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Stock Compensation Plans - Stock Option Transactions Under Various Stock-Based Employee Compensation Plans (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]      
Outstanding, Beginning Balance, Shares 2,702,629    
Granted, Shares 68,000    
Exercised, Shares (586,563) (113,359) (368,178)
Canceled, Shares (59,180)    
Outstanding, Ending Balance, Shares 2,124,886 2,702,629  
Exercisable, Ending Balance, Shares 1,506,925    
Outstanding, Beginning Balance, Weighted Average Exercise Price $ 21.27    
Granted, Weighted Average Exercise Price $ 33.04    
Exercised, Weighted-Average Exercise Price $ 17.66    
Canceled, Weighted Average Exercise Price $ 31.57    
Outstanding, Ending Balance, Weighted Average Exercise Price $ 22.36 $ 21.27  
Exercisable, Ending Balance, Weighted Average Exercise Price $ 23.30    
Outstanding, Ending balance, Weighted Average Remaining Contractual Term 6 years 1 month 24 days    
Exercisable, Ending Balance, Weighted Average Remaining Contractual Term 5 years 10 months 21 days