Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Schedule of Assumptions Used to Determine Grant Date Fair Value of Employee and Director Options Granted (Details)

v3.19.1
Share-Based Compensation - Schedule of Assumptions Used to Determine Grant Date Fair Value of Employee and Director Options Granted (Details)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Volatility 60.00% 60.00% 60.00%
Dividend rate 0.00% 0.00% 0.00%
Risk-free interest rate   1.63% 2.00%
Risk-free interest rate, minimum 2.16%    
Risk-free interest rate, maximum 2.91%    
Minimum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected term in years 1 year    
Maximum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected term in years 6 years 3 months 6 years 3 months 6 years 3 months