Trade Accounts Receivable, Net of Allowance

9 Months Ended

Sep. 30, 2013

Trade Accounts Receivable, Net of Allowance

5.  TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCE

(in thousands)	September 30,     2013		December 31,     2012
Trade accounts receivable	$	58,037	$	112,106
Unbilled trade accounts receivable		33,318		22,923
Total accounts receivable		91,355		135,029
Allowance for sales credit memos		(772)		(963)
	$	90,583	$	134,066

Unbilled trade accounts receivable relate to services earned under time and material arrangements, and maintenance and license arrangements that had not been invoiced as of September 30, 2013 and December 31, 2012, respectively.