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Share-Based Payments (Weighted Average Assumptions for Employee Stock Purchase Plan and Other Option) (Details)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Employee Stock Purchase Plan [Member]
     
Risk-free interest rate 0.12% 0.13% 0.20%
Expected term 6 months 6 months 6 months
Dividend yield 2.90% 3.00% 3.30%
Expected volatility 24.00% 19.00% 28.00%
Stock Option [Member]
     
Risk-free interest rate 0.00% 0.00% 2.30%
Expected term 0 months 0 months 5 years
Dividend yield 0.00% 0.00% 3.30%
Expected volatility 0.00% 0.00% 34.00%