Summary of Significant Accounting Policies - Narrative (Details)		3 Months Ended
		Mar. 31, 2018 USD ($) customer	Mar. 31, 2017 USD ($) customer	Dec. 31, 2017 USD ($)
Revenues attributable to sales [Line Items]
Warranty reserves		$ 428,000		$ 350,000
Percentage of net revenue		40.40%	34.80%
Numbers of customers | customer		2	2
Revenues	[1]	$ 7,837,000	$ 7,703,000
Line of Credit Maintained		$ 1,000,000
Avnet
Revenues attributable to sales [Line Items]
Percentage of net revenue		27.30%	25.30%
Significant Customers | Avnet
Revenues attributable to sales [Line Items]
Percentage of net revenue		40.40%

[1] Represents the portfolio of available for sale securities that is included in restricted investments and short-term investments in the Company’s condensed consolidated balance sheets