Investment in Persol Holdings - Narrative (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 29, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 30, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 29, 2019	Dec. 30, 2018	Dec. 31, 2017	Jan. 01, 2018
Gain (Loss) on Securities [Line Items]
Gain (loss) on investment in Persol Holdings	$ 0.7	$ (39.3)	$ 61.2	$ 13.2	$ (83.2)	$ 15.8	$ (52.5)	$ 23.7	$ 35.8	$ (96.2)	$ 0.0
OCI & AOCI
Gain (Loss) on Securities [Line Items]
Cumulative effect of new accounting principle in period of adoption												$ 140.0
Cumulative effect of new accounting principle in period of adoption, taxes												$ 69.9