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						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (20,175)	$ (19,638)	$ (18,676)	$ (17,449)	$ (15,144)	$ (11,138)	$ (58,489)	$ (43,731)
Dividends, Paid-in-kind	0			0			(8,239)	0
Net loss attributable to common stockholders	$ (20,175)			$ (17,449)			$ (66,728)	$ (43,731)
Denominator:
Weighted average common shares outstanding—basic and diluted (in shares)	26,609,000			20,085,000			24,667,000	20,035,000
Net loss per share attributable to common stockholders—basic and diluted	$ (0.76)			$ (0.87)			$ (2.71)	$ (2.18)