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Weighted-Average Assumptions Used to Estimate Grant Date Fair Values for Stock Options Granted (Detail) - Employee Stock Option
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Volatility 37.95% 35.89% 41.36%
Expected term (in years) 5 years 5 years 5 years
Dividend yield 2.00% 1.17% 0.89%
Risk-free interest rate 1.37% 1.76% 0.70%