Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Options
Outstanding at beginning of period | shares	1,168,222
Granted | shares	603,482
Forfeited | shares	(81,009)
Outstanding at end of period | shares	1,690,695
Exercisable at September 30, 2020 | shares	860,401
Weighted-Average Exercise Price
Outstanding at beginning of period | $ / shares	$ 16.77
Granted | $ / shares	5.86
Forfeited | $ / shares	17.06
Outstanding at end of period | $ / shares	12.86
Exercisable at September 30, 2020 | $ / shares	$ 17.58
Weighted-Average Remaining Contractual Term
Outstanding at September 30, 2020	7 years 6 months
Exercisable at September 30, 2020	6 years 14 days
Aggregate Intrinsic Value
Outstanding at end of year | $	$ 230,000
Exercisable at end of year | $	$ 18,000