Receivables
 12 Months Ended
Dec. 31, 2017
Receivables [Abstract]  
Receivables
RECEIVABLES
Receivables were comprised of the following:
 
 
December 31,
(In thousands)
 
2017
 
2016
Billed receivables
 
$
50,595

 
$
41,992

Unbilled contract receivables
 
121,601

 
127,150

Other
 
2,799

 
2,930

Receivables
 
$
174,995

 
$
172,072


As of December 31, 2017 and 2016, all billed receivables are due from the U.S. government, either directly as prime contractor to the U.S. government or as subcontractor to another prime contractor to the U.S. government. Because the Company’s billed receivables are with the U.S. government, the Company does not believe it has a material credit risk exposure.
Unbilled contract receivables represent revenue recognized on long-term contracts in excess of amounts billed as of the balance sheet date. We estimate that approximately $6.7 million of our unbilled contract receivables as of December 31, 2017 may not be collected within the next twelve months. These amounts relate to the timing of the U.S. government review of indirect rates and contract line item realignments with our customers.