Concentration Risk (Details) (Customer Concentration Risk [Member], Sales Revenue, Net [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Western Refining, Inc. [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	28.90%	25.90%	24.50%
Western Refining, Retail Business [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	23.60%	24.20%	23.80%
Kroger [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	23.00%	27.10%	26.20%