Net Income (Loss) Per Share - Reconciliation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income (loss)	$ 5,785	$ (3,533)
Less: preferred stock dividends	70	12
Net income (loss) attributable to common stockholders	$ 5,715	$ (3,545)
Denominator:
Weighted-average number of shares of common stock for basic and diluted net income (loss) per share (in shares)	37,603	35,611
Add effect of dilutive securities:
Shares of common stock issuable upon conversion of preferred stock	1,706	0
Warrants	38	0
Weighted-average number of shares of common stock for diluted net income (loss) per share (in shares)	41,440	35,611
Basic net income (loss) per share (in dollars per share)	$ 0.15	$ (0.10)
Diluted net income (loss) per share (in dollars per share)	$ 0.14	$ (0.10)
RSUs
Add effect of dilutive securities:
Unvested RSUs/Unvested restricted stock	1,752	0
Restricted Stock
Add effect of dilutive securities:
Unvested RSUs/Unvested restricted stock	341	0