Trade Accounts Receivable, Net Of Allowances

3 Months Ended

Mar. 31, 2012

Trade Accounts Receivable, Net Of Allowances [Abstract]

Trade Accounts Receivable, Net Of Allowances

6.     TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCES

(in thousands)	March 31, 2012		December 31, 2011
Trade accounts receivable	$	74,846	$	77,123
Unbilled trade accounts receivable		33,262		22,096
Total accounts receivable		108,108		99,219
Allowance for doubtful accounts		—		(31)
Allowance for sales credit memos		(1,256)		(895)
Total allowance		(1,256)		(926)
	$	106,852	$	98,293

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 March 31, 2012 and December 31, 2011, respectively.