Income. See Note 5, Investments in Real Estate Ventures and Note 9, Fair Value Measurements for additional information on Investments in real estate ventures. |
| Share-based Payment Arrangement [Policy Text Block] | Stock-Based Compensation Stock-based compensation in the form of restricted stock units ("RSUs") and performance stock units ("PSUs") is an important element of our compensation programs. We determine the fair value of RSUs, subject only to service requirements, based on the closing market price of our common stock on the grant date. PSUs are subject to service requirements and performance measures. All PSUs contain one or more performance conditions, such as a pre-defined target based on the Company’s cumulative earnings per share over a multi-year period. For certain executives there is an additional performance measure, a market condition, based on total shareholder return ("TSR") against a peer group. The number of shares that will be issued upon vesting of these PSUs can range from 0% to 150% of the target award, depending on the achievement of each performance condition. We determine the fair value of PSUs based on the (i) closing market price of our common stock on the grant date taking, (ii) the achievement probability for each performance condition, and (iii) the market condition valuation, as applicable, based on the output of Monte Carlo simulations. We periodically assess the achievement probability for performance conditions. As of December 31, 2020, less than 3% of unvested shares were subject to a market condition. Employees of a specific age, with a sum of age plus years of service with the Company which meets or exceeds 65, based on the terms of the Jones Lang LaSalle 2019 Stock Award and Incentive Plan ("SAIP"), are eligible to be considered for receipt of retirement benefits upon departure from the Company. These award provisions require acceleration of compensation expense such that all expense is recognized by the time these employees are considered retirement eligible. We do not estimate forfeitures; instead, we recognize forfeitures in Compensation & benefits expense as they occur. We also have a "noncompensatory" Employee Stock Purchase Plan ("ESPP") for U.S. employees and a Jones Lang LaSalle Savings Related Share Option Plan ("Save As You Earn" or "SAYE") for U.K. employees. The fair value of options granted under the SAYE plan are determined on the grant date and amortized over the associated vesting period. See Note 6, Stock-Based Compensation, for additional information on our stock-based compensation plans. |
| Income Tax, Policy [Policy Text Block] | Income Taxes We account for income taxes under the asset and liability method. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in our financial statements or tax returns. Under this method, we determine deferred tax assets and liabilities based on the differences between the financial reporting and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. An increase or decrease in a deferred tax asset or liability that results from a change in circumstances, and that causes a change in our judgment about expected future tax consequences of events, would be included in the tax provision when the changes in circumstances and our judgment occurs. Deferred income taxes also reflect the impact of operating loss and tax credit carryforwards. A valuation allowance is established if we believe it is more-likely-than-not all or some portion of a deferred tax asset will not be realized. An increase or decrease in a valuation allowance that results from a change in circumstances, and that causes a change in our judgment about the ability to realize the related deferred tax asset, would be included in the tax provision when the changes in circumstances and our judgment occurs. See Note 8, Income Taxes, for additional information on income taxes. |
| Derivatives, Policy [Policy Text Block] | Derivatives and Hedging Activities We do not enter into derivative financial instruments for trading or speculative purposes. However, in the normal course of business, we do use derivative financial instruments in the form of foreign currency forward contracts to manage our foreign currency exchange rate risk. We currently do not use hedge accounting for these contracts, which are marked-to-market each period with changes in unrealized gains or losses recognized in earnings and offset by foreign currency gains and losses on associated intercompany loans and other foreign currency balances. Gains and losses from the revaluation of these contracts are recognized as a component of Operating, administrative and other expense and are offset by the gains and losses recognized on the revaluation of intercompany loans and other foreign currency balances such that the impact to net income was not significant for the three years ended December 31, 2020. For presentation and disclosure, we net our exposure by counterparty for all counterparties subject to International Swaps and Derivatives Association Master Agreements. We have considered the counterparty credit risk related to these forward foreign currency exchange contracts and do not deem any counterparty credit risk to be material as of December 31, 2020, in part due to the short-term nature of these contracts. In addition, certain loan commitments and forward sales commitments related to our Warehouse receivables meet the definition of a derivative and are recorded at fair value on the Consolidated Balance Sheets. The estimated fair value of loan commitments includes the fair value of the expected net cash flows associated with servicing of the loan, other net cash flows associated with origination and sale of the loan, and the effects of market interest rate movements. The estimated fair value of forward sale commitments includes the effects of market interest rate movements. Therefore, the effect of market interest rate movements on estimated fair value offset between the loan commitments and the forward sale commitments. Adjustments to fair value related to loan and forward sale commitments are included within Revenue on the Consolidated Statements of Comprehensive Income. See Note 9, Fair Value Measurements, for additional information on derivative financial instruments. |
| Lessee, Leases [Policy Text Block] | Leases Substantially all of our operating leases are related to office space we lease in various buildings for our own use. The terms of these non-cancelable operating leases typically require us to pay rent and a share of operating expenses and real estate taxes, generally with an inflation-based rent increase included. We also lease equipment under both operating and finance lease arrangements. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. Operating lease right-of-use assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments (e.g. rent) over the lease term beginning at the commencement date. The Operating lease right-of-use assets are adjusted for lease incentives, deferred rent, and initial direct costs, if incurred. Our leases generally do not include an implicit rate; therefore, we use an incremental borrowing rate based on information available at the lease commencement date in determining the present value of future minimum lease payments. The related lease expense is recognized on a straight-line basis over the lease term. Finance leases are included in Property and equipment, net of accumulated depreciation, Short-term borrowings, and Other liabilities on our Consolidated Balance Sheets. Our finance leases do not represent a significant portion of our leasing activity. See Note 11, Leases, for additional information on leases. |
| Foreign Currency Transactions and Translations Policy [Policy Text Block] | Foreign Currency Translation We prepare the financial statements of our subsidiaries located outside the U.S. using local currency as the functional currency. The assets and liabilities of these subsidiaries are translated to U.S. dollars at the rates of exchange as of the balance sheet date with the resulting translation adjustments included as a separate component of equity on the Consolidated Balance Sheets (Accumulated other comprehensive loss) and on the Consolidated Statements of Comprehensive Income (Other comprehensive income-foreign currency translation adjustments). See Note 15, Accumulated Other Comprehensive Income (Loss), for additional information on the components of Accumulated other comprehensive loss. Income and expenses are translated at the average monthly rates of exchange. We include gains and losses from foreign currency transactions in net earnings as a component of Operating, administrative and other expense. For the years ended December 31, 2020, 2019 and 2018 we had net foreign currency transaction losses of $4.6 million, $2.4 million, and $4.1 million, respectively. The effect of foreign currency exchange rate changes on Cash, cash equivalents and restricted cash is presented as a separate caption in the Consolidated Statements of Cash Flows. |
| Cash Held for Others [Policy Text Block] | Cash Held for Others We manage significant amounts of cash and cash equivalents in our role as agent for certain of our investment, facility management and property management clients. We do not include such amounts on the Consolidated Balance Sheets. |
| Taxes Collected from Clients and Remitted to Governmental Authorities [Policy Text Block] | Taxes Collected from Clients and Remitted to Governmental Authorities We account for tax assessed by a governmental authority that is based on a revenue or transaction value (i.e., sales, use and value-added taxes) on a net basis, excluded from revenue, and recorded as current liabilities until paid. |
| Commitments and Contingencies, Policy [Policy Text Block] | Other Commitments and Contingencies We are subject to various claims and contingencies related to disputes, lawsuits and taxes as well as commitments under contractual obligations. Many of these claims are covered under our current insurance programs, subject to deductibles. Our current insurance programs include professional, auto and general liability. For professional indemnity coverage, the level of risk retained by our captive insurance company is limited per claim, inclusive of the deductible. We contract third-party insurance companies to provide coverage of risk in excess of the policy limits. We recognize the liability associated with a loss contingency when a loss is probable and estimable. See Note 13, Commitments and Contingencies, for additional information on our captive insurance company as well as our commitments and contingencies. |
| Earnings Per Share, Policy [Policy Text Block] | Earnings Per Share; Net Income Available to Common Shareholders The difference between basic weighted average shares outstanding and diluted weighted average shares outstanding represents the dilutive impact of our common stock equivalents. Common stock equivalents consist of shares to be issued under employee stock-based compensation programs. Anti-dilutive shares were de minimus for all periods presented. See Note 6, Stock-Based Compensation, for additional information on our stock-based compensation plans. |
| New Accounting Pronouncements, Policy [Policy Text Block] | New Accounting Standards Recently adopted accounting guidance In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments - Credit Losses (ASC Topic 326) , which created a new framework to evaluate financial instruments, such as trade receivables, for expected credit losses. This new framework replaced the existing incurred loss approach and is expected to result in more timely recognition of credit losses. On January 1, 2020, we adopted ASU No. 2016-13 using a modified-retrospective approach, as required by the ASU. The adoption impacted our methodology of reserving for (i) Trade receivables, (ii) other receivable-related financial assets, specifically contract assets, and (iii) off-balance sheet credit exposures within the scope of this ASU. Specifically, we evaluated our historical reserve balances for Trade receivables and the related write-off activity and developed a forward-looking process for adoption. We also evaluated our loss-sharing guarantee obligation for certain mortgage loans we originate, sell and retain the servicing rights. The following table details the cumulative impact to Retained earnings upon adoption of ASC Topic 326. Published Adjustment due to Reported Under ASC Topic 326 (in millions) December 31, 2019 adoption of ASC Topic 326 on January 1, 2020 Assets Allowance for trade receivables $ (68.1) (3.6) $ (71.7) Deferred tax assets, net 245.4 5.5 250.9 Allowance for contract assets (1) — (1.7) (1.7) Liabilities and equity Loan loss guarantee reserve (2) $ — 15.1 $ 15.1 Retained earnings 3,588.3 (14.9) 3,573.4 (1) The portion of the allowance for long-term contract assets is included within Other assets on the Consolidated Balance Sheets. (2) Included within Other liabilities on the Consolidated Balance Sheets In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) , which increased transparency and comparability by requiring the recognition of lease assets and lease liabilities on the balance sheet, as well as requiring the disclosure of key information about leasing arrangements. On January 1, 2019, we adopted this, on a modified retrospective basis under the optional transition method. Therefore, the application of the provisions of this ASU are effective January 1, 2019, and any prior periods are presented in accordance with ASC Topic 840. Additionally, we elected the package of practical expedients permitted under the transition guidance within the new standard, which allowed us to carry forward (i) our historical lease classification and assessments for expired and existing leases, and (ii) our historical accounting for initial direct costs for existing leases. We elected not to record on the Consolidated Balance Sheets any lease whose term is 12 months or less and does not include a purchase option that we are reasonably certain to exercise. We also elected to account for the non-lease components within our leases as part of the single lease component to which they are related. The most significant impact of the adoption of this ASU was an increase to the Consolidated Balance Sheets to reflect operating lease right-of-use assets and lease liabilities, which are primarily associated with our office leases around the world. Our accounting for finance leases was not materially impacted. |
