Stock-based Compensation - Performance Share Unit Awards - Activity (Details) - Performance Share Unit Awards - $ / shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Awards | |||
| Unvested at the beginning of the period (in shares) | 539,188 | ||
| Granted (in shares) | 551,252 | ||
| Forfeited (in shares) | (55,235) | ||
| Vested (in shares) | (168,877) | ||
| Unvested at the end of the period (in shares) | 866,328 | 539,188 | |
| Weighted Average Grant Date Fair Value per Share | |||
| Unvested at the beginning of the period (in dollars per share) | $ 14.22 | ||
| Granted (in dollars per share) | 4.75 | $ 10.27 | $ 21.65 |
| Forfeited (in dollars per share) | 13.27 | ||
| Vested (in dollars per share) | 21.65 | ||
| Unvested at the end of the period (in dollars per share) | $ 6.81 | $ 14.22 | |