Segment Disclosures - Schedule of Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 29, 2024	Dec. 31, 2023	Jan. 01, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	$ 4,331.8	$ 4,835.7	$ 4,965.4
Cost of services	3,449.2	3,874.3	3,953.6
SG&A expenses	708.5	831.4	874.1
SG&A expenses	818.4	934.7	943.5
Goodwill impairment charge	72.8	0.0	41.0
Asset impairment charge	(13.5)	(2.4)
Business unit profit (loss)	101.3	127.6	96.7
Earnings (loss) from operations	(15.1)	24.3	14.8
Loss on disposal	0.0	0.0	(18.7)
Gain on sale of assets	5.4	0.0	6.2
Gain on sale of EMEA staffing operations	1.6	0.0	0.0
Amortization of intangible assets	(51.5)	(40.1)	(37.1)
Loss on investment in Persol Holdings	0.0	0.0	(67.2)
Loss on currency translation from liquidation of subsidiary			(20.4)
Other income (expense), net	(6.8)	0.6	1.6
Earnings (loss) before taxes and equity in net earnings of affiliate	(21.9)	24.9	(71.2)
Science, Engineering & Technology
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	1,422.8	1,190.8	1,265.4
Goodwill impairment charge	72.8	0.0
Education
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Goodwill impairment charge	0.0	0.0
Outsourcing & Consulting
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	468.3	454.7	468.0
International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	0.0	812.1	887.0
Reporting Segments | Professional & Industrial
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	1,470.7	1,539.5	1,709.9
Cost of services	1,209.4	1,262.4	1,396.8
Direct salaries	141.2	163.5	185.1
Other segment expenses	85.4	97.3	108.4
SG&A expenses	226.6	260.8	293.5
Goodwill impairment charge	0.0		0.0
Asset impairment charge		(0.3)
Business unit profit (loss)	34.7	16.0	19.6
Reporting Segments | Science, Engineering & Technology
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	1,422.8	1,190.8	1,265.4
Cost of services	1,087.2	918.8	968.4
Direct salaries	170.5	127.1	141.7
Other segment expenses	75.3	69.8	76.3
SG&A expenses	245.8	196.9	218.0
Goodwill impairment charge	72.8		0.0
Asset impairment charge		(0.1)
Business unit profit (loss)	17.0	75.0	79.0
Reporting Segments | Education
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	972.3	841.9	636.2
Cost of services	832.5	713.2	535.9
Direct salaries	60.5	59.6	50.8
Other segment expenses	35.4	32.8	30.7
SG&A expenses	95.9	92.4	81.5
Goodwill impairment charge	0.0		0.0
Asset impairment charge		0.0
Business unit profit (loss)	43.9	36.3	18.8
Reporting Segments | Outsourcing & Consulting
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	468.3	454.7	468.0
Cost of services	322.4	291.2	298.4
Direct salaries	104.3	116.6	114.8
Other segment expenses	35.9	42.7	39.8
SG&A expenses	140.2	159.3	154.6
Goodwill impairment charge	0.0		41.0
Asset impairment charge		(2.0)
Business unit profit (loss)	5.7	2.2	(26.0)
Reporting Segments | International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	0.0	812.1	887.0
Cost of services		692.0	755.2
Direct salaries		83.6	85.1
Other segment expenses		38.4	41.4
SG&A expenses		122.0	126.5
Goodwill impairment charge			0.0
Asset impairment charge		0.0
Business unit profit (loss)		(1.9)	5.3
Less: Intersegment revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	(2.3)	(3.3)	(1.1)
Cost of services	(2.3)	(3.3)	(1.1)
SG&A expenses	0.0	0.0	0.0
Goodwill impairment charge	0.0		0.0
Asset impairment charge		0.0
Business unit profit (loss)	0.0	0.0	0.0
Corporate
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
SG&A expenses	$ (58.4)	$ (63.2)	$ (32.3)