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Stock-Based Compensation (Details 5)
9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Assumptions used for computing share-based employee compensation expense    
Risk-free interest rate 1.74% 3.32%
Dividend yield 2.00% 2.00%
Stock price volatility 32.88% 28.86%
Expected term 10 years 10 years