Investment in Persol Holdings	6 Months Ended
	Jun. 28, 2020
Investment in Persol Holdings [Abstract]
Investment in Persol Holdings	Investment in Persol HoldingsThe Company has a yen-denominated investment through the Company's subsidiary, Kelly Services Japan, Inc., in the common stock of Persol Holdings Co., Ltd. ("Persol Holdings"), the Company’s joint venture partner in PersolKelly Pte. Ltd. (the "JV"). As our investment is a noncontrolling interest in Persol Holdings, this investment is recorded at fair value based on the quoted market price of Persol Holdings stock on the Tokyo Stock Exchange as of the period end (see Fair Value Measurements footnote). A gain on the investment of $29.6 million and a loss on the investment of $48.2 million in the second quarter and June year to date 2020, respectively, and a gain on the investment of $61.2 million and $74.4 million in the second quarter and June year to date 2019, respectively, was recorded in gain (loss) on investment in Persol Holdings in the consolidated statements of earnings.