Net Periodic Benefit Expense - Defined Benefit Pension Plans (Details) - Pension plans, defined benefit [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Service costs--increase in benefit obligation earned	$ 45	$ 100
Interest cost on projected benefit obligation	75	180
Expected return on plan assets	(23)	(58)
Amortization of net actuarial loss	44	182
Amortization of prior service cost	16	16
Net pension expense of defined benefit pension plans	$ 157	$ 420