Accounts Receivable, Net

6 Months Ended

Jun. 30, 2013

Accounts Receivable, Net [Abstract]

Accounts Receivable, Net

3.  Accounts Receivable, Net

     Accounts receivable, net consists of the following:

	June 30,			December 31,
	2013			2012
Trade receivables	$	58,261		$	50,876
Unbilled revenue		24,328			12,372
Other receivables		4,666			6,198
		87,255			69,446
Less: Allowance for doubtful accounts		(231	)		(287	)
Accounts receivable, net	$	87,024		$	69,159

Under contract accounting, unbilled revenue on long-term contracts arise when the sales or revenues based on performance  attainment, though appropriately recognized, cannot be billed yet under terms of the contract as of the balance sheet date.  Accounts receivable expected to be collected after one year is not material.