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Summary Of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2011
Summary Of Significant Accounting Policies [Abstract]  
Summary Of Adjustments In Allowances For Doubtful Accounts And Sales Adjustments
     Years ended December 31,  
     2011     2010     2009  

Balance at beginning of year

    $ 1,603      $ 2,389      $ 2,115   

Provisions for losses — accounts receivable

      805        1,161        1,538   

Collection of accounts previously reserved

      (142 )      4        —     

Deductions for accounts charged off or credits issued

      (1,276 )      (1,951 )      (1,264 ) 
  

 

 

    

 

 

    

 

 

  

Balance at end of year

    $ 990      $ 1,603      $ 2,389