Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenues	$ 6,478	$ 9,586	$ 21,151	$ 29,501
Cost of revenues	1,798	1,959	5,824	6,148
Gross profit	4,680	7,627	15,327	23,353
Operating expenses:
Selling and marketing	2,541	2,220	7,389	6,639
Research and development	4,174	3,480	12,204	10,268
General and administrative	2,522	2,695	7,878	8,437
Total operating expenses	9,237	8,395	27,471	25,344
Operating loss	(4,557)	(768)	(12,144)	(1,991)
Other expense:
Change in fair value of warrant liability	335		335
Change in fair value of contingent liability	11		668
Interest expense	(83)		(81)
Other income (expense), net	(9)	4	(30)	3
Loss before provision for income taxes	(4,303)	(764)	(11,252)	(1,988)
Provision for income tax expense	11	6	48	23
Net loss	(4,314)	(770)	(11,300)	(2,011)
Other comprehensive income, before tax:
Unrealized holding gains on available-for-sale securities			2	1
Other comprehensive income, net of tax			2	1
Comprehensive loss	$ (4,314)	$ (770)	$ (11,298)	$ (2,010)
Net loss per share:
Basic and diluted	$ (0.35)	$ (0.07)	$ (0.96)	$ (0.17)
Weighted average shares outstanding:
Basic and diluted	12,209	11,540	11,826	11,494