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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Number of shares
Outstanding at beginning of period (in shares)	7,060,966
Granted (in shares)	2,786,291
Exercised (in shares)	(16,619)
Forfeitures (in shares)	(102,899)
Outstanding at end of period (in shares)	9,727,739
Weighted average exercise price per share
Weighted average exercise price per share, Outstanding at beginning of period (in usd per share)	$ 4.55
Weighted average exercise price per share, Exercised (in usd per share)	2.45
Weighted average exercise price per share, Forfeitures (in usd per share)	4.79
Weighted average exercise price per share, Outstanding at end of period (in usd per share)	$ 4.42
Aggregate intrinsic value
Aggregate intrinsic value, Outstanding, balance	$ 1,913		$ 2,831
Officers and Directors
Number of shares
Granted (in shares)	1,249,292
Exercised (in shares)	(16,619)	(107,287)
Weighted average exercise price per share
Weighted average exercise price per share, Granted (in usd per share)	$ 3.84
Employees
Number of shares
Granted (in shares)	1,536,999
Weighted average exercise price per share
Weighted average exercise price per share, Granted (in usd per share)	$ 4.30