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Equity Awards - Fair Value of Warrants Exercised Using Black Scholes Option Pricing Model (Details) - $ / shares
1 Months Ended 12 Months Ended
Apr. 20, 2017
Apr. 30, 2017
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock price (in dollars per share)     $ 1.01 $ 4.01
Expected dividend yield     0.00% 0.00%
Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Common stock Issued through cashless exercise   292,668    
Warrants        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Warrants exercised (in shares)   1,181,235 18,405 1,181,235
Stock price (in dollars per share) $ 4.84      
Exercise price (in dollars per share) $ 3.64      
Term in years 4 years 3 months 15 days      
Expected volatility 101.93%      
Expected dividend yield 0.00%      
Risk-free interest rate 1.65%