Quarterly Financial Data (Unaudited) Quarterly Financial Data (Immaterial Restatement) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supply and logistics									$ 1,612,570	$ 3,323,028	$ 3,689,795
Revenues	$ 491,011	$ 572,334	$ 656,327	$ 526,857	$ 847,282	$ 964,114	$ 1,015,049	$ 1,019,719	2,246,529	3,846,164	4,134,830
Supply and logistics costs									1,577,497	3,277,052	3,649,328
Costs and Expenses									2,089,662	3,713,613	4,024,073
Operating income (loss)	$ 57,870	$ 44,798	$ 29,380	$ 24,819	$ 30,624	$ 35,268	$ 31,257	$ 35,402	$ 156,867	$ 132,551	$ 110,757