Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenues	$ 5,463	$ 5,576
Cost of revenues	1,309	1,283
Gross profit	4,154	4,293
Operating expenses:
Selling and marketing	1,730	1,793
Research and development	2,255	2,497
General and administrative	2,190	2,189
Restructuring expense		392
Total operating expenses	6,175	6,871
Operating loss	(2,021)	(2,578)
Other expense:
Interest expense, net	(171)	(284)
Change in fair value of warrant liability	(139)
Other expense	(40)	(10)
Loss before provision for income taxes	(2,371)	(2,872)
Provision for income tax expense	10	8
Net loss	$ (2,381)	$ (2,880)
Net loss per share:
Basic and diluted	$ (0.16)	$ (0.24)
Weighted average shares outstanding:
Basic and diluted	15,299	12,163
Preferred dividends per share	$ 25.56