Equity Compensation (Fair Value) (Details) - Stock options - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Stock options | ||
| Total fair value for the awards vested during the period | $ 700 | |
| Intrinsic-value | ||
| Options Exercised | 2,765 | $ 3,119 |
| Options Exercisable | 15,335 | 14,761 |
| Options Vested and Expected to Vest | $ 17,203 | $ 16,121 |