Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (9,679)	$ (10,645)	$ (8,393)	$ (12,162)
Unrealized gains (losses)	517	1,295	(1,062)	2,498
Amounts reclassified from accumulated other comprehensive income (loss)	197	254	593	760
Tax effect	(51)	(97)	(154)	(289)
Net of tax amount	663	1,452	(623)	2,969
Ending balance	(9,016)	(9,193)	(9,016)	(9,193)
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,884)	(4,297)	(3,305)	(5,500)
Unrealized gains (losses)	517	1,295	(1,062)	2,498
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Tax effect	0	0	0	0
Net of tax amount	517	1,295	(1,062)	2,498
Ending balance	(4,367)	(3,002)	(4,367)	(3,002)
Defined benefit pension plans [member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,795)	(6,348)	(5,088)	(6,662)
Unrealized gains (losses)	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	197	254	593	760
Tax effect	(51)	(97)	(154)	(289)
Net of tax amount	146	157	439	471
Ending balance	$ (4,649)	$ (6,191)	$ (4,649)	$ (6,191)