Summary of Significant Accounting Policies - Summary of Numerators and Denominators in Calculation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerators:
Net loss	$ (10,134)	$ (9,948)
Denominator:
Weighted average shares used to compute basic net loss per share	217,537	195,745
Dilutive common shares from stock options and ESPP	0	0
Weighted average shares used to compute diluted net loss per share	217,537	195,745
Net Income (loss) per share
Basic	$ (0.05)	$ (0.05)
Diluted	$ (0.05)	$ (0.05)