Summary of Significant Accounting Policies - Schedule of Recognized Revenue Net of Payments (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 29, 2019	Jun. 30, 2020	Jun. 29, 2019
Accounting Policies [Abstract]
Gross revenue from sales to customers		$ 3,923	$ 6,215	$ 12,166	$ 11,505
Less: clinical trial payments reducing revenue		532	549	1,245	1,163
Total net revenue	[1]	$ 3,391	$ 5,666	$ 10,921	$ 10,342

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