Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ (11,469)	$ (3,102)
Weighted Average Number of Shares Outstanding, Basic	36,045,137	35,665,811
Basic net income (loss) per share	$ (0.32)	$ (0.09)
Shares used in computing diluted net income (loss) per share	36,045,137	35,665,811
Diluted net income (loss) per share	$ (0.32)	$ (0.09)
Shares excluded from diluted net loss per share computations	10,307,431	10,233,980