Significant Accounting Policies - Schedule of Computation of Basic and Diluted EPS(Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss	$ (42,854)	$ (67,982)
Accretion and dividends on convertible preferred stock		(131)
Net loss applicable to common stockholders	$ (42,854)	$ (68,113)
Denominator:
Weighted average common shares outstanding—basic and diluted	26,735,175	18,311,333
Net loss per share applicable to common stockholders—basic and diluted	$ (1.60)	$ (3.72)