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Stock-Based Compensation | 12 Months Ended
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Dec. 31, 2018
Share-based Compensation [Abstract] |
Stock-Based Compensation | STOCK-BASED COMPENSATION During the years ended December 31, 2018, 2017 and 2016 the Company’s stock-based compensation cost was $11.3 million, $10.6 million and $12.3 million, respectively, of which the Company capitalized $4.5 million, $4.2 million and $4.9 million, respectively, relating to its exploration and development efforts. The following table summarizes restricted stock activity for the twelve months ended December 31, 2018, 2017 and 2016:
| Number of Unvested Restricted Shares |  | Weighted Average Grant Date Fair Value
Unvested shares as of January 1, 2016 | 484,239 |  |  | $ | 43.51 |
Granted | 451,241 |  |  | 27.78 |
Vested | (252,566 | ) |  | 43.94 |
Forfeited | (69,858 | ) |  | 33.43 |
Unvested shares as of December 31, 2016 | 613,056 |  |  | $ | 32.90 |
Granted | 876,846 |  |  | $ | 15.14 |
Vested | (423,977 | ) |  | 29.90 |
Forfeited | (89,898 | ) |  | 27.91 |
Unvested shares as of December 31, 2017 | 976,027 |  |  | $ | 18.71 |
Granted | 1,579,911 |  |  | 9.90 |
Vested | (626,671 | ) |  | 18.05 |
Forfeited | (393,456 | ) |  | 12.23 |
Unvested shares as of December 31, 2018 | 1,535,811 |  |  | $ | 11.57 |
Unrecognized compensation expense as of December 31, 2018 related to outstanding stock options and restricted shares was $13.9 million. The expense is expected to be recognized over a weighted average period of 1.60 years.

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- Definition The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -URI http://asc.fasb.org/topic&trid=2228938 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 50 -URI http://asc.fasb.org/subtopic&trid=2208855 + Details
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