Segment Reporting and Geographic Data - Financial data by geographical area (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 29, 2019	Jun. 30, 2020	Jun. 29, 2019
Net revenue by country:
Net revenue	[1]	$ 3,391	$ 5,666	$ 10,921	$ 10,342
United States [Member]
Net revenue by country:
Net revenue	[1]	2,440	4,302	7,648	7,255
United Kingdom [Member]
Net revenue by country:
Net revenue	[1]	355	405	1,467	974
All Other Countries [Member]
Net revenue by country:
Net revenue	[1]	$ 596	$ 959	$ 1,806	$ 2,113

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