Pension and Postretirement Benefit Obligations - Components of Net Periodic Postretirement Benefit Cost (Detail) - Net Postretirement Benefits Activity - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 376	$ 389	$ 1,128	$ 1,167
Interest cost	504	694	1,511	2,080
Recognized net actuarial loss	88	196	263	587
Amortization of prior service cost	0	(324)	0	(970)
Net periodic pension/postretirement benefit cost	$ 968	$ 955	$ 2,902	$ 2,864