Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 6,214	$ 9,613	$ 20,823	$ 21,809
Cost of revenue	2,983	4,874	9,567	10,862
Gross profit	3,231	4,739	11,256	10,947
Operating expenses
Research and development	1,578	1,686	5,499	4,762
Selling, general and administrative	1,695	1,442	5,327	4,939
Total operating expenses	3,273	3,128	10,826	9,701
Income (loss) from operations	(42)	1,611	430	1,246
Other income - net	42	2	196	41
Income before income taxes		1,613	626	1,287
Income tax provision	26	156	170	113
Net income (loss)	$ (26)	$ 1,457	$ 456	$ 1,174
Net income (loss) per share:
Basic	$ 0.00	$ 0.08	$ 0.03	$ 0.07
Diluted	$ 0.00	$ 0.08	$ 0.03	$ 0.07
Weighted average shares outstanding in computing net income (loss) per share
Basic	17,619,958	17,316,172	17,559,438	17,239,544
Diluted	17,619,958	17,899,140	17,877,310	17,850,360
Comprehensive income (loss):
Net income (loss)	$ (26)	$ 1,457	$ 456	$ 1,174
Other comprehensive income, net of tax:
Unrealized gain (loss) on available-for-sale debt securities	(13)		81
Comprehensive income (loss)	$ (39)	$ 1,457	$ 537	$ 1,174