This excerpt taken from the VZ 10-K filed Feb 26, 2010.
Performance Stock Units
The Plan also provides for grants of Performance Stock Units (PSUs) that generally vest at the end of the third year after the grant. As defined by the Plan, the Human Resources Committee of the Board of Directors determines the number of PSUs a participant earns based on the extent to which the corresponding goals have been achieved over the three-year performance cycle. All payments are subject to approval by the Human Resources Committee. The PSUs are classified as liability awards because the PSU awards are paid in cash upon vesting. The PSU award liability is measured at its fair value at the end of each reporting period and, therefore, will fluctuate based on the price of Verizons stock as well as performance relative to the targets. Dividend equivalent units are also paid to participants at the time that the PSU award is determined and paid, and in the same proportion as the PSU award.
The following table summarizes Verizons Performance Stock Unit activity:
As of December 31, 2009, unrecognized compensation expense related to the unvested portion of Verizons RSUs and PSUs was approximately $304 million and is expected to be recognized over a weighted-average period of approximately two years.