Stock-Based Compensation Plans (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
|
| Stock based compensation plans: | ||||
| Stock-based compensation expense | $ 2.2 | $ 2.4 | $ 4.7 | $ 5.1 |
| Tax benefits from stock-based compensation expense | $ 0.5 | $ 0.9 | $ 1.2 | $ 1.9 |
| Grants in period, options (in shares) | 0 | 0 | ||
| Restricted stock | ||||
| Stock based compensation plans: | ||||
| Grants in period, other than options (in shares) | 244,448 | 280,853 | ||
| Performance and market-based stock | ||||
| Stock based compensation plans: | ||||
| Grants in period, other than options (in shares) | 97,966 | 99,933 | ||