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Net Loss Per Share - Potential Dilutive Outstanding Securities Excluded From Diluted Net Loss Per Common Share (Detail) - shares
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of diluted weighted-average shares outstanding (in shares) 5,941,193 4,294,398
Employee Stock Option [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of diluted weighted-average shares outstanding (in shares) 2,190,360 543,396
Warrants [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of diluted weighted-average shares outstanding (in shares) 3,750,833 3,751,002