Restructuring and other strategic initiatives - Restructuring Reserve Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Restructuring reserves
Balance as of the beginning of the period	$ 2.9	$ 2.6
Utilized during the period	(2.0)	(2.0)
Net charge for the period	2.4	3.3
Released during the period	(0.5)	0.0
Foreign currency translation	0.1	(0.1)
Balance as of the end of the period	$ 2.9	$ 3.8