Net Loss per Share - Summary of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (13,150)	$ (5,072)	$ (9,956)	$ (10,644)	$ (18,222)	$ (20,600)
Denominator:
Weighted average common shares outstanding, basic and diluted	17,667,620		14,376,529		17,445,600	14,372,876
Net loss per share, basic and diluted	$ (0.74)		$ (0.69)		$ (1.04)	$ (1.43)