Employee Benefit Plans - Components of Net Periodic Pension Cost for Defined Benefit Pension Plan and Retirement Plan (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Retirement Benefits [Abstract]
Service cost	$ 150	$ 132	$ 300	$ 265
Interest cost	317	333	634	665
Expected return on plan assets	(446)	(382)	(892)	(765)
Amortization of actuarial losses	186	202	372	405
Net periodic pension cost	$ 207	$ 285	$ 414	$ 570