Segment Disclosures - Segment Revenue Per Service (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016
Revenue from Services
Segment revenue from services	$ 1,328.8	$ 1,247.8	$ 3,952.1	$ 3,972.4
Less: Intersegment revenue
Revenue from Services
Segment revenue from services	(4.6)	(4.7)	(13.2)	(14.4)
Americas Staffing | Reporting Segments
Revenue from Services
Segment revenue from services	554.8	518.2	1,703.5	1,614.7
Global Talent Solutions | Reporting Segments
Revenue from Services
Segment revenue from services	503.0	495.0	1,495.8	1,486.5
International Staffing | Reporting Segments
Revenue from Services
Segment revenue from services	$ 275.6	$ 239.3	$ 766.0	$ 885.6