Net Loss Per Share - Computation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net loss	$ (1,689)	$ (590)	$ (2,974)	$ (1,258)
Less: preferred stock dividends	3	3	6	6
Net loss attributable to common stockholders	$ (1,692)	$ (593)	$ (2,980)	$ (1,264)
Denominator:
Weighted-average number of shares of common stock for basic and diluted net loss per share (in shares)	47,359	37,168	46,802	37,168
Basic and diluted net loss per share (in dollars per share)	$ (0.04)	$ (0.02)	$ (0.06)	$ (0.03)