Pension and Postretirement Benefit Obligations - Components of Net Periodic Postretirement Benefit Cost (Detail) - Net  Postretirement Benefits Activity - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 376	$ 389	$ 752	$ 778
Interest cost	504	693	1,007	1,386
Recognized net actuarial loss	87	195	175	391
Amortization of prior service cost	0	(322)	0	(646)
Net periodic pension/postretirement benefit cost	$ 967	$ 955	$ 1,934	$ 1,909