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Common Stock and Stockholders' Equity - Narrative 2 (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended 87 Months Ended
Oct. 31, 2012
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2019
Class of Stock [Line Items]        
Proceeds from stock options exercised (less than in 2018 and 2017)   $ 3 $ 1  
Stock options        
Class of Stock [Line Items]        
Weighted average grant date fair value of employee stock options (in dollars per share)   $ 0.52 $ 8.63  
Total intrinsic value of stock options exercised (less than in 2018 and 2017)   $ 100    
Proceeds from stock options exercised (less than in 2018 and 2017)   100 $ 100  
Compensation cost related to non-vested awards not yet recognized   $ 1,200   $ 1,200
Weighted-average recognition period of compensation cost related to non-vested awards not yet recognized   1 year 8 months 24 days    
RSUs outstanding        
Class of Stock [Line Items]        
Compensation cost related to non-vested awards not yet recognized   $ 400   $ 400
Weighted-average recognition period of compensation cost related to non-vested awards not yet recognized   9 months    
Employee Stock Purchase Plan 2012        
Class of Stock [Line Items]        
Percentage of participants eligible compensation 15.00%      
Shares issued (in shares)   4,035   91,948
Common stock shares reserved for future issuance and authorized for purchase (in shares)   192,687   192,687
Option One - at inception of enrollment period        
Class of Stock [Line Items]        
Percentage of fair market value of common stock 85.00%      
Option Two - at applicable purchase date        
Class of Stock [Line Items]        
Percentage of fair market value of common stock 85.00%