Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Beginning Balance, Shares at Dec. 31, 2016	37,545
Beginning Balance, Amount at Dec. 31, 2016	$ 37	$ 55,160	$ (45,223)	$ 9,974
Adjustment to retained earnings: cumulative effect of initially applying ASC 606				0
Issuance of common stock, net of offering costs, Shares	15,593
Issuance of common stock, net of offering costs, Amount	$ 16	47,579		47,595
Exercise of stock options, Shares	885
Exercise of stock options, Amount	$ 1	3,037		3,038
Vested restricted stock, Shares	674
Vested restricted stock, Amount	$ 1	(1)
Share-based compensation, Amount		4,605		4,605
Net loss			(11,378)	(11,378)
Ending Balance, Shares at Dec. 30, 2017	54,697
Ending Balance, Amount at Dec. 30, 2017	$ 55	110,380	(56,601)	53,834
Adjustment to retained earnings: cumulative effect of initially applying ASC 606			164	164,000
Exercise of stock options, Shares	132
Exercise of stock options, Amount		529		529
Repurchase of common stock, Shares	(75)
Repurchase of common stock, Amount		(404)		(404)
Vested restricted stock, Shares	2
Share-based compensation, Amount	$ 333	6,371		6,371
Net loss			(33,316)	(33,316)
Ending Balance, Shares at Dec. 31, 2018	55,089
Ending Balance, Amount at Dec. 31, 2018	$ 55	$ 116,876	$ (89,753)	$ 27,178