Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Revenues	$ 5,862	$ 7,459	$ 11,438	$ 14,673
Cost of revenues	1,285	1,913	2,568	4,026
Gross profit	4,577	5,546	8,870	10,647
Operating expenses:
Selling and marketing	1,461	2,478	3,254	4,848
Research and development	2,174	4,107	4,671	8,030
General and administrative	2,239	2,870	4,428	5,356
Restructuring expense	322		714
Total operating expenses	6,196	9,455	13,067	18,234
Operating loss	(1,619)	(3,909)	(4,197)	(7,587)
Other expense:
Change in fair value of warrant liability	(561)		147
Change in carrying value of contingent liability		657		657
Interest (expense) income, net	(390)	(2)	(734)
Other expense	1	(15)	(9)	(19)
Loss before provision for income taxes	(2,569)	(3,269)	(4,793)	(6,949)
Provision for income tax expense	5	11	13	37
Net loss	(2,574)	(3,280)	(4,806)	(6,986)
Other comprehensive income, before tax:
Unrealized holding gains on available-for-sale securities				2
Other comprehensive income, net of tax				2
Comprehensive loss	$ (2,574)	$ (3,280)	$ (4,806)	$ (6,984)
Net loss per share:
Basic and diluted	$ (0.20)	$ (0.28)	$ (0.38)	$ (0.60)
Weighted average shares outstanding:
Basic and diluted	13,179	11,741	12,674	11,632