Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 26,285	$ 22,974
Cost of revenues	4,333	5,082
Gross profit	21,952	17,892
Operating expenses:
Selling and marketing	5,784	6,186
Research and development	8,602	8,952
General and administrative	8,607	8,551
Restructuring expenses	173	(123)
Total operating expenses	23,166	23,566
Operating loss	(1,214)	(5,674)
Non-operating expense:
Change in fair value of warrant liability	(812)
Loss on debt extinguishment	(203)	(405)
Interest expense, net	(472)	(1,120)
Other expense, net	(26)	(8)
Loss before provision for income taxes	(2,727)	(7,207)
Provision for income tax expense (benefit)	13	(546)
Net loss	(2,740)	(6,661)
Other comprehensive loss, before tax:
Unrealized holding losses on available-for-sale securities	(1)
Other comprehensive loss, net of tax	(1)
Comprehensive loss	$ (2,741)	$ (6,661)
Net loss per share:
Basic and diluted	$ (0.14)	$ (0.49)
Weighted average shares outstanding:
Basic and diluted	22,322	13,489