Quarterly Financial Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of selected quarterly financial information
Net revenues	$ 1,735	$ 1,126	$ 865	$ 1,014	$ 1,009	$ 1,076	$ 1,084	$ 548	$ 2,320	$ 1,679	$ 1,974	$ 1,164	$ 4,740	$ 3,717	$ 7,137
Cost of revenues	469	422	452	166	199	765	662	16	385	337	494	249	1,509	1,642	1,465
Gross margin	1,266	704	413	848	810	311	422	532	1,935	1,342	1,480	915	3,231	2,075	5,672
Net loss	$ (3,107)	$ (3,245)	$ (3,874)	$ (4,008)	$ (3,047)	$ (3,343)	$ (3,120)	$ (3,570)	$ (2,128)	$ (2,144)	$ (3,427)	$ (1,588)	$ (14,234)	$ (13,080)	$ (9,287)
Net loss per basic and diluted common share	$ (0.08)	$ (0.08)	$ (0.10)	$ (0.11)	$ (0.08)	$ (0.09)	$ (0.09)	$ (0.11)	$ (0.07)	$ (0.06)	$ (0.10)	$ (0.05)	$ (0.36)	$ (0.37)	$ (0.28)