Other Income (Expense) - Net - Computation of Other Income (Expense) - Net (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Dec. 30, 2017	Dec. 31, 2016
Other Income and Expenses [Abstract]
Interest income	$ 0.1	$ 0.0	$ 0.4	$ 0.2
Net foreign exchange loss	(1.8)	(2.0)	(4.2)	(5.7)
Net periodic pension and postretirement benefits (costs) – non-service	1.3	0.4	2.7	(0.3)
Settlement of treasury lock	0.0	0.0	13.3	0.0
Loss on early extinguishment of debt	0.0	0.0	(7.8)	0.0
Other	(0.6)	(0.1)	(3.2)	(0.2)
Total other income (expense) – net	$ (1.0)	$ (1.7)	$ 1.2	$ (6.0)	$ (7.8)	$ (7.5)