Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Details)

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Stockholders' Equity (Details) - USD ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2020
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Aug. 14, 2020
Subsidiary, Sale of Stock [Line Items]          
Common stock, shares authorized (in shares) 1,000,000,000 1,000,000,000      
Common stock, par value (in dollars per share) $ 0.0001 $ 0.0001   $ 0.0001  
Common stock, shares outstanding (in shares) 45,452,422 45,452,422   39,817,917  
Restricted shares subject to repurchase for unvested shares related to early option exercises under stock equity plans (in shares) 1,198 1,198   6,219  
Proceeds from issuance of common stock   $ 1,341,000 $ 0    
Cash exercises for warrants (in shares)       617,296  
Aggregate gross proceeds       $ 6,184,000  
Stock issued, warrants exercised (in shares)       10,913,146  
Sales Agreement          
Subsidiary, Sale of Stock [Line Items]          
Aggregate offering price         $ 15,000,000
Common Stock          
Subsidiary, Sale of Stock [Line Items]          
Sale of common stock (in shares) 1,301,665 1,302,000      
Proceeds from issuance of common stock $ 1,493,000 $ 1,493,000      
Payments of stock offering costs $ 152,000 $ 152,000      
Cash          
Subsidiary, Sale of Stock [Line Items]          
Aggregate gross proceeds       $ 6,092,000  
Digital Currencies          
Subsidiary, Sale of Stock [Line Items]          
Aggregate gross proceeds       $ 92,000  
Cash and Cashless Exercises          
Subsidiary, Sale of Stock [Line Items]          
Aggregate shares issued (in shares)       11,530,442  
Cashless Exercises          
Subsidiary, Sale of Stock [Line Items]          
Warrants exercised (in shares)       13,975,359