Potential Dilutive Shares Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	35,386,620	30,997,640
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	22,705,571	22,272,727
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	11,072,894	6,572,191
Stock Options | Two Thousand Twelve Stock Option Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	97,500	863,333
Unvested Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,510,655	1,289,389