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Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Feb. 15, 2018
Feb. 13, 2018
Apr. 12, 2017
Dec. 31, 2018
Dec. 31, 2019
Dec. 31, 2017
Stockholders Equity Disclosure [Line Items]            
Preferred stock, shares issued       0 0  
Preferred stock, shares outstanding       0 0  
Net proceeds from sale of common stock $ 106.8          
Warrants to purchase common stock     2,070,000      
Warrants exercise price     $ 5.50 $ 155.73 $ 53.61 $ 6.46
Proceeds allocated to warrants, net     $ 5.0      
Number of warrants outstanding       10,194 7,857 1,751,708
April 2017 Underwritten Public Offering            
Stockholders Equity Disclosure [Line Items]            
Number of warrants outstanding         0  
Convertible Preferred Stock            
Stockholders Equity Disclosure [Line Items]            
Conversion of preferred stock to common stock, shares       (3,680)    
Common Stock            
Stockholders Equity Disclosure [Line Items]            
Conversion of preferred stock to common stock, shares       736,000    
Firm commitment underwritten public offering shares   2,941,176        
Issuance of stock, shares 3,382,352          
Common stock price, per share $ 34.00          
Common Stock | Overallotment Option            
Stockholders Equity Disclosure [Line Items]            
Issuance of stock, shares 441,176