Pension and Postretirement Benefit Obligations - Components of Net Periodic Postretirement Benefit Cost (Detail) - Net Postretirement Benefits Activity [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 503	$ 572	$ 1,005	$ 1,144
Interest cost	696	911	1,392	1,822
Recognized net actuarial loss	499	648	998	1,296
Amortization of prior service cost	(462)	(746)	(924)	(1,492)
Net periodic pension cost	$ 1,236	$ 1,385	$ 2,471	$ 2,770