12.	Stock-Based Compensation

The Company recognizes stock-based compensation expense for all equity-based awards issued to employees, directors and non-employees that are expected to vest. Stock-based compensation expense is based on the fair value of awards as of the grant date. The Company recognized $570,000 and $595,000 of stock-based compensation expense related to equity awards for the three months ended March 31, 2019 and 2018, respectively, under the fair value method. In addition to the stock-based compensation expense recognized, the Company also recognized $27,000 and $32,000 of expense related to the change in the fair value of cash-settled restricted stock units (RSUs) during the three months ended March 31, 2019 and 2018, respectively.

During the three months ended March 31, 2019, the Company granted approximately three hundred thousand time-vesting RSUs to employees with an aggregate fair value of $0.8 million. During the three months ended March 31, 2018, the Company granted approximately two hundred thousand time-vesting RSUs to employees with an aggregate fair value of $0.7 million. A portion of the time-vesting RSUs vest quarterly in equal amounts over the course of eight quarters and the remainder vest annually in equal amounts over the course of three years. The fair value of the time-vesting RSUs is expensed ratably over the requisite service period, which ranges from one to three years.

The Company's 1995 long-term incentive program (LTIP) provides for the issuance of performance-vesting and time-vesting restricted stock units to certain executives and other Company employees. Vesting of the performance-vesting restricted stock units (PRSU's) is contingent upon the employee's continued employment and the Company's achievement of certain performance goals during designated performance period as established by the Compensation Committee of the Board of Directors. We recognize compensation expense, net of estimated forfeitures, for PRSU's on a straight-line basis over the performance period based on the probable outcome of achievement of the financial targets. At the end of each reporting period, we estimate the number of PRSUs that are expected to vest, based on the probability and extent to which the performance goals will be met, and take into account these estimates when calculating the expense for the period. If the number of shares expected to be earned changes during the performance period, we make a cumulative adjustment to compensation expense based on the revised number of shares expected to be earned.

During the three months ended March 31, 2019, the Company granted approximately three hundred fifty thousand performance-vesting RSUs to employees with an aggregate fair value of $0.9 million. During three months ended March 31, 2018, the Company did not grant any performance-vesting RSUs. The Company did not any grant stock options for the three months ended March 31, 2019 and 2018.