9. 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 during the second quarter of 2017, 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, (h) stock bonuses, (i) dividend equivalents, and (j) any combination of such awards.

The company grants time-vested stock awards in the form of restricted stock awards, restricted stock units or equity-settled phantom stock. During the three months ended March 31, 2018, the Company granted 68,665 shares of time-vested stock awards under the LTIP, which primarily vest ratably over three years, at a weighted average grant date fair value of $30.14. Additionally, 62,369 shares of time-vested stock awards vested during the three months ended March 31, 2018, at a weighted average grant date fair value of $29.47.

During the three months ended March 31, 2018, the Company granted 66,764 performance share awards under the LTIP at target, which cliff vest on December 31, 2020, at a weighted average grant date fair value of $34.52. The number of shares actually 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 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 common shares of the Company’s stock. During the three months ended March 31, 2018, management concluded that it was probable that the minimum performance criteria would not be met for certain performance shares that were granted during 2016. As a result, during the first quarter of 2018, the Company reversed $0.4 million in stock compensation from previous accruals.

During the three months ended March 31, 2018, plan participants exercised 24,009 stock options with a weighted average exercise price of $24.23.

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. The Company recognizes stock-based compensation expense related to market-based performance awards based on the grant date fair value, which is computed using a Monte Carlo simulation. The fair value is expensed over the service period, which is approximately 2.8 years. The Company recognizes stock-based compensation expense related to internal measure-based performance awards 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 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 potential achievement of the performance target at each reporting date.