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Stockholders' Equity (Summary Of Fair Value Assumptions For Options Granted) (Details) (USD $)
3 Months Ended
Mar. 31, 2012
Y
April 19, 2011 [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate 2.10%
Expected life of option in years 5.00
Expected dividend yield 1.60%
Expected stock volatility 39.33%
Estimated fair value of stock option $ 11.20
April 20, 2010 [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate 2.60%
Expected life of option in years 5.00
Expected dividend yield 1.50%
Expected stock volatility 39.10%
Estimated fair value of stock option $ 8.14
April 21, 2009 [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate 1.90%
Expected life of option in years 5.00
Expected dividend yield 1.00%
Expected stock volatility 38.80%
Estimated fair value of stock option $ 3.64
April 15, 2008 [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate 2.70%
Expected life of option in years 5.00
Expected dividend yield 1.00%
Expected stock volatility 30.93%
Estimated fair value of stock option $ 7.75
April 17, 2007 [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate 4.60%
Expected life of option in years 4.85
Expected dividend yield 1.00%
Expected stock volatility 31.59%
Estimated fair value of stock option $ 5.63