Annual report pursuant to Section 13 and 15(d)

Capital Stock (Details Textual)

v2.4.0.6
Capital Stock (Details Textual) (USD $)
In Thousands, except Share data, unless otherwise specified
12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2011
Y
Dec. 31, 2010
Dec. 31, 2009
Jun. 30, 2010
Colombian Partners [Member]
Dec. 31, 2011
Employee Stock Option [Member]
Dec. 31, 2009
Employee Stock Option [Member]
Dec. 31, 2011
2008 Grant [Member]
Dec. 31, 2010
2008 Grant [Member]
Dec. 31, 2010
2009 Grant [Member]
Dec. 31, 2011
Restricted Stock Units [Member]
Y
Dec. 31, 2010
Restricted Stock Units [Member]
Dec. 31, 2009
Restricted Stock Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award (Textual) [Abstract]                        
Common stock Issued       1,112,723                
Percentage of restricted stock units vest 100.00%                      
Number of Restricted Stock Units Forfeited 0                      
Compensation expense                   $ 3,101 $ 3,424 $ 759
Actual cumulative forfeitures (in units) 19,918                      
Assumed maximum IRR for all grants 12.50%                      
Unrecognized Compensation expense related to outstanding stock options           1,152       5,213    
Remaining unrecognized compensation expense for outstanding options         0              
Compensation expense recognition period (in years) 2                 2    
Approximate incremental compensation expense to reach internal rate of return level               823 377      
Percentage of IRR expected restricted stock units grants             12.50%   12.50%      
Number of hypothetical shares of common stock 153,727 396,429 303,168             1,037,770    
Treasury Stock and Share Based Awards (Textual) [Abstract]                        
Common stock repurchased value as result of restricted stock forfeitures and canceled $ 0.001                      
Stock options were exercised range Lower $ 14.85                      
Stock options were exercised range Upper $ 15.17                      
Number of Restricted Units Vested During Period 0                      
Market Value of Restricted Shares $ 19.60                      
Intrinsic value of options exercised 699 9,836 28,083                  
Recognized tax benefit on options exercised 238 2,680 7,545                  
Average remaining contractual life of options outstanding 3                      
Shares of Restricted Stock Granted 424,436 683,921 472,881                  
Minimum fair value of restricted stock granted $ 19.35                      
Maximum fair value of restricted stock granted $ 20.71                      
Minimum forfeiture rate for restricted stock awards 0.00%                      
Maximum forfeiture rate for restricted stock awards 5.00%                      
Award vesting period range for restricted stock granted to directors Over one year                      
Incremental compensation expense   435                    
Award vesting period range for restricted stock granted to employees 4 years                      
Compensation expense related to restricted stock awards 6,591 4,928 2,393                  
Unrecognized Compensation expense related to restricted stock awards 13,688                      
Total fair value of vested shares 5,658 3,272 762                  
Tax benefit recognized on vested shares $ 2,188 $ 1,087 $ 287                  
Percentage of IRR, which is the threshold 8.50%                      
Percentage of IRR, which is the target 10.50%                      
Percentage of IRR, which is the maximum 12.50%