Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenues	$ 5,576	$ 7,214
Cost of revenues	1,283	2,113
Gross profit	4,293	5,101
Operating expenses:
Selling and marketing	1,793	2,370
Research and development	2,497	3,923
General and administrative	2,189	2,486
Restructuring expense	392
Total operating expenses	6,871	8,779
Operating loss	(2,578)	(3,678)
Other expense:
Change in fair value of warrant liability	708
Interest income (expense), net	(344)	1
Other expense	(10)	(3)
Loss before provision for income taxes	(2,224)	(3,680)
Provision for income tax expense	8	26
Net loss	(2,232)	(3,706)
Other comprehensive income, before tax:
Unrealized holding gains on available-for-sale securities		2
Other comprehensive income, net of tax		2
Comprehensive loss	$ (2,232)	$ (3,704)
Net loss per share:
Basic and diluted	$ (0.18)	$ (0.32)
Weighted average shares outstanding:
Basic and diluted	12,163	11,524