Pension and Other Postretirement Obligations - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Pension Obligations
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 942	$ 1,251	$ 2,075	$ 2,343
Interest cost	1,905	1,874	3,781	3,569
Expected return on plan assets	(2,508)	(2,567)	(5,028)	(4,928)
Amortization of prior service credit	(12)	(9)	(22)	(20)
Actuarial losses	612	645	1,277	1,233
Net periodic benefit cost	939	1,194	2,083	2,197
Other Postretirement Obligations
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	13	26	27
Interest cost	260	329	524	656
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	0	0	0	0
Actuarial losses	0	23	0	45
Net periodic benefit cost	$ 273	$ 365	$ 550	$ 728