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Stock-Based Compensation - Assumptions Used for Estimating Fair Value of Employee Stock Options (Detail) (Employee Stock Option [Member])
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected dividend yield of stock 0.00% 0.00% 0.00%
Expected volatility 0.88%    
Minimum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 1.50% 0.74% 0.93%
Expected life of option (in years) 5 years 4 months 10 days 5 years 4 months 24 days 5 years 4 months 21 days
Expected volatility   0.87% 0.83%
Maximum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 1.88% 1.34% 2.11%
Expected life of option (in years) 5 years 4 months 17 days 5 years 6 months 29 days 5 years 4 months 28 days
Expected volatility   0.88% 0.86%