Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 29, 2018
Statement Of Financial Position [Abstract]
Allowances for doubtful accounts	$ 200	$ 170
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	47,000,000	47,000,000
Common stock, shares issued	24,842,959	24,372,193
Common stock, shares outstanding	24,842,959	24,372,193