Annual report pursuant to Section 13 and 15(d)

Income Taxes - Narrative (Details)

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Income Taxes - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Current federal and state income tax expense (benefit) $ 0 $ 0
Deferred federal and state income tax expense (benefit) 0 0
Increase (decrease) in valuation allowance 3,899,000 5,608,000
Federal    
Operating loss carryforwards 155,352,000  
Federal | Options to Purchase Common Stock    
Net operating loss attributed to stock-based compensation deductions in excess of book expense   1,749,000
Federal | Research and Development Tax Credit    
Operating loss carryforwards 1,943,000  
State    
Operating loss carryforwards 99,966,000  
State | Options to Purchase Common Stock    
Net operating loss attributed to stock-based compensation deductions in excess of book expense   $ 689,000
State | Research and Development Tax Credit    
Operating loss carryforwards 608,000  
Foreign    
Operating loss carryforwards 8,785,000  
Generated Before 2018, Expire 2027 | Federal    
Operating loss carryforwards 120,792,000  
Generated Before 2018, Carryforward Indefinitely | Federal    
Operating loss carryforwards $ 34,560,000