Retirement Plans (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Summary of Components of Net Periodic Pension Cost

The following table summarizes the components of net periodic pension cost for the three and six-month periods ended June 30, 2018 and June 25, 2017.

	Three Months Ended				Six Months Ended
	June 30, 2018		June 25, 2017		June 30, 2018		June 25, 2017
(Dollars in thousands)
Service cost	$	—	$	—	$	—	$	—
Interest cost		272		298		543		596
Net amortization		109		67		219		134
Net periodic pension cost	$	381	$	365	$	762	$	730