Document and Entity Information - shares	3 Months Ended
	Apr. 01, 2018	Apr. 30, 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	Accelerated Filer
Document Period End Date	Apr. 01, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		35,350,825
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,431,972