Segment Disclosures - Segment Revenue From Service (Details) - Service - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2020	Mar. 31, 2019
Revenue from Services
Segment revenue from services	$ 1,261.1	$ 1,382.6
Less: Intersegment revenue
Revenue from Services
Segment revenue from services	(3.1)	(3.8)
Americas Staffing | Reporting Segments
Revenue from Services
Segment revenue from services	533.4	626.5
Global Talent Solutions | Reporting Segments
Revenue from Services
Segment revenue from services	503.2	501.0
International Staffing | Reporting Segments
Revenue from Services
Segment revenue from services	$ 227.6	$ 258.9