Related Party Transactions (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Related party transactions entered into for the time periods presented
Sales revenues	$ 193,061	$ 182,870
Service fee revenues	5,479	5,167
Purchases of product	148,809	128,997
Lease income	1,878	1,252
Labor and benefits reimbursement	2,741	2,773
Other expenses	139	19
Accounts receivable at March 31	12,544	21,879
Accounts payable at March 31	$ 21,677	$ 21,035