Postretirement Health Care Plans - Net Periodic Postretirement Health Care Cost (Detail) - Postretirement Health Coverage - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Postretirement Health Care Plans [Line Items]
Interest cost	$ 0.5	$ 0.5	$ 1.4	$ 1.5
Expected return on plan assets	(0.2)	(0.2)	(0.6)	(0.6)
Amortization of unrecognized gain	(0.1)	(0.1)	(0.3)	(0.2)
Net periodic pension cost	$ 0.2	$ 0.2	$ 0.5	$ 0.7