Retirement Plans - Schedule of Net Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 25, 2017	Jun. 30, 2018	Jun. 25, 2017
Retirement Benefits [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	272	298	543	596
Net amortization	109	67	219	134
Net periodic pension cost	$ 381	$ 365	$ 762	$ 730