Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2018	Feb. 03, 2019	Jul. 01, 2018
Document Information [Line Items]
Entity Registrant Name	Kelly Services Inc
Document Type	10-K
Current Fiscal Year End Date	--12-30
Entity Public Float			$ 709.7
Amendment Flag	false
Entity Central Index Key	0000055135
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		35,440,000
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,432,072