Loss Per Common Share - Schedule of Basic and Diluted Loss Per Common Share (Detail) - 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)	$ 10,785	$ (5,995)	$ (7,825)	$ (19,618)
Net income (loss) attributable to Series A Preferred Stock	135	(915)	(168)	(3,238)
Income (loss) attributable to common stockholders - basic	10,650	(5,080)	(7,657)	(16,380)
Effect of dilutive securities:
Change in fair value of warrant liability	(17,776)	269	(12,524)	673
Numerator for dilutive EPS-Earnings(loss) attributable to common stockholders after assumed conversions	$ (7,126)	$ (5,080)	$ (20,181)	$ (16,380)
Denominator:
Weighted-average number of common shares used in earnings (loss) per share - basic	29,737,632	22,552,341	28,723,500	22,219,666
Effect of dilutive securities:
Nonparticipating warrants			792,200
Denominator for diluted EPS-Adjusted weighted average shares	29,737,632	22,552,341	29,515,700	22,219,666
Earnings (loss) per share - basic	$ 0.36	$ (0.23)	$ (0.27)	$ (0.74)
Loss per share - diluted	$ (0.24)	$ (0.23)	$ (0.68)	$ (0.74)