Consolidated Statements of Equity (USD $)
Total
Common Stock
Additional Paid-in Capital
Retained Earnings
Accumulated Other Comprehensive Income
Noncontrolling Interest
Total shareholders’ equity, beginning at Dec. 31, 2011 $ 671,038,000 $ 394,769,000 $ 37,936,000 $ 238,333,000 $ 0 $ 0
Common stock, shares, beginning at Dec. 31, 2011   124,767,322        
Activities during the period (unaudited) [Roll Forward]            
Net income 26,342,000     26,342,000    
Less: Net income attributable to non-controlling interest 0          
Net income 26,342,000          
Exercise of stock options, shares   317,153        
Exercise of stock options, amount 3,334,000 4,722,000 (1,388,000)      
Vesting of restricted stock units, shares   173,256        
Vesting of restricted stock units, amount 0 12,335,000 (12,335,000)      
Tax benefit on options exercised 7,789,000   7,789,000      
Stock-based compensation 2,789,000   2,789,000      
Other comprehensive income, net of tax 0          
Total shareholders’ equity, ending at Mar. 31, 2012 711,292,000 411,826,000 34,791,000 264,675,000 0 0
Common stock, shares, ending at Mar. 31, 2012   125,257,731        
Total shareholders’ equity, beginning at Dec. 31, 2012 4,609,861,000 4,180,778,000 73,530,000 354,991,000 (2,191,000) 2,753,000
Common stock, shares, beginning at Dec. 31, 2012 205,399,102 205,399,102        
Activities during the period (unaudited) [Roll Forward]            
Net income 51,408,000     51,408,000    
Less: Net income attributable to non-controlling interest 5,376,000         5,376,000
Net income 56,784,000          
Exercise of stock options, shares   133,264        
Exercise of stock options, amount 785,000 1,125,000 (340,000)      
Vesting of restricted stock units, shares   373,018        
Vesting of restricted stock units, amount 0 20,898,000 (20,898,000)      
Tax benefit on options exercised 4,928,000   4,928,000      
Stock-based compensation 6,644,000   6,644,000      
Distribution to non-controlling interest (2,114,000)         (2,114,000)
Other comprehensive income, net of tax 261,000       261,000  
Total shareholders’ equity, ending at Mar. 31, 2013 $ 4,677,149,000 $ 4,202,801,000 $ 63,864,000 $ 406,399,000 $ (1,930,000) $ 6,015,000
Common stock, shares, ending at Mar. 31, 2013 205,905,384 205,905,384