Compensation Plans	3 Months Ended
Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation Plans	Note 7 - Compensation Plans Performance Share Units Under the Equity Incentive Compensation Plan The Company grants performance share units (“PSUs”) to eligible employees as a part of its long-term equity compensation program. The number of shares of the Company’s common stock issued to settle PSUs ranges from 0% to 200% of the number of PSUs awarded and is determined based on certain performance criteria over a three-year measurement period. The performance criteria for the PSUs are based on a combination of the Company’s annualized Total Shareholder Return (“TSR”) for the performance period and the relative performance of the Company’s TSR compared with the annualized TSR of certain peer companies for the performance period. Compensation expense for PSUs is recognized within general and administrative and exploration expense over the vesting periods of the respective awards. Total compensation expense recorded for PSUs for the three months ended March 31, 2016, and 2015, was $2.9 million and $2.3 million, respectively. As of March 31, 2016, there was $15.2 million of total unrecognized compensation expense related to unvested PSU awards, which is being amortized through 2018. There have been no material changes to the outstanding and non-vested PSUs during the three months ended March 31, 2016. Restricted Stock Units Under the Equity Incentive Compensation Plan The Company grants restricted stock units (“RSUs”) as part of its long-term equity compensation program. Each RSU represents a right to receive one share of the Company’s common stock upon settlement of the award at the end of the specified vesting period. Compensation expense for RSUs is recognized within general and administrative expense and exploration expense over the vesting periods of the award. Total compensation expense recorded for RSUs was $3.2 million and $2.9 million for the three months ended March 31, 2016, and 2015, respectively. As of March 31, 2016, there was $15.4 million of total unrecognized compensation expense related to unvested RSU awards, which is being amortized through 2018. There have been no material changes to the outstanding and non-vested RSUs during the three months ended March 31, 2016.

Note 7 - Compensation Plans

Performance Share Units Under the Equity Incentive Compensation Plan

The Company grants performance share units (“PSUs”) to eligible employees as a part of its long-term equity compensation program. The number of shares of the Company’s common stock issued to settle PSUs ranges from 0% to 200% of the number of PSUs awarded and is determined based on certain performance criteria over a three-year measurement period. The performance criteria for the PSUs are based on a combination of the Company’s annualized Total Shareholder Return (“TSR”) for the performance period and the relative performance of the Company’s TSR compared with the annualized TSR of certain peer companies for the performance period. Compensation expense for PSUs is recognized within general and administrative and exploration expense over the vesting periods of the respective awards.

Total compensation expense recorded for PSUs for the three months ended March 31, 2016, and 2015, was $2.9 million and $2.3 million, respectively. As of March 31, 2016, there was $15.2 million of total unrecognized compensation expense related to unvested PSU awards, which is being amortized through 2018. There have been no material changes to the outstanding and non-vested PSUs during the three months ended March 31, 2016.

Restricted Stock Units Under the Equity Incentive Compensation Plan

The Company grants restricted stock units (“RSUs”) as part of its long-term equity compensation program. Each RSU represents a right to receive one share of the Company’s common stock upon settlement of the award at the end of the specified vesting period. Compensation expense for RSUs is recognized within general and administrative expense and exploration expense over the vesting periods of the award.

Total compensation expense recorded for RSUs was $3.2 million and $2.9 million for the three months ended March 31, 2016, and 2015, respectively. As of March 31, 2016, there was $15.4 million of total unrecognized compensation expense related to unvested RSU awards, which is being amortized through 2018. There have been no material changes to the outstanding and non-vested RSUs during the three months ended March 31, 2016.