Accounts Receivable (Schedule Of Accounts Receivable) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accounts Receivable [Abstract]
Trade customers	$ 391,401	$ 353,035
Affiliates	122	475
Allowance for doubtful accounts	(10,969)	(9,710)
Receivables from trade customers and affiliates, net	380,554	343,800
Federal and state taxes	16,113	15,499
Other	10,705	3,564
Accounts receivable, net	$ 407,372	$ 362,863