Net Periodic Benefit Expense - Defined Benefit Pension Plans (Details) - Pension plans, defined benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Defined Benefit Plan Disclosure [Line Items]
Service costs--increase in benefit obligation earned	$ 132	$ 90	$ 265	$ 190
Interest cost on projected benefit obligation	264	310	527	627
Expected return on plan assets	(170)	(276)	(339)	(553)
Settlement loss	0	0	0	453
Amortization of net actuarial loss	238	237	475	480
Amortization of prior service cost	15	0	31	0
Net pension expense of defined benefit pension plans	$ 479	$ 361	$ 959	$ 1,197