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						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net loss	$ (640)	$ (875)	$ (598)	$ (1,470)	$ (1,689)	$ (1,285)	$ (2,113)	$ (4,444)
Less: preferred stock dividends	4			3			23	9
Net loss attributable to common stockholders	$ (644)			$ (1,473)			$ (2,136)	$ (4,453)
Denominator:
Weighted-average number of shares of common stock for basic and diluted net loss per share (in shares)	5,184			4,885			5,128	4,749
Basic and diluted net loss per share (in dollars per share)	$ (0.12)			$ (0.30)			$ (0.42)	$ (0.94)