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Stockholders' Equity - Additional Information (Detail) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Mar. 31, 2021
Nov. 10, 2020
Jun. 30, 2020
Nov. 08, 2017
Class of Stock [Line Items]                
Fair value of warrants         $ 29,442,000   $ 40,483,000  
Aggregate value of securities available under shelf registration statement         100,000      
Common stock Value Issued $ 3,136,000 $ (8,000) $ 48,451,000 $ 159,000        
Unsold Securities Shares and Warrants Under Agreement         107,500,000      
Aggregate Value of Securities Available Under Agreement         $ 175,700,000      
Number of warrants exercised         2,617      
Number of shares issued on warrant exercise         964      
Warrant [Member]                
Class of Stock [Line Items]                
Exercise price         $ 2.54      
Warrants outstanding         16,058,985      
ATM Sales Agreement                
Class of Stock [Line Items]                
Common stock share issued         958,083      
Common stock Value Issued         $ 3,100,000      
Two Thousand And Twenty At The Market Sale Agreement                
Class of Stock [Line Items]                
Aggregate value of securities available under shelf registration statement         60,000,000      
Maximum                
Class of Stock [Line Items]                
Sale of shares and warrants under agreement         200,000,000      
Maximum | ATM Sales Agreement                
Class of Stock [Line Items]                
Sale of shares under agreement               $ 30,000,000
Maximum | Two Thousand And Twenty At The Market Sale Agreement                
Class of Stock [Line Items]                
Sale of shares under agreement         $ 60,000,000 $ 60,000,000