Stockholders' Equity - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) $ / shares shares
Number of shares
Outstanding at beginning of period (in shares) | shares		7,060,966
Exercised (in shares) | shares		(155,690)
Forfeitures (in shares) | shares		(539,802)
Outstanding at end of period (in shares) | shares	7,060,966	9,557,979
Weighted average exercise price per share
Weighted average exercise price per share, Outstanding at beginning of period (in usd per share) | $ / shares		$ 4.55
Weighted average exercise price per share, Exercised (in usd per share) | $ / shares		2.90
Weighted average exercise price per share, Forfeitures (in usd per share) | $ / shares		4.72
Weighted average exercise price per share, Outstanding at end of period (in usd per share) | $ / shares	$ 4.55	$ 4.40
Aggregate intrinsic value
Aggregate intrinsic value, Outstanding, balance | $	$ 2,831	$ 8,589
Officers and Directors
Number of shares
Granted (in shares) | shares		1,345,292
Weighted average exercise price per share
Weighted average exercise price per share, Granted (in usd per share) | $ / shares		$ 3.83
Employees
Number of shares
Granted (in shares) | shares		1,847,213
Weighted average exercise price per share
Weighted average exercise price per share, Granted (in usd per share) | $ / shares		$ 4.20