Accounts Receivable (Schedule Of Accounts Receivable) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accounts Receivable [Abstract]
Trade customers	$ 432,927	$ 391,401
Affiliates	134	122
Allowance for doubtful accounts	(10,818)	(10,969)
Receivables from trade customers and affiliates, net	422,243	380,554
Federal and state taxes	7,169	16,113
Other	15,197	10,705
Accounts receivable, net	$ 444,609	$ 407,372