Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 28, 2018	Dec. 29, 2017
Statement Of Financial Position [Abstract]
Account receivable, allowance	$ 235	$ 69
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	39,001,184	33,664,940
Common stock, shares outstanding	39,001,184	33,664,940
Treasury stock, shares	601,944	601,944

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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