Business Segments, Concentration of Credit Risk and Significant Customers - Segments/Concentration (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) segment item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Segments
Number of business segments \| segment	1
Number of measurements of profitability \| item	1
Total net revenue	$ 8,842	$ 6,024	$ 4,390
North America
Business Segments
Total net revenue	6,531	3,816	2,222
Japan
Business Segments
Total net revenue	1,520	1,303	667
Taiwan
Business Segments
Total net revenue	613	804	1,396
Rest of world
Business Segments
Total net revenue	$ 178	$ 101	$ 105

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration