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Stock-Based Compensation (Detail) - (Table 4) - $ / shares
9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dividend yield 0.00% 0.00%
Weighted average fair value $ 8.91 $ 7.01
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Volatility 23.00% 22.20%
Risk free interest rate 1.48% 0.90%
Expected life in years 3 years 5 months 3 years 5 months
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Volatility 26.40% 26.20%
Risk free interest rate 1.99% 1.73%
Expected life in years 5 years 5 years