Net Income (Loss) Per Share Available to Common Stockholders - Schedule of basic and diluted net loss per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Numerator:
Undistributed net income (loss) available to common stockholders	$ 4,090	$ (9,342)	$ (11,991)	$ (22,434)
Undistributed net income available to nonvested restricted stockholders	9	0	0	0
Net income (loss) available to common stockholders—basic	$ 4,099	$ (9,342)	$ (11,991)	$ (22,434)
Denominator:
Weighted average common shares outstanding—basic	60,415,866	6,441,838	35,806,520	6,103,756
Dilutive effect of stock equivalents resulting from stock options (in shares)	5,608,822	0	0	0
Dilutive effect of RSUs (in shares)	1,802	0	0	0
Weighted average common shares outstanding—diluted	66,026,490	6,441,838	35,806,520	6,103,756
Net income (loss) per share available to common stockholders—basic (in dollars per share)	$ 0.07	$ (1.45)	$ (0.33)	$ (3.68)
Net income (loss) per share available to common stockholders—diluted (in dollars per share)	$ 0.06	$ (1.45)	$ (0.33)	$ (3.68)