Share-Based Compensation - Assumptions (Details) - Class B common stock issued to management holders [Member] - Employee Stock Option [Member] |
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% |
| Risk free interest rate | 1.64% | 1.69% | 1.63% |
| Expected term | 6 years 4 months | 6 years 5 months | 5 years |
| Expected volatility | 56.00% | 55.00% | 73.00% |