Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net loss	$ (1,069)	$ (5,407)	$ (13,379)	$ (17,573)
Denominator for basic and diluted EPS:
Weighted-average common shares outstanding (in shares)	42,925	33,667	39,163	32,783
Net loss per share attributable to common shareholders (basic and diluted) (in dollars per share)	$ (0.02)	$ (0.16)	$ (0.34)	$ (0.54)
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) excluded from diluted net loss per common share (in shares)			5,300	5,400