| Share-Based and Cash-Based Incentive Compensation (Tables)
 | 12 Months Ended | 
      
        | Dec. 31, 2013 | 
      
        | Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity | 
A summary of activity related to restricted stock is as follows:    
|   |    | 2013 |   |    | 2012 |   |    | 2011 |   |  
|   |    | RestrictedShares
 |   |   | WeightedAverage
 Grant Date
 Price
 Per Share
 |   |    | RestrictedShares
 |   |   | WeightedAverage
 Grant Date
 Price
 Per Share
 |   |    | RestrictedShares
 |   |   | WeightedAverage
 Grant Date
 Price
 Per Share
 |   |  
| Nonvested, beginning of period |    |   | 43,687 |    |   | $ | 18.69 |    |    |   | 51,870 |    |   | $ | 15.81 |    |    |   | 470,392 |    |   | $ | 7.42 |    |  
| Granted |    |   | 27,450 |    |   |   | 12.75 |    |    |   | 21,954 |    |   |   | 19.13 |    |    |   | 20,433 |    |   |   | 25.45 |    |  
| Vested |    |   | (27,297 | )  |   |   | 17.09 |    |    |   | (27,475 | )  |   |   | 13.59 |    |    |   | (404,422 | )  |   |   | 7.31 |    |  
| Forfeited |    |   | — |    |   |   | — |    |    |   | (2,662 | )  |   |   | 18.78 |    |    |   | (34,533 | )  |   |   | 6.83 |    |  
| Nonvested, end of period |    |   | 43,840 |    |   | $ | 15.96 |    |    |   | 43,687 |    |   | $  | 18.69 |    |    |   | 51,870 |    |   | $  | 15.81 |    |    | 
      
        | Schedule of Restricted Stock Awards Outstanding | 
Subject to the satisfaction of service conditions, the restricted shares outstanding as of December 31, 2013 are expected to vest as follows:    
|   |    | Shares |   |  
| 2014 |    |   | 19,445 |    |  
| 2015 |    |   | 15,245 |    |  
| 2016 |    |   | 9,150 |    |  
| Total |    |   | 43,840 |    |    | 
      
        | Summary of Share Activity Related to Restricted Stock Units | 
A summary of activity related to RSUs is as follows:    
|   |    | 2013 |   |    | 2012 |   |    | 2011 |   |  
|   |    | RSUs |   |   | WeightedAverage
 Fair Value
 Price
 Per RSU
 |   |    | RSUs |   |   | WeightedAverage
 Fair Value
 Price
 Per RSU
 |   |    | RSUs
 |   |   | WeightedAverage
 Fair Value
 Price
 Per RSU
 |   |  
| Nonvested, beginning of period |    |   | 969,820 |    |   | $ | 22.70 |    |    |   | 1,732,703 |    |   | $ | 14.67 |    |    |   | 1,266,617 |    |   | $ | 9.36 |    |  
| Granted |    |   | 969,919 |    |   |   | 13.23 |    |    |   | 764,654 |    |   |   | 18.64 |    |    |   | 534,375 |    |   |   | 26.93 |    |  
| Vested |    |   | (468,925 | )  |   |   | 26.93 |    |    |   | (1,198,208 | )  |   |   | 9.36 |    |    |   | — |    |   |   | — |    |  
| Forfeited |    |   | (139,061 | )  |   |   | 16.50 |    |    |   | (329,329 | )  |   |   | 19.56 |    |    |   | (68,289 | )  |   |   | 12.03 |    |  
| Nonvested, end of period |    |   | 1,331,753 |    |   | $  | 14.96 |    |    |   | 969,820 |    |   | $  | 22.70 |    |    |   | 1,732,703 |    |   | $  | 14.67 |    |    | 
      
        | Schedule of Restricted Stock Awards Outstanding | 
Subject to the satisfaction of service conditions, the RSUs outstanding as of December 31, 2013 are eligible to vest in the year indicated in the table below:    
|   |    | RSUs |   |  
| 2014 – subject to service requirements |    |   | 359,785 |    |  
| 2014 – subject to service and other requirements (1) |    |   | 67,877 |    |  
| 2015 – subject to service requirements |    |   | 719,971 |    |  
| 2015 – subject to service and other requirements (1) |    |   | 184,120 |    |  
| Total |    |   | 1,331,753 |    |  
| (1)  | In addition to service requirements, these RSUs are also subject to TSR performance requirements not yet measureable, with awards ranging from 0% to 200% of amounts granted.  | 
 | 
      
        | Summary of Compensation Expense under Share-Based Payment Arrangements and Related Tax Benefit | 
A summary of compensation expense under share-based payment arrangements and the related tax benefit is as follows (in thousands):    
|   |    | Year Ended December 31, |   |  
|   |    | 2013 |   |    | 2012 |   |    | 2011 |   |  
| Share-based compensation expense from: |    |   |   |   |    |   |   |   |    |   |   |   |  
| Restricted stock |    | $ | 397 |    |    | $ | 399 |    |    | $ | 2,377 |    |  
| Restricted stock units |    |   | 11,128 |    |    |   | 11,999 |    |    |   | 7,333 |    |  
| Total |    | $ | 11,525 |    |    | $ | 12,398 |    |    | $ | 9,710 |    |  
| Share-based compensation tax benefit: |    |   |   |   |    |   |   |   |    |   |   |   |  
| Tax benefit computed at the statutory rate |    | $ | 4,034 |    |    | $ | 4,339 |    |    | $ | 3,399 |    |    | 
      
        | Summary of Incentive Compensation Expense | 
A summary of incentive compensation expense is as follows (in thousands):    
|   |    | Year Ended December 31, |   |  
|   |    | 2013 |   |    | 2012 |   |    | 2011 |   |  
| Share-based compensation expense included in: |    |   |   |   |    |   |   |   |    |   |   |   |  
| Lease operating expense |    | $ | — |   |    | $ | — |   |    | $ | 466 |    |  
| General and administrative |    |   | 11,525 |    |    |   | 12,398 |    |    |   | 9,244 |    |  
| Total charged to operating income |    |   | 11,525 |    |    |   | 12,398 |    |    |   | 9,710 |    |  
| Cash-based incentive compensation included in: |    |   |   |   |    |   |   |   |    |   |   |   |  
| Lease operating expense |    |   | 3,482 |    |    |   | 3,787 |    |    |   | 3,700 |    |  
| General and administrative |    |   | 8,817 |    |    |   | 6,558 |    |    |   | 12,213 |    |  
| Total charged to operating income |    |   | 12,299 |    |    |   | 10,345 |    |    |   | 15,913 |    |  
| Total incentive compensation charged to operating income |    | $ | 23,824 |    |    | $ | 22,743 |    |    | $ | 25,623 |    |    |