Quarterly report pursuant to Section 13 or 15(d)

Capitalization and Equity Structure - Additional Information (Details)

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Capitalization and Equity Structure - Additional Information (Details) - USD ($)
1 Months Ended 3 Months Ended 12 Months Ended
Jan. 30, 2019
Aug. 21, 2018
Dec. 31, 2015
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Class of Stock [Line Items]            
Common stock, shares authorized (in shares)       141,429,000   141,429,000
Preferred Stock, shares authorized (in shares)       10,000,000   10,000,000
Common stock, shares outstanding (in shares)       5,843,000   5,795,000
Common stock, shares issued (in shares)       5,843,000   5,795,000
Preferred stock, shares outstanding (in shares)       0   0
Preferred stock, shares issued (in shares)       0   0
Loss on modification of warrants       $ 0 $ 257,000  
May 2019 Warrants            
Class of Stock [Line Items]            
Exercise price (in dollars per share)       $ 5.70    
2015 Warrants            
Class of Stock [Line Items]            
Exercise price (in dollars per share)       41.25   $ 56.10
Warrants issued (in shares)     141,000      
2017 Information Agent Warrants            
Class of Stock [Line Items]            
Exercise price (in dollars per share)       $ 22.50    
Common Stock            
Class of Stock [Line Items]            
Number of shares sold (in shares) 205,000          
Price per share sold (in dollars per share) $ 24.45          
Amount received from sale of shares $ 5,000,000          
Direct financing costs $ 8,000          
Common Stock | At-The-Market Offering            
Class of Stock [Line Items]            
Aggregate value of offering   $ 25,000,000        
Value of stock available for issuance       $ 17,241,000    
Warrant            
Class of Stock [Line Items]            
Warrants exercised (in shares)       0   35,000