Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Shares (Detail)

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Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Shares (Detail) - shares
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 10,879,564 15,111,905
Outstanding stock options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 2,050,094 1,371,606
Outstanding restricted stock units    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 981,841 96,974
Warrants to purchase common stock associated with June 2016 Public Offering | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 0 421,867
March 2018 Public Offering Series 2 | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 798,810 798,810
December 2019 Public Offering | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 0 4,472,205
December 2020 Public Offering Series 2 | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 6,800,000 6,800,000
Warrants to purchase common stock associated with Loan Agreement | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 198,819 0
Warrants to purchase common stock associated with Solar loan agreement | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 0 12,243
Common stock associated with March 2019 Notes    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 0 1,138,200
Warrants to purchase common stock associated with Danforth | Warrant    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 50,000 0