Stockholders' Equity - Summary of Stock Option Transactions (Detail) - Stock Options [Member] - $ / shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted	47,500	0	500,150	565,785
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance			2,123,117
Options granted			500,150
Options exercised			(8,518)
Options canceled/forfeited			(101,010)
Ending balance	2,513,739		2,513,739		2,123,117
Options vested at end of period (shares)			1,447,808
Options vested and expected to vest at end of period (shares)	2,513,739		2,513,739
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)			$ 4.62
Options granted (in dollars per share)			3.26
Options exercised (in dollars per share)			1.96
Options canceled/forfeited (in dollars per share)			2.34
Ending balance (in dollars per share)	$ 4.45		4.45		$ 4.62
Options vested at end of period (in dollars per share)			5.95
Options vested and expected to vest at end of period (in dollars per share)	$ 4.45		$ 4.45
Weighted Average Remaining Contractual Term
Options outstanding at end of period			7 years 6 months 29 days		7 years 10 months 13 days
Options vested at end of period			6 years 9 months 3 days
Options vested and expected to vest at end of period			7 years 6 months 29 days