Retirement Plans (Tables)

3 Months Ended

Mar. 31, 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 first three months of 2018 and 2017.

	Three Months Ended
	March 31, 2018		March 26, 2017
(Dollars in thousands)
Interest cost	$	272	$	298
Net amortization		109		67
Net periodic pension cost	$	381	$	365