Annual report pursuant to Section 13 and 15(d)

Warrants - Summary of Warrant Activity (Detail)

v3.21.1
Warrants - Summary of Warrant Activity (Detail) - $ / shares
shares in Thousands
12 Months Ended
Oct. 28, 2020
Dec. 31, 2020
Dec. 31, 2019
Jan. 09, 2019
Class of Warrant or Right [Line Items]        
Exercise price (usd per share) $ 2.42 $ 104.18   $ 7.43
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   279 336  
Warrants Issued (shares) 94 94 66  
Warrants Expired (shares)   (115) (123)  
Warrants Exchanged (shares)   (52)    
Warrants Outstanding, Ending Balance (shares)   206 279  
2016 Offerings        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 67.50 $ 67.50  
Non-Derivative Warrants: | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 115.54    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   213 147  
Warrants Issued (shares)   94 66  
Warrants Expired (shares)   (115) 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   192 213  
Non-Derivative Warrants: | Financing | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 300.00    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   8 8  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   8 8  
Non-Derivative Warrants: | Financing | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 450.00    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   9 9  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   9 9  
Non-Derivative Warrants: | 2017 Debt | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 27.60    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   15 15  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   15 15  
Non-Derivative Warrants: | 2015 Offering | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 150.00    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   115 115  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   (115) 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   0 115  
Non-Derivative Warrants: | 2019 Offering | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 7.43    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   31 0  
Warrants Issued (shares)   0 31  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   31 31  
Non-Derivative Warrants: | 2019 Offering | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 7.59    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   35 0  
Warrants Issued (shares)   0 35  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   35 35  
Non-Derivative Warrants: | 2020 Offering | Warrant Issued With        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 2.42    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   0 0  
Warrants Issued (shares)   94 0  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   94 0  
Derivative Warrants: | Warrant Issued For        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 67.50    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   66 189  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 (123)  
Warrants Exchanged (shares)   (52)    
Warrants Outstanding, Ending Balance (shares)   14 66  
Derivative Warrants: | 2016 Offerings | Warrant Issued For        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 67.50    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   66 66  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 0  
Warrants Exchanged (shares)   (52)    
Warrants Outstanding, Ending Balance (shares)   14 66  
Derivative Warrants: | 2017 Offering | Warrant Issued For        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 70.50    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   0 117  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 (117)  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   0 0  
Derivative Warrants: | 2017 Offering | Warrant Issued For        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share)   $ 75.00    
Class of Warrants Outstanding [Roll Forward]        
Warrants Outstanding, Beginning Balance (shares)   0 6  
Warrants Issued (shares)   0 0  
Warrants Expired (shares)   0 (6)  
Warrants Exchanged (shares)   0    
Warrants Outstanding, Ending Balance (shares)   0 0