Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts Receivable, Net [Abstract]
Trade customers	$ 375,389	$ 391,401
Affiliates	226	122
Allowance for doubtful accounts	(10,487)	(10,969)
Receivables from trade customers and affiliates, net	365,128	380,554
Federal and state taxes	13,151	16,113
Other	15,313	10,705
Accounts receivable, net	$ 393,592	$ 407,372