Selected Quarterly Results of Operations Data -Summary of Quarterly Statement of Operations Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2020		Dec. 31, 2020	Dec. 28, 2019
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 7,627	$ 7,091	$ 3,391	$ 7,530	$ 6,057	$ 7,205	$ 5,666	$ 4,676	$ 25,639	[1]	$ 25,639	$ 23,604	[1]
Gross profit	4,828	5,038	1,909	4,860	3,741	4,216	3,333	2,573			16,635	13,863
Loss from operations	(5,896)	(4,610)	(7,861)	(8,017)	(8,694)	(7,242)	(7,705)	(5,962)			(26,384)	(29,603)
Net loss	$ (6,311)	$ (5,088)	$ (8,497)	$ (8,852)	$ (9,177)	$ (8,280)	$ (9,195)	$ (6,895)	$ (28,748)		$ (28,748)	$ (33,547)
Net loss per share (basic and diluted)	$ (0.23)	$ (0.19)	$ (0.36)	$ (0.42)	$ (0.43)	$ (0.39)	$ (0.70)	$ (4.86)			$ (1.16)	$ (2.36)

[1] Net revenue by country is categorized based on the location of the end customer.