Net Loss Per Share - Dilutive Securities Excluded from Calculation of Diluted Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options To Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities excluded from calculation of diluted earnings per share	8,142,348	11,165,846	11,603,708
Warrants To Purchase Common Stock - Liability Classified
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities excluded from calculation of diluted earnings per share	2,156,153	2,156,153	2,840,147
Warrants To Purchase Common Stock - Equity Classified
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities excluded from calculation of diluted earnings per share	1,418,116	1,457,866	1,586,097
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities excluded from calculation of diluted earnings per share	8,046,399	4,379,777	1,736,234