Defined Benefit Pension Plans (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 29, 2017	Sep. 30, 2016	Sep. 29, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 126	$ 155	$ 380	$ 466
Interest cost		15	19	43	54
Expected return on plan assets		(25)	(24)	(71)	(69)
Net amortization of transitional obligation	[1]	3	3	9	10
Actuarial loss recognized in current period	[1]	17	24	51	70
Total		$ 136	$ 177	$ 412	$ 531

[1] Amounts reclassified from accumulated other comprehensive loss.