Stockholders' Equity, Restricted Stock Units (Details) - Restricted Stock Units ("RSUs") [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted stock units, number of shares [Roll Forward]
Outstanding RSUs, beginning of period (in shares)	351,921	565,965
Awarded (in shares)	102,880	203,449
Released (in shares)	(153,714)	(270,132)
Forfeited (in shares)	(164,758)	(147,361)
Outstanding RSUs, end of period (in shares)	136,329	351,921	565,965
Restricted stock units, weighted average fair value [Abstract]
Outstanding RSUs, beginning of period (in dollars per share)	$ 4.59	$ 6.75
Awarded (in dollars per share)	2.43	2.65
Released (in dollars per share)	3.45	7.14
Forfeited (in dollars per share)	5.78	5.57
Outstanding RSUs, end of period (in dollars per share)	$ 2.80	$ 4.59	$ 6.75
Restricted stock units, additional disclosures [Abstract]
Outstanding RSUs, weighted average remaining contractual term	9 months 18 days	1 year 22 days	1 year 4 months 28 days
Outstanding RSUs, aggregate intrinsic value	$ 329	$ 908	$ 1,715
Compensation cost not yet recognized [Abstract]
Unrecognized compensation cost related to restricted stock units	$ 206
Weighted average period of recognition for unrecognized compensation cost	9 months 18 days