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Share-Based Compensation - Fair Value of Each Option Grant Estimated (Detail)
6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected option life 6 years 5 years 9 months
Risk-free interest rate   1.32%
Expected volatility   35.55%
Dividend yield 0.00% 0.00%
Minimum [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 2.31%  
Expected volatility 36.74%  
Maximum [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 2.73%  
Expected volatility 37.20%