Benefit Plans - Components of Net Periodic Postretirement Benefit Cost (Detail) - Postretirement Benefits - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 29, 2019	Dec. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,454	$ 1,496	$ 1,854
Interest cost	2,031	2,750	2,694
Recognized net actuarial loss	383	730	1,889
Amortization of prior service cost	0	(1,293)	(1,847)
Net periodic pension/postretirement benefit cost	$ 3,868	$ 3,683	$ 4,590