Annual report pursuant to Section 13 and 15(d)

Employee Benefits and Share-Based Compensation - Fair value assumptions of Share Option Awards (Details)

v3.10.0.1
Employee Benefits and Share-Based Compensation - Fair value assumptions of Share Option Awards (Details)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Time Based Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield     0.00%
Expected share price volatility, minimum     30.36%
Expected share price volatility, maximum     33.01%
Risk-free interest rate, minimum     1.20%
Risk-free interest rate, maximum     1.48%
Expected term     6 years
Performance Based Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield 0.00% 0.00% 0.00%
Expected share price volatility   25.97%  
Expected share price volatility, minimum 31.50%   25.97%
Expected share price volatility, maximum 32.20%   30.21%
Risk-free interest rate, minimum 2.48%   1.01%
Risk-free interest rate, maximum 2.58%   1.93%
Risk-free interest rate   1.81%  
Expected term   4 years 2 months 12 days  
Performance Based Options | Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term 3 years 8 months 19 days   4 years 4 months 17 days
Performance Based Options | Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term 4 years 2 months 19 days   5 years 1 month 17 days