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Significant Accounting Policies (Weighted Average Assumptions Of Options Granted) (Details)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Employee Stock Options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 29.59% 30.54% 35.00%
Risk-free interest rate 2.04% 1.63% 2.61%
Dividend yield 0.00% 0.00% 0.00%
Expected term (years) 3.81 2.97 3.62
Employee Stock Purchase Plan [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 23.94% 20.20% 46.90%
Risk-free interest rate 0.14% 0.16% 0.31%
Dividend yield 0.00% 0.00% 0.00%
Expected term (years) 0.5 0.5 0.5