Equity Incentive Plans and Stock Based Compensation - Summary of Stock Option Activity Under Equity Incentive Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding Options Number of Shares, Beginning Balance	4,763,062	4,002,999
Number of Shares, Options granted	2,453,506	2,023,600
Number of Shares, Options exercised	(261,260)	(286,479)
Number of shares, Options cancelled	(257,381)	(977,058)
Outstanding Options Number of Shares, Ending Balance	6,697,927	4,763,062	4,002,999
Outstanding Options Number of Shares, Vested and expected to vest, December 31, 2020	6,697,927
Outstanding Options Number of Shares, Exercisable at December 31, 2020	2,845,501
Weighted Average Exercise Price, Beginning Balance	$ 6.36	$ 10.43
Weighted Average Exercise Price, Options granted	14.06	6.00
Weighted Average Exercise Price, Options exercised	3.99	6.10
Weighted Average Exercise Price, Options cancelled	9.99	22.39
Weighted Average Exercise Price, Ending Balance	9.13	$ 6.36	$ 10.43
Weighted Average Exercise Price, Vested and expected to vest, December 31, 2020	9.13
Weighted Average Exercise Price, Exercisable at December 31, 2020	$ 6.66
Weighted-Average Remaining Contractual Term, Outstanding	7 years 9 months 3 days	8 years 1 month 6 days	6 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest, December 31, 2020	7 years 9 months 3 days
Weighted-Average Remaining Contractual Term, Exercisable at December 31, 2020	6 years 8 months 4 days
Aggregate Intrinsic Value, Outstanding	$ 13,790	$ 36,630	$ 1,500
Aggregate Intrinsic Value, Vested and expected to vest, December 31, 2020	13,790
Aggregate Intrinsic Value, Exercisable at December 31, 2020	$ 8,850

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Number of options outstanding, including both vested and non-vested options.

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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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