Accounts receivable (Tables)
12 Months Ended
Dec. 31, 2013
Accounts receivable [Abstract]  
Accounts receivable
Accounts receivable consist of the following:

 
December 31,
 
(in thousands)
2013
 
2012
 
Billed
 
$
45,757
  
$
76,155
 
Unbilled
  
14,830
   
19,888
 
Total
 
$
60,587
  
$
96,043