Pension and Postretirement Benefit Obligations - Components of Net Periodic Postretirement Benefit Cost (Detail) - Net Postretirement Benefits Activity [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 389	$ 502
Interest cost	693	696
Recognized net actuarial loss	196	499
Amortization of prior service cost	(324)	(462)
Net periodic benefit cost	$ 954	$ 1,235