Financial Instruments (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Margin Deposit Assets	3.2	$ 0.8
Commodity Contract [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	2.2	2.5
Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member]
Offsetting Assets [Line Items]
Concentration Risk, Percentage	35.00%
Customer Concentration Risk [Member] | Cost of Goods, Total [Member]
Offsetting Assets [Line Items]
Concentration Risk, Percentage	37.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Offsetting Assets [Line Items]
Concentration Risk, Percentage	33.00%
Customer Concentration Risk [Member] | Crude [Member] | Sales Revenue, Goods, Net [Member]
Offsetting Assets [Line Items]
Number of Customers	2
Customer Concentration Risk [Member] | Crude [Member] | Cost of Goods, Total [Member]
Offsetting Assets [Line Items]
Purchases of product	71.2
Number of Suppliers	2
Customer Concentration Risk [Member] | Crude [Member] | Accounts Receivable [Member]
Offsetting Assets [Line Items]
Number of Customers	2