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Earnings Per Share (Schedule Of Diluted Earnings Per Share) (Details) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Earnings Per Share        
Diluted earnings per share for Common and Class B common stock $ 1.09 $ 1.08 $ 1.32 $ 1.20