Net Loss per Share - Schedule of Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (12,798)	$ (13,285)	$ (12,344)	$ (12,946)	$ (11,931)	$ (10,748)	$ (14,591)	$ (11,165)	$ (51,373)	$ (48,435)
Denominator:
Weighted-average common shares outstanding - basic and diluted									30,284,068	23,882,685
Net loss per share - basic and diluted	$ (0.37)	$ (0.39)	$ (0.45)	$ (0.51)	$ (0.47)	$ (0.43)	$ (0.59)	$ (0.55)	$ (1.70)	$ (2.03)