Stock-Based Compensation - Schedule of Non-Qualified Stock Options, Activity (Details) - Non-Qualified Stock Options (NQO) - $ / shares shares in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Shares | |||
| Outstanding at beginning of year (in shares) | 384 | 486 | 446 |
| Granted (in shares) | 75 | 87 | 58 |
| Exercised (in shares) | (110) | (158) | (18) |
| Forfeited, canceled or expired (in shares) | (24) | (31) | 0 |
| Outstanding at end of year (in shares) | 325 | 384 | 486 |
| Options exercisable (in shares) | 201 | 214 | 212 |
| Weighted Average Exercise Price Per Share | |||
| Outstanding at beginning of year (in dollars per share) | $ 21.47 | $ 19.25 | $ 17.43 |
| Granted (in dollars per share) | 22.82 | 20.06 | 31.52 |
| Exercised (in dollars per share) | 18.41 | 13.63 | 13.37 |
| Forfeited, canceled or expired (in dollars per share) | 22.61 | 22.51 | 0.00 |
| Outstanding at end of year (in dollars per share) | 22.74 | 21.47 | 19.25 |
| Options exercisable (in dollars per share) | $ 22.57 | $ 20.35 | $ 16.13 |