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Summary of Significant Accounting Policies - Securities (Details) - shares
 3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Class of Stock [Line Items]    
Anti-dilutive securities excluded from computation (in shares) 2,656,276 2,068,616
Warrants to purchase common stock    
Class of Stock [Line Items]    
Anti-dilutive securities excluded from computation (in shares) 426,827 436,581
Common stock options    
Class of Stock [Line Items]    
Anti-dilutive securities excluded from computation (in shares) 2,041,580 1,630,014
Restricted stock units    
Class of Stock [Line Items]    
Anti-dilutive securities excluded from computation (in shares) 185,000 0
Employee stock purchase plan    
Class of Stock [Line Items]    
Anti-dilutive securities excluded from computation (in shares) 2,869 2,021