Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (6,586)	$ (5,269)	$ (5,403)	$ (5,034)
Unrealized gains (losses)	629	(384)	(610)	823
Amounts reclassified from accumulated other comprehensive income (loss)	38	22	114	(1,573)
Tax effect	(9)	(5)	(29)	148
Net of tax amount	658	(367)	(525)	(602)
Ending balance	(5,928)	(5,636)	(5,928)	(5,636)
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,872)	(4,612)	(4,633)	(5,819)
Unrealized gains (losses)	629	(384)	(610)	823
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Tax effect	0	0	0	0
Net of tax amount	629	(384)	(610)	823
Ending balance	(5,243)	(4,996)	(5,243)	(4,996)
Defined benefit pension plans [member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(714)	(657)	(770)	785
Unrealized gains (losses)	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	38	22	114	(1,573)
Tax effect	(9)	(5)	(29)	148
Net of tax amount	29	17	85	(1,425)
Ending balance	$ (685)	$ (640)	$ (685)	$ (640)