Net Loss Per Share - Computation of Net Loss Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net loss	$ (31,276)	$ (29,031)	$ (28,613)	$ (23,467)	$ (17,000)	$ (18,126)	$ 9,007	$ (3,502)	$ (112,387)	$ (29,621)	$ (3,214)
Denominator:
Weighted average number of shares outstanding-basic and diluted									40,118,522	22,892,640	10,248,337
Net loss per share-basic and diluted	$ (0.66)	$ (0.65)	$ (0.83)	$ (0.70)					$ (2.80)	$ (1.29)	$ (0.31)