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Assumptions of Weighted Average for ESPP Purchases Utilizing Black-Scholes Model (Detail) (Employee Stock Purchase Plan, USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Employee Stock Purchase Plan
     
Share Based Compensation [Line Items]      
Dividend yield 0.80% 0.90% 0.80%
Risk-free interest rate 0.11% 0.11% 0.16%
Expected life in years 6 months 6 months 6 months
Expected volatility 16.00% 26.00% 17.00%
Fair value $ 20.08 $ 21.21 $ 19.63