Long-term Debt - Schedule of Long-term Debt Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 28, 2019
Debt Disclosure [Abstract]
Principal amount of long-term debt	$ 35,000	$ 35,000
Less: Current portion of long-term debt	0
Long-term debt, net of current portion	35,000	35,000
Debt discount, net of accretion	(912)	(1,139)
Accrued end-of-term payment	437	285
Long-term debt, net of discount and current portion	$ 34,525	$ 34,146