Postretirement Health Care Plans - Net Periodic Postretirement Health Care Cost (Detail) - Postretirement Health Coverage - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Postretirement Health Care Plans [Line Items]
Interest cost	$ 0.3	$ 0.5	$ 0.7	$ 1.0
Expected return on plan assets	(0.1)	(0.2)	(0.3)	(0.4)
Amortization of unrecognized gain	0.0	(0.2)	0.0	(0.4)
Net periodic cost	$ 0.2	$ 0.1	$ 0.4	$ 0.2