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Stock-Based Compensation (Detail) - (Table 3) (USD $)
9 Months Ended 12 Months Ended
Sep. 30, 2011
Dec. 31, 2012
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield 0.00% 0.00% 0.00%
Weighted average fair value $ 10.97 $ 14.15 $ 8.53
Minimum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Volatility 43.00% 40.00% 47.00%
Risk free interest rate 0.61% 0.47% 0.84%
Expected life in years 2 years 3 years 3 years
Maximum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Volatility 49.00% 47.00% 52.00%
Risk free interest rate 1.78% 0.87% 2.16%
Expected life in years 4 years 5 years 4 years