Net Loss Per Share - Weighted Average Number of Common Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Loss from continuing operations	$ (5,424)	$ (4,248)
Loss from discontinued operations	(91)	(2,369)
Net loss	$ (5,515)	$ (6,617)
Denominator:
Weighted average common shares outstanding	9,089	8,513
Weighted average unvested common shares subject to repurchase	(84)	(47)
Weighted average common shares outstanding—basic	9,005	8,466
Effect of dilutive securities:
Effect of dilutive securities: conversion of preferred stock	0	0
Effect of dilutive securities: options	0	0
Effect of dilutive securities: warrants	0	0
Weighted average common shares outstanding—diluted	9,005	8,466
Net loss per share, basic and diluted:
Continuing operations, net loss per share, basic and diluted (in dollars per share)	$ (0.60)	$ (0.50)
Discontinued operations, net loss per share, basic and diluted	(0.01)	(0.28)
Net loss per basic and diluted share (in dollars per share)	$ (0.61)	$ (0.78)