Stock-Based Compensation (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2015	Jul. 04, 2014	Jul. 03, 2015	Jul. 04, 2014
Schedule of Employee Service Share-based Compensation [Line Items]
Total stock compensation expense	$ 829	$ 1,683	$ 1,823	$ 3,183
Amounts capitalized as part of inventory	129	71	251	149
Total	958	1,754	2,074	3,332
Cost of Sales [Member]
Schedule of Employee Service Share-based Compensation [Line Items]
Total stock compensation expense	6	39	23	77
General and administrative [Member]
Schedule of Employee Service Share-based Compensation [Line Items]
Total stock compensation expense	548	1,033	1,124	1,970
Marketing and selling [Member]
Schedule of Employee Service Share-based Compensation [Line Items]
Total stock compensation expense	104	306	355	580
Research and development [Member]
Schedule of Employee Service Share-based Compensation [Line Items]
Total stock compensation expense	$ 171	$ 305	$ 321	$ 556