Accounts Receivable, net (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts receivable, net
Gross accounts receivable	$ 113,423	$ 111,637
Allowance for doubtful accounts	(10,460)	(9,932)
Total accounts receivable, net	$ 102,963	$ 101,705