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Registered Offering and Warrants - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Mar. 17, 2020
Dec. 31, 2020
Dec. 31, 2018
Class Of Stock [Line Items]      
Warrants to purchase   19,000,000  
Shares issued for common stock at-the-market, net of issuance costs $ 90,439   $ 160,792
Issuance costs incurred on registered offering $ 5,150    
Daily cash penalty 1.00%    
Level 3 [Member]      
Class Of Stock [Line Items]      
Estimated fair value of warrant liability per warrant   $ 6.35  
Other Expense (Income) [Member]      
Class Of Stock [Line Items]      
Issuance costs incurred on registered offering $ 3,953    
Pre funded Warrants [Member]      
Class Of Stock [Line Items]      
Warrant exercise price   $ 0.0001  
Warrant Liability [Member]      
Class Of Stock [Line Items]      
Shares issued for common stock at-the-market, net of issuance costs $ 69,414    
Common Stock Class Two      
Class Of Stock [Line Items]      
Shares issued for common stock at-the-market, net of issuance costs, shares 7,250,000 16,131,487  
Sale price $ 4.76    
Warrants to purchase 19,000,000    
Warrant exercise price $ 5.95    
Shares issued for common stock at-the-market, net of issuance costs $ 21,025    
Issuance costs incurred on registered offering $ 1,197 $ 2,541  
Common Stock Class Two | Minimum [Member]      
Class Of Stock [Line Items]      
Warrants expire period 6 months    
Common Stock Class Two | Maximum [Member]      
Class Of Stock [Line Items]      
Warrants expire period 5 years    
Common Stock Class Two | Pre funded Warrants [Member]      
Class Of Stock [Line Items]      
Sale price $ 4.7599    
Warrants to purchase 11,750,000    
Warrant exercise price $ 0.0001