Pension and Postretirement Benefit Obligations - Components of Net Periodic Postretirement Benefit Cost (Detail) - Net Postretirement Benefits Activity [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 389	$ 502	$ 1,167	$ 1,507
Interest cost	694	696	2,080	2,088
Recognized net actuarial loss	196	499	587	1,497
Amortization of prior service cost	(324)	(462)	(970)	(1,386)
Net periodic benefit cost	$ 955	$ 1,235	$ 2,864	$ 3,706