Stock-Based Compensation	9 Months Ended
Sep. 30, 2019
Stock-Based Compensation
Stock-Based Compensation	10. Stock-Based Compensation The Company maintains two equity compensation plans under which stock-based compensation has been granted: the 2017 Long-Term Incentive Plan, (the “LTIP”) and the 2007 Long-Term Incentive Plan (the “2007 Plan”). Upon the adoption of the LTIP, awards were no longer granted under the 2007 Plan. The LTIP provides for grants of (a) incentive stock options qualified as such under U.S. federal income tax laws, (b) stock options that do not qualify as incentive stock options, (c) stock appreciation rights, (d) restricted stock awards, (e) restricted stock units, (f) performance share awards, (g) phantom stock units, (h) stock bonuses, (i) dividend equivalents, and (j) any combination of such grants. The company grants time-vested stock awards in the form of restricted stock awards, restricted stock units or equity-settled phantom stock. During the nine months ended September 30, 2019, the Company granted 85,640 shares of time-vested stock awards under the LTIP, which vest ratably over three years for employee awards and one year for director awards, at a weighted average grant date fair value of $34.22. Additionally, 99,655 shares of time-vested stock awards vested during the nine months ended September 30, 2019, at a weighted average grant date fair value of $30.51. During the nine months ended September 30, 2019, the Company granted 72,932 performance share awards under the LTIP at target, which cliff vest on December 31, 2021, at a weighted average grant date fair value of $39.26. The number of shares ultimately earned under a performance award may vary from zero to 200% of the target shares awarded, based upon the Company’s performance compared to certain metrics. The metrics used were determined at the time of the grant by the Compensation Committee of the Board of Directors and were either based on internal measures, such as the Company’s financial performance compared to target, or on a market-based metric, such as the Company’s stock performance compared to a peer group. Performance awards cliff vest upon attainment of the stated performance targets and minimum service requirements and are paid in shares of the Company’s common stock. During the nine months ended September 30, 2019, plan participants exercised options to purchase 13,788 shares of the Company's common stock with a weighted average exercise price of $23.57. The Company recognizes stock-based compensation expense related to restricted stock awards, phantom stock awards and restricted stock units based on the grant date fair value, which was the closing price of the Company’s stock on the date of grant. The fair value is expensed over the service period, which is generally three years. For performance awards, the Company recognizes stock-based compensation expense based on the grant date fair value of the award. The fair value of internal metric-based performance awards is determined by the closing stock price of the Company’s common stock on the date of the grant. The fair value of market-based performance awards is computed using a Monte Carlo simulation. Performance awards are expensed over the service period of approximately 2.8 years, and the Company adjusts the stock-based compensation expense related to internal metric-based performance awards according to its determination of the shares expected to vest at each reporting date.

10. Stock-Based Compensation

The Company maintains two equity compensation plans under which stock-based compensation has been granted: the 2017 Long-Term Incentive Plan, (the “LTIP”) and the 2007 Long-Term Incentive Plan (the “2007 Plan”). Upon the adoption of the LTIP, awards were no longer granted under the 2007 Plan. The LTIP provides for grants of (a) incentive stock options qualified as such under U.S. federal income tax laws, (b) stock options that do not qualify as incentive stock options, (c) stock appreciation rights, (d) restricted stock awards, (e) restricted stock units, (f) performance share awards, (g) phantom stock units, (h) stock bonuses, (i) dividend equivalents, and (j) any combination of such grants.

The company grants time-vested stock awards in the form of restricted stock awards, restricted stock units or equity-settled phantom stock. During the nine months ended September 30, 2019, the Company granted 85,640 shares of time-vested stock awards under the LTIP, which vest ratably over three years for employee awards and one year for director awards, at a weighted average grant date fair value of $34.22. Additionally, 99,655 shares of time-vested stock awards vested during the nine months ended September 30, 2019, at a weighted average grant date fair value of $30.51.

During the nine months ended September 30, 2019, the Company granted 72,932 performance share awards under the LTIP at target, which cliff vest on December 31, 2021, at a weighted average grant date fair value of $39.26. The number of shares ultimately earned under a performance award may vary from zero to 200% of the target shares awarded, based upon the Company’s performance compared to certain metrics. The metrics used were determined at the time of the grant by the Compensation Committee of the Board of Directors and were either based on internal measures, such as the Company’s financial performance compared to target, or on a market-based metric, such as the Company’s stock performance compared to a peer group. Performance awards cliff vest upon attainment of the stated performance targets and minimum service requirements and are paid in shares of the Company’s common stock.

During the nine months ended September 30, 2019, plan participants exercised options to purchase 13,788 shares of the Company's common stock with a weighted average exercise price of $23.57.

The Company recognizes stock-based compensation expense related to restricted stock awards, phantom stock awards and restricted stock units based on the grant date fair value, which was the closing price of the Company’s stock on the date of grant. The fair value is expensed over the service period, which is generally three years.

For performance awards, the Company recognizes stock-based compensation expense based on the grant date fair value of the award. The fair value of internal metric-based performance awards is determined by the closing stock price of the Company’s common stock on the date of the grant. The fair value of market-based performance awards is computed using a Monte Carlo simulation. Performance awards are expensed over the service period of approximately 2.8 years, and the Company adjusts the stock-based compensation expense related to internal metric-based performance awards according to its determination of the shares expected to vest at each reporting date.