Compensation Plans	6 Months Ended
Jun. 30, 2015
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 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. PSUs are recognized as general and administrative and exploration expense over the vesting periods of the award. Total expense recorded for PSUs for the three months ended June 30, 2015, and 2014, was $2.7 million and $3.6 million, respectively, and $5.0 million and $6.8 million for the six months ended June 30, 2015, and 2014, respectively. As of June 30, 2015, there was $13.0 million of total unrecognized compensation expense related to unvested PSU awards, which is being amortized through 2017. There were no material changes to the outstanding and non-vested PSUs during the six months ended June 30, 2015. Subsequent to June 30, 2015, the Company granted 320,753 PSUs with a fair value of $14.5 million as part of its regular annual long-term equity compensation program. These PSUs will fully vest on the third anniversary of the date of the grant. Also, subsequent to June 30, 2015, the Company settled PSUs that were granted in 2012, which earned a 1.0 times multiplier, by issuing a net 188,279 shares of the Company’s common stock in accordance with the terms of the respective PSU awards. The Company and the majority of grant participants mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, 100,683 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those PSUs. Restricted Stock Units Under the Equity Incentive Compensation Plan The Company grants restricted stock units (“RSUs”) as part of its equity compensation program. Each RSU represents a right for one share of the Company’s common stock to be delivered upon settlement of the award at the end of the specified vesting period. RSUs are recognized as general and administrative expense and exploration expense over the vesting periods of the award. Total expense recorded for RSUs was $2.9 million for each of the three months ended June 30, 2015, and 2014, and $5.8 million and $5.7 million for the six months ended June 30, 2015, and 2014, respectively. As of June 30, 2015, there was $14.3 million of total unrecognized compensation expense related to unvested RSU awards, which is being amortized through 2017. There were no material changes to the outstanding and non-vested RSUs during the six months ended June 30, 2015. Subsequent to June 30, 2015, the Company granted 356,246 RSUs with a fair value of $15.6 million as part of its regular annual long-term equity compensation program. These RSUs will vest 1/3^rd on each of the next three anniversary dates of the grant. Also, subsequent to June 30, 2015, the Company settled 236,342 RSUs that related to awards granted in previous years. The Company and the majority of grant participants mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, the Company issued 163,433 net shares of common stock. The remaining 72,909 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those RSUs. Director Shares During the first half of 2015 and 2014, the Company issued 37,950 and 23,009 shares, respectively, of its common stock to its non-employee directors, under the Company’s Equity Incentive Compensation Plan. The Company recorded approximately $1.2 million of compensation expense related to these awards for the three and six months ended June 30, 2015, and 2014. All shares of common stock issued to the Company’s non-employee directors are earned over the one-year service period following the date of grant, unless five years of service has been provided by the director, in which case that director’s shares vest upon the earlier of the completion of the one-year service period or the director retiring from the Board of Directors. Employee Stock Purchase Plan Under the Company’s Employee Stock Purchase Plan (“ESPP”), eligible employees may purchase shares of the Company’s common stock through payroll deductions of up to 15 percent of eligible compensation, without accruing in excess of $25,000 in value from purchases for each calendar year. The purchase price of the stock is 85% of the lower of the fair market value of the stock on the first or last day of the purchase period, and shares issued under the ESPP have no restriction period. The ESPP is intended to qualify under Section 423 of the Internal Revenue Code (“IRC”). The Company had 1.1 million shares available for issuance under the ESPP as of June 30, 2015. There were 96,285 and 35,249 shares issued under the ESPP during the second quarters of 2015 and 2014, respectively. The fair value of ESPP grants is measured at the date of grant using the Black-Scholes option-pricing model. Net Profits Plan Cash payments made or accrued under the Company’s Net Profits Plan totaled $1.9 million and $2.2 million for the three months ended June 30, 2015, and 2014, respectively, and $3.2 million and $5.4 million for the six months ended June 30, 2015, and 2014, respectively, the majority of which were recorded as general and administrative expense within the accompanying statements of operations. Additionally, the Company accrued or made cash payments under the Net Profits Plan of $3.8 million for the three-month and six-month periods ended June 30, 2015, and $8.5 million for the three-month and six-month periods ended June 30, 2014, as a result of the divestitures of properties subject to the Net Profits Plan. These cash payments are accounted for as a reduction in the net gain on divestiture activity line item in the accompanying statements of operations. The Company records changes in the present value of estimated future payments under the Net Profits Plan as a separate line item in the accompanying statements of operations. The change in the estimated liability is recorded as a non-cash expense or benefit in the current period. The amount recorded as an expense or benefit associated with the change in the estimated liability is not allocated to general and administrative expense or exploration expense because it is associated with the future net cash flows from oil and gas properties in the respective pools rather than results being realized through current period production. If the Company allocated the change in liability to these specific functional line items, based on the current allocation of actual distributions made by the Company, such expenses or benefits would predominately be allocated to general and administrative expense. As time has passed, the amount distributed relating to prospective exploration efforts has become insignificant as more is paid to employees that have terminated employment and do not provide ongoing exploration support to the Company.

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 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. PSUs are recognized as general and administrative and exploration expense over the vesting periods of the award.

Total expense recorded for PSUs for the three months ended June 30, 2015, and 2014, was $2.7 million and $3.6 million, respectively, and $5.0 million and $6.8 million for the six months ended June 30, 2015, and 2014, respectively. As of June 30, 2015, there was $13.0 million of total unrecognized compensation expense related to unvested PSU awards, which is being amortized through 2017. There were no material changes to the outstanding and non-vested PSUs during the six months ended June 30, 2015.

Subsequent to June 30, 2015, the Company granted 320,753 PSUs with a fair value of $14.5 million as part of its regular annual long-term equity compensation program. These PSUs will fully vest on the third anniversary of the date of the grant. Also, subsequent to June 30, 2015, the Company settled PSUs that were granted in 2012, which earned a 1.0 times multiplier, by issuing a net 188,279 shares of the Company’s common stock in accordance with the terms of the respective PSU awards. The Company and the majority of grant participants mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, 100,683 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those PSUs.

Restricted Stock Units Under the Equity Incentive Compensation Plan

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

Total expense recorded for RSUs was $2.9 million for each of the three months ended June 30, 2015, and 2014, and $5.8 million and $5.7 million for the six months ended June 30, 2015, and 2014, respectively. As of June 30, 2015, there was $14.3 million of total unrecognized compensation expense related to unvested RSU awards, which is being amortized through 2017. There were no material changes to the outstanding and non-vested RSUs during the six months ended June 30, 2015.

Subsequent to June 30, 2015, the Company granted 356,246 RSUs with a fair value of $15.6 million as part of its regular annual long-term equity compensation program. These RSUs will vest 1/3^rd on each of the next three anniversary dates of the grant. Also, subsequent to June 30, 2015, the Company settled 236,342 RSUs that related to awards granted in previous years. The Company and the majority of grant participants mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings as provided for in the plan document and award agreements. As a result, the Company issued 163,433 net shares of common stock. The remaining 72,909 shares were withheld to satisfy income and payroll tax withholding obligations that occurred upon delivery of the shares underlying those RSUs.

Director Shares

During the first half of 2015 and 2014, the Company issued 37,950 and 23,009 shares, respectively, of its common stock to its non-employee directors, under the Company’s Equity Incentive Compensation Plan. The Company recorded approximately $1.2 million of compensation expense related to these awards for the three and six months ended June 30, 2015, and 2014.

All shares of common stock issued to the Company’s non-employee directors are earned over the one-year service period following the date of grant, unless five years of service has been provided by the director, in which case that director’s shares vest upon the earlier of the completion of the one-year service period or the director retiring from the Board of Directors.

Employee Stock Purchase Plan

Under the Company’s Employee Stock Purchase Plan (“ESPP”), eligible employees may purchase shares of the Company’s common stock through payroll deductions of up to 15 percent of eligible compensation, without accruing in excess of $25,000 in value from purchases for each calendar year. The purchase price of the stock is 85% of the lower of the fair market value of the stock on the first or last day of the purchase period, and shares issued under the ESPP have no restriction period. The ESPP is intended to qualify under Section 423 of the Internal Revenue Code (“IRC”). The Company had 1.1 million shares available for issuance under the ESPP as of June 30, 2015. There were 96,285 and 35,249 shares issued under the ESPP during the second quarters of 2015 and 2014, respectively. The fair value of ESPP grants is measured at the date of grant using the Black-Scholes option-pricing model.

Net Profits Plan

Cash payments made or accrued under the Company’s Net Profits Plan totaled $1.9 million and $2.2 million for the three months ended June 30, 2015, and 2014, respectively, and $3.2 million and $5.4 million for the six months ended June 30, 2015, and 2014, respectively, the majority of which were recorded as general and administrative expense within the accompanying statements of operations.

Additionally, the Company accrued or made cash payments under the Net Profits Plan of $3.8 million for the three-month and six-month periods ended June 30, 2015, and $8.5 million for the three-month and six-month periods ended June 30, 2014, as a result of the divestitures of properties subject to the Net Profits Plan. These cash payments are accounted for as a reduction in the net gain on divestiture activity line item in the accompanying statements of operations.

The Company records changes in the present value of estimated future payments under the Net Profits Plan as a separate line item in the accompanying statements of operations. The change in the estimated liability is recorded as a non-cash expense or benefit in the current period. The amount recorded as an expense or benefit associated with the change in the estimated liability is not allocated to general and administrative expense or exploration expense because it is associated with the future net cash flows from oil and gas properties in the respective pools rather than results being realized through current period production. If the Company allocated the change in liability to these specific functional line items, based on the current allocation of actual distributions made by the Company, such expenses or benefits would predominately be allocated to general and administrative expense. As time has passed, the amount distributed relating to prospective exploration efforts has become insignificant as more is paid to employees that have terminated employment and do not provide ongoing exploration support to the Company.