Quarterly Financial Data (Unaudited) Quarterly Financial Data (Immaterial Restatement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supply and logistics									$ 3,842,337	$ 3,095,054	$ 2,173,896
Revenues	961,035	1,090,293	1,068,694	1,014,808	919,056	895,023	797,705	755,577	4,134,830	3,367,361	2,437,797
Supply and logistics costs									3,754,004	3,004,293	2,115,454
Costs and Expenses									4,024,073	3,252,651	2,355,219
Operating income (loss)	$ 23,300	$ 24,092	$ 33,360	$ 30,005	$ 30,228	$ 29,236	$ 28,112	$ 27,134	$ 110,757	$ 114,710	$ 82,578