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Receivables (Tables)
6 Months Ended
Jun. 30, 2011
Receivables [Abstract]  
Receivables
Receivables consisted of the following (in thousands):

   
June 30,
  
December 31,
 
   
2011
  
2010
 
Billed
 $61,774  $56,035 
Unbilled
  385,644   270,508 
Total
 $447,418  $326,543