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Stock-Based Compensation - Summary of Stock Option and PRSU Activity (Details) - Stock Option and PRSU [Member] - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Shares Issuable Under Options and PRSU      
Outstanding, beginning balance 974,817 782,340  
Granted 815,400 267,950  
Exercised   (15,120)  
PRSUs vested (78,450)    
Forfeited / Canceled (11,500) (60,353)  
Outstanding, ending balance 1,700,267 974,817 782,340
Stock awards vested and expected to vest as of December 31, 2019 1,645,267    
Options exercisable as of December 31, 2019 882,576    
Weighted Average Exercise Price      
Outstanding, beginning balance $ 12.31 $ 14.28  
Granted 1.75 5.02  
Exercised   4.74  
PRSUs vested 4.83    
Forfeited / Canceled 4.41 7.31  
Outstanding, ending balance 7.64 $ 12.31 $ 14.28
Stock awards vested and expected to vest as of December 31, 2019 7.64    
Options exercisable as of December 31, 2019 $ 12.49    
Weighted Average Remaining Contractual Term (In years)      
Outstanding as of January 1, 2018 8 years 2 months 12 days 8 years 2 months 12 days 8 years 9 months 18 days
Stock awards vested and expected to vest as of December 31, 2019 8 years 2 months 12 days    
Options exercisable as of December 31, 2019 7 years 3 months 18 days    
Aggregate Intrinsic Value      
Aggregate intrinsic value, Outstanding     $ 8,500