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Stock-Based Compensation - Additional Information (Detail) - USD ($)					3 Months Ended		9 Months Ended
	Sep. 18, 2020	Jun. 30, 2020	May 26, 2020	Jan. 06, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 29, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued					6,572,191		6,572,191			5,842,879
Stock options, granted					203,178	140,000	1,252,178	1,835,755
Options available for future grant					6,986,610		6,986,610
Weighted-average grant date fair value					$ 1.96	$ 3.05	$ 2.45	$ 1.90
Number of shares issued for accrued annual performance bonus				446,428
Number of options vested	113,350	31,220	448,130
Adiitional stock compensation expenses					$ 65,000		$ 154,000
Acceleration Of Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Adiitional stock compensation expenses					(250)		(250)
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options vested	25,281
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested	15,890		45,277
Unvested Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to unvested restricted stock outstanding					8,000,000.0		$ 8,000,000.0
Expected recognition period							1 year 9 months 25 days
Unvested Restricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to unvested restricted stock outstanding					$ 3,000,000.0		$ 3,000,000.0
Expected recognition period							1 year 6 months 25 days
Number of shares vested							64,917
Outside 2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding options issued					863,333		863,333
2020 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for new issue									21,000,000
2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for future grant									0
2003 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for future grant									0