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Share-Based Compensation - Fair Value of Each Option Grant Estimated (Details)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield 0.00% 0.00% 0.00%
Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected option life 4 years 8 months 12 days 4 years 9 months 18 days 5 years 6 months
Risk-free interest rate 1.27% 1.49% 1.61%
Expected volatility 39.58% 36.29% 36.74%
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected option life 6 years 5 years 6 months 6 years
Risk-free interest rate 1.35% 1.73% 2.73%
Expected volatility 55.58% 53.83% 40.50%