Net Income (Loss) per Share - EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator
Net income (loss) attributable to common stockholders, basic	$ 10,416	$ 6,165	$ (36,704)	$ 1,889
Net income (loss) attributable to common stockholders, diluted	$ 10,416	$ 6,165	$ (36,704)	$ 1,889
Denominator
Weighted average shares of common stock outstanding, basic	19,217,623	16,699,102	18,989,334	16,483,169
Denominator (diluted):
Weighted average shares of common stock outstanding, basic	19,217,623	16,699,102	18,989,334	16,483,169
Effect of potential dilutive securities:
Weighted average dilutive effect of contingently issuable shares	273,886
Weighted average dilutive effect of common shares from warrants				12,441
Weighted average shares of common stock outstanding, diluted	22,288,873	18,646,031	18,989,334	18,411,800
Net income (loss) per share attributable to common stockholders, basic (in dollars per share)	$ 0.54	$ 0.37	$ (1.93)	$ 0.11
Net income (loss) per share attributable to common stockholders, diluted (in dollars per share)	$ 0.47	$ 0.33	$ (1.93)	$ 0.10
Stock options
Effect of potential dilutive securities:
Weighted average dilutive effect of share-based awards	1,898,543	1,235,883		1,308,202
Restricted stock
Effect of potential dilutive securities:
Weighted average dilutive effect of share-based awards	898,821	711,046		607,988