Stock-Based Compensation - Restricted Stock (Details) - Restricted stock awards - $ / shares |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Awards | ||
| Outstanding, beginning of period (in shares) | 1,009,716 | |
| Granted (in shares) | 199,320 | |
| Vested (in shares) | (63,367) | |
| Forfeited (in shares) | (25,948) | |
| Outstanding, end of period (in shares) | 1,119,721 | |
| Weighted Average Grant Date Fair Value | ||
| Outstanding, beginning of period (in dollars per share) | $ 17.64 | |
| Granted (in dollars per share) | 19.00 | $ 18.82 |
| Vested (in dollars per share) | 18.50 | |
| Forfeited (in dollar per share) | 16.85 | |
| Outstanding, end of period (in dollars per share) | $ 17.85 | |