Trade Accounts Receivable, Net (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Trade Accounts Receivable, net
Trade accounts receivable	$ 78,642	$ 70,781
Allowance for doubtful accounts	(991)	(1,344)
Allowance for sales discounts	(1,231)	(1,181)
Trade accounts receivable, net	$ 76,420	$ 68,256
Trade accounts receivable | Largest customer
Trade accounts receivable, net
Percentage of trade accounts receivable from the largest customer	12.00%