XML 37 R14.htm IDEA: XBRL DOCUMENT v3.8.0.1
Accounts receivable
 12 Months Ended
Dec. 31, 2017
Accounts receivable [Abstract]  
Accounts receivable
6. Accounts receivable

Accounts receivable consist of the following:

 
December 31,
 
(in thousands)
2017
 
2016
 
Billed
 
$
118,918
  
$
90,439
 
Unbilled
  
24,735
   
48,039
 
Total
 
$
143,653
  
$
138,478
 

 As of December 31, 2017 and 2016, the Company's accounts receivable balances were comprised of 89% and 83%, respectively, from the U.S. government. The overall increase in the percentage of accounts receivable attributed to U.S. government was due primarily to the timing of shipments of product and payments received for BioThrax product sales under the Company's contract with the CDC. Unbilled accounts receivable relates to various service contracts for which work has been performed, though invoicing has not yet occurred. Unbilled accounts receivable has decreased by $23.3 million due primarily to the timing of billings under our contract with the U.S. government related to the Company's CIADM program.