Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Stock Options Number Outstanding
Beginning Balance | shares	550,769
Cancelled or Expired | shares	(4,642)
Exercised | shares	(18,651)
Ending Balance | shares	527,476	550,769
Vested or expected to vest as of September 30, 2021 | shares	527,476
Exercisable as of September 30, 2021 | shares	527,476
Stock Options Average Exercise Price per share
Beginning Balance | $ / shares	$ 5.56
Cancelled or Expired | $ / shares	21.39
Exercised | $ / shares	7.94
Ending Balance | $ / shares	5.34	$ 5.56
Vested or expected to vest as of September 30, 2021 | $ / shares	5.34
Exercisable as of September 30, 2021 | $ / shares	$ 5.34
Stock Options Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Term (Years)	4 years 3 months 10 days	4 years 10 months 17 days
Vested or expected to vest as of September 30, 2021	4 years 3 months 10 days
Exercisable as of September 30, 2021	4 years 3 months 10 days
Stock Options Aggregate Intrinsic Value
Aggregate intrinsic value | $	$ 7,126,485	$ 1,875,719
Vested or expected to vest as of September 30, 2021 | $	7,126,485
Exercisable as of September 30, 2021 | $	$ 7,126,485