Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

No definition available.

Name:	dei_AmendmentFlag
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

PCAOB issued Audit Firm Identifier

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 10-K
-Number 249
-Section 310

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 20-F
-Number 249
-Section 220
-Subsection f

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 40-F
-Number 249
-Section 240
-Subsection f

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Feb. 04, 2024	Jul. 02, 2023
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	0-1088
Entity Registrant Name	KELLY SERVICES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	38-1510762
Entity Address, Address Line One	999 West Big Beaver Road
Entity Address, City or Town	Troy
Entity Address, State or Province	MI
Entity Address, Postal Zip Code	48084
City Area Code	248
Local Phone Number	362-4444
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 559.1
Documents Incorporated by Reference	The proxy statement of the registrant with respect to its 2024 Annual Meeting of Stockholders is incorporated by reference in Part III.
Amendment Flag	false
Entity Central Index Key	0000055135
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Detroit, Michigan
Auditor Firm ID	238
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		31,967,008
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,321,601
NASDAQ Global Market \| Class A common stock
Document Information [Line Items]
Title of 12(b) Security	Class A Common
Trading Symbol	KELYA
Security Exchange Name	NASDAQ
NASDAQ Global Market \| Class B common stock
Document Information [Line Items]
Title of 12(b) Security	Class B Common
Trading Symbol	KELYB
Security Exchange Name	NASDAQ