Basis of Presentation (Policies)	3 Months Ended
Basis of Presentation (Policies)	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The accompanying unaudited consolidated financial statements of Kelly Services, Inc. (the “Company,” “Kelly,” “we” or “us”) have been prepared in accordance with Rule 10-01 of Regulation S-X and do not include all the information and notes required by generally accepted accounting principles (“GAAP”) for complete financial statements. In the opinion of management, all adjustments, including normal recurring adjustments, necessary for a fair statement of the results of the interim periods, have been made. The results of operations for such interim periods are not necessarily indicative of results of operations for a full year. The unaudited consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and notes thereto for the fiscal year ended December 31, 2023, included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 20, 2024 (the 2023 consolidated financial statements). There were no changes in accounting policies as disclosed in the Form 10-K. The Company’s first fiscal quarter ended on March 31, 2024 and April 2, 2023, each of which contained 13 weeks.
Reclassifications	Certain reclassifications have been made to the prior year's consolidated financial statements to conform to the current year's presentation. Specifically, as discussed in the Segment Disclosures footnote, the Company has made a change to its reportable segments during the first quarter of 2024. We have also reclassified the presentation of our retirement plan assets, which represents our investment in life insurance contracts, and intangibles, net from the other assets line item to separate line items within our consolidated balance sheet.
New Accounting Pronouncements	New Accounting Pronouncements Not Yet Adopted In October 2023, the FASB issued Accounting Standards Update ("ASU") 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC's Disclosure Update and Simplification Initiative, which modifies several disclosure and presentation requirements in the FASB accounting standard codification to align them with the SEC regulations. The effective date for each amendment will be the date on which the SEC's removal of that related disclosure from Regulation S-X or Regulation S-K becomes effective, with early adoption permitted, by June 30, 2027. For any amendments in which the SEC has not yet removed the applicable requirement from their regulations by June 30, 2027, the pending content of the related amendment in the FASB codification will not be effective. We do not expect this update to have a material impact to our consolidated financial statements. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires all public companies to provide more enhanced disclosures for significant segment expenses. This ASU is effective for annual reporting periods beginning after December 15, 2024, including interim reporting periods within those annual periods, with early adoption permitted. We are currently evaluating the impact of the new guidance on our consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments to enhance income tax disclosures primarily through changes to the rate reconciliation and income taxes paid information. This ASU is effective for annual reporting periods beginning after December 15, 2024, with early adoption permitted. We are currently evaluating the impact of the new guidance on our consolidated financial statements and related disclosures. Management has evaluated other recently issued accounting pronouncements and does not believe that any of these pronouncements will have a significant impact on our consolidated financial statements and related disclosures.