Business Segment, Concentration of Credit Risk and Significant Customers - Schedule of Revenue from Shipment of Product and Licensing of its Technologies to Customers by Geographical Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Segments
Total net revenue	$ 6,795	$ 10,086
North America [Member]
Business Segments
Total net revenue	5,454	7,585
Japan [Member]
Business Segments
Total net revenue	675	1,734
Taiwan [Member]
Business Segments
Total net revenue	459	345
Rest of world [Member]
Business Segments
Total net revenue	$ 207	$ 422