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Share-Based Compensation (Schedule Of Weighted Average Option Fair Values And Assumptions) (Details) (USD $)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Weighted average fair value of grants $ 12.30 $ 9.56 $ 5.32
Dividend yield 1.46% 1.51% 2.35%
Volatility 32.72% 33.43% 32.53%
Expected life (in years) 6.14 5.98 5.85
Minimum [Member]
     
Risk-free forward interest rate 0.28% 0.32% 0.69%
Maximum [Member]
     
Risk-free forward interest rate 5.61% 5.67% 4.63%