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Stock-Based Compensation (Detail) - (Table 4) (USD $)
6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dividend yield 0.00% 0.00%
Weighted average fair value $ 14.44 $ 14.03
Minimum [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Volatility 36.90% 41.10%
Risk free interest rate 0.37% 0.48%
Expected life in years 4 years 1 month 3 years 1 month
Maximum [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Volatility 44.80% 47.40%
Risk free interest rate 0.76% 0.87%
Expected life in years 5 years 1 month 4 years 7 months 7 days