Annual report pursuant to Section 13 and 15(d)

Capitalization and Equity Structure - Narrative (Details)

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Capitalization and Equity Structure - Narrative (Details) - USD ($)
 1 Months Ended 12 Months Ended 17 Months Ended
Dec. 20, 2019
May 24, 2019
Jan. 30, 2019
Dec. 31, 2019
Aug. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2019
Sep. 30, 2017
Dec. 31, 2015
Jan. 15, 2014
Class of Warrant or Right [Line Items]                      
Common stock, shares authorized (in shares)       141,429,000   141,429,000 141,429,000 141,429,000      
Preferred stock, shares authorized (in shares)       10,000,000   10,000,000 10,000,000 10,000,000      
Common stock, shares issued (in shares)       86,920,000   86,920,000 62,963,000 86,920,000      
Common stock, shares outstanding (in shares)       86,920,000   86,920,000 62,963,000 86,920,000      
Preferred stock, shares issued (in shares)       0   0 0 0      
Preferred stock, shares outstanding (in shares)       0   0 0 0      
Number warrants called (in shares)                   2,122,000 89,000
Warrants issued (in shares)           15,778,000          
Issuance of stock and warrants for services or claims           $ 1,096,000 $ 0        
Merger/PPO warrant shares exercised (in shares)           0          
Loss on modification of warrants           $ 257,000 $ 0        
Direct Offering                      
Class of Warrant or Right [Line Items]                      
Aggregate proceeds       $ 5,000,000              
Issuance costs       $ 777,000              
Over-Allotment Option                      
Class of Warrant or Right [Line Items]                      
Aggregate proceeds   $ 10,000,000                  
At-The-Market Offering                      
Class of Warrant or Right [Line Items]                      
Aggregate proceeds           $ 2,776,000   $ 7,206,000      
Common Stock                      
Class of Warrant or Right [Line Items]                      
Number of shares sold (in shares)     3,067,000                
Number warrants called (in shares)       88,000   88,000   88,000      
Sale of shares (in dollars per share)     $ 1.63                
Exercise price (in dollars per share)       $ 9.66   $ 9.66   $ 9.66      
Issuance costs     $ 8,000                
Value of shares sold     $ 5,000,000                
Common Stock | Direct Offering                      
Class of Warrant or Right [Line Items]                      
Number warrants called (in shares)       8,333,000   8,333,000   8,333,000      
Sale of shares (in dollars per share)       $ 0.45   $ 0.45   $ 0.45      
Aggregate proceeds       $ 2,493,000              
Issuance costs       $ 388,000              
Common Stock | Over-Allotment Option                      
Class of Warrant or Right [Line Items]                      
Number of shares sold (in shares)   6,667,000                  
Number warrants called (in shares)   6,667,000                  
Sale of shares (in dollars per share)   $ 1.5                  
Aggregate proceeds   $ 2,666,000                  
Issuance costs   963,000                  
Issuance of stock and warrants for services or claims   706,000                  
Adjustments to additional paid in capital, stock issued, issuance costs   257,000                  
Common Stock | At-The-Market Offering                      
Class of Warrant or Right [Line Items]                      
Number of shares sold (in shares)           2,150,000   4,182,000      
Sale of shares (in dollars per share)       $ 1.35   $ 1.35   $ 1.35      
Value of aggregate offering         $ 25,000,000            
Stock available for issuance           $ 17,241,000          
Common Stock | At-The-Market Offering, Inception To Year End                      
Class of Warrant or Right [Line Items]                      
Sale of shares (in dollars per share)       $ 1.86   $ 1.86   1.86      
Warrants for Common Stock                      
Class of Warrant or Right [Line Items]                      
Number warrants called (in shares)                     5,151,000
Exercise price (in dollars per share)                     $ 7
Warrants for Common Stock | Direct Offering                      
Class of Warrant or Right [Line Items]                      
Issuance costs       $ 389,000              
2019 Warrants                      
Class of Warrant or Right [Line Items]                      
Aggregate proceeds   $ 7,334,000                  
Exercise price (in dollars per share)       $ 0.5402   $ 0.5402   0.5402      
Class of warrant or right expiration period       5 years   5 years          
2019 Warrants | Common Stock | Direct Offering                      
Class of Warrant or Right [Line Items]                      
Number of shares sold (in shares)       11,111,000              
December 2019 Placement Agent Warrants                      
Class of Warrant or Right [Line Items]                      
Exercise price (in dollars per share)       $ 0.5625   $ 0.5625   0.5625      
Class of warrant or right expiration period       5 years   5 years          
Class of warrant or right cash fee percentage       7.00%              
Class of warrant or right cash fee       $ 350,000              
Class of warrant or right management fee percentage       1.00%              
Class of warrant or right management fee       $ 50,000              
Percentage of warrants issued to purchase shares of common stock       7.00%              
Warrants issued (in shares)       778,000              
Other expenses       $ 95,000              
Merger/PPO warrant shares exercised (in shares)           0          
December 2019 Placement Agent Warrants | Common Stock | Direct Offering                      
Class of Warrant or Right [Line Items]                      
Issuance costs       200,000              
2019 Warrants and December 2019 Placement Agent Warrants                      
Class of Warrant or Right [Line Items]                      
Aggregate proceeds       $ 2,507,000              
May 2019 Warrants                      
Class of Warrant or Right [Line Items]                      
Exercise price (in dollars per share)       $ 0.38   $ 0.38   $ 0.38      
Class of warrant or right expiration period   5 years       5 years          
Warrants issued (in shares)           6,667,000          
Merger/PPO warrant shares exercised (in shares)           0          
Information Agent Warrants                      
Class of Warrant or Right [Line Items]                      
Number warrants called (in shares)                 200,000    
Exercise price (in dollars per share)                 $ 1.5    
2015 Warrants                      
Class of Warrant or Right [Line Items]                      
Merger/PPO warrant shares exercised (in shares)           0 518,000        
Loss on modification of warrants           $ 257,000          
Conversion Price | December 2019 Placement Agent Warrants                      
Class of Warrant or Right [Line Items]                      
Conversion price (in dollars per share) $ 0.5625         $ 0.5625          
Conversion Price | May 2019 Warrants                      
Class of Warrant or Right [Line Items]                      
Conversion price (in dollars per share)   $ 2.00       0.38          
Conversion Price | 2015 Warrants                      
Class of Warrant or Right [Line Items]                      
Conversion price (in dollars per share)           $ 2.75 $ 3.74        
Minimum | Common Stock                      
Class of Warrant or Right [Line Items]                      
Sale of shares (in dollars per share)     $ 1.30                
Minimum | Warrants for Common Stock                      
Class of Warrant or Right [Line Items]                      
Exercise price (in dollars per share)                   $ 3.74