Stock Option Activity Under Stock Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Number of Shares
Beginning Balance	6,840,719
Granted	4,314,438	896,000
Exercised	(352,442)
Cancelled	(84,337)
Ending Balance	10,718,378		6,840,719
Options exercisable, at end of period	3,562,744		3,596,315
Options available for future grant	1,267,888
Weighted Average Exercise Price
Beginning Balance	$ 3.81
Granted	3.79
Exercised	2.89
Cancelled	3.53
Ending Balance	3.83		$ 3.81
Options exercisable, at end of period	$ 4.23		$ 4.17
Weighted Average Contractual Term (Years)
Outstanding, at end of period	13 years 4 months 24 days
Options exercisable, at end of period	6 years 8 months 4 days		6 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding, at end of period	$ 4,926
Options exercisable, at end of period	$ 2,176		$ 598

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

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.