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Weighted-Average Assumptions Used to Estimate Grant Date Fair Values for Stock Options Granted (Detail) - Employee Stock Option
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Volatility 34.87% 35.11%
Expected term (in years) 5 years 5 years
Dividend yield 0.42% 2.05%
Risk-free interest rate 1.20% 1.40%