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Investments and Other Marketable Securities (Tables)
 6 Months Ended
Jun. 30, 2011
Investments And Other Marketable Securities (Tables) [Abstract]  
Investments and other marketable securities
                                 
    Investments in marketable securities  
            Gross     Gross        
            Unrealized     Unrealized     Estimated  
    Cost     Losses     Gains     Fair Value  
Equity securities
  $ 10,443     $ (1,387 )   $ —     $ 9,056  
 
                       
 
  $ 10,443     $ (1,387 )   $ —     $ 9,056