Goodwill - Changes in the Carrying Value of Goodwill (Details) $ in Thousands	9 Months Ended
	Oct. 01, 2017 USD ($)
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 95,280
Goodwill, Ending Balance	113,208
ViDi Systems S.A.
Goodwill [Line Items]
Acquisition of ViDi Systems S.A.	18,333
Acquisition of GVi Ventures, Inc.	18,333
GVi Ventures, Inc.
Goodwill [Line Items]
Acquisition of ViDi Systems S.A.	1,476
Acquisition of GVi Ventures, Inc.	1,476
EnShape
Goodwill [Line Items]
Adjustment to EnShape goodwill	$ (1,881)