Segment Disclosures - Segment Earnings (loss) From Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Earnings (loss) from Operations
Gross profit	$ 191.0	$ 227.7	$ 603.5	$ 723.3
SG&A expenses	(193.4)	(210.6)	(591.0)	(666.9)
Earnings (loss) from operations	(2.4)	17.1	(103.1)	68.7
Gain (loss) on investment in Persol Holdings	16.8	(39.3)	(31.4)	35.1
Other income (expense), net	(0.7)	(0.2)	3.6	(1.1)
Earnings (loss) before taxes and equity in net earnings (loss) of affiliate	13.7	(22.4)	(130.9)	102.7
Less: Intersegment
Earnings (loss) from Operations
Gross profit	0.0	0.0	0.0	0.0
SG&A expenses	0.0	0.0	0.0	0.0
Earnings (loss) from operations	0.0	0.0	0.0	0.0
Corporate
Earnings (loss) from Operations
Earnings (loss) from operations	(19.9)	(18.8)	(178.9)	(56.7)
Professional & Industrial | Reporting Segments
Earnings (loss) from Operations
Gross profit	77.1	91.8	241.1	291.6
SG&A expenses	(65.3)	(77.6)	(210.4)	(246.9)
Earnings (loss) from operations	11.8	14.2	30.7	44.7
Science, Engineering & Technology | Reporting Segments
Earnings (loss) from Operations
Gross profit	50.7	58.3	156.0	171.8
SG&A expenses	(31.3)	(36.0)	(99.1)	(111.4)
Earnings (loss) from operations	19.4	22.3	56.9	60.4
Education | Reporting Segments
Earnings (loss) from Operations
Gross profit	4.1	8.6	28.8	49.9
SG&A expenses	(11.6)	(13.8)	(37.7)	(41.5)
Earnings (loss) from operations	(7.5)	(5.2)	(8.9)	8.4
Outsourcing & Consulting | Reporting Segments
Earnings (loss) from Operations
Gross profit	29.1	29.5	87.1	90.7
SG&A expenses	(25.4)	(29.1)	(79.1)	(90.9)
Earnings (loss) from operations	3.7	0.4	8.0	(0.2)
International | Reporting Segments
Earnings (loss) from Operations
Gross profit	30.0	39.5	90.5	119.3
SG&A expenses	(39.9)	(35.3)	(101.4)	(107.2)
Earnings (loss) from operations	$ (9.9)	$ 4.2	$ (10.9)	$ 12.1