Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 14,223	$ 13,309	$ 10,336	$ 9,121
Components of other comprehensive income/(loss), net of tax:
Foreign currency translation adjustments	881	245	1,203	1,997
Amortization of defined benefit pension items:
Net actuarial loss	147	146	294	508
Prior service cost	10	0	20	0
Defined benefit pension plan adjustments	157	146	314	508
Other comprehensive income, net of tax	1,038	391	1,517	2,505
Comprehensive income	$ 15,261	$ 13,700	$ 11,853	$ 11,626