|6 Months Ended|
Jun. 30, 2019
|Share-based Payment Arrangement, Noncash Expense [Abstract]|
The Company has granted restricted stock units to employees and directors pursuant to the 2013 Restated Incentive Stock Plan ("2013 Plan"), as discussed below. During the three and six months ended June 30, 2019, the Company’s stock-based compensation cost was $2.8 million and $5.6 million, respectively, of which the Company capitalized $1.1 million and $2.3 million, respectively, relating to its exploration and development efforts. During the three and six months ended June 30, 2018, the Company's stock-based compensation cost was $3.3 million and $6.0 million, respectively, of which the Company capitalized $1.3 million and $2.4 million, respectively, relating to its exploration and development efforts. Stock compensation costs, net of the amounts capitalized, are included in general and administrative expenses in the accompanying consolidated statements of operations.
The following table summarizes restricted stock unit activity for the six months ended June 30, 2019:
Restricted Stock Units
Restricted stock units awarded under the 2013 Plan generally vest over a period of one year in the case of directors and three years in the case of employees and vesting is dependent upon the recipient meeting applicable service requirements. Stock-based compensation costs are recorded ratably over the service period. The grant date fair value of restricted stock units represents the closing market price of the Company's common stock on the date of grant. Unrecognized compensation expense as of June 30, 2019 related to restricted stock units was $13.8 million. The expense is expected to be recognized over a weighted average period of 1.90 years.
Performance Vesting Restricted Stock Units
During the six months ended June 30, 2019, the Company awarded performance vesting units to its Chief Executive Officer under the 2013 Plan. The number of shares of common stock that will ultimately be issued will be determined by comparing the Company's total stockholder return relative to the total stockholder return of a predetermined group of peer companies at the end of the 36-month performance period. The grant date fair value was determined using the Monte Carlo simulation method and is being recorded ratably over the performance period. Expected volatilities utilized in the Monte Carlo model were estimated using a historical period consistent with the remaining performance period of approximately three years. The risk-free interest rate was based on the U.S. Treasury rate for a term commensurate with the expected life of the grant. The Company assumed a risk-free interest rate of 2.42% and a range of expected volatilities of 30.5% to 72.6% to estimate the fair
value of performance vesting units granted during the six months ended June 30, 2019. Unrecognized compensation expense as of June 30, 2019 related to performance vesting restricted shares was $1.9 million. The expense is expected to be recognized over a weighted average period of 2.51 years.
The entire disclosure for share-based payment arrangement.
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef