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Stock Based Compensation - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Long-term equity incentive plan, termination date October 19, 2014    
Number of shares authorized under plan 8,550,000    
Options and restricted stock granted, net of forfeitures 8,040,958    
Total intrinsic value of options exercised $ 9,500,000 $ 2,800,000 $ 2,400,000
Stock Options
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation cost related to stock option awards granted under the equity incentive plan 0    
Restricted Stock
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation cost related to stock option awards granted under the equity incentive plan $ 21,100,000    
Vesting period of equity awards granted to employees, years 4 years    
Expected weighted-average period to recognize the cost of stock awards (in years) 2 years 6 months