XML 12 R1.htm IDEA: XBRL DOCUMENT v3.20.2
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2020
Oct. 27, 2020
Document and Entity Information [Abstract]    
Entity Registrant Name Jones Lang LaSalle Incorporated  
Entity Central Index Key 0001037976  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   51,302,899
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q3  
Document Type 10-Q  
Amendment Flag false  
Entity Incorporation, State or Country Code MD  
Document Period End Date Sep. 30, 2020  
Entity Shell Company false  
Entity Current Reporting Status Yes