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Weighted-Average Assumptions used to Estimate Fair Value of Options Granted (Detail) (Stock Options)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Stock Options
     
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Weighted Average Fair Values [Line Items]      
Risk-free interest rate 0.75% 0.81% 1.92%
Expected life of option 4 years 10 months 13 days 4 years 10 months 6 days 4 years 8 months 12 days
Expected dividend yield 1.73% 2.28% 2.34%
Expected volatility 24.65% 28.46% 26.82%