v3.10.0.1
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 29, 2018
Document Information [Line Items]    
Entity Registrant Name KELLY SERVICES INC  
Document Type 10-Q  
Current Fiscal Year End Date --12-30  
Amendment Flag false  
Entity Central Index Key 0000055135  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Entity Emerging Growth Company false  
Entity Small Business false  
Class A Common Stock    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   35,434,862
Class B Common Stock    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   3,432,072