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Stock-Based Compensation Plans (Tables) | 3 Months Ended
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Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
Restricted Stock Awards | A summary of the restricted stock awards as of March 31, 2018, along with the changes during the three months then ended, is as follows:
|  | Awards |  | Weighted Average Grant Date Fair Value
Nonvested at December 31, 2017 |  | 702,778 |  |  | $ | 68.23 |
Granted |  | 194,421 |  |  | 75.72 |
Vested |  | (167,934 | ) |  | 61.63 |
Forfeited |  | (14,180 | ) |  | 70.34 |
Nonvested at March 31, 2018 |  | 715,085 |  |  | $ | 71.78 |

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- Definition Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
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