Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (13,420)	$ (14,333)	$ (25,093)	$ (30,694)
Denominator:
Weighted-average common shares outstanding, basic and diluted (in shares)	48,451,562	46,279,947	48,141,474	45,746,513
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.28)	$ (0.31)	$ (0.52)	$ (0.67)