Document and Entity Information - shares	9 Months Ended
	Oct. 01, 2017	Oct. 30, 2017
Document Information [Line Items]
Entity Registrant Name	KELLY SERVICES INC
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Entity Central Index Key	0000055135
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Document Period End Date	Oct. 01, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		34,991,496
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,434,362