Stock-Based Compensation (Details) 1 (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 6 Months Ended 0 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2012
Common Stock
May 16, 2012
Public Offering
May 16, 2012
Public Offering
Common Stock
Jul. 02, 2012
Catalyst
Common Stock
Jun. 30, 2013
LTIP [Member]
Jun. 30, 2013
Assumed Plans
Stockholders' Equity [Line Items]                    
Shares from public offering         11,960,000   12,000,000 66,800,000    
Share price to public             $ 45.30      
Proceeds from public offering, net of issuance costs     $ 0 $ 519,260   $ 519,100        
Warrants issued               500,000    
Stock-based compensation $ 6,500 $ 4,100 $ 13,131 $ 6,853            
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant                 6,822,705 1,136,442